Coxsackie virus and adenovirus receptor (CXADR) is a member of the immunoglobulin superfamily as well as a member of the junctional adhesion molecule family of adhesion receptor. In human pre-implantation embryos, CXADR was detected and co-localized with tight junction (TJ) proteins on the membrane of the trophectoderm. However, its physiological roles were not elucidated in terms of blastocyst formation. Here, we reported expression patterns and biological functions of CXADR in porcine pre-implantation embryos. The transcripts of CXADR were detected at all stages of pre-implantation. Particularly, its expression dramatically increased and preferentially localized at the edge of cell–cell contacts, rather than in the nucleus from the eight-cell stage onwards. CXADR expression was knocked down (KD) by microinjecting double-stranded RNA into one-cell parthenotes. The vast majority of CXADR KD embryos failed to develop to the blastocyst stage, and a few developed KD blastocysts did not expand fully. Analysis of adherens junction (AJ)- and TJ-associated genes/proteins using qRT-PCR, immunocytochemistry and assessment of TJ permeability using FITC-dextran uptake assay revealed that the developmental failure and relatively small cavities are attributed to the defects of TJ assembly. In summary, CXADR is necessary for the AJ and TJ assembly/biogenesis during pre-implantation development.
Jeong-Woo Kwon, Nam-Hyung Kim and Inchul Choi
Zhe-Long Jin, Xing-Hui Shen, Liang Shuang, Jeong-woo Kwon, Min-Jeong Seong and Nam-Hyung Kim
Homologous recombination (HR) plays a critical role in facilitating replication fork progression when the polymerase complex encounters a blocking DNA lesion, and it also serves as the primary mechanism for error-free DNA repair of double-stranded breaks. DNA repair protein RAD51 homolog 1 (RAD51) plays a central role in HR. However, the role of RAD51 during porcine early embryo development is unknown. In the present study, we examined whether RAD51 is involved in the regulation of early embryonic development of porcine parthenotes. We found that inhibition of RAD51 delayed cleavage and ceased development before the blastocyst stage. Disrupting RAD51 activity with RNAi or an inhibitor induces sustained DNA damage, as demonstrated by the formation of distinct γH2AX foci in nuclei of four-cell embryos. Inhibiting RAD51 triggers a DNA damage checkpoint by activating the ataxia telangiectasia mutated (ATM)–p53–p21 pathway. Furthermore, RAD51 inhibition caused apoptosis, reactive oxygen species accumulation, abnormal mitochondrial distribution and decreased pluripotent gene expression in blastocysts. Thus, our results indicate that RAD51 is required for proper porcine parthenogenetic activation (PA) embryo development.