Genomic evaluation and gene expression analysis of preimplantation embryos for enhancing cattle breeding and in vitro embryo production.

Genomic selection using genomic estimated breeding values (GEBVs) based on single nucleotide polymorphism (SNP) genotyping has been widely adopted for efficient breeding of cattle. Recent advances in DNA analysis technologies have enabled comprehensive SNP genotyping using a small number of cells. Implementation of a preimplantation genomic selection (PGS) system, wherein GEBVs are calculated from a limited number of embryonic cells, can further enhance breeding efficiency through the selective production of genetically superior animals by embryo transfer. In addition, the use of bovine embryos produced by in vitro fertilization (IVF) has increased worldwide in recent years. However, the implantation potential of bovine IVF embryos is lower than that of in vivo-derived (IVD) embryos, and aberrant epigenetic modifications and gene expression are considered major contributing factors to the reduced developmental competence of bovine IVF embryos. Therefore, the differences in the gene expression characteristics of bovine IVD and IVF embryos need to be better understood for improved bovine in vitro production (IVP) systems. This review outlines the development and applications of PGS systems using bovine blastocysts, elongating conceptuses, and demi-embryos derived from blastomere separation. It also discusses the utility of gene expression profiling as a method for evaluating the quality of bovine preimplantation embryos, which may contribute to improvements in bovine IVP systems.