Involvement of connexin 43 in human trophoblast cell fusion and differentiation

Abstract

The syncytiotrophoblast is the principal component of the human placenta involved in feto-maternal exchanges and hormone secretion. The syncytiotrophoblast arises from the fusion of villous cytotrophoblasts. We recently showed that functional gap junctional intercellular communication(GJIC) is an important prerequisite for syncytiotrophoblast formation and that connexin 43 (Cx43) is present in cytotrophoblasts and in the syncytiotrophoblast. To determine whether Cx43 is directly involved in trophoblast fusion, we used an antisense strategy in primary cultures of human villous cytotrophoblasts that spontaneously differentiate into the syncytiotrophoblast by cell fusion. We assessed the morphological and functional differentiation of trophoblasts by desmoplakin immunostaining, by quantifying hCG (human chorionic gonadotropin) production and by measuring the expression of specific trophoblast genes (hCG and HERV-W). Furthermore, we used the gap-FRAP (fluorescence recovery after photobleaching) method to investigate functional GJIC. Cytotrophoblasts treated with Cx43 antisense aggregated and fused poorly. Furthermore, less HERV-W env mRNA, hCGβ mRNA and hCG secretion were detected in Cx43 antisense-treated cytotrophoblasts than in cells treated with scrambled antisense. Treatment with Cx43 antisense dramatically reduced the percentage of coupled trophoblast cells. Taken together, these results suggest that Cx43 is directly involved in human trophoblast cell-cell communication, fusion and differentiation.

A PKA-ezrin-connexin 43 signaling complex controls gap junction communication and thereby trophoblast cell fusion

“…Interestingly, Cx43 is shown to be the key gap junction protein expressed in fusioncompetent human cytotrophoblasts (Dunk et al, 2012;Frendo et al, 2003a). Here, we report a direct interaction between ezrin and Cx43 in trophoblasts and demonstrate that the anchoring of PKA through the AKAP ezrin is necessary to provide spatiotemporal control of Cx43 phosphorylation and hCG-stimulated gap junction communication, which initiates trophoblast fusion.…”

“…Ezrin colocalizes with PKA, Cx43 and ZO-1 A complex of the gap junction protein Cx43 and the tight junction protein ZO-1 has been shown to play an important role in trophoblast fusion (Frendo et al, 2003a;. For this reason, we investigated the possibility of a physical interaction between PKA, ezrin and the Cx43-ZO-1 complex.…”

“…In particular, zona occludens-1 (ZO-1, also known as TJP1), cadherins and connexins have been reported to be involved in the apposition and communication stages prior to cell fusion (Charrasse et al, 2007;Frendo et al, 2003a;Mbalaviele et al, 1995;. Moreover, syncytins have been shown to play a fundamental role in placentation, fertilization and myoblast and osteoclast fusion Frendo et al, 2003b;Søe et al, 2011).…”

ADAM12-directed ectodomain shedding of E-cadherin potentiates trophoblast fusion

“…5,6 PKA directs multiple pathways important in trophoblast fusion, including the expression of the transcription factor glial cell missing 1 (GCM1). 7,8 Coordination and propagation of the fusion signal is controlled via gap junctions, 9,10 cytoskeletal reorganization 11,12 and remodeling of intercellular adhesion complexes. 13,14 Intercellular adherens junctions, composed of members of the cadherin family of cell adhesion molecules, are dynamically regulated during trophoblast syncytialization.…”

Mechanism of Congenital Chagas Disease: Effective Infection Depends on the Interplay Between Trypanosoma cruzi and the Different Tissue Compartments in the Chorionic Villi of the Human Placenta

“…c. Other membrane proteins: Presence of gap junctions is considered as a prerequisite for trophoblast syncytialization (Gauster et al, 2009). Inhibition of connexin 34 expression by antisense techniques impairs cell fusion in primary trophoblast cultures (Frendo et al, 2003). …”