SELECTIVE EXPRESSION OF PDGF-A AND ITS RECEPTOR DURING EARLY MOUSE EMBRYOGENESIS

Murine homologs of the PDGF A, PDGF B, and PDGF receptor α subunit genes were cloned. These were used, together with a mouse PDGF receptor β subunit cDNA clone, to monitor gene expression in early postimplantation mouse embryos and in F9 embryonal carcinoma cells. RNAse protection analysis shows that PDGF A chain, but not B chain, mRNA is expressed in 6.5- to 8.5-day embryonic and extraembryonic tissues. Both α and β receptor subunit mRNAs are expressed in early embryos, however, α subunit mRNA appears earlier and is more abundant than β subunit mRNA. Undifferentiated F9 embryonal carcinoma stem cells express abundant levels of A chain, but not B chain, mRNA. Neither of the PDGF receptor genes is expressed in stem cells. Treatment with retinoic acid stimulates expression of both PDGF receptor genes. As in postimplantation mouse embryos, α receptor subunit mRNA appears earlier and is substantially more abundant than β subunit mRNA. Collectively, these data demonstrate that the genes encoding the two chains of PDGF and their receptors are regulated independently during development and suggest that the two systems have some nonoverlapping functions in vivo. PDGF A, but not PDGF B, may be particularly important in modulating early events in mouse embryonic development. © 1990.