BIPN 144 – Spring 2015 Ethan Bier Week 3 Handout A. Drosophila Neural Induction- Specification of the neuroectoderm 1. Dpp PATTERNING What is the default state of cells? What are the two functions of Dpp? How is Dpp autoactivation prevented? Describe what happens in the following mutants • Dpp- = • Dpp-/Sog- double mutant= • Sog-/Brk- double mutant= Page 1 of 5 BIPN 144 – Spring 2015 Ethan Bier B. Vertebrate Neural Induction 1. MANGOLD-SPEMANN EXPERIMENT Describe the results of the Mangold-Spemann experiment. Why is it significant? 2. ANIMAL CAP EXPERIMENT • Take a section from the Animal Cap Animal Cap animal hemisphere & culture in a dish formed Dorsal Mesoderm epidermal tissue • Cultured animal cap on top of layer of dorsal mesoderm  formed neural tissue (even with filter in between) Epidermis Neural This experiment further supported the conclusion that the formation of neural tissue was eural inducing factors. due to the dorsal mesoderm (Spemann organizer) secreting n Page 2 of 5 BIPN 144 – Spring 2015 Ethan Bier 3. ECTODERM DISSOCIATION EXPERIMENT The cells of the animal cap were dissociated (preventing the cells from communicating with each other), then treated and re-‐aggregated. Conditions Resulting Tissue Dissociated cells only Dissociated cells + BMP4 Dissociated cells + BMP4 + Chordin What conclusions can be made from this experiment? C. Neuronal Competence & Identity 1. NEURONAL COMPETENCE Define the following terms • Fate Map= • Determination= • Community Effect= Neuronal Competence= 2. NEURAL IDENTITY GENES  Neural identity genes Msh, Ind, Vnd further divide the neuroectoderm into 3 rows of neuroblasts (neural precursor cells) *REVIEW: Two opposing gradients in the fly embryo • _______________is high ventrally and low dorsally activate neural identity genes • _______________is high dorsally and low ventrally represses neural identity genes • Page 3 of 5 BIPN 144 – Spring 2015 Ethan Bier Fill in the diagram with the appropriate neural identity genes How do the different levels of Dpp and Dorsal affect neural identity genes? Neural Identity Gene Dpp Effect Dorsal Effect Msh (TF) Ind (TF) Vnd (TF) ROW 3 (Dorsal)= __________ is active ROW 2 (Lateral) = _________ is active ROW 1 (Ventral)= _________ is active Page 4 of 5 BIPN 144 – Spring 2015 Ethan Bier What is meant by ventral dominant repression? Describes what happens in the following mutants • Dpp- = • Vnd- = • Ind- = • Vnd-/Ind- double mutant= • Sna-/ Vnd-/ Ind-/ Dpp- mutant= How do vertebrate neural identity genes compare to flies? Page 5 of 5