Myelin-associated glycoprotein MAG and a cytoskeletal-linking protein, periaxin, are initially located in Schwann cell membranes in contact with axon. May modulte interaction, but periaxin not in oligodendrocytes

L1 is required for initiation of myelination in Schwann cells, but not present in oligodendrocytes

Neuregulins e.g. glial growth factor (GGF) expressed by motor neurons and in neurons of peripheral ganglia. Stimulates differentiation and proliferation of Schwann cell precursors

Migration of Schwann cells progenitors never stops throughout their lives

neuregulins also contribute to the cell death of Schwann cell precursors through receptors that are yet unknwon

The Krox20 zinc finger transcription factor inhibits Schwann cell differentiation, is expressed in Schwann cell progenitors and downregulated as myelination starts

Are still dependent on neuregulin

Autocrine survival allows Schwann cells to survive death of axon but stimulation of nerve regrowth requires growth factors and cannot be done by the Schwann cell

Survival is promoted by neurotrophin-3, insulin-like growth factor 2 and platelet-derived growth factor BB

BMP

MAG

Po

NGF

NT-3

MBP

PMP-22

PLP

PLP is the most abundunt protein in PNS myelin

The cytosolic component of the sheath becomes filled with proteins essential for compatcion and stability of the myelin sheath

Po is the most abundunt protein in the PNS myelin