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3 Cards in this Set
- Front
- Back
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Origin of Neural Crest Cells
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NCC's form at the boundary where prospective neural plate meets prospective epidermis. They come from both layers. In amniotes, the NCC forms where moderate levels of BMP's, Wnt's and FgF's are prsent. These induce the NEURAL PLATE BORDER SPECIFIERS transcription factors (which keep cells from being neural plate). The NEURAL CREST SPECIFIERS (Slug and FoxD3) are induced by these transcription factors. FoxD3 is critical for specification of ectodermal cells as neural crest, and Slug is required for movement.
Ex. Transplanting tissue from a pigemented salamander to an unpigmented salamander gastrulae showed that salamander NCC appear to come from both prospective epidermis and prospective neural plate. Ex. When FoxD3 is expressed by electroporating it into neural plate cells, those neural plate cells express proteins characteristic of neural crest. |
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NCC - Ventral Migration
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The NCC's that do this travel through the anterior sclerotome. This is controlled by the extracellular matrices and chemotactic factors. The extracellular matrix is important because of the fibronectin roads, collagen molecules, and proteoglycans. THROMBOSPONDIN is found in the ANTERIOR SCLEROTOME. and is a good substrate for NCC adhesion and migration. Thrombospondin cooperates with fibronectin and laminin to promote NCC migration. EPHRINS and SEMAPHORIN-3F impede migration and are found int he POSTERIOR SCLEROTOME. These prevent NCC from entering the posterior portion.
Ex. If NCC cells are plated on a culture dish containing alternate stripes of immobilized anterior or posterior sclerotome cell membrane proteins, the anterior containing thrombospondin and the posterior containing ephrins, the NCC will leave the ephrin containing regions and move along stripes containing thrombospondin. |
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NCC - Differentiation
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Some NCC are pluripotent when they leave the neural crest, others are determined before migration due to Hox gene products. Some are restricted soon aver they leave the neural tube and are constrained by transcription factors. The final differentitation is due to morphogen gradients in the endorgan.
ex. Wnt1 instructs NCC's to become melanocytes or sensory organs. If just exposed to Wnt1 they become sensory organs, but if they are exposed along with Endolethin-3 they become melanocytes. |
