RNA-seq transcriptome profiling of equine inner cell mass and trophectoderm.

Formation of the inner cell mass (ICM) and trophectoderm (TE) marks the first differentiation event in mammalian development. These two cell types have completely divergent fates for the remainder of the developmental process. The molecular mechanisms that regulate ICM and TE formation are poorly characterized in horses. The objective of this study was to establish the transcriptome profiles of ICM and TE cells from horse blastocysts using RNA sequencing (RNA-seq). A total of 12 270 genes were found to be expressed in either lineage. Global analysis of the transcriptome profiles by unsupervised clustering indicated that ICM and TE samples presented different gene expression patterns. Statistical analysis indicated that 1662 genes were differentially expressed (adjusted P < 0.05 and fold change > 2) between ICM and TE. Genes known to be specific to the ICM and TE were expressed primarily in their respective tissue. Transcript abundance for genes related to biological processes important for horse blastocyst formation and function is presented and discussed. Collectively, our data and analysis serve as a valuable resource for gene discovery and unraveling the fundamental mechanisms of early horse development.