Stage specific expression of cell cycle genes during in vivo or in vitro development of ovarian follicles in sheep

• Studied the expression of cyclin genes during the development of sheep ovarian follicle.
• Significant decrease in CCNB1 & CCND1 in the in vivo developed cumulus cells in large antral follicles.
• Different patterns of expression of cyclins in vitro grown cumulus cells and oocytes.
• Deranged expression of cyclins compromises development potential of cultured follicles.

Quantitative expression patterns of cell cycle genes (CCNB1 and CCND1) were studied at different in vivo and corresponding in vitro stages of development of ovarian follicles in sheep.In the cumulus cells from in vivo grown ovarian follicles, the expression of CCNB1 and CCND1 decreased significantly at the large antral stage relative to all the other stages of development except the decrease in CCND1 from antral to large antral stage. However, in the cumulus cells from in vitro cultured ovarian follicles, such significant decrease in the expression of CCNB1 and CCND1 was absent. The expression of CCNB1 and CCND1 in the oocytes from in vivo grown ovarian follicles increased significantly up to the large antral stage. In the oocytes from in vitro grown ovarian follicles, however, the pattern of expression of these genes was different.In vitro maturation of cumulus oocyte complexes (COCs) for 24 h stimulated the expression of CCNB1 and CCND1 in the cumulus cells derived from both in vivo and in vitro grown ovarian follicles. In similarly treated oocytes, while the CCND1 expression was unaffected, the expression of CCNB1 was suppressed.It is concluded that the cell cycle genes follow specific patterns of expression during ovarian folliculogenesis synchronous with different development events. In vitro culture deranged the expression patterns of these genes.