Sexually dimorphic gene expression responses of bovine embryos to the maternal microenvironment

This study investigated the sexual dimorphic gene expression patterns of day 13 embryos developed in Holsteins Frisian cows and heifers. Accordingly, embryos developed in the cows exhibited sexually dimorphic expression of genes associated with steroid biosynthesis and metabolism as well as genes associated with the formation of the primary germ layer whereas those developed in heifers sexually dimorphic expression of genes involved in developmental processes, gonadal development or female sex differentiation, and transmembrane transports. This result may partly explain the possible causes of a skewed sex ratio during development and at birth. To generate the day 13 female and male embryos, in vitro-produced presumptive male and female embryos were transferred to multiparous Holsteins Frisian cows and nulliparous heifers on day 2 of the oestrous cycle. The embryos were recovered at day 13 of the gestation period and classified into four groups according to their sex and origin as male or female embryos developed in cows or heifers. The total RNA was isolated from each group of embryos (n =5) was subjected to the next-generation transcriptome sequencing. Adapters and non-informative sequences were removed and clean reads were mapped to the bovine reference genome. Quantification and annotation of expressed genes in each embryo group were performed using the Seqmonk tool and differential expression analysis between the embryo groups was performed using the edgeR Bioconductor package.