R. Bruzzone et al., INTERCELLULAR CHANNELS IN TELEOSTS - FUNCTIONAL-CHARACTERIZATION OF 2CONNEXINS FROM ATLANTIC CROAKER, FEBS letters, 358(3), 1995, pp. 301-304
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.