Gene expression during the peri-folliculogenic period in the neonatal hamster ovary

Abstract

Mammalian ovarian organogenesis is characterized temporally by oogonial mitosis, oogonial apoptosis, rescue of germ cells via interaction with somatic cells to form primordial follicles, and entrance into meiosis. Recent studies suggest that germ cells actively participate in these processes via production of local regulatory factors. GDF-9, a novel transforming growth factor-b family member, is expressed in ovaries of various species as a crucial factor in ovarian follicular development. The transcription factor GCNF, an orphan member of the nuclear receptor family, is a candidate in the regulation and development of the early mammalian ovary. GCNF appears to suppress expression of GDF-9 and Oct-4, a transcription factor restricted to stem cells including the germ cell line. Recently, our lab has become interested in the pattern of expression associated with GDF-9, GCNF, and Oct-4 pertaining to ovarian organogenesis and follicle formation in the neonatal hamster ovary. Consensus oligonucleotide primer pairs for GDF-9, GCNF, and Oct-4 were determined by analyzing gene sequences for human, mouse, rat, bovine and pig for use in the hamster. mRNA for these factors in the hamster ovary were detected by RT/PCR using total RNA at days 1, 3, 5, and 6-9 post delivery, reflecting periods of active oogonial mitosis, oogonial atresia, and primordial follicle formation. Reports have suggested that GCNF represses Oct-4 and GDF-9 in the oocyte and GDF-9 is not expressed in primordial follicles. Our results suggest GDF-9 expression in oogonia prior to and during primordial follicle formation, likely reflecting differential cellular expression of GDF-9/Oct-4 (oogonia/oocyte) and GCNF (somatic pre-granulosa cells).