THE POLARIZED HEPATIC HUMAN RAT HYBRID WIF-12-1 AND WIF-B CELLS COMMUNICATE EFFICIENTLY IN-VITRO VIA CONNEXIN 32-CONSTITUTED GAP-JUNCTIONS/

Gap junction intercellular communication (GJIC) plays an essential rol e in the control of growth, differentiation, and functions of differen t tissues. The expression of connexins (Cxs), the structural proteins of gap junctions, is developmentally regulated and tissue-specific. In vivo hepatocytes express Cx32 and Cx26. Most currently available in v itro hepatic cell systems express Cx43 instead of the expected Cxs. Th is work analyzes the GJIC competence and Cx expression of the highly d ifferentiated and polarized hepatoma-derived hybrid cell lines, WIF 12 -1 and WIF-B. It shows (using two dye transfer assays) that both lines communicate efficiently and that the acquisition of GJIC competence p recedes the formation of bile canaliculi. Interestingly, these cells c ommunicate via Cx32 expression, whereas Cx26 and Cx43 are not expresse d, as demonstrated by Western and Northern blotting, immunocytochemist ry and confocal microscopy: The human fibroblast WI38 parent communica tes via Cx43, whereas the rat hepatoma parent Fao and the subclone WIF 12-1 TGF, that has lost the human X chromosome, do not communicate, t he expression of Cx32 being restricted to the mRNA in these two lines. The GJIC competence of WIF cells could thus result from the activatio n of the human X chromosome-linked Cx32 gene.