NAG - A SODIUM CHANNEL-LIKE MESSENGER-RNA SHARED BY SCHWANN-CELLS ANDOTHER NEURAL CREST DERIVATIVES

NaG, a member of subfamily 2, was originally characterized as a ''glia l'' sodium channel, and is expressed at high levels in Schwann cells i n vivo. However, NaG has also been shown by in situ hybridization to b e highly expressed in rat dorsal root ganglion (DRG) neurons, which, l ike Schwann cells, are neural crest derivatives. In the present study, we used non-isotopic in situ hybridization with a riboprobe for NaG, in conjunction with RT-PCR, to determine whether NaG is expressed in t issues related to the DRG either by neural crest origin or sensory fun ction. We found that the expression of significant levels of NaG mRNA was restricted to derivatives of the neural crest (neurons of DRG, tri geminal ganglion and mesencephalic nucleus of the trigeminal nerve, an d Schwann and satellite cells); the absence of NaG from superior cervi cal ganglion neurons and adrenal medulla chromaffin cells indicates th at not all neural crest derived neural elements express NaG. NaG was n ot observed in sensory neurons (retina, vestibular ganglion, spiral ga nglion, olfactory epithelium) that are not of neural crest origin. Our results indicate that NaG mRNA is expressed not only in Schwann cells , but also in a spectrum of neuronal cell types with afferent function of neural crest origin. NaG thus appears to represent a transcript en coding a sodium channel or sodium channel-like protein that is uniquel y expressed by both Schwann cells and afferent neurons of neural crest origin. (C) 1997 Wiley-Liss, Inc.