2 FORMS OF THE BASIC FIBROBLAST GROWTH-FACTOR RECEPTOR-LIKE MESSENGER-RNA ARE EXPRESSED IN THE DEVELOPING MOUSE-BRAIN

The embryonic neuroepithelium gives rise to the components of the central nervous system in the mature animal. To study the early development of the murine central nervous system, we have sought to isolate growth factor receptors from the neuroepithelium of the neural tube of 10-day-old mouse embryos. Because many growth factor receptors are members of the protein-tyrosine kinase family, we have used the polymerase chain reaction to amplify mRNA sequences from 10-day-old mouse embryo neuroepithelium; these sequences lie between the nucleotide sequences of two highly conserved amino acid motifs from the catalytic domain of protein-tyrosine kinases. By using this technique we have isolated a clone encoding the murine basic fibroblast growth factor receptor (bFGF-R), as well as a shorter form of this mRNA. This latter cDNA comprised 75% of the bFGF-R cDNA clones isolated from the immortalized neuroepithelial cell lines. This variant mRNA, designated here as N-bFGF-R, appears to be expressed at higher levels in neuronal cells in early stages of development. The bFGF-R is a member of a multigene family, as demonstrated by Southern blot analysis and the cloning of two other members of this family.