SOX10, A NOVEL TRANSCRIPTIONAL MODULATOR IN GLIAL-CELLS

Sox proteins are characterized by possession of a DNA-binding domain w ith similarity to the high-mobility group domain of the sex determinin g factor SRY. Here, we report on Sox10, a novel protein with predomina nt expression in glial cells of the nervous system. During development Sox10 first appeared in the forming neural crest and continued to be expressed as these cells contributed to the forming PNS and finally di fferentiated into Schwann cells. In the CNS, Sox10 transcripts were or iginally confined to glial precursors and later detected in oligodendr ocytes of the adult brain. Functional studies failed to reveal autonom ous transcriptional activity for Sox10. Instead, Sox10 functioned syne rgistically with the POU domain protein Tst-1/Oct6/SCIP with which it is coexpressed during certain stages of Schwann cell development. Syne rgy depended on binding to adjacent sites in target promoters, was med iated by the N-terminal regions of both proteins, and could not be obs erved between Sox10 and several other POU domain proteins. Interesting ly Sox10 also modulated the function of Pax3 and Krox-20, two other tr anscription factors involved in Schwann cell development. We propose a role for Sox10 in conferring cell specificity to the function of othe r transcription factors in developing and mature glia.