Effect of sex on gene expression in equine blastocysts

Male mammalian embryos grow faster than female; but in equine, embryo size varies greatly and the relationship to sex and gene expression has not been reported. This study aimed to evaluate gene expression according to sex in equine blastocysts. Nonlactating, Saddlebred mares located on two experimental farms were inseminated with the semen of one stallion. At 8 days post ovulation, 17 and 11 embryos from each farm and each from a different dam, were recovered and bisected to obtain samples of pure trophoblast (TE) or inner cell mass enriched trophoblast (TE-ICM) . RNA expression was analyzed separately in the TE-ICM and the TE of 16 female and 12 male embryos using paired end, non-oriented RNA sequencing (Illumina, NextSeq500). To discriminate gene expression in the ICM from that in the TE, deconvolution (DeMixT) was used on the TE-ICM data. Differential expression was analyzed (DESeq2) with farm and embryo size as cofactors using a false discovery rate (FDR)