CLAUDIN7 modulates trophectoderm barrier function to maintain blastocyst development in pigs.

Trophectoderm (TE) barrier function is an essential prerequisite for blastocyst development. CLAUDIN7 (CLDN7), a member of CLAUDINS family, is involved in regulating intercellular exchange and cell polarity in epithelium cells. However, the role of CLDN7 in porcine early embryo development is yet to be explored. Here, we found that CLDN7 was highly conserved in different species and was widely expressed in different tissues. Remarkably, CLDN7 expression maintained a low level from GV oocyte to 4-cell stage whereas its expression exhibited a higher level from 8-cell stage onwards. Microinjection of siRNA into cytoplasm effectively knocked down expression of CLDN7 mRNA and protein in porcine embryos. CLDN7 knockdown not only significantly reduced blastocyst rates of embryos derived from parthenogenetic activation and in vitro fertilization, but also reduced number of total cells and TE cells in the resulting blastocysts. Furthermore, CLDN7 knockdown led to a significant reduction in expression of multiple genes associated with tight junction assembly and fluid accumulation. A permeability assay revealed that CLDN7 knockdown disrupted tight junction assembly and paracellular sealing in the TE epithelium. Taken together, these results demonstrate that CLDN7 regulates porcine blastocyst development via modulating trophectoderm barrier function.