LOCALIZATION OF MESSENGER-RNA ENCODING C-KIT DURING THE INITIATION OFFOLLICULOGENESIS IN OVINE FETAL OVARIES

The c-kit protein is a transmembrane tyrosine kinase receptor that bin ds the growth factor stem cell factor. Mutant alleles of the genes cod ing for both the receptor (c-kit) and its ligand (stem cell factor) af fect gametogenesis, development of melanoblasts and some aspects of ha ematopoiesis. The aim of this study was to examine expression of the c -kit gene during folliculogenesis in fetal sheep ovaries using in situ hybridization. A 422 bp cDNA encoding the extracellular domain of the c-kit protein was amplified from sheep ovarian RNA using reverse-tran scription-polymerase chain reaction (RT-PCR), cloned and sequenced. Ri boprobes transcribed from the ovine cDNA encoding c-kit were used to d etect the presence of mRNA encoding c-kit within the ovaries of fetal sheep on days 90, 100, 120 and 135 of gestation (term = 147 days). In day 90 and 100 fetal ovaries, mRNA encoding c-kit was not detected in association with oogonia during the period of meiosis (to prophase I) but was present in some of the isolated oocytes. In ovaries from day 9 0 to day 135, mRNA encoding c-kit was detected in the oocytes at every stage of follicular growth - primordial through to antral follicles. This pattern of localization is consistent with that demonstrated in m ice.