Transcriptome of Hypothalamus and Pituitary Gland of Pre- and Post-pubertal Brangus Heifers

Puberty is a complex event as hormones, neuropeptides, and neurotransmitters influence synthesis and secretion of gonadotropin releasing hormone and gonadotropins from the hypothalamus and pituitary gland. Objectives of this study were to characterize the transcriptome of these tissues in pre- (PRE) and post- (POST) pubertal Brangus heifers. Heifers (n = 6) were 3/8 Brahman x 5/8 Angus, puberty status was determined with serum concentrations of progesterone, and POST tissues collected during the luteal phase of the estrous cycle. Using the Illumina HiSeq technology, 30 to 40 million single reads of 100 bp were generated from RNAseq libraries of each tissue sample. Reads were assembled and analyzed using the annotated UMD 3.1 bovine assembly. For both tissues, RNA-Seq analyses revealed 22,416 genes. The average number of genes expressed (reads per kilobase per million mapped reads; RPKM > 0.2) in the hypothalamus of PRE and POST heifers were 15,094 and 15,107, whereas the number of genes expressed in the pituitary gland of PRE and POST samples were 14,904 and 14,889, respectively. The number of differentially expressed genes (P < 0.05) among PRE and POST heifers for hypothalamus and pituitary were 457 and 289, respectively. Gene ontology of the highest expressed genes in the hypothalamus included neuro-cytoskeleton, synapse, and transmembrane receptors, whereas in the pituitary gland these were hormones, transcription factors, cell signaling, and DNA-binding. Characterizing the transcriptome of reproductive tissues will aid physiological understanding and development of genomic selection strategies for fertility traits in indicine x taurine composite breeds of cattle.