PAX3 - A PAIRED DOMAIN GENE AS A REGULATOR IN PNS MYELINATION

Pax3 RNA is expressed in neural crest when Schwann cell (SC) precursor s migrate to the PNS. Pax3 RNA and SC markers were monitored in sciati c nerves of mice during development and nerve repair. An inverse corre lation was observed between expression of Pax3 RNA and myelin basic pr otein (MBP). Inverse correlation was also observed in SC primary cultu res. Treating cultures with forskolin, an adenylate cyclase agonist, r epressed Pax3 RNA, GFAP, NGFR, N-CAM, and L1 and elevated MBP. Subsequ ent microinjection with Pax3 expression vector elevated Pax3 RNA, GFAP , NGFR, N-CAM, and L1 and repressed MBP. Thus, Pax3 is likely involved in the differentiation pathway to myelinating SCs. Pax3 repressed a 1 .3 kb MBP promoter fragment in cotransfection assays, suggesting that it represses MBP transcription.