The oocyte and its surrounding granulosa cells co-exist in a closed compartment called a follicle, although they receive many signals from other parts of the body. It is well established that the intercellular communications between the oocyte and granulosa cells are required for normal oocyte development and ovulation during folliculogenesis. Gap junctions are intercellular channels allowing the direct transmission of ions and small molecules between coupled cells. Several lines of studies have shown that multiple connexins (Cx, subunits of gap junction) are expressed in mammalian ovarian follicles. Among them, two major connexins Cx37 and Cx43 are expressed in different manner. While the gap junction channels formed by Cx37 are localized between the oocyte and encompassing granulosa cells, the intercellular channels by Cx43 are located between granulosa cells. In this review, I will summarize the general properties of gap junction channels and discuss their possible formation (or compatibility) of intercellular channels formed by the oocyte and granulosa cells.

INTRODUCTION   STRUCTURE OF GAP JUNCTION   CONNEXIN GENE FAMILY   MODULATION OF GAP JUNCTION    Physphorylation of Cx43   IONIC SELECTIVITY AND MOLECULAR PERMEABILITY    Cx37 Gap Junction Channels    Cx43 Gap Junction Channels   INTERCELLULAR CHANNEL FORMATION    Heterotypic Channels    Heteromeric Channels    Heteromeric Channels between Cx37 and Cx43 in Exogenous System    'Chimeric' Channels Formation in Ovarian Follicles   CONCLUSIONS   REFERENCES

• Oh Seunghoon(Department of Physiology, College of Medicine, Dankook University)