The Dynamics of Connexin Expression, Degradation and Localisation Are Regulated by Gonadotropins during the Early Stages of In Vitro Maturation of Swine Oocytes

Abstract

Gap junctional communication (GJC) plays a primordial role in oocyte maturation and meiotic resumption in mammals by directing the transfer of numerous molecules between cumulus cells and the oocyte. Gap junctions are made of connexins (Cx), proteins that regulate GJC in numerous ways. Understanding the dynamic regulation of connexin arrangements during in vitro maturation (IVM) could provide a powerful tool for controlling meiotic resumption and consequently in vitro development of fully competent oocytes. However, physiological events happening during the early hours of IVM may still be elucidated. The present study reports the dynamic regulation of connexin expression, degradation and localization during this stage. Cx43, Cx45 and Cx60 were identified as the main connexins expressed in swine COC. Cx43 and Cx45 transcripts were judged too static to be a regulator of GJC, while Cx43 protein expression was highly responsive to gonadotropins, suggesting that it might be the principal regulator of GJC. In addition, the degradation of Cx43 expressed after 4.5 h of IVM in response to equine chorionic gonadotropin appeared to involve the proteasomal complex. Cx43 localisation appeared to be associated with GJC. Taken together, these results show for the first time that gonadotropins regulate Cx43 protein expression, degradation and localisation in porcine COC during the first several hours of IVM. Regulation of Cx43 may in turn, via GJC, participate in the development of fully competent oocytes.

Effects of meiotic inhibitors and gonadotrophins on porcine oocytes in vitro maturation, fertilization and development

“…Two factors should be taken into account. First, our results support the hypothesis that in swine, spontaneous resumption oocyte meiosis or GVBD is substantially slower than in any other mammal (Santiquet, Robert, & Richard, ), and the greatest maturation occurs in the presence of Gns. Second, our results suggest that the presence of MINs themselves in the maturation medium does not improve the rate of nuclear maturation.…”

Granulosa cells of prepubertal cattle respond to gonadotropin signaling and upregulate genes that promote follicular growth and prevent cell apoptosis

“…In addition, we observed that transcripts abundance of CX43 and FOXO1 increased with age in the GCs of untreated animals. These genes encode key regulators of GC function, proliferation, and survival, and their expression was shown to be regulated by FSH in different species (Ackert, Gittens, O'Brien, Eppig, & Kidder, 2001;Cunningham, Zhu, Unterman, & Hammond, 2003;Fang et al, 2015;Nuttinck et al, 2000;Santiquet, Robert, & Richard, 2013;Shen et al, 2014;Ting & Zelinski, 2017).…”

Methods of RNA preparation affect mRNA abundance quantification of reference genes in pig maturing oocytes

“…(), while the other four ( YWHAG/RPL4/HRPT1/PPIA ) are different. The reason we selected these seven genes for RT‐qPCR normalization is that they were reported within recent 5 years (year 2012 to 2015) (Choi et al., ; Gu et al., ; Kuchipudi et al., ; Nagyova et al., ; Park et al., ; Santiquet et al., ; Spate et al., ), comparing to the report published in year 2007 (Kuijk et al., ). In addition, YWHAG, one candidate gene included in the present study but not in Kuijk et al.…”

“…All seven candidate genes ( GAPDH, 18S, YWHAG, BACT, RPL4, HRPT1 and PPIA ) were chosen primarily based on their relatively stable expression in different types of pig tissues, cells and oocytes, as reported previously (Choi et al., ; Gu et al., ; Kuchipudi et al., ; Nagyova, Nemcova, Mlynarcikova, Scsukova, & Kalous, ; Park et al., ; Santiquet, Robert, & Richard, ; Spate et al., ). Detailed information on these genes was summarized as in Table .…”

“…and PPIA) were chosen primarily based on their relatively stable expression in different types of pig tissues, cells and oocytes, as reported previously (Choi et al, 2013;Gu et al, 2014;Kuchipudi et al, 2012;Nagyova, Nemcova, Mlynarcikova, Scsukova, & Kalous, 2013;Park et al, 2015;Santiquet, Robert, & Richard, 2013;Spate et al, 2014).…”