Comparative transcriptomics in the hypothalamic-pituitary-gonad axis of mammals and poultry.

The hypothalamic-pituitary-gonad (HPG) axis is vital for reproductive activities in vertebrates. The large-scale comparative analyses of gene expression in the HPG axis across vertebrates have not been carried out yet. Here we collected 175 high-quality RNA-seq samples of hypothalamus, pituitary, ovary and testis from eight species (four mammals and four poultry) to compare transcriptome in the HPG axis, and to detect key pathways and related genes associated with reproduction. We demonstrated the distinguished difference in gene expression of the HPG axis between mammalian and avian species by a series of bioinformatics analysis, including gene differential expression, the phylogeny analysis of gene expression, and their functional annotations. We revealed two pathways, i.e., neuroactive ligand-receptor interaction and calcium signaling pathway, which play important roles in animal reproduction. In these two pathways, we detected 17 differentially expressed genes shared in 4 tissues, while 13, 27, and 27 were specifically differentially expressed genes in hypothalamus, pituitary and ovary, respectively. Our study on the comparative transcriptomics in the HPG axis across species will provide novel knowledge for exploring the molecular mechanism underlying reproductive traits in animals.