INTERCELLULAR CHANNELS IN TELEOSTS - FUNCTIONAL-CHARACTERIZATION OF 2CONNEXINS FROM ATLANTIC CROAKER

Gap junction channels, composed of protein subunits termed connexins, are believed to play a critical role in the process of oocyte differen tiation and maturation. We have used the paired Xenopus oocyte assay t o characterize functionally two connexin genes, connexin-32.2 and conn exin-32.7, recently cloned from the ovary of the Atlantic croaker (Mic ropogania undulatus), a species that has emerged as a useful model to study the process of maturation of the ovarian follicle. We have found that, while both connexin proteins were expressed at comparable level s in Xenopus oocytes, only one, connexin-32.2, was functionally compet ent to induce the formation of intercellular channels. Connexin-32.2 c hannels exhibited voltage-dependent closure that was similar to, but d istinct from that of previously characterized mammalian connexins. In addition, the silent connexin-32.7 was unable to functionally interact with connexin-32.2, either in heterotypic channels or as dominant neg ative inhibitor. Because connexin-32.2 expression is strikingly regula ted during oocyte maturation, these data provide further evidence for a role of intercellular channels in the control of oocyte-follicular c ell interactions.