FGF AND EGF ARE MITOGENS FOR IMMORTALIZED NEURAL PROGENITORS

Individual neural progenitors, derived from the external germinal laye r of neonatal murine cerebellum, were previously immortalized by the r etrovirus-mediated transduction of avian myc (v-myc). C17-2 is one of those clonal multipotent progenitor cell lines (Snyder et al., 1992, C ell 68: 33-51; Ryder et al., 1990, J. Neurobiol. 21:356-375). When tra nsplanted into newborn mouse cerebellum (CB), the cells participate in normal CB development; they engraft in a cytoarchitecturally appropri ate, nontumorigenic manner and differentiate into multiple CB cell typ es(neuronal and glial) similar to endogenous progenitors (Snyder et al ., 1992, as above). They also appear to engraft and participate in the development of multiple other structures along the neural axis and at multiple other stages (Snyder et al., 1993, Sec. Neurosci. Abstr. 19) . Thus conclusions regarding these immortalized progenitors may be app licable to endogenous neural progenitors in vivo. To help identify and analyze factors that promote differentiation of endogenous progenitor s, we first investigated the ability to maintain C17-2 cells in a defi ned, serum-free medium (N2). The cells survive in vitro in N2 but unde rgo mitosis at a very low rate, Addition of epidermal growth factor (E GF), however, either from mouse submaxillary gland or the human recomb inant protein, appreciably stimulates thymidine incorporation and cell division approximately threefold. Basic fibroblast growth factor (bFG F) is an even more potent mitogen, promoting thymidine incorporation, cell division, and a net increase in cell number equal to that in seru m. Both EGF and bFGF are active at very low nanomolar concentrations, suggesting that they interact with their respective receptors rather t han a homologous receptor system. The findings demonstrate that C17-2 cells can be maintained and propagated in a fully defined medium, prov iding the basis for analysis of other growth and differentiation facto rs. That EGF and particularly bFGF are mitogenic for these cells is in accord with recent observations on primary neural tissue (Reynolds an d Weiss, 1992, Science 255:1707-1710; Kilpatrick and Bartlett, 1993, N euron 10:255-265; Ray et al., 1993, Proc. Natl. Acad. Sci. USA 90: 360 2-3606) suggesting that bFGF and EGF responsiveness may be fundamental properties of neural progenitors. (C) 1994 John Wiley and Sons, Inc.