Comparison of neuregulin-1 expression in olfactory ensheathing cells, schwann cells and astrocytes

Recently we demonstrated that a member of the neuregulin-1 (NRG-1) family o f growth factors is a mitogen and survival factor for olfactory ensheathing cells (OECs). OECs are specialized glial cells within the olfactory system that are believed to play a role in the continual nerve re-growth of this tissue. OECs share properties with both astrocytes and Schwann cells but ar e likely to be a distinct glial cell type. NRG-1s have been found to be imp ortant regulators of Schwann cells in vivo, but the role of NRG-1 for OECs is less clear. The nrg-1 gene produces at least 12 different isoforms, that are likely to have different functions, due to alternative splicing of its mRNA. in this study, the expression of NRG-1 mRNAs in OECs was compared wi th other glial cells and their corresponding tissue sources. Cultured glial cells, unlike their tissue sources, expressed NRG-1 mRNAs containing the o r EGF-like domain and expressed only the type Ip isoform that lacks the gly cosylated spacer domain. This correlated with expression of these isoforms during olfactory nerve degeneration in vivo. Although OECs expressed mRNA f or all NRG-1 isoforms, the protein could not be detected in concentrated su pernatant, or an the cell surface by immunofluorescence, but was detected i n the nucleus or cytoplasm (depending on the isoform). These data support t he hypothesis that NRG-1s play a functional role in OEC biology. (C) 2000 W iley-Liss, Inc.