1. health and fitness
2. disease
3. infertility

Chapter I
Introduction
Introduction
1.0. Infertility
Infertility is “the inability of a sexually active, non-contraception couples to achieve
pregnancy in one year” [1]. Approximately 13-18% of couples in the reproductive age
group worldwide are affected by infertility regardless of race and ethnic group [2]. Recent
growth of the Indian population has been unprecedented; it stands currently over one billion
and is expected to touch 2 billion by 2035 with an average growth rate of 2% [3]. Albeit
curtailing population growth is a major national concern, a substantial number of infertile
couples in our population have an equally great concern, that of having a child. Although,
infertility is not life threatening, it is usually a traumatic condition associated with social
stigma, resulting in intense societal and parental pressure to attain biological parenthood
[4].
1.1. Classification
Infertility is classified into primary and secondary, based on the ability to achieve a pregnancy
regardless of the outcome. Infertility is either primary (67-71%) when no pregnancy has
ever occurred or secondary (29-33%), where there has been a pregnancy, irrespective of
the outcome [5]. About one in ten couples are affected with infertility for various possible
reasons; both sexes contribute equally to this problem (40% each), while remaining 20% of
infertile couples are childless due to unknown etiology. Female factors include ovulation
disorder, tubal damage, endometriosis, hyperprolactinemia, reproductive tract disease,
ectopic pregnancy and unsafe abortions [6].
1.2. Causes of male infertility
It was assumed that most reproductive problems could be attributed to the female partner;
but research in recent years has demonstrated that 50% of cases are associated with male
factor infertility. Male infertility is a multifactorial syndrome encompassing a wide variety of
disorders. Among infertile men, ~70% of the underlying etiological cause(s) can be detected
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[8], while the remaining 30% are referred to as unknown (idiopathic), could be congenital or
acquired [9]. The distribution of infertility is shown in Figure 1.1.
Figure 1.1. Distribution of infertility
Female factor
40%
Idiopathic
40%
Male factor
40%
Source: [7].
The etiology of male factor infertility is associated with genetic conditions, such as consequence
of a developmental disorder [10] and non-genetic factors including genital infections, structural
abnormalities of the male genital tract, varicoceles, congenital absence of unilateral/bilateral
vas deferens (CABUD/CABVD), chronic illness, hypogonadotrophic hypogonadism, previous
scrotal or inguinal surgery, medications, exposure to chemicals, life style and environment [11].
A large proportion of male infertility is associated with either systemic defect such as diabetes,
obesity, immunological factors or with imbalance in levels of gonadal steroids, trophic hormones
[testosterone, dihydrotestosterone, follicle stimulating hormone (FSH), leuteinizing hormone
(LH), and androgen receptor] [12].
Genetic factor accounts for ~10-15% of severe male infertility, including single gene defects,
inherited disease, interactions of multiple genes, chromosomal aberrations, microdeletion on
the Y chromosome and mutations or polymorphisms [13]. The frequency of genetic factors
associated with male-factor infertility, is depicted in Figure 1.2.
Further, there appears to be a geographical variation in the prevalence of male infertility amongst
infertile couples. This is as high as 59% in France, 26-32% in the UK and Kashmir Valley in
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India, and about 36% in South Africa, Indonesia and Finland [17]. Thus, available reports
indicate that ethnic, climatic, occupational factors influence on mean sperm concentration,
counts and quality of spermatozoa and male infertility.
1.3. Lifestyle factors
The life style and environmental factors include lack of exercise, smoking, alcohol consumption,
substance abuse, air pollution, phthalates, pesticides, heavy metal exposure and poor nutrition
that might affect gamete and embryo development, reduced sperm quality leading to infertility
[18].
Figure 1.2. Contribution of genetic factors with male-factor infertility
60%
1-55%
50%
40%
30%
23.4%
2.1-19.6%
20%
10%
1-2%
0%
CFTR gene
polymorphism
Chromosomal
abnormalities
Yq
microdeletions
Others
Source: [14, 15, 16].
An altered environmental milieu due to oxidative stress has shown to affect the spermatogenic
process as well as the quality and quantity of sperm. Many factors are reported for an enhanced
oxidative stress due to accumulation of reactive oxygen species (ROS). Obesity produces
oxidative stress as adipose tissue releases pro-inflammatory cytokines that increase leukocyte
production of ROS [19]. In addition, the accumulation of adipose tissue within the groin region
results in heating of the testicle which has been linked with oxidative stress and decreased
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sperm quality [20]. Excessive exercise activity has been associated with oxidative stress; since
muscle aerobic metabolism is known to create a large amount of ROS in humans and rodents
[21]. Studies have shown that cigarette smoking in infertile men is correlated with impaired
sperm motility, fertilization capacity and sperm membrane oxidation [22].
Similarly, excessive alcohol consumption causes an increase in systemic oxidative stress
as ethanol stimulates the production of ROS. Many alcohol abusers have diets deficient in
protective antioxidants. It was also suggested that the presence of oxidative stress within the
testicle could be due to significant reduction in plasma testosterone, increase in serum lipid
peroxidation byproducts and a drop in antioxidants [23]. However, no study to date has directly
examined the correlation between alcohol intake and sperm oxidative damage.
1.4. Environmental factors
Consistent with life style, several environmental pollutants have been associated with testicular
oxidative stress. Significantly increased frequency of sperm with abnormal morphology and
reduced motility was observed in infertile men with medium and high exposure to air pollution
which may result in sperm DNA damage and thereby increase the rates of male-mediated
infertility, miscarriage, and other adverse reproductive outcomes [24]. Phthalates are used as
plasticizers, employed in a wide range of food packaging and personal care products. Exposure
to phthalates can take place through food consumption, dermal absorption or inhalation have
been linked with impaired spermatogenesis and increased sperm DNA damage [25]. Oral
administration of phthalate esters to rats have shown an increase of ROS generation within the
testis and a decrease in antioxidant levels, culminating in impaired spermatogenesis [26].
Pesticides such as lindane, methoxychlor and herbicide dioxin-TCDD have all been linked
with testicular oxidative stress in rodent models [27]. The commonly used preservative sulfur
dioxide has also been shown to produce testicular oxidative stress in laboratory animals [28].
Heavy metal exposure has been conclusively linked with an increase in testicular oxidative
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stress and a resultant increase in sperm DNA oxidation [29]. The increase in infertility and
miscarriage observed in the partners of welders and battery/paint factory workers may be due
to oxidative damage to sperm DNA initiated by the inhalation of metal fumes [30].
Recent prospective studies have shown a correlation of psychological stress with reduction
in sperm quality mediated by an increase in seminal plasma ROS generation and antioxidant
protection [31]. Injury to testicles may also have issues with sperm production. Varicocele is
a varicosity or varicose vein in the testicle that damages the blood flow to the testes, slowing or
stopping the sperm production.
1.5. Infections
Post-testicular genital tract infection and inflammation (e.g., combined inflammation of the
epididymis, testis or the prostate gland), like prostatitis, result in leukocytospermia, have been
associated with increased levels of ROS and subsequent sperm DNA damage [32]. Bacteria
responsible for prostate infection may originate from the urinary tract or can be sexually
transmitted. Typical non-sexually transmitted pathogens include Streptococci (S. viridans
and S. pyogens), coagulase-negative Staphylococci (S. epidermidis and S. haemolyticus),
gram-negative bacteria (Escherchia coli, Proteus mirabilis) and atypical mycoplasma strains
(Ureaplasma urealyticum, Mycoplasma hominis) [33]. All these pathogens create an acute
inflammatory response with an influx of leukocytes into the genital tract and result in the increase
in ROS production [34] and have high degrees of sperm oxidative pathology [35]. Several
studies have reported the influence of current or past Chlamydial infection, viral pathogens such
as Cytomegalovirus, Herpes Simplex Virus, and Epstein-Barr virus with initiation or increase in
oxidative damage to sperm. Herpes simplex DNA is found in 4–50% of infertile men’s semen. The IgM antibodies being associated with a 10-fold increase in the rate of leukospermia and
oxidative stress [36].
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1.6. Immunological causes
Immunological factor operates at every stage of human reproductive process; may be due
to elevated level of antisperm antibodies caused by infective or auto-immune diseases of
male reproductive system. Antisperm antibodies can impair fertilization in various ways;
interfering with sperm motility by immobilizing or agglutinating the sperm, disturb transport
of the spermatozoa, zygote development by impairing early cleavage, or even damaging the
implantation process [37].
1.7. Biochemical factors/hormones
Spermatogenesis is hormonally regulated [38], problems that can affect male fertility are associated
with (i) disorders involving hypothalamic secretion or action; (ii) pituitary development
disorders; (iii) primary disorders of pituitary LH, FSH secretion or action. As LH and FSH
are trophic hormones for the testes and ovaries, reduced secretion of these gonadotrophins
(hypogonadotrophism) results in malfunctioning of the sex organs (hypogonadism) [39].
Most often, impaired male fertility arises from direct testicular injury to the germ cells or the
supporting somatic (Sertoli) or steroidogenic (Leydig) cells, following testicular injury. The
release of hypothalamic GnRH stimulates pituitary gonadotrophin secretion: the resultant LH
predominantly acts on Leydig cells to promote steroidogenesis, whilst FSH acts on Sertoli
cells. Testosterone, acting as an androgen, is important in the negative feedback control of both
gonadotrophins, although hypothalamic aromatization to estradiol also increases the degree of
inhibition. Many other hormones, including leptin, growth hormone and insulin-like growth
factor-1 (IGF-1) may also play a role in spermatogenesis [40].
1.8. Sperm disorders
Research over the past few years has clearly demonstrated that infertile men with normal
somatic karyotypes have an increased risk of producing aneuploid sperm [41]. Most of the
human aneuploidy is considered to be of germ-cell origin arising from errors in maternal
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and paternal meiotic chromosomal segregation. In turn, aneuploid sperm might result in an
abnormal offspring with major or minor congenital malformations, severe dysmorphogenesis,
chromosomally abnormal fetuses and pregnancy loss [42, 43]. The chances of live birth and
conception rate drastically decreases when DNA fragmentation index is >30% [44]. Evenson
et al., (2002) had reported that the spontaneous abortion rate as about 1.7 fold higher in sperms
containing fragmented DNA [45]. The most common causes of male infertility are related
to problems with the sperm maturation, abnormal morphology, unable to move properly
(progressive motility) which occurs at the different stages of spermatogenesis.
There are various reasons where the volume of the semen sample may be reduced. Majority
of the secretion might be from prostate or seminal vesicles that reflect abnormalities in sex
gland with an obstruction in the reproductive tract. Hematospermia is a condition, where the
presence of red blood cell count (RBC) in semen, may appear brown in color. Large volumes
of semen are found in association with varicocele or after relatively long periods of sexual
abstinence. The pH of the semen sample ranges between 7.2 and 8.0 that are determined by
acidic and alkaline secretions of the prostate and seminal vesicles. If the pH exceeds 8.0, the
semen sample is suspected to have infection due to decreased secretion of acidic products by
the prostate, such as citric acid or occlusion of seminal vesicles.
1.8.1. Causes of sperm DNA damage
The causes of sperm DNA damage have been attributed to intra or extratesticular factors which
were clearly associated with male infertility. Sperm DNA is unique and regulates timely
maturation of the zygote. Damage to sperm DNA may occur due to life style or environmental
factors.
Different theories have been proposed to explain the origin of DNA damage
in spermatozoa; either it could occur at the time, during the result of DNA packing and/or
transition of histone to protamine complex at different stages of spermiogenesis. Maturation of
spermatozoa is a unique process involving a series of meiotic and mitotic changes in cytoplasmic
architecture. Topological rearrangements, alteration in transcription replacement of somatic
cell-like histones with transition proteins, and the final addition of protamines leading to a
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highly organized and condensed chromatin protects the genetic integrity during transport of the
paternal genome through the male and female reproductive tracts [46]. Infertile men manifest
various nuclear alterations in chromosomes, including an abnormal chromatin structure,
microdeletions, aneuploidies and DNA strand breaks (single and double). Depending upon
the count and motility of spermatozoa, the semen sample is classified as normozoospermia,
oligozoospermia,
asthenozoospermia,
teratozoospermia,
oligoasthenoteratozoospermia,
azoospermia and globozoospermia as shown in Table 1.1.
Table 1.1. Nomenclature for semen variables [Source: 47]
Clinical finding
Terminology
Normozoospermia
Normal ejaculate
Oligozoospermia
≤ 10 million sperm/ml of semen
Asthenozoospermia
≥ 50% spermatozoa with low motility
Teratozoospermia
≥ 50% sperm with abnormal morphology
Oligoasthenoteratozoospermia
Signifies disturbance of oligozoospermia,
asthenozoospermia and teratozoospermia
Azoospermia
Complete absence of sperm
Aspermia
Ejaculation does not emit any sperm
Necrospermia
Non viable/dead sperm
Hematospermia
Red blood cells present in the semen
Pyospermia
White blood cells present in the semen
Globozoospermia
Round-headed sperm
1.8.2. Azoospermia
Azoospermia is absence of both spermatozoa and spermatogenic cells in semen sample; might
be due to complete obstruction of seminal ducts, which is often accompanied by secretary
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dysfunction of the gonads. The spermatozoa is found to be completely absent in the seminal fluid
which causes male infertility. The prevalence of azoospermia in the general population has been
estimated at 2%; it was also found to be as high as 10-20%. Testicular histology shows different
degrees of spermatogenic alterations, ranging from tubular damage to hypospermatogenesis.
1.8.3. Oligoasthenoteratozoospermia (OAT)
Oligozoospermia is a condition where semen sample shows a decreased sperm concentration
with significant abnormalities in sperm morphology and motility. Studies on infertile men
with OAT have reported an increased frequency of chromosomal abnormalities in sperm. It
has been previously suggested that oligozoospermia might be a greatest risk factor because
quantitative problems in sperm production have been associated with pairing abnormalities in
both autosomes and sex chromosomes, resulting in partial or complete meiotic arrest [11]; that
can lead to aneuploidy in cells capable of completing spermatogenesis and meiotic arrest in
other cells causing oligozoospermia. Oligozoospermia is categorized according to sperm count
into those with severe, moderate or mild (ranging from ≤ 5-10 million sperm/ml). 1.8.4. Globozoospermia
Semen with round-head sperms are termed as globozoospermia, few studies have analyzed sperm
aneuploidy in spermatozoa from globozoospermic patients. The acrosomeless globozoospermia
seems to be the most severe type among sperm abnormalities. The association between this
globzoospermia and numerical chromosomal abnormalities is unclear [48].
1.9. Genetic causes of male infetility
In addition to the above-discussed factors 15-30% of genetic factors have been reported
as a cause in spermatogenesis failure.
Genes control various physiological processes,
such as hypothalamus-pituitary-gonadal axis, germ cell development and differentiation.
Spermatogenesis is a complex process, and is influenced by the molecular mechanism of
many genes. It has been estimated that over 10% of genes are involved in the regulation of
human spermatogenesis [49]. Genetic causes in infertile men include numerical and structural
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chromosomal abnormalities, (reciprocal and robertsonian translocations) [50, 51] deletions of
the azoospermia factor region (AZF) of chromosome-Y [52], mutations or polymorphisms in
the cystic fibrosis transmembrane conductance regulator (CFTR) gene commonly associated
with congenital absence of vas deferens [53], mitochondrial DNA mutations, multifactorial
and endocrine disorders may be of genetic origin [9]. The prevalence of genetic abnormality
associated with abnormal spermiogram of male infertility has been shown in Table 1.2.
Table 1.2. Genetic abnormalites of male infertility
Prevalence (%)
Genetic abnormality
Normozoospermia Azoospermia Oligozoospermia
Chromosomal abnormalities
5
Klinefelter syndrome
5
Robertsonian translocation
Y chromosome microdeletion
15
10
0.8
0.09
1.6
Less than 2%
10-15
5-10
AZFa deletion
(sertoli cell-only syndrome)
0.5 –1.0
AZFb deletion
(spermatogenic arrest)
0.5 -1.0
AZFc deletion
(severe oligozoospermia to
nonobstructive azoospermia)
0.5 -1.0
Partial AZFc deletion
3-5
Source: [54]
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1.9.1. Chromosomal abnormalities (CA)
Chromosomal abnormalities pertain to presence or absence of whole chromosomes (numerical
chromosomal abnormalities); gain or loss of an entire or segment of chromosome (structural
chromosomal abnormalities) that result in aneuploidy which occurs during various genetic
levels [55]. Aneuploidy is one of the most common forms of chromosomal abnormalities; it
is responsible for a large portion of human morbidity and mortality, infertility and pregnancy
loss. The origin of CA associated with male infertility arises from errors in maternal and
paternal meiotic chromosomal segregation. They are of two types: i). karyotype alterations
affecting cells of both somatic and germ cell-lines, and ii) meiotic abnormalities which can
produce infertility, either by spermatogenetic arrest or formation of chromosomally unbalanced
gametes. This might either lead to spontaneous abortions, offspring with mental deficiency [56]
or congenital malformations [57]. The incidence of CA in male infertility is reported to be 2.1
to 19.6% worldwide [9], which is higher than in general population (0.5-1%) [58]; similarly,
the sample size varies between 72 and 2600 infertile men [59]. Nevertheless, all of them point
to an increasing percentage of CA concomitant with decreasing sperm count. In addition,
the nature of CA differs depending on whether a patient has oligoasthenoteratozoospermia or
azoospermia. Therefore, chromosomal errors are a pertinent area of research to determine the
role of genetics in male factor infertility.
1.9.2. Numerical chromosomal abnormality
Aneuploidy involves both autosomes and sex chromosomes that occur in around 4% of
pregnancies [60]. However, it is estimated that up to 60% of conceptions are aneuploid and
aborted spontaneously, even before a pregnancy is clinically recognized. It is also evident
that loss (monosomy) of a chromosome is much more detrimental than gain (trisomy) of a
chromosome. Monosomy X is the only non-mosaic condition that is compatible with life, and is
largely attributed to X-chromosome inactivation. The most common numerical CA is paternal
in origin and associated with sex chromosome and the incidence is reported to be 1:1000 live
births [61]. Autosomal aneuploidies are much less frequent i.e., 1:7000 in trisomy 18 and
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1:10000 for trisomy 13; [62] duplications and/or deficiencies are observed occasionally that
result from the abnormal segregation of a structural rearrangement in a carrier father or mother
[63]. Numerical chromosome errors are a frequent cause of male infertility. The incidence is
inversely proportional to the number of sperms. The reported frequency of sex and autosomal
CA in infertile men are shown in Table 1.3.
Table 1.3. Frequency of constitutional chromosomal abnormalities
associated with male infertility
Frequency (%)
Country
Reference
8.00
Turkey
[64]
4.20
France
[65]
25.80
Germany
[66]
11.40
Germany
[67]
10.60
Netherlands
[68]
10.20
India
[69]
4.40
India
[70]
15.50
Iran
[59]
11.20
Turkey
[71]
8.50
China
[72]
11.74
Turkey
[73]
18.30
Kuwait
[14]
1.9.3. Sex chromosome abnormalities
Sex chromosome abnormalities are the most frequent chromosome-related cause of infertility,
arise de novo and are associated with an increased rate of sperm chromosome aneuploidy among
infertile men [63]. The frequency of karyotype alterations is 7% and it inversely correlates with
sperm count; it has been reported that 17.5%, 13.7% and 4.6% of chromosomal alterations are
observed in severe oligozoospermia, azoospermia and oligozoospermic men respectively [83].
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1.9.4. 47,XYY
The XYY karyotype occurs amongst 1:1000 live male births, that results from non-disjunction
during cell division at a post-zygotic stage of mitosis which receives an extra Y chromosome,
producing a 47,XYY karyotype. In a majority of cases the phenotypic features remain normal,
which hampers further management based on the specific requirements associated with an
etiology and produces 46,XY/47,XYY mosaics. El-Dahtory and Elsheikha (2009) investigated
four cases of infertile men (4 out of 132) with azoospermia or severe oligozoospermia showed
karyotype of 47,XYY [75]. Men with a 47,XYY karyotype are generally fertile and there is no
evidence of transmission of the extra Y chromosome to their progeny because the supernumerary
Y-chromosome is eliminated during meiosis; and some XYY germ cells can complete meiosis
and produce mature aneuploid sperm.
1.9.5. Klinefelter syndrome
Klinefelter syndrome is the most common sex CA occurring at a rate of 1:500 live male births.
Phenotypically, patients present with increased height, decreased intelligence quotient, obesity,
diabetes mellitus, small firm testes, decreased Leydig cell function and sperm production,
an increased risk of leukemia, extragonadal germ cell tumors, and breast cancer. Etiology is
related to paternal or maternal sex chromosomal nondisjunction during meiosis which result
in 90% and 10% of patients with nonmosaic 47,XXY and mosaic 46,XY/47,XXY karyotype. It has been reported that primordial 47,XXY germ cells enter meiosis theoretically; 50% of
the spermatozoa will carry a 24,XX or 24,XY karyotype, and 50% will have a normal 23,X
or 23,Y karyotype. However, based on the reproductive outcomes of men and women with
comparable numerical chromosome abnormalities (47,XXY or 47,XXX) it can be extrapolated
that the Klinefelter male, who reproduces spontaneously has a chance of having a child with
three sex chromosomes of less than 1%. This relative low risk is due to natural selection in
favor of normal euploid sperm. Previously, it was believed that Klinefelter syndrome is sterile
and has been estimated that 25% of non-mosaic patients to have sperm in their ejaculate [69,
76] but men with the mosaic form of the disease may have residual spermatogenesis in their
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seminiferous tubules. These patients may try to achieve pregnancy using intra cytoplasmic
sperm injection as they have large numbers of aneuploid gametes and are at a risk of producing
offspring with CA [77].
1.9.6. Structural chromosomal aberrations
Structural CA include the rearrangement, translocation and deletions of single genes that are
known to be present in ~15% of azoospermic subjects. The rate of congenital chromosomal
abnormalities in newborns is found to be 0.5% [78, 79]. 1.9.7. Reciprocal translocation
Reciprocal translocation is defined as the exchange of chromosomal material between the arms
of two heterologous chromosomes, thus changing the order, but not the amount of genetic
material. Chromosomes 12, 22 and Y are involved more often than expected on the basis of
their relative lengths. A balanced reciprocal Y; autosome translocation has been demonstrated
between almost every autosome carriers of balanced translocations in infertiles are at high risk,
either leads to recurrent spontaneous abortions or an affected offspring that are found in 0.2%
of the neonatal population [65, 80]; 0.6% of infertile couples [67]; 2 to 3.2% with severe male
factor infertility [81] and 9.2% of fertile couples experiencing recurrent miscarriages [82]. 1.9.8. Robertsonian translocation
These chromosomal translocations are mainly observed in D (13, 14, 15) and G group
chromosomes (21, 22 and Y). Robertsonian translocations are one of the most common
structural chromosomal aberrations observed in humans with an incidence of 1.23:1000 live
births of which ~50% are de novo; [83] this has been shown that the frequencies are nine times
higher in infertile men [84] more common in oligozoospermic and azoospermic men [58] with
rates of 1.6 and 0.09%, respectively [67]. In general, carriers are phenotypically normal but are
at increased risk for spontaneous abortions, are chromosomally unbalanced and lack gamete
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production [76]. The D/D translocation is the most frequent type, including a high predominance
of 13;14 translocation. These translocations originate through centric fusion of the long arms
of the acrocentric chromosomes with the translocated chromosome bearing either one or two
centromeres with a simultaneous loss of both short arms resulting in a balanced karyotype of
45 chromosomes. Whilst the chromosomes pair during meiosis, translocated chromosomes and
their homologues appear as trivalent can lead to reduced fertility [85]. Malsegregation of these
abnormal chromosomes could result in trisomy or monosomy of complete chromosomes [86].
1.9.9. Marker chromosome
Marker chromosomes are defined as unidentified structurally abnormal chromosomes and their
consequences may range from being harmless to detrimental. Most of the marker chromosomes
are supernumerary marker chromosomes (SMCs) that occur in addition to the 46 normal
chromosomes or as constituents of the 46 chromosomes by replacing normal chromosomes
[74]. The prevalence of SMCs at birth is estimated at 0.6-1.5:1,000 newborns [87]. About 80%
of SMCs arise de novo and more frequently with advanced maternal age [88, 89], infertile men;
without clinical features present a karyotype of 47,XY,+mar.
1.9.10. Variant chromosome
Chromosomal alterations include minor or “normal” polymorphic chromosomal variants of
heterochromatin regions in addition to major chromosomal abnormalities. The term “variant”
represents the deviations from type of chromosome morphology, and “heteromorphic”
designates the homologous chromosomes with arms of different length or variable bands [90].
Heterochromatin are of two types: facultative and constitutive. Facultative heterochromatin is
a reversible form, not rich in satellite DNA and becomes transcriptionally active in some phases
of the cell cycle. Constitutive heterochromatin remains transcriptionally inert during the entire
cell cycle [91]. Though, several reports on male infertility had discussed about the presence
of chromosomal variants, most authors state that a person carrying a variant chromosome do
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not have an increased risk of having spontaneous abortion, abnormal offspring, or any other
reproductive problem.
1.10. The Y chromosome
Male spermatogenesis involves different genes regulating mitotic and meiotic cell divisions,
as well as subsequent differentiation to spermatozoa [92] of which some are responsible for
spermatogenesis, development and maintenance of male gonads [11, 93, 94]. The Y chromosome
is male-specific, 60 megabases (Mb) in size, consisting of 80 different proteins and 60 million
nucleotides, but has the least number of genes compared to any other chromosome.
Figure 1.3. Genes located on chromosome Y
Yp11.32
Centromere
Short arm
Yp11.31
Yp11.2
Yp11.1
Yq11.1
AZFa
Long arm
Yq11.21
Yq11.22
Yq11.23
AZFb
AZFc
USP9Y, DBY
(400–800 kb)
RBMY
(1–3 Mb)
DAZ
(3.5 Mb)
Yq12
Twenty seven genes on the Y chromosome were identified, nine are located on the Yp (short
arm) and the remaining 18 on the Yq (long arm). Skaletsky et al., (2003) had reported the
complete sequence of the euchromatin segment (23 Mb), in which male specific region of the
Y is designated as MSY. Figure 1.3. shows the diagrammatic view of some genes present on
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chromosome-Y [95]. Despite intense efforts, only a few human “spermatogenic genes” have
been identified but their precise function remains unknown. It has been reported that in certain
ethnic group, men with specific haplotype might have lower sperm concentration; the frequency
of haplotype (II) is more common in azoospermic men compared with normal men [96].
1.10.1. Y chromosomal polymorphism
Y chromosome polymorphisms have been preferentially seen in azoospermia and severe
oligozoospermia. The variation in the length of Y chromosome is usually due to the distal part
of the long arm that is known to contain heterochromatin. The incidence of Yqh+ in infertile
men is reported to be 4.5-7.9% [97]. Nagvenkar et al., 2005 had reported the occurrence of
long (Yqh+) and short (Yqh-) as 3.4 and 27.3 per cent respectively [69]. Minocherhomji et
al., (2008) found Yqh+ variant in 26.9% (102 of 380) infertile men, but other authors have
not reported any association between an increased risk of pregnancy loss and Yqh- variant in
carriers [98].
1.10.2. Inversion
The structural rearrangements in infertile men were found to be 0.1%. Inversion occurs when
two chromosomes break on the same chromosome and join after 180 degrees rotation [99].
During meiosis, chromosomes are forced to form inversion loops which enables the homologous
chromosomes to pair. The formation of these inversion loops can influence fertility due to the
mechanism and time limitations. Pericentric inversion of Y chromosome are reported to be
more prevalent among infertile men than in newborns.
1.10.3. Yq microdeletion
Germ cell development is under the control of several genes located on autosomes and Y
chromosome in mammals [100]. The Y chromosome is the smallest chromosome that contains
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Introduction
many genes that are critical for the development of male gonads and spermatogenesis. The
variation present on the Y chromosome and deletions of large segments of the chromosome
involving multiple genes make it difficult to determine the exact cause of certain infertile
phenotypes in men. The prevalence of Y chromosome microdeletions in infertile men is
estimated to be 1:2000 to 1:3000. The frequency in azoospermia or severe oligozoospermia
men is about 5-12%, although there is a marked difference reported in different world
regions.
Tiepolo and Zuffardi (1976) had hypothesized a correlation between Yq microdeletions and
male infertility. These deletions were clustered in interval 5 and 6 of the Y chromosome was
defined as “Azoospermia Factor” (AZF), individuals observed with its terminal deletions were
azoospermic [116]. Based on the molecular results, Y chromosome has been subdivided into
seven deletion intervals from A-G [117]. Three regions were defined: AZFa, AZFb and AZFc,
which map on the long arm (Yq) from the centromere to the telomere. A fourth region, named
AZFd, located between AZFb and AZFc was also reported [118]. Y-chromosomal genes involved
in spermatogenesis mostly reside on the AZFa, b and c regions.
In the AZFa region, USP9Y is an important functional gene involves in spermatogenesis. The
main candidate gene in the AZFb region is the RBMY (RNA binding motif) gene family, which
has a restricted expression in the testis [119]. The AZFc region also has a specific expression in
the testis and therefore, has been shown to play a crucial role [120], which represents the most
frequently deleted region in infertile men. The prevalance of Yq microdeletions among infertile
men from different regions are given in Table 1.4. Several genes located on critical region
Yq which is defined as a chromosomal deletion that spans but not large enough to be detected
using conventional cytogenetic methods and Polymerase Chain Reaction (PCR) is an important
screening tool.
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Table 1.4. Prevalance of Yq microdeletions in infertile men
Country
India
India
Kuwait
Pakistan
Chinese
Seria
Kuwait
Russia
Saudi Arabia
Croatian
Turkey
Egypt
Slovenia
Belgium
Israel
Korea
United States
United States
Prevalence (%)
Reference
5.0
3.33
7.14
17.6
6.4
15.6
10.4
7.5
3.2
0.95
9.1
12
4.4
3.9
6
20
7.7
17. 2
[7]
[101]
[14]
[102]
[72]
[103]
[104]
[105]
[106]
[107]
[108]
[109]
[110]
[111]
[112]
[113]
[114]
[115]
1.10.3.1. Azoospermia factor a (AZFa)
The AZFa spans around 400-600kb of DNA and is located in the proximal portion of deletion
interval 5. The two main protein encoding genes located in the AZFa region are USP9Y and
DBY also called as DDX3Y [121]. Deletions in the AZFa region that remove both of these
genes cause Sertoli cell–only syndrome, a condition characterized by the presence of complete
Sertoli cells in the testes but a lack of spermatozoa in the ejaculate DBY, has a probable role in
infertility because it is localized in the testis and is involved in the development of pre-meiotic
germ cells [122]. The Lardone et al., (2007) had studied transcriptional activity of several genes
on AZF region and found that men with Sertoli cell–only syndrome had shown reduced levels
of DBY transcripts, suggesting that DBY may play an important role in spermatogenesis [123].
The USP9Y is also involved in spermatogenesis, as shortening or deletion of the USP9Y causes
azoospermia [124] or oligoasthenoteratozoospermia [125]. These findings suggests that DBY
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Introduction
gene has a more critical role in spermatogenesis than the USP9Y gene. Further research must
be performed to determine the exact role of these genes in fertility to develop more targeted Y
chromosome screening practices for infertile men.
1.10.3.2. Azoospermia factor b (AZFb)
The AZFa spans around 1-3Mb of DNA and is located on the distal portion of deletion interval
5 to the proximal end of deletion interval 6. Deletions of the AZFb region cause arrest of
spermatogenesis at the primary spermatocyte stage indicating that the region is essential for
fertility [122]. The protein coding genes in the AZFb region are RBMY and PRY located on the
ampliconic region. RBMY1 codes for an RNA binding protein, [126] which is a testis-specific
splicing factor expressed in the nuclei of spermatogonia, spermatocytes, and spermatids [52].
Lavery et al. (2007) had a expression of RBMY1 in azoospermic men. PRY genes are involved
in the regulation of apoptosis, an essential process that removes abnormal sperm from the
population of spermatozoa [127]. The deletions of RBMY and PRY genes were studied in
patients presenting with hypospermatogenesis, if both of them were removed, spermatogenesis
was arrested completely, indicating that these are the major genes involved in fertility [119].
1.10.3.3. Azoospermia factor c (AZFc)
A deletion in the AZFc region produces a wide range of phenotypes, many of which are
associated with low sperm concentration due to reduced spermatogenesis [52]. The AZFc
spans about 3.5Mb of euchromatin and is located at the distal part of deletion interval 6 of
chromosome Y. The first identified gene in the in the AZFc was “Deletion in Azoospermia
Factor” (DAZ) encodes RNA-binding proteins that are expressed in the germ cells. Deletion
in AZFc has been reported in approximately 12% and 6% of non-obstructive azoospermia and
severe oligozoospermia cases [128]. Studies demonstrate that AZFa and AZFb regions are
merely needed to initiate spermatogenesis but without the AZFc region, spermatogenesis will
not be completely normal [77]. The complete deletions of the AZFc region may occur in two
different ways: either as a result of a previous deletion within the AZFc or spontaneously from
a normal AZFc region.
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Introduction
1.10.4. Sex determining region on Y (SRY) gene
Genetic analysis of cases with abnormal sexual development, presenting with chromosomal
abnormalities like translocations, deletions or duplications, has resulted in the identification
of many genes playing a role in sex determination [129]. The presence or absence of
Y chromosome determines the sex in mammals [130]. SRY is thought to direct the sexdetermination pathway towards male development [131]. SOX9 and DAX1 have recently
been proposed to function downstream to SRY gene in male sex-determination pathway
[132]. A karyotype of 46,XX male syndrome is a rare disorder with a frequency of 1:20 000–
25,000 men, exist in three medical categories: (a) 46,XX males with normal genitalia; (b)
ambiguous genitalia; and (c) true hermaphrodites with ovarian and testicular tissues [133]. An
increasing number of reports suggest that the male phenotype can develop even in the absence
of SRY gene [134] and apparently there are no other reports on Y-chromosome sequences.
According to the presence or absence of the Y-chromosome sequences, approximately 90%
of the cases carry varying amount of the Y sequences due to a recombination between X
and Y chromosomes, whereas 10% do not have any Y-chromosome sequences. Most of
the 46,XX men with SRY have normal genitalia, whereas most SRY-negative cases have
ambiguous genitalia [135].
The testes differentiation pathway is active in sex determination and the absence of the signals
results in ovary development. Except a few studies, the etiology of development in 46,XX men
(SRY-negative) remains unexplained [136]. The development of the testis and normal male
genitals in 46,XX (SRY-negative) males provides an indication to the autosomal or X-linked
genes during the sex-determining pathway. Genetic analysis of these cases may help to study
new gene(s) involved in the sex-determining pathway [137].
1.10.5. SOX gene
Camptomelic dysplasia is a rare, often lethal, congenital osteochondrodysplasia, dominantly
inherited, associated with male-to-female autosomal sex reversal in two-thirds of the affected
21
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Introduction
men. This is located on the X chromosome, expressed in the urogenital ridge, from which the
gonads develop, and this continues to be expressed in the adult gonads of both sexes [138].
Like the Y-located testis-determining gene SRY, SOX9 is a member of the SOX gene family of
transcription factors that share an amino acid sequence identity of 60% or more in their highmobility group (HMG) domain present in SRY [100]. The HMG domain is an 80 amino acid
DNA-binding and bending motif that characterizes, besides the SOX proteins, a whole class
of transcription factors, as these mutations are all heterozygous and appear to cause loss of
function of SOX9. In humans, a large deletion (including SOX3) of the X chromosome has
been reported in men with small testes had shown deletions [139]. Thus, SOX gene should
still be considered in future studies of male infertility, till other commonly affected genes are
identified.
1.11. Genotype-phenotype correlations of Yq microdeletion
Severe combined clinical and molecular studies have sought to define recurrently deleted regions
of Yq is to determine the incidence of microdeletions among azoospermic and oligozoospermic
men, and to correlate the size and position of the deletions that causes infertile phenotype.
The reported incidence of microdeletions in infertile men is reported to be 1–55% that varies
enormously and also depends on study design and sample size. The study populations for Yq
microdeletion includes: azoospermic, oligozoospermic, azoospermic/oligozoospermic patients
or normospermic men. Most clinical studies select individuals with idiopathic azoospermia
or oligozoospermia, although others include unselected infertile men with known or unknown
causes of infertility. Unfortunately, however, there is no general agreement on what constitutes
idiopathic infertility. Varicocele and history of cryptorchidism are considered idiopathic in some
studies and non-idiopathic in others. Another variable that affects Yq microdeletion frequency
is marker density or the position of markers. Despite these, it is possible that differences in
deletion frequency and/or localization, between studies, may reflect on genuine geographic
or ethnic differences, perhaps related to a particular Y chromosome haplogroup, the genetic
background, or environmental influences.
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Introduction
Vogt et al., (1996) originally proposed that AZFa deletions result in Sertoli-cell only syndrome
(SCOS) type I, in which no spermatogonia develop, whereas deletions in AZFb cause
spermatogenic arrest, usually at the spermatocyte stage, and deletions in AZFc are associated
with a more variable phenotype, ranging from type II SCOS-absence of germ cells in most testis
tubules to hypospermatogenesis-presence of all germ-cell types, albeit in reduced numbers.
In general, subsequent studies have supported these findings, but there have been exceptions:
both AZFa and b deletions have been reported in oligozoospermic men [52]. Another problem
in the definition of genotype/phenotype correlations is the variability of the phenotype in the
same man, over time. In one study, an individual with an AZFc deletion showed a progressive
decrease in sperm concentration, from severe oligozoospermia to azoospermia [140].
First, microdeletions are found almost exclusively in males affected by azoospermia, severe
oligozoospermia or occasionally in patients with other abnormal andrological findings. Second, a higher frequency of Yq deletions is found in azoospermic men, compared with
oligozoospermic men or in men with well-defined idiopathic infertility. Third, large deletions
generally are associated with mild-severe spermatogenic defects. Finally, the frequency of
AZFa deletions is reported to be 1–5% is generally associated with SCOS type I, whereas
AZFc, AZFa and AZFb deletions, may be associated with a variety of spermatogenetic defects,
including oligozoospermia [141].
1.12. Genes associated with male infertility
1.12.1. DNA polymerase gamma (POLG) gene
Mitochondrion has the genetic material that is capable of producing many essential components
of the respiratory chain. The sperm mitochondrial DNA (mtDNA) is a small, circular DNA
that is not bound to proteins, exhibits a high rate of mutation, which might affect the amount
of energy for sperm motility because of aberrations in the mitochondrial sheath [142]. The
inheritance of mtDNA is primarily maternal, paternal transmission of mutations have been
reported but not more than 1% of inheritance. Sperm mitochondria plays an important role in
23
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Introduction
spermatozoa functionality; because of the high adenosine triphosphate (ATP) [143] alterations
to mtDNA may have consequences for normal fertilization or an impact on quality of sperm
production in male factor infertility. The nuclear enzyme involved in the elongation and repair
of mtDNA strands is DNA polymerase gamma (POLG), supposed to be the only polymerase
acting in the mitochondria. The catalytic subunit of POLG is encoded by the POLG gene,
which has been mapped to Yq15 (15q25). Studies have indicated an association between POLG
polymorphisms or mutations in the mitochondrial genome and sperm dysfunction [144] such
as asthenozoospermia.
1.12.2. Sex hormone-binding globulin (SHBG) gene
The SHBG gene (located on chromosome 17) is shown to be involved in both delivering sex
hormones to target tissues and controls concentration of androgens in the testis. Androgens
play an essential role in sexual differentiation and spermatogenetic process; if androgen levels
are interrupted, fertility might decrease. Several studies have revealed that SHBG alleles were
associated with altered levels of spermatogenesis and male infertility.
1.12.3. Follicle stimulating hormone receptor (FSHR) gene
The FSH is an essential hormone necessary for the normal functioning of gonads which
mediates its function by binding with its receptor. The FSH receptor-FSHR gene is located on
chromosome 2; it has been shown that partial deletions of the FSHR gene might have slight
effects on spermatogenesis [145] . In addition, FSHR Single-Nucleotide Polymorphism (SNP)
had been reported in the male infertility [76].
1.12.4. Deleted in azoospermia-like (DAZL) gene
The autosomal homologue of the DAZL gene is located on chromosome 3 and codes for the
RNA binding proteins that are involved in the regulation of protein expression and meiosis
[146]. Tung et al., in 2006 had identified four new mutations and haplotypes in the DAZL gene
related to sperm count, but further studies are required to determine their effects [147] on male
factor infertility.
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Introduction
1.12.5. Methylenetetrahydrofolate reductase (MTFHR) gene
The MTHFR gene is located on the short arm of chromosome 1 [148]. It codes for an enzyme
the tetrahydrofolate reductase, involved in folate metabolism, an essential factor in DNA
methylation and spermatogenetic process. The polymorphism 677C/T causes the substitution
of an alanine for a valine, which decreases the activity of the enzyme. The reduced activity of
MTHFR can lead to the dysregulation of folic acid metabolism, causing errors in the methylation
of genomic DNA and subsequent implications in spermatogenesis. Further studies are required
to confirm the role of this gene on spermatogenesis [146].
1.12.6. Insulin-like factor 3 (INSL3) gene
Mutations in the INSL3 gene (located on chromosome 19) and its receptor LGR8 gene (relaxin/
insulin-like family peptide receptor 2) (located on chromosome 13) have been associated with
cryptorchidism. The first phase of normal testicular descent is controlled by INSL3 [149] and
may have a role in testicular dysgenesis syndrome (TDS), that are associated with hypospadias,
testicular cancer, and infertility [150].
1.12.7. Estrogen receptor gene
Estrogen receptor genes (ESR1 and ESR2) have a possible involvement in fertility. Recent
reports have identified the relationship between abnormal spermatogenesis and estrogen
insufficiency. ESR1 gene is located on chromosome 6 this has several different polymorphisms.
The promoter region of ESR1 has a variable number of tandem repeats, (TA)n polymorphism
that is related to sperm output: a higher number of repeats on both alleles is correlated with
lower levels of spermatogenesis. These genes have been studied for their role in male factor
infertility, especially in relation to severe oligozoospermia, with varied results and that may be
most likely due to gene interactions, environment factors and different ethnic groups [151].
1.12.8. Cystic fibrosis transmembrane conductance regulator (CFTR) gene
Congenital unilateral/bilateral absence of vas deferens is a frequent cause of azoospermia. About
1-2% male infertility is associated with mutations and polymorphisms in CFTR gene [152].
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Introduction
Polymorphisms outside and within the CFTR gene may affect transcription or function of the
CFTR protein eg: F508del mutation and R347H, M470V polymorphism [76, 153]. Mutation
analysis of the CFTR gene in CBAVD cases has shown that a large proportion of these sterile
men carry a mutation in at least one of their CFTR genes. It has been suggested that the CFTR
protein may also be involved in the process of spermatogenesis or sperm maturation apart from
the development of epididymal glands and vas deferens.
1.12.9. Androgen receptor (AR) gene
Androgen insensitivity syndrome is alternatively called as the testicular feminization syndrome
is a disease characterized by variable defects in virilization. It occurs due to loss of functional
mutations in the androgen receptor gene that results in peripheral androgen resistance for
development and maintenance of the male phenotype [154] and spermatogenesis [155]. It is a
single copy gene that spans ~90Kb of genomic DNA and lies on the Xq11-12 region on long
arm of X-chromosome., expressed in the testis and involves conversion of spermatocytes to
round spermatids during spermatogenesis.
1.12.10. Kallman syndrome-1 sequence (KAL1) gene
Kallmann syndrome is another genetic condition that can cause male infertility and has
both X-linked and autosomal genetic components, defined as idiopathic hypogonadotropic
hypogonadism combined with anosmia or hyposmia. This disorder is caused by a defect
in the migration of the GnRH neurons and characterized by low levels of sex steroids in
combination with low to normal levels of FSH and LH [156]. This leads to the absence or
low levels of sex steroids inhibit; stunt sexual development and spermatogenesis in men.
KAL1 gene is located on the short arm of the X chromosome, involved in the migration of the
GnRH neurons, and codes for anosmin-1, a cell adhesion molecule.
26
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Introduction
1.13. Paternal age
There is a general belief that the fertility potential of older man is fairly well preserved. However,
recent evidence support the concept that advanced paternal age is associated with an increase
in sperm chromosomal aneuploidies. Moskovtsev et al., (2006) demonstrated that the rate of
sperm with fragmented DNA doubled in men at the age of 45 years and above when compared
to those less than 30 years old [157]. Siddighi et al., (2007) showed increased necrosis, DNA
damage and apoptosis while rapid progression and total motility declined with advancing male
age beginning as early as 35 years [158] . DNA damage in sperm is promutagenic, it does not
impair fertilization or cleavage as paternal genome is transcriptionally inactive till two days
after fertilization. However, once the paternal genome is active it results in poor blastocyst
development, unequal cleavage, implantation failure or early fetal loss. Plastira et al., (2007)
demonstrated that increased age in infertile patients was associated with an increase in sperm
DNA fragmentation and poor chromatin packaging, as well as with a decline in semen volume,
sperm morphology and motility [159]. Several studies have reported that sperm DNA damage
increases with advancing age in both fertile and infertile men.
The scrutiny of literature suggests that the genetic basis of infertility is unequivocal and
varying; it includes chromosomal abnormalities, mutations as well as polymorphisms and is
multifactorial. It is very difficult to accurately assess the overall importance and contribution
of individual genes and role to infertility. At present, with the advent of assisted reproductive
technologies and the possibility of vertical iatrogenic transmission of genetic anomalies to the
offspring, diagnosis of a genetic etiology is very significant, which helps to counsel these patients
about the risk of an offspring being born with genetic anomalies. An association between male
infertility and genetic abnormalities has been reported that there is an increased risk of embryos
with chromosomal abnormalities, which could be one of the main reasons for implantation
failure or recurrent spontaneous abortions.
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Introduction
Therefore, the aim of the study is to investigate the chromosomal aberrations, azoospermia
factor (AZF), cystic fibrosis transmembrane regulatory (CFTR) gene mutations in the
peripheral blood lymphocytes (PBL) of infertile men with abnormal sperm parameter
and compare it with healthy control subjects to delineate the genetic causes of male
infertility.
OBJECTIVES OF THE STUDY
• To study the prevalence of chromosomal abnormalities (CA) in the entire
genome of infertile men with abnormal spermiogram (azoospermia (AZ);
oligoasthenoteratozoospermia (OAT) severe oligoasthenoteratozoospermia (SOAT)
globozoospermia and compare it with fertile controls.
• To characterize the most common forms of chromosomal abnormalities such as
numerical (CA), structural (CA) and variants.
• To screen microdeletion in the AZFa (sY84, sY86), AZFb (sY127, sY134) and AZFc
(sY254, sY255) genes on Y chromosome.
• To study M470Vpolymorphism in the CFTR gene in relevance to male infertility.
28
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Introduction
References
1. World Health Organization. WHO laboratory manual for the examination of human semen
and sperm-cervical mucus interaction. 5th Ed. Cambridge: Cambridge University Press,
2010.
2. Jones HW and Toner JP. The infertile couple. N Eng J Med. 1993; 29: 710-15.
3. Seshagiri PB. Molecular insights into the causes of male infertility. J Biosci. 2001;26(4):
429-35.
4. Abid S, Maitra A, Meherji P, Patel Z, Kadam S, Shah J. Clinical and laboratory evaluation
of idiopathic male infertility in a secondary referral center in India. J Clin Lab Anal. 2008;
22(1):29-38.
5. Irvine DS. Epidemiology and aetiology of male infertility. Hum Reprod. 1998;13(1):33-44.
6. Zenzes MT. Smoking and reproduction: gene damage to human gametes and embryos.
Hum Reprod Update. 2000;6(2):122-31.
7. Mahanta R, Gogoi A, Roy A, Bhattacharyya IK and Sharma P. Prevalence of azoospermia
factor (AZF) deletions in idiopathic infertile males in North-East India. Int J Hum Genet.
2011;11(2):99-104.
8. Krausz C, Forti G. Clinical aspects of male infertility. In: McElreavey K (Ed): The genetic
basis of male infertility. Berlin: Springer-Verlage. 2000:1-21.
9. Poongothai J, Gopenath TS, Manonayaki S. Genetics of human male infertility. Singapore
Med J. 2009;50(4):336-47.
10. Fernandes S, Huellen K, Goncalves J, Dukal H, Zeisler J, Rajpert De Meyts E, et al. High
frequency of DAZ1/DAZ2 gene deletions in patients with severe oligozoospermia. Mol
Hum Reprod. 2002;8(3):286-98.
11. Egozcue S, Blanco J, Vendrell JM, Garcia F, Veiga A, Aran B, et al. Human male infertility:
chromosome anomalies, meiotic disorders, abnormal spermatozoa and recurrent abortion.
Hum Reprod Update. 2000;6(1):93-105.
29
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
12. Hargreave TB. Genetic basis of male infertility. Br Med Bull. 2000;56(3);650-71.
13. Ferlin A, Bogatcheva NV, Gianesello L, Pepe A, Vinanzi C, Agoulnik AI, et al. Insulinlike factor 3 gene mutations in testicular dysgenesis syndrome: Clinical and functional
characterization. Mol Hum Reprod. 2006;12(6):401-06.
14. Alkhalaf M, Al-Shoumer K. Cytogenetic abnormalities and azoospermia factor (AZF). J
Mol Genet Med. 2010;(4):232-42.
15. Tur-Kaspa I, Aljadeff G, Rechitsky S, Grotjan HE, Verlinsky Y. PGD for all cystic fibrosis
carrier couples: novel strategy for preventive medicine and cost analysis. Reprod BioMed
Online. 2010;21(2):186-95.
16. Shamsi MB, Kumar K, Dada R. Genetic and epigenetic factors: Role in male infertility.
Ind J Urol. 2011;27(1):110-20.
17. Thonneau P, Marchand S, Tallec A, Ferial ML, Ducot B, Lansac J, et al. Incidence and
main causes of infertility in a resident population (1,850,000) of three French regions
(1988-1989). Hum Reprod. 1991;6(6):811-16.
18. Sharpe RM. Lifestyle and environmental contribution to male infertility. Br Med Bull.
2000;56(3):630-42.
19. Singer G, Granger DN. Inflammatory responses underlying the microvascular dysfunction
associated with obesity and insulin resistance. Microcirculation. 2007;14:(4-5):375-87.
20. Pérez-Crespo M, Pintado B, Gutiérrez-Adán A. Scrotal heat stress effects on sperm viability,
sperm DNA integrity, and the offspring sex ratio in mice. Mol Reprod Dev. 2007;75(1): 40-47.
21. Manna I, Jana K, Samanta PK. Effect of different intensities of swimming exercise on
testicular oxidative stress and reproductive dysfunction in mature male albino Wistar rats.
Ind J Exp Biol. 2004;42(8):816-22.
22. Saleh RA, Agarwal A, Sharma RK, Nelson DR, Thomas AJ, Jr. Effect of cigarette smoking
on levels of seminal oxidative stress in infertile men: A prospective study. Fertil Steril.
2002a;(78):491-99.
30
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
23. Maneesh M, Dutta S, Chakrabarti A, Vasudevan DM. Alcohol abuse-duration dependent
decrease in plasma testosterone and antioxidants in males. Ind J Physiol Pharmacol. 2006;
50(3):291-96.
24. Rubes J, Selevan SG, Evenson DP, Zudova D, Vozdova M, Zudova Z, et al. Episodic air
pollution is associated with increased DNA fragmentation in human sperm without other
changes in semen quality. Hum Reprod. 2005;20(10):2776–83.
25. Hauser R, Meeker JD, Singh NP, Silva MJ, Ryan L, Duty S, et al. DNA damage in human
sperm is related to urinary levels of phthalate monoester and oxidative metabolites. Hum
Reprod. 2007;22(3):688-95.
26. Lee E, Ahn MY, Kim HJ, Kim IY, Han SY, Kang TS, et al. Effect of di(n-butyl) phthalate
on testicular oxidative damage and antioxidant enzymes in hyperthyroid rats. Environ
Toxicol. 2007;22(3):245-55.
27. Latchoumycandane C, Mathur PP. Induction of oxidative stress in the rat testis after short-term
exposure to the organochlorine pesticide methoxychlor. Arch Toxicol. 2002;76(12):692-98.
28. Meng Z, Bai W. Oxidation damage of sulfur dioxide on testicles of mice. Environ Res.
2004;96(3):298-304.
29. Xu DX, Shen HM, Zhu QX, Chua L, Wang QN, Chia SE, et al. The associations among
semen quality, oxidative DNA damage in human spermatozoa and concentrations of
cadmium, lead and selenium in seminal plasma. Mutat Res. 2003;534(1-2):155-63.
30. Naha N, Chowdhury AR. Inorganic lead exposure in battery and paint factory: effect on
human sperm structure and functional activity. J UOEH. 2006;28(2):157-71.
31. Eskiocak S, Gozen AS, Taskiran A, Kilic AS, Eskiocak M, Gulen S. Effect of psychological
stress on the L-arginine-nitric oxide pathway and semen quality. Braz J Med Biol Res.
2006;39(5):581-88.
32. Schaeffer AJ. Epidemiology and demographics of prostatitis. Andrologia. 2003;35(5):
252-57.
31
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
33. Fraczek M, Sanocka D, Kamieniczna M, Kurpisz M. Proinflammatory cytokines as an
intermediate factor enhancing lipid sperm membrane peroxidation in in vitro conditions. J
Androl. 2008;29(1):85-92.
34. Potts JM, Sharma R, Pasqualotto F, Nelson D, Hall G, Agarwal A. Association of ureaplasma
urealyticum with abnormal reactive oxygen species levels and absence of leukocytospermia.
J Urol. 2000;163(6):1775-78.
35. Brackett NL, Ibrahim E, Grotas JA, Aballa TC, Lynne CM. Higher sperm DNA damage in
semen from men with spinal cord injuries compared to controls. J Androl. 2008;29(1):93-9.
36. Bezold G, Lange M, Perter RU. Homozygous methelenetetrahydrofolate reductase C677T
mutation and male infertility. N Engl J Med. 2001;344(15):1172-73.
37. Lombardo F, Gandini L, Dondero F, Lenzi A. Antisperm immunity in natural and assisted
reproduction. Hum Reprod Update. 2001;7(5):450-56.
38. McLachlan RI, de Krester D. Male infertility: The case for continued research. Med J
Aust. 2001;174(3):116-7.
39. Huynh T, Mollard R, Trounson A. Selected genetic factors associated with male infertility.
Hum Reprod Update. 2002;8(2):183-98.
40. Steinman N, Gamzu R, Yogev L, Botchan A, Schreiber L, Yavetz, H. Serum leptin
concentrations are higher in azoospermic than in normozoospermic men. Fertil Steril.
2001;75(4):821-22.
41. Moosani N, Pattinson HA, Carter MD, Cox DM, Rademaker AW, Martin RH. Chromosomal
analysis of sperm from men with idiopathic infertility using sperm karyotyping and
fluorescence in situ hybridization. Fertil Steril. 1995;64(4):811-17.
42. Blanco J, Gabau E, Gomez D, Baena N, Guitart M, Egozcue J, Vidal F. Chromosome 21
disomy in spermatozoa of the fathers of children with trisomy 21, in a population with a
high prevalence of Down Syndrome: Increased incidence in cases of paternal origin. Am J
Hum Genet. 1998;63(4):1067-72.
32
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
43. Martinez-Pasarell O, Nogues C, Bosch M, Egozcue J, Templado C. Analysis of sex
chromosome aneuploidy in sperm from fathers of Turner Syndrome patients. Hum Genet.
1999;104(4):345-49.
44. Hoeijmakers JHJ. Genome maintenance mechanism for preventing cancer. Nature. 2001;
411(6835):366-74.
45. Evenson DP, Larson KL, Jost LK. Sperm chromatin structure assay: Its clinical use
for detecting sperm DNA fragmentation in male infertility and comparisons with other
techniques. J Androl. 2002;23(1):25-43.
46. Agarwal A. What is the future of the sperm analysis. J Clin Embryol. 2009;12:3-4.
47. World Health organization. WHO laboratory manual for the examination of human semen
and semen-cervical mucus interaction. New York: Cambridge University Press, 1999.
48. Morel F, Douet-Guilbert N, Moerman A, Duban B, Marchetti C, Delobel B, et al.
Chromosome aneuploidy in the spermatozoa of two men with globozoospermia. Mol Hum
Reprod. 2004;10(11):835-8.
49. Gianotten J, Lombardi MP, Zwinderman AH, Lilford RJ, van der Veen F. Idiopathic
impaired spermatogenesis: genetic epidemiology is unlikely to provide a short-cut to better
understanding. Hum Reprod Update. 2004;10(6):533-39.
50. Chandley AC. Chromosome anomalies and Y chromosome microdeletions as causal factors
in male infertility. Hum Reprod. 1998;13(1):45-50.
51. Martin RH. Cytogenetic determinants of male fertility. Hum Reprod Update. 2008;14(4):
379-90.
52. Vogt PH, Edelmann A, Kirsch S, Henegariu O, Hirschmann P, Kiesewetter F, et al. Human
Y chromosome azoospermia factors (AZF) mapped to different subregions in Yq11. Hum
Mol Genet. 1996;5(7):933-43.
53. Jaffe T, Oates RD. Genetic abnormalities and reproductive failure. Urol Clin North Am.
1994;21(3):389-408.
33
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
54. O’Flynn O’Brien KL, Varghese AC, Agarwal A. The genetic causes of male factor infertility:
a review. Fertil Steril. 2010;93(1):1-12.
55. Hassold T, Hunt P. To err (meiotically) is human: the genesis of human aneuploidy. Nat
Rev Genet. 2001;2(4):280-91.
56. De Braekeleer M, Dao TN. Cytogenetic studies in couples experiencing repeated pregnancy
losses. Hum Reprod. 1990;5(5):519-28.
57. Van Assche E, Bonduelle M, Tournaye H, Joris H, Verheyen G, Devroey P, et al. Cytogenetics
of infertile men. Hum Reprod. 1996;11 Suppl 4:1-24; discussion 25-6.
58. Johnson MD. Genetic risks of intracytoplasmic sperm injection in the treatment of male
infertility: recommendations for genetic counseling and screening. Fertil Steril. 1998;
70(3):397-411.
59. Salahshourifar I, Gilani MAS, Masoudi NS, Gourabi H. Chromosomal abnormalities in
Iranian infertile males who are candidates for assisted reproductive techniques. Iranian
Journal of Fertility and Sterility. 2007;1(2):75-9.
60. Hassold T, Hunt PA, Sherman S. Trisomy in humans: incidence, origin and etiology. Curr
Opin Genet Dev. 1993;3(3):398-403.
61. Bonduelle M, Wilikens A, Buysse A, Van Assche E, Wisanto A, Devroey P, Van Steirteghem
AC, Liebaers I. Prospective follow-up study of 877 children born after intracytoplasmic sperm
injection (ICSI), with ejaculated epididymal and testicular spermatozoa and after replacement
of cryopreserved embryos obtained after ICSI. Hum Reprod. 1996;11(4): 131-55.
62. Palermo GD, Colombero LT, Schattman GL, Davis OK, Rosenwaks Z. Evolution of
pregnancies and initial follow-up of newborns delivered after intracytoplasmic sperm
injection. JAMA. 1996;276(23):1893-97.
63. Van Opstal D, Los FJ, Ramlakhan S, Van Hemel JO, Van Den Ouweland AM, Brandenburg H,
et al. Determination of the parent of origin in nine cases of prenatally detected chromosome
aberrations found after intracytoplasmic sperm injection. Hum Reprod. 1997;12(4):682-86.
34
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
64. Cuneyt T, Kubilay V, Semra K, Suat O, Ahmet ZI, Kutay B. The frequency of chromosomal
abnormalities in men with azoospermia and oligospermia; a preliminary study. Tr J Med
Sci. 1988;28:93-95.
65. Testart J, Gautier E, Brami C, Rolet F. Sedbon E, Thebault A. Intracytoplasmic sperm
injection in infertile patients with structural chromosome abnormalities. Hum Reprod.
1996;11(12):2609-612.
66. Montag M, van der Ven K, Ved S, Schmutzler A, Prietl G, Krebs D, et al. Success of
intracytoplasmic sperm injection in couples with male and/or female chromosome
aberrations. Hum Reprod. 1997;12(12):2635-640.
67. Meschede D, Lemcke B, Exeler JR, De Geyter C, Behre HM, Nieschlag E, et al. Chromosome
abnormalities in 447 couples undergoing intracytoplasmic sperm injection – prevalence,
types, sex distribution and reproductive relevance. Hum Reprod. 1998;13(3):576-82.
68. Dohle GR, Halley DJ, Van Hemel JO, van den Ouwel AM, Pieters MH, Weber RF, et al.
Genetic risk factors in infertile men with severe oligozoospermia and azoospermia. Hum
Reprod. 2002;17(1):13-16.
69. Nagvenkar P, Desai K, Hinduja I, Zaveri K. Chromosomal studies in infertile men with
oligozoospermia and non-obstructive azoospermia. Ind J Med Res. 2005;122(1):34–42.
70. Rajangam S, Tilak P, Aruna, Rema Devi. Karyotyping and counseling in bad obstetric
history and infertility. IJRM. 2007;5(1):7-12.
71. Balkan M, Tekes S, Gedik A. Cytogenetic and Y chromosome microdeletion screening
studies in infertile males with Oligozoospermia and Azoospermia in Southeast Turkey. J
Assist Reprod Genet. 2008(11-12);25:559-65.
72. Ng PP, Tang MH, Lau ET, Ng LK, Ng EH, Tam PC, et al. Chromosomal anomalies and
Y-microdeletions among Chinese subfertile men in Hong Kong. Hong Kong Med J. 2009;
159(1):31-8.
35
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
73. Akgul M, Ozkinay F, Ercal D, Cogulu O, Dogan O, Altay B, et al. Cytogenetic abnormalities
in 179 cases with male infertility in Western Region of Turkey: report and review. J Assist
Reprod Genet. 2009;26(2-3):119-22.
74. Robinson DO, Jacobs PA. The origin of the extra Y chromosome in males with a 47,XYY
karyotype. Hum Mol Genet. 1999;8(12):2205-09.
75. El-Dahtory F, Elsheikha HM. Male infertility related to an aberrant karyotype, 47,XYY:
four case reports. Cases Journal. 2009;2:28.
76. Ferlin A, Arredi B, Speltra E, Cazzadore C, Selice R, Garolla A, et al. Molecular and clinical
characterization of Y chromosome microdeletions in infertile men: a 10-year experience in
Italy. J Clin Endocrinol Metab. 2007; 92(3):762-70.
77. Georgiou I, Syrrou M, Pardalidis N, Karakitsios K, Mantzavinos T, Giotitsas N, et al.
Genetic and epigenetic risks of intracytoplasmic sperm injection method. Asian J Androl
2006;8(6):643-73.
78. Micic M, Micic S, Diklic V. Chromosomal constitution of infertile men. Clin Genet. 1984;
25(1):33-6.
79. Bourrouillou G, Dastugue N, Colombies P. Chromosome studies in 952 infertile males
with a sperm count below 10 million/ml. Hum Genet. 1985;71(4):366-7.
80. Hsu LYF. Phenotype/karyotype correlations of Y chromosome aneuploidy with emphasis
on structural aberrations in postnatally diagnosed cases. Am J Med Genet. 1994;53(2):
108-40.
81. van der Ven K, Montag M, Peschka B, Leygraaf J, Schwanitz G, Haidl G, et al.
Combined cytogenetic and Y chromosome microdeletion screening in males undergoing
intracytoplasmic sperm injection. Mol. Hum. Reprod. 1997;3(8):699-704.
82. Stern JJ, Dorfmann AD, Gutierrez-Najar AJ, Cerrillo M, Coulam CB. Frequency of
abnormal karyotypes among abortuses from women with and without a history of recurrent
spontaneous abortion. Fertil Steril. 1996;65(2):250-53.
36
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
83. De Braekeleer M, Dao TN. Cytogenetic studies in male infertility: a review. Hum Reprod.
1991;6(2):245-50.
84. Anton E, Blanco J, Egozcue J, Vidal F. Sperm FISH studies in seven male carriers of
Robertsonian translocation t(13;14)(q10;q10). Hum Reprod. 2004;19(6):1345-51.
85. Pellestor F. Analysis of meiotic segregation in a man heterozygous for a 13;15 Robertsonian
translocation and a review of the literature. Hum Genet. 1990;85(1):49-54.
86. Munne S. Analysis of chromosome segregation during preimplantation genetic diagnosis
in both male and female translocation heterozygotes. Cytogenet Genome Res. 2005; (111):
305-9
87. Buckton KE, Spowart G, Newton MS, Evans HJ. Forty four probands with an additional
“marker” chromosome. Hum Genet. 1985;69(4):353-70.
88. Hook EB, Schreinemachers DM, Willey AM, Cross PK. Rates of mutant structural
chromosome rearrangements in human fetuses: data from prenatal cytogenetic studies and
associations with maternal age and parental mutagen exposure. Am J Hum Genet. 1983;
35(1):96-109.
89. Woo HY, Cho HJ, Kong SY, Kim HJ, Jeon HB, Kim EC, et al. Marker Chromosomes in
Korean patients: incidence, identification and diagnostic approach. J Korean Med Sci.
2003;18(6):773-8.
90. B
hasin MK. Human population cytogenetics: A review. Int J Hum Genet. 2005;5(2):83-152.
91. Yakin K, Balaban B, Urman B. Is there a possible correlation between chromosomal
variants and spermatogenesis? Int J Urol. 2005;12(11):984-9.
92. Wolgemuth DJ, Rhee K, Wu S, Ravnik SE. Genetic control of mitosis, meiosis and cellular
differentiation during mammalian spermatogenesis. Reprod Fertil Dev. 1995;7(4):669-83.
93. Stuppia L, Gatta V, Mastroprimiano G, Pompetti F, Calabrese G, Guanciali Franchi P, et al.
Clustering of Y chromosome deletions in subinterval E of interval 6 supports the existence of
an oligozoospermia critical region outside the DAZ gene. J Med Genet. 1997;34(1): 881-83.
37
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
94. Diemer T, Desjardins C. Developmental and genetic disorders in spermatogenesis. Hum
Reprod Update. 1999;5(2):120-40.
95. Skaletsky H, Kuroda-Kawaguchi T, Minx PJ, Cordum HS, Hillier L, Brown LG, et al. The
male-specific region of the human Y chromosome is a mosaic of discrete sequence classes. Nature. 2003;423(6942):825-37.
96. Kuroki Y, Iwamoto T, Lee J, Yoshiike M, Nozawa S, Nishida T, et al. Spermatogenic
ability is different among males in different Y chromosome lineage. Hum Genet. 1999;
44(5):289-92.
97. Penna Videau S, Araujo H, Ballesta F, Ballesca JL, Vanrell JA. Chromosomal abnormalities
and polymorphisms in infertile men. Arch Androl. 2001;46(3):205-10.
98. Minocherhomji S, Athalye AS, Madon PF, Kulkarni D, Uttamchandani SA, Parikh FR. A
case-control study identifying chromosomal polymorphic variations as forms of epigenetic
alterations associated with the infertility phenotype. Fertil Steril. 2009; 92(1):88-95.
99. Meza-Espinoza JP, Anguiano LO, Rivera H. Chromosomal abnormalities in couples with
reproductive disorders. Gynecol Obstet Invest. 2008;66(4):237-40.
100. Goodfellow PN, Lovell-Badge R. SRY and sex determination in mammals. Annu Rev
Genet. 1993;27:71-92.
101. Pandey LK, Pandey S, Gupta J and Saxena AK. Loss of the AZFc region due to a human
Y-chromosome microdeletion in infertile male patients. Genet Mol Res. 2010;9(2):126773.
102. Siddiqi S, Siddiq A, Majeed K, Mansoor A, Qamer R, Mazhar K, et al. Y-chromosomal
deletions-a risk factor for male infertility. Int J Agric Biol. 2009;(11):110-2.
103. Ristanovic M, Bunjevacki V, Tulic C, Novakovic I, Nikolic A. Molecular analysis of Y
chromosome microdeletions in idiopathic cases of male infertility in Serbia. Genetika.
2007;43(6):850-54.
38
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
104. Mohammed F, Al-Yatama F, Al-Bader M, Tayel SM, Gouda S, Naguib KK. Primary male
infertility in Kuwait: a cytogenetic and molecular study of 289 infertile Kuwaiti patients.
Andrologia. 2007;39(3):87-92.
105. Chernykh VB, Chukhrova AL, Beskorovaĭnaia TS, Grishina EM, Sorokina TM, Shileĭko
LV, et al. Types of Y chromosome deletions and their frequency in infertile men. Genetika.
2006;42(8):1130-36.
106. Hellani A, Al-Hassan S, Iqbal MA, Coskun S. Y chromosome microdeletions in infertile
men with idiopathic oligo- or azoospermia. J Exp Clin Assist Reprod. 2006;(3):1.
107. Medica I, Gligorievska N, Prenc M, Peterlin B. Y microdeletions in the Istria county,
Croatia. Asian J Androl. 2005;7(2):213-6.
108. Vicdan A, Vicdan K, Gunlao S, Kence A, Akarsu C, Isik AZ, Sozen E. Genetic aspects of
human male infertility: the frequency of chromosomal abnormalities and Y chromosome
microdeletions in severe male factor infertility. Eur J Obstet Gynecol Reprod Biol. 2004;
117(1);49-54.
109. El Awady MK, El Shater SF, Ragaa E, Atef K, Shaheen IM, Megiud NA. Molecular study
on Y chromosome microdeletions in Egyptian males with idiopathic infertility. Asian J
Androl. 2004;6(1):53-7.
110. Peterlin B, Kunej T, Sinkovec J, Gligorievska N, Zorn B. Screening for Y chromosome
microdeletions in 226 Slovenian subfertile men. Hum Reprod. 2002;17(1):17-24.
111. Van Landuyt L, Lissens W, Stouffs K, Tournaye H, Liebaers I, Van Steirteghem A.
Validation of a simple Yq deletion screening programme in an ICSI candidate population.
Mol Hum Reprod. 2000;6(4):291-97.
112. Kleiman SE, Yogev L, Gamzu R, Hauser R, Botchan A, Lessing JB, et al. Genetic
evaluation of infertile men. Hum Reprod. 1999;14:33-8.
113. Kim B, Lee Y, Kim Y, Lee KH, Chun S, Rhee K, et al. Polymorphic expression of DAZ
proteins in the human testis. Hum Reprod. 2009;24(6):1507-15.
39
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
114. Brandell RA, Mielnik A, Liotta D, Ye Z, Veeck LL, Palermo GD, Schlegel PN. AZFb
deletions predict the absence of spermatozoa with testicular sperm extraction: preliminary
report of a prognostic genetic test. Hum Reprod. 1998;13(10):2812-15.
115. Silber SJ, Alagappan R, Brown LG, Page DC. Y chromosome deletions in azoospermic
and severely oligozoospermic men undergoing intracytoplasmic sperm injection after
testicular sperm extraction. Hum Reprod. 1998;13(12):3332-37.
116. Tiepolo L and Zuffardi O. Localization of factors controlling spermatogenesis in the
nonfluorescent portion of the human Y chromosome long arm. Hum Genet. 1976;34(2):
119-24.
117. Vergnaud G, Page DC, Simmler MC, Brown L, Rouyer F, Noel B, et al. A deletion map
of the human Y chromosome based on DNA hybridization. Am J Hum Genet. 1986;38(2):
109-24.
118. Esteves SC, Agarwal A. Novel concepts in male infertility. Int Braz J Urol. 2011;37(1):
5-15.
119. Ferlin A, Moro E, Rossi A, Dallapiccola B, Foresta C. The human Y chromosome’s
azoospermia factor b (AZFb) region: sequence, structure and deletion analysis in infertile
men. J Med Genet. 2003;40(1):18-24.
120. Raicu F, Popa L, Apostol P, Cimponeriu D, Dan L, Ilinca E, Dracea LL, Marinescu B,
Gavrila L. Screening for microdeletions in human Y chromosome–AZF candidate genes
and male infertility. J Cell Mol Med. 2003;7(1):43-8.
121. Sun C, Skaletsky H, Birren B, Devon K, Tang Z, Silber S, et al. An azoospermic man
with a de novo point mutation in the Y-chromosomal gene USP9Y. Nat Genet 1999; 23
(4):429-32.
122. Vogt PH. AZF deletions and Y chromosomal haplogroups: history and update based on
sequence. Hum Reprod Update. 2005;11(4):319-36.
40
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
123. Lardone MC, Parodi DA, Valdevenito R, Ebensperger M, Piottante A, Madariaga M, et
al. Quantification of DDX3Y, RBMY1, DAZ and TSPY mRNAs in testes of patients with
severe impairment of spermatogenesis. Mol Hum Reprod. 2007;13(10):705-12.
124. Galan JJ, Guarducci E, Nuti F, Gonzalez A, Ruiz M, Ruiz A, et al. Molecular analysis
of estrogen receptor alpha gene AGATA haplotype and SNP12 in European populations:
potential protective effect for cryptorchidism and lack of association with male infertility.
Hum Reprod. 2007;22(2):444-49.
125. Brown GM, Furlong RA, Sargent CA, Erickson RP, Longepied G, Mitchell M, et al.
Characterization of the coding sequence and fine mapping of the human DFFRY gene
and comparative expression analysis and mapping to the Sxrb interval of the mouse Y
chromosome of the Dffry gene. Hum Mol Genet. 1998; 7(1): 97–107.
126. Elliott DJ. The role of potential splicing factors including RBMY, RBMX, hnRNPG-T
and STAR proteins in spermatogenesis. Int J Androl. 2004; 27(6): 328–334.
127. Lavery R, Glennon M, Houghton J, Nolan A, Egan D, Maher M. Investigation of DAZ
and RBMY1 gene expression in human testis by quantitative real-time PCR. Arch Androl.
2007; 53(2): 71–73.
128. Kuroda-Kawaguchi T, Skaletsky H, Brown LG, Minx PJ, Cordum HS, Waterston RH, et
al. The AZFc region of the Y chromosome features massive palindromes and uniform
recurrent deletions in infertile men. Nat Genet. 2001;29(3):279-86.
129. Bennett CP, Docherty Z, Robb SA, Ramani P, Hawkins JR, Grant D. Deletion 9p and sex
reversal. J Med Genet. 1993;30(6):518-20.
130. Sinclair AH, Berta P, Palmer MS, Hawkins JR, Griffiths BL, Smith MJ, et al. A gene from
the human sex-determining region encodes a protein with homology to a conserved DNAbinding motif. Nature. 1990;346(6281):240-44.
131. Brennan J, Capel B. One tissue, two fates: molecular genetic events that underlie testis
versus ovary development. Nat Rev Genet. 2004;5(7):509-21.
41
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
132. Meeks JJ, Weiss J, Jameson JL. Dax1 is required for testis determination. Nat Genet.
2003;34(1):32-33.
133. de la Chapelle A. The Y-chromosomal and autosomal testis-determining genes. Dev.
1987;101(Suppl):33-38.
134. Abusheikha N, Lass A and Brinsden P. XX males without SRY gene and with infertility.
Hum Reprod. 2001;16(4):717-18.
135. Zenteno JC, Lopez M, Vera C, Mendez JP, Kofman-Alfaro S. Two SRY-negative XX
male brothers without genital ambiguity. Hum Genet. 1997;100(5-6):606-10.
136. Seeherunvong T, Perera EM, Bao Y, Benke PJ, Benigno A, Donahue RP, et al. 46,XX sex
reversal with partial duplication of chromosome arm 22q. Am J Med Genet. 2004;(127):
149-51.
137. Rajender S, Rajani V, Gupta NJ, Chakravarty B, Singh L, Thangaraj K. SRY-negative
46,XX male with normal genitals, complete masculinization and infertility. Mol Hum
Reprod. 2006;12(5):341-46.
138. Collignon J, Sockanathan S, Hacker A, Cohen-Tannoudji M, Norris D, Rastan S, et al. A
comparison of the properties of Sox-3 with Sry and two related genes, Sox-1 and Sox-2.
Dev. 1996;122(2):509-20.
139. Weiss J, Meeks JJ, Hurley L, Raverot G, Frassetto A, Jameson JL. Sox3 is required for
gonadal function, but not sex determination, in males and females. Mol Cell Biol. 2003;
23(22):8084-91.
140. Girardi S, Mielnik A, Schlegel PN. Submicroscopic deletions in the Y chromosome of
infertile men. Hum Reprod. 1997;12(8):1635-41.
141. Oehninger S. Clinical and Laboratory Management of Male Infertility: an Opinion on its
Current Status. J Androl. 2000;21(6):814-21.
42
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
142. Piasecka M, Kawiak J. Sperm mitochondria of patients with normal sperm motility and
with asthenozoospermia: morphological and functional study. Folia Histochem Cytobiol.
2003;41(3):125-39.
143. Diez-Sanchez C, Ruiz-Pesini E, Lapena AC, Montoya J, Pe’rez-Martos A, Enry’quez JA, et al.
Mitochondrial DNA content of human spermatozoa. Biol Reprod. 2003;68(1):180-85.
144. St John JC, Jokhi RP, Barratt CL. Men with oligoasthenoteratozoospermia harbour higher
numbers of multiple mitochondrial DNA deletions in their spermatozoa, but individual
deletions are not indicative of overall aetiology. Mol Hum Reprod. 2001;7(1):103-11.
145. Tapanainen JS, Aittomaki K, Min J, Vaskivuo T, Huhtaniemi IT. Men homozygous for
an inactivating mutation of the follicle-stimulating hormone (FSH) receptor gene present
variable suppression of spermatogenesis and fertility. Nat Genet. 1997;15(2):205-6.
146. Tuttelmann F, Rajpert-De Meyts E, Nieschlag E, Simoni M. Gene polymorphisms and
male infertility—a meta-analysis and literature review. Reprod Biomed Online 2007;
15(6):643-58.
147. Tung JY, Rosen MP, Nelson LM, Turek PJ, Witte JS, Cramer DW, et al. Novel missense
mutations of the Deleted-in-AZoospermia-Like (DAZL) gene in infertile women and
men. Reprod Biol Endocrinol. 2006;(4):40.
148. Maglott D, Ostell J, Pruitt KD, Tatusova T. Entrez Gene: gene-centered information at
NCBI. Nucleic Acids Res. 2005;(33):54-8.
149. Zimmermann S, Steding G, Emmen JM, Brinkmann AO, Nayernia K, Holstein AF, et al.
Targeted disruption of the Insl3 gene causes bilateral cryptorchidism. Mol Endocrinol.
1999;13(5):681-91.
150. Olesen IA, Sonne SB, Hoei-Hansen CE, Rajpert-DeMeyts E, Skakkebaek NE. Environment,
testicular dysgenesis and carcinoma in situ testis. Best Pract Res Clin Endocrinol Metab.
2007;21(3):462-78.
43
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005
Introduction
151. Guarducci E, Nuti F, Becherini L, Rotondi M, Balercia G, Forti G, et al. Estrogen receptor
alpha promoter polymorphism: stronger estrogen action is coupled with lower sperm
count. Hum Reprod. 2006;21(4):994-1001.
152. Radpour R, Gourabi H, Gilani MA, Dizaj AV. Molecular study of (TG)m(T)n polymorphisms
in Iranian males with congenital bilateral absence of the vas deferens. J Androl. 2007;
28(4):541-47.
153. Sharma S, Singh M, Kaur G, Thapa BR, Prasad R. Identification and characterization of
CFTR gene mutations in Indian CF patients. Ann Hum Genet. 2009;73(1):26-33.
154. Quigley CA, De Bellis A, Marschke KB, el-Awady MK, Wilson EM, French FS. Androgen
receptor defects: historical, clinical, and molecular perspectives. Endocr Rev. 1995; 16
(3):271-321.
155. Hiort O, Holterhus PM, Horter T, Schulze W, Kremke B, Bals-Pratsch M, et al. Significance
of mutations in the androgen receptor gene in males with idiopathic infertility. J Clin
Endocrinol Metab. 2000;85(8):2810-5.
156. Crowley WF Jr, Filicori M, Spratt DI, Santoro NF. The physiology of gonadotropinreleasing hormone (GnRH) secretion in men and women. Recent Prog Horm Res. 1985;
41:473-531.
157. Moskovtsev SI, Willis J, Mullen JB. Age-related decline in sperm deoxyribonucleic acid
integrity in patients evaluated for male infertility. Fertil Steril. 2006;85(2):496-9.
158. Siddighi S, Chan CA, Patton WC, Jacobson JD, Chan PJ. Male age and sperm necrosis
in assisted reproductive technologies. Urol Int. 2007;79(3):231-4.
159. Plastira K, Msaouel P, Angelopoulou R, Zanioti K, Plastiras A, Pothos A, et al. The effects
of age on DNA fragmentation, chromatin packaging and conventional semen parameters
in spermatozoa of oligoasthenoteratozoospermic patients. J Assist Reprod Genet. 2007;
24(10):437-43.
44
Genetic Studies of Male Infertility – Ph.D/99-P.T./V/2005