Involvement of gap junctional communication and connexin expression in trophoblast differentiation of the human placenta

Gap junctional intercellular communication (GJIC) permits coordinated cellu lar activities during development and differentiation processes, and its dy sfunction or mutation of connexin genes have been implicated in pathologies . In the human placenta, two distinct differentiation pathways of cytotroph oblastic cell coexist leading to a double model: fusion phenotype (villous trophoblast) and proliferative/invasive phenotype (extravillous trophoblast ). This review focuses on current knowledge on the connexin expression and the implication of GJIC in trophoblastic differentiation. Experimental evid ence obtained in human placenta demonstrates the involvement of connexin 43 -gap junctions in the trophoblastic fusion process and of a connexin switch during the spatially and temporally controlled proliferation/invasion proc ess.