(W375) REGULATORY GENES IN EARLY FOLLICULOGENESIS.
Nandedkar, Tarala1, Dharma, Shalmali 1, Mukherjee, Srabani1, 1 National Institute for Research in Reproductive Health, Mumbai, Maharashtra, India
ABSTRACT- FSH stimulates development of antral follicles to Graffian stage and LH induces ovulation in mammalian ovary. However, development of primordial to preantral stage follicles is independent of gonadotropin stimulation. Primordial follicles (Pdf) which contain primordial germ cells, are not recruited at one time. What are the genes responsible for the growth of Pdf to preantral stage. To have an insight into the regulation of early follicular development present work was initiated. The development of follicle was monitored in the neonatal period. On D2, Pdfs were present while on D4 and D6 development to primary and preantral follicles, respectively, was noted. The global expression of genes involved in differentiation, proliferation and cell cycle regulation was studied in D2, D4 & D6 ovaries by cDNA arrays. The results revealed that only few genes were expressed in D2 ovaries. Cell cycle regulated genes were upregulated during development of Pdf to primary follicle while transcription factors were expressed during transition of primary to preantral stage. IGFBPs, GDF-9, cKit, TNF, MAPK genes were also found to be upregulated. Further, to substantiate the gene expression results, the immunolocalization of proteins such as Growth Differentiation Factor (GDF-9), a differentiation marker and proliferating cell nuclear antigen (PCNA), a marker for proliferation, were studied in the ovaries of neonatal mice. Expression of GDF-9 was observed in the oocytes of primary follicles of D4 ovaries, while expression of PCNA was seen in the granulosa cells of preantral follicles of D6 ovaries. In conclusion, these studies demonstrated that 1. Mostly cell cycle regulatory genes and transcription factor genes were upregulated along with growth factors during early follicular development. 2. GDF-9 from oocyte of primary follicles enhanced proliferation of granulosa cells suggesting oocyte-granulosa cell interaction. (Partly supported by DBT)
KEY WORDS: neonatal ovary, gene expression, GDF-9, oocyte-granulosa cell