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Embryonic events in neural development Evaluation • Evaluation – – – – – Mid-term test, 30%, in class March 15, Final exam, 30%, non-cumulative, exam period Research Paper 30% - Oral or Written presentation and Annotated Bibliography 5% Class Participation 5% Neural development occurs within the context of the development of the entire animal Cell division, cell movement and cell interaction are essential Blastula • Research Gastrulation – Objective – discuss the impact and importance of a paper you are given, with emphasis on how the paper influenced further research in the field of developmental neurobiology • Written – 10 double spaced pages (~3500 words) • Oral - 20-25 minutes + 5 minutes Gastrula Formation of cell layers •Endoderm •Mesoderm •Ectoderm Egg Embryonic events in neural development Vegetal Pole Animal Pole Epidermis & nervous system Drosophila (Fig 1.6, 1.7) Mesoderm – muscle, skeleton Vegetal Pole gut Blastula Synctial blastoderm Cellular blastoderm Ventral Frog (Fig 1.8, 1.9) Cellular blastoderm Dorsal Formation of a Neurogenic region Formation of a Neurogenic region Gastrula Invagination of the Mesoderm Invagination of the Mesoderm Formation of Neuroblasts from neurogenic Ventral ectoderm Formation of Neural Plate from Dorsal ectoderm Delamination of Neuroblasts into the embryo Invagination of Neural Tube & Neural Crest 1 Drosophila embryos Neurons descend from a lineage of cell division In the worm, C.elegans neurons arise from the AB blastomere of the first cell division Drosophila embryogenesis 2 Xenopus gastrulation http://faculty.virginia.edu/shook/ShowMovies/index.htm Neural Plate Mesoderm Notochord Neural crest Neural tube 3 Tissue from dorsal lip of IMZ Pigmented donor blastula • Cells moving into the blastocoel at the IMZ form the mesoderm • Do the mesoderm cells play a role in determining the neurogenic region? Albino host blastula Primary neural tube Secondary neural tube – Possibilities: • No, the neurogenic cells are predetermined • Yes, the mesoderm cells provide something that is instructive for neurogenic region • The secondary neural tube and body structures were mostly non-pigmented tissue • Indicates that transplanted tissue can act to ‘organize’ surrounding tissue ‘Spemann and Mangold transplantation’ • Specific regions of the IMZ organize specific body parts lateral aspects of IMZ → tails medial aspects of IMZ → heads 4 Must there be a vertical signal from mesoderm to ectoderm to induce neurogenic region? Keller sandwich http://faculty.virginia.edu/shook/ShowMovies/index.htm • What are the molecular factors that contribute to defining the neural region? 5 Nervous system dorsal Normal embryo ventral UV Organizer region Ventralized embryo 3 neural inducing molecules • Noggin • Chordin • Follastatin All are secreted molecules Normal embryo UV Known to inhibit activity of a TGF-β receptor related to BMP receptors Pool & Isolate cDNA Noggin cDNA Noggin + protein neurogenic BMP noggin, chordin or follastatin mesoderm Y BMP receptor • BMP signalling between ectoderm cells, normally inhibits neurogenic fate neurogenic • Interference of BMP signalling by noggin, chordin or follastatin, leads to neural fate ectoderm • Therefore, neural fate is the default fate mesoderm Y ectoderm 6
