| Abstract: | X-chromosome inactivation (XCI) is an epigenetic process that equalizes expression of X-borne genes between
male and female eutherians. This process is observed in early eutherian embryo development in a
species-specific manner. Until recently, various pluripotent factors have been suggested to regulate the
process of XCI by repressing XIST expression, which is the master inducer for XCI. Recent
insights into the process and its regulation have been restricted in mouse species despite the evolutionary
diversity of the process and molecular mechanism among the species. OCT4A is one of the
represented pluripotent factors, the gate-keeper for maintaining pluripotency, and an XIST
repressor. Therefore, in here, we examined the relation between OCT4A and X-linked genes in
porcine preimplantation embryos. Three X-linked genes, XIST,
LOC102165544, and RLIM, were selected in present study because their
orthologues have been known to regulate XCI in mice. Expression levels of OCT4A were
positively correlated with XIST and LOC102165544 in female blastocysts.
Furthermore, overexpression of exogenous human OCT4A in cleaved parthenotes generated
blastocysts with increased XIST expression levels. However, increased XIST
expression was not observed when exogenous OCT4A was obtained from early blastocysts. These
results suggest the possibility that OCT4A would be directly or indirectly involved in
XIST expression in earlier stage porcine embryos rather than blastocysts. |
