Expression of CSF-1/c-fms and SF/c-kit mRNA during preimplantation mouse development.

c-fms and c-kit are structurally related tyrosine kinase receptors for colony-stimulating factor-1 (CSF-1) and for steel factor (SF), respectively. The level of c-fms mRNA, like c-kit mRNA, increases during the maturation of oocytes and is an abundant maternal message found in the unfertilized oocyte. Following fertilization, the level of both c-fms and c-kit oocyte mRNAs decreases rapidly until they are no longer detected by the early 2-cell stage. By the late 2-cell stage, both mRNAs are reexpressed, albeit at low levels. This low level of mRNA expression continues throughout preimplantation development. CSF-1 and SF transcripts are not detected in early preimplantation embryos, but are detected in cumulus cells, oviduct, and uterus, suggesting a paracrine action of these growth factors during the preimplantation period. The patterns of CSF-1/c-fms mRNA and SF/c-kit mRNA expression are consistent with the hypothesis that these two ligand/receptor systems may act in a compensatory or synergistic manner during preimplantation development.