The Ets domain transcription factor Erm distinguishes rat satellite glia from Schwann cells and is regulated in satellite cells by neuregulin signaling

Distinct glial cell types of the vertebrate peripheral nervous system (PNS) are derived from the neural crest. Here we show that the expression of the Ets domain transcription factor Erm distinguishes satellite glia from Schw ann cells beginning early in rat PNS development. In developing dorsal root ganglia (DRG), Erm is present both in presumptive satellite glia and in ne urons. In contrast, Erm is not detectable at any developmental stage in Sch wann cells in peripheral nerves. In addition, Erm is downregulated in DRG-d erived glia adopting Schwann cell traits in culture. Thus, Erm is the first described transcription factor expressed in satellite glia but not in Schw ann cells. In culture, the Neuregulin1 (NRG1) isoform GGF2 maintains Erm ex pression in presumptive satellite cells and reinduces Erm expression in DRG -derived glia but not in Schwann cells from sciatic nerve. These data demon strate that there are intrinsic differences between these glial subtypes in their response to NRG1 signaling. In neural crest cultures, Erm-positive p rogenitor cells give rise to two distinct glial subtypes: Erm-positive, Oct -6-negative satellite glia in response to GGF2, and Erm-negative, Oct-6-pos itive Schwann cells in the presence of serum and the adenylate cyclase acti vator forskolin. Thus, Erm-positive neural crest-derived progenitor cells a nd presumptive satellite glia are able to acquire Schwann cell features. Gi ven the in vivo expression of Erm in peripheral ganglia, we suggest that ga nglionic Erm-positive cells may be precursors of Schwann cells. (C) 2000 Ac ademic Press.