Expression of two c-fms-related gene products in rat muscular stem cells.

Two c-fms related transcripts 2.0 and 3.7 kb long are continuously expressed during the growth of rat myogenic cells (L6 alpha 1 line) and both are progressively eliminated when cell monolayers reach contact inhibition and differentiate. The 3.7 kb species apparently spans the three domains (intracytoplasmic, transmembrane, extracellular) of the putative c-fms gene(s) while the 2.0 kb species corresponds to the intracytoplasmic domain. In cell-free translation assays, these transcripts directed the synthesis of two proteins of 116 kD and 69 kD respectively. Both transcripts were found to exist in the various lines of rat myoblasts and muscular tumors investigated, and also at low levels in fetal and neonatal muscles. These data and other ones, still preliminary, strongly suggest that two types of c-fms-related gene products have a role in the normal and neoplastic growth of muscular cells.