Comparing spatial expression dynamics of bovine blastocyst under three different procedures: in-vivo, in-vitro derived, and somatic cell nuclear transfer embryos.

There has been no work on spatiotemporal transcriptomic differences of blastocysts using in vivo- and in vitro-derived, and somatic cell nuclear transfer (SCNT) embryos. Here, we first compared the lineage-differentially transcriptomic profiles of in vivo- and in vitro-derived embryos by microarray analysis using divided into inner cell mass (ICM)-and trophectoderm (TE)-side samples, as well as those derived from SCNT in order to explore lineage-differentially expressed genes that are associated with preimplantation development in cattle. The transcriptomic profiles of the ICM-specific and TE-specific genes were similar between in vitro-derived embryos and in vivo-derived embryos, whereas SCNT embryos exhibited unusual lineage-differentially gene expression regulation at the blastocyst stage. The genes expressed in a spatiotemporal manner between developmentally normal in-vivo derived blastocysts and developmentally abnormal SCNT blastocysts might play critical roles for preimplantation development. Comparing spatial expression dynamics of bovine blastocyst under three different procedures revealed that CIITA was expressed in ICM-side samples of all the embryo types. CIITA is known as the master regulator of major histocompatibility complexes (MHC) class II genes that express in antigen-presenting cells but its biological function in preimplantation embryo is still unknown in mammals. Knockdown of CIITA expression in in vitro-derived embryos did not affect cleavage, but disrupted development of embryos into the blastocyst stage. These findings provide the novel transcriptomic information on blastocyst formation, raising the possibility that immune function-related gene directly plays important roles in bovine preimplantation development.

Transcriptional wiring for establishing cell lineage specification at the blastocyst stage in cattle.

Mice and cattle use distinct pathways for the first cell segregation into inner cell mass (ICM) and trophectoderm (TE) lineages at the blastocyst stage. However, limited knowledge is available regarding the reliable transcriptional networks that orchestrate the complex developmental processes at this stage in nonrodent species. In order to elucidate the site-dominant transcriptomic properties of bovine blastocysts, we separated cell samples into the ICM and TE using both mechanical and chemical methods and performed in silico prescreening for candidate genes that were site-dominantly expressed in bovine blastocysts. We further performed quantitative real-time PCR and in situ hybridization using the site-specific cell samples. As a result, we identified seven ICM-dominant genes and five TE-dominant genes not found in earlier studies. Our findings provide novel insights into the mechanism of cell-fate specification in the pre-implantation bovine embryo.