神経堤
Neural crest cells are found in the dorsal neural tube from which nerves and glia alike grow and Neural crest cells are the precursors to many various tissue types including enteric neurons and glia. Schwann cell precursors (a first derivative of Neural crest cells) are present as the nerve axon grows from the dorsal neural tube, but it has been shown that these glial precursors are not essential to axonal growth. The transition from neural crest cells to Schwann cell precursors is characterized by Sox10 and generally occurs around embryonic day 12-13 in rats. Schwann cell precursors then differentiate into Immature Schwann cells from which myelinating and non-myelinating Schwann cells are directly descended. These cells generally appear around embryonic day 13-15 in rats. The differentation of Immature Schwann cells occurs after birth and is dependent on the axons in which the glia are associated. This differentation is known to be reversible, as seen in regeneration models. Perisynaptic Schwann cells develop as non-myelinating Schwann cells and encapsulate the NMJ. PSCs can be attributed to glial lineage by the presence of Calcium binding proteins S100, Glial fibrillary acidic protein (GFAP), and Protein 0. These proteins are seen in other glial cells such as Myelinating Schwann cells and Neural Crest cells. While the lineage of non-Myelinating Schwann cells is known from neural crest cells, the exact development of PSCs from non-Myelinating Schwann cells is not fully understood.