Spatial and temporal distribution of Oct-4 and acetylated H4K5 in rabbit embryos

Abstract

Rabbit is a unique species to study human embryology; however, there are limited reports on the key transcription factors and epigenetic events of rabbit embryos. This study examined the Oct-4 and acetylated H4K5 (H4K5ac) patterns in rabbit embryos using immunochemistry staining. The average intensity of the Oct-4 signal in the nuclei of the whole embryo spiked upon fertilization, then decreased until the 8-cell stage and increased afterwards until the compact morula (CM) stage. It decreased thereafter from the CM stage to the early blastocyst (EB) stage, with a minimum at the expanded blastocyst (EXPB) stage and came back to a level similar to that of the CM-stage embryos in the hatching blastocysts (HB). The Oct-4 signal was observed in both the inner cell mass (ICM) and the trophectoderm (TE) cells of blastocysts. The average H4K5ac signal intensity of the whole embryo increased upon fertilization, started to decrease at the 4-cell stage, reached a minimum at the 8-cell stage, increased again at the EXPB stage and peaked at the HB stage. While TE cells maintained similar levels of H4K5ac throughout the blastocyst stages, ICM cells of HB showed higher levels of H4K5ac than those of EB and EXPB.

Candidate gene expression patterns in rabbit preimplantation embryos developed in vivo and in vitro

“…This could in turn reflect in the expression of other genes. The peak expression at ZGA phase in this study shows a positive correlation to the lowest acetylation levels in rabbit embryo reported earlier [40]. In cattle, HDAC1 expression in the in vitro embryos was low until 8-cell stage, but increased eight to ten times at the blastocyst stage [52].…”

“…In the bovine blastocysts, a similar OCT4 localization was reported [59,73]. A nuclear localisation in the early stages of rabbit development and a decline in protein levels recovering after ZGA were reported earlier [40]. The difference in these observations needs to be addressed further.…”

“…The discordance between mRNA and protein levels of HDAC1 was observed during both in vivo and in vitro embryo development. This may be attributed to the significant decrease of HDAC1 expression post ZGA and lineage specification [40]. However in this study, it is difficult to rule out the effect of in vitro conditions.…”

“…Earlier studies on rabbit embryo development were confined to the OCT4 expressions at transcriptional and translational levels [37][38][39][40][41] though it is very well established that BCLXL, HDAC1, SOX2, NANOG and KLF4 are also crucial for preimplantation embryo development. As more studies are needed in the context of preimplantation embryo development, this study was an attempt for the first time to monitor and compare expression of SOX2, NANOG, KLF4, HDAC1 and BCLXL simultaneously in addition to OCT4, both at the transcriptional and translational levels in rabbit preimplantation developmental stages (pronuclear, 2-cell, 4-cell, 8-cell, 16-cell, morula and blastocyst) between in vivo fertilized embryos, which were developed in vivo and in vitro.…”

Derivation of Rabbit Embryonic Stem Cells from Vitrified–Thawed Embryos

“…In support of this notion, it has been shown that, compared to mouse embryos, rabbit embryos have a more similar pattern of preimplantational development and lineage formation to that of human embryos. For example, in human and rabbit embryos, Oct4 expression was present in both the inner cell mass (ICM) and the trophectoderm (TE) cells (Berg et al, 2011;Chen et al, 2012a;Chen et al, 2012b;Hansis et al, 2000;Kirchhof et al, 2000), whereas in mice, Oct4 is expressed restrictively in the ICM, but not in the TE (Dietrich and Hiiragi, 2007;Ovitt and Scholer, 1998;Palmieri et al, 1994;Pesce et al, 1998;Yeom et al, 1996).…”