ABSTRACT
Neuroectoderm gives rise to a large number of cell types, both neurons and glia, each with their own identity or phenotype. The process by which cell precursors are transformed into mature cells is differentiation and the sequence of cell types that lead from precursor to mature cell is the cell lineage. Cells deprived of proneural gene function either develop as epidermoblasts or embark on a neural fate which is aborted by apoptosis. Notch protein is a membrane bound protein with a large extracellular domain containing numerous epidermal growth factor (EGF)-like repeats that act as a receptor for the smaller Delta protein, also a transmembrane protein with extracellular EGF-like repeats. The rostral primary motor neuron axon grows to the lateral muscle, the middle primary motor neuron innervates the dorsal muscle, while the caudal primary projects to the ventral muscle. Single progenitors in the neural tube or neural crest can give rise to either neurons or glial cells.
