Figure 9.

Proposed model for the role of the ATX–LPA axis in OLG differentiation. ATX, which has been found secreted by OLGs throughout the early stages of the lineage, generates the lipid signaling molecule LPA via its enzymatically active lysoPLD site. LPA, in turn, activates one (or more) of its cognate receptors (LPARs) on the surface of OLG progenitors, which leads to the downstream activation of HDAC1/2 in the nucleus. Histone deacetylation mediates the repression of transcriptional inhibitors of OLG differentiation and thereby promotes gene expression changes associated with the differentiation from an OLG progenitor (OPC) to an early differentiating OLG (Pro-OLG). Expression markers identifying individual stages of the OLG lineage are listed below each OLG stage. Markers in black were used in both the zebrafish and rodent studies, whereas markers in light and dark gray are unique for the zebrafish and rodent studies, respectively.