Hypothalamic and pituitary transcriptome profiling using RNA-sequencing in high-yielding and low-yielding laying hens.

The reproductive physiology and laying performance of laying hens are regulated by the hypothalamus and pituitary. To understand the mechanism of egg laying regulation, we sequenced and analysed the hypothalamus and pituitary expression profiles in high- and low-yielding laying Chinese Dagu Chickens (CDC) using RNA-seq. More than 46 million clean reads and 24,873 tentative genes were obtained using the Gallus gallus genome as a reference. Transcriptome analysis in hypothalamus and pituitary revealed seven and 39 differentially expressed genes (DEGs) between high- and low-yielding CDC hens, respectively. A total of 24 and 22 DEGs were up-regulated and down-regulated, respectively, and 13 novel genes were identified. Functional annotation and pathway enrichment analysis showed that DEGs in the hypothalamus were mainly enriched in glycosaminoglycan biosynthesis. DEGs significantly enriched in the pituitary primarily affected the extracellular matrix, the protein extracellular matrix, and the extracellular space. Pathways involving phenylalanine metabolism, 2-oxocarboxylic acid metabolism, the glycosphingolipid biosynthesis-ganglion series, and local adhesion were significantly enriched in the pituitary. Eight DEGs, PRDX6, TRIB2, OVCH2, CFD, Peptidase M20, SLC7A10, and two other amino acid transporters, are involved in the metabolism and transport of amino acids. To our knowledge, this is the first study comparing the hypothalamus and pituitary transcriptomes of high- and low-yielding laying hens. Our findings suggest that putative differences in gene expression can provide a base for further research in this field. Moreover, we identified increased expression of genes involved in amino acid metabolism, glycosaminoglycan biosynthesis, and oestrogen negative feedback systems in low-yielding laying hens, highlighting their potential as biomarkers of egg production.