DEVELOPMENTALLY-REGULATED EXPRESSION OF FIBROBLAST GROWTH-FACTOR RECEPTOR GENES AND SPLICE VARIANTS BY MURINE EMBRYONIC STEM AND EMBRYONAL CARCINOMA-CELLS

The expression of the four fibroblast growth factor receptor (FGF-R) g enes was examined in murine embryonic stem (ES) cells, embryonal carci noma (EC) cells, and their differentiated derivatives. FGF-R1 and FGF- R4 were found to be expressed constitutively in all samples examined. The expression of FGF-R2 and FGF-R3 was, however found to increase sig nificantly upon differentiation of both ES and EC cells. Examination o f splice variants of the third immunoglobulin domain (IgIII) of the ex tracellular region of the FGF-R2 revealed that whilst IgIIIc transcrip ts were expressed upon ES cell differentiation, IgIIIb transcripts (wh ich confer specificity for the ligand FGF-7) were expressed in both ES cells and their differentiated progeny. FGF-R3 transcripts were also expressed in ES cells, but variant FGF-R3 transcripts containing the I gIIIb region were expressed upon differentiation. The findings suggest that the repertoire of FGF-R expression in embryonic cell types is de velopmentally regulated at the level of both gene expression, and alte rnative splicing and different members of the FGF-R family can exhibit distinct patterns of both gene and splice variant expression. (C) 199 4 Wiley-Liss, inc.