Characterization of the Sheep Hypothalamus and Pituitary Transcriptomes

The sheep (Ovis aries) is a valuable model organism for understanding the relationship between energy balance and fertility in both ruminants and humans. As a first step towards identifying molecular pathways that couple energy sensing to reproduction, we characterized the transcriptomes of the sheep hypothalamus and pituitary using RNA-sequencing (RNA-Seq). Ribonucleic acid samples from hypothalamus and pituitary of five Suffolk-cross wethers were deeply sequenced (Hypothalamus: 468,912,732; Pituitary: 515,106,092 reads per sample) using an Illumina Hi-Seq platform and aligned to the Bos taurus and Ovis aries genomes using BLAST (v 2.2.26). Approximately, 56% (264,870,861) and 69% (356,686,163) of reads mapped to known genes in hypothalamus and pituitary, respectively. Of the 23,569 known genes to which reads mapped, 3,593 were expressed only in hypothalamus and 3,354 genes only in pituitary. Fragments per Kilobase of transcripts per Million (FPKM) normalized counts were averaged and ranked to identify the most highly expressed (top 1000) genes in each tissue. Gene Ontology (GO) analysis of these two gene sets (using DAVID Bioinformatics Resources (v. 6.7)) identified metabolic and reproduction-related genes shared by both tissues as well as functional categories with tissue-specific enrichment. These transcriptomes will provide an important foundation for identifying molecular mechanisms of energy sensing and fertility using the sheep model.