Category Archives: Follicle

Although a role for KITL and KIT in these processes is well established in rodents, there is a paucity of information regarding the functional significance of KITL and KIT during primordial follicle activation in other species. The limited information available for the human indicates that, similar to mice, the oocytes of primordial follicles in human fetal ovaries express KIT, and expression initially intensifies in growing preantral follicles, only to decrease again with antrum formation. (more…)

The expression of KITL and KIT is well characterized in the developing mouse ovary. It has been reported that with the exception of oocytes undergoing the first stages of meiosis, in which Kit mRNA expression is downregulated, oocytes at all stages of development express Kit mRNA and protein. Similarly, the granulosa cells of follicles at all stages of development express Kitl mRNA and protein, although expression is very low in the squamous granulosa cells of primordial follicles. Given that KITL is derived from granulosa cells and KIT is expressed by oocytes and theca cells, this receptor-ligand pair is an excellent example of how paracrine interactions between oocytes and their companion somatic cells control many aspects of follicle formation and development. (more…)

Kit ligand (KITL) is a pleiotropic growth factor that exerts an influence on target cells through binding the tyrosine kinase receptor, KIT. KITL and KIT are expressed by a variety of developmentally distinct cell lineages during both embryogen-esis and adult life, and roles for KITL and KIT in gametogenesis, melanogenesis, and hematopoiesis have been described. In mice KITL and KIT are products of the steel and white spotting loci, respectively, and mutations at these loci are associated with reduced fertility or sterility, depending on the nature of the defect. Numerous studies have shown that in the ovaries of rodents KITL and KIT are important for the migration, proliferation, and survival of primordial germ cells; primordial follicle activation; oocyte growth and survival; granulosa cell proliferation; the maintenance of meiotic arrest; theca cell recruitment; and the regulation of ovarian steroidogenesis. Therefore, KITL and KIT have diverse roles during oogenesis and folliculogenesis, and they are fundamentally important to fertility in rodents. However, many of these effects are yet to be confirmed in other species, including the human.