Quantitative patterns of expression of gap junction genes during in vivo or in vitro development of ovarian follicles in sheep

• First study on gap junction genes during development of ovarian follicles in sheep.
• Cx43 and 32 expressed at all in vivo and corresponding in vitro development stages.
• Connexins follow a stage specific pattern of expression during ovarian folliculogenesis.
• Expression of Cx43 in mammalian oocytes reported for the first time.
• Stage specific changes in expression found in in vivo follicles were altered in cultured ones.

Expression of gap junction genes CX32 and Cx43 was studied in different stages of in vivo and cultured ovarian follicles in sheep. In the in vivo grown follicles, CX43 expression in the cumulus cells did not change with development but in the oocytes a significant decrease was noted in the early antral follicles. Although CX32 expression in the cumulus cells appeared to decrease continuously, it was significant only from early antral to antral follicles. However, Cx32 expression in oocytes showed an increasing pattern although the increase from early antral to antral stage was not significant. In the cultured follicles CX43 expression in cumulus cells decreased significantly from preantral to early antral follicles, then increased significantly at the antral stage and decreased again in the large antral follicles. The pattern of CX32 expression was similar except for the significant decrease observed with CX43 expression in the large antral follicles. In the oocytes CX43 expression increased significantly from preantral to early antral stage, and decreased significantly at antral and large antral stages. On the other hand CX32 expression increased significantly from early antral to antral follicle stage and then decreased significantly in the large antral follicles. Subsequent to in vitro maturation for 24 h of COCs from in vivo grown large antral follicles, CX43 expression was supressed both in the cumulus cells and oocytes but CX32 expression was compromised only in the oocytes. In the similarly treated COCs’ from in vitro grown large antral follicles, CX43 expression was stimulated both in the cumulus cells and oocytes but CX32 expression was augmented only in the cumulus cells. It is concluded that (i) the gap junction genes follow a stage specific pattern of expression during ovarian follicular development and (ii) in vitro culture adversely influenced the expression of the gap junction genes.