Transcriptomics of the HPG axis from in vitro or in vivo-produced dairy male calves

In cattle, two of the most common technologies for embryo production are “in vivo” (MOET) or “in vitro” (IVP). IVP can sometimes impact fetal growth, resulting in large offspring, although most IVP calves are born apparently healthy. However, gene regulation changes in the organs involved in the developmental process in phenotypically normal postnatal calves are unknown and could indicate physiological programming. The objective of this study was to compare the transcriptomic modifications in organs of the hypothalamus-pituitary-gonadal and adrenal (HPGA) axes between IVP and MOET male calves of three months of age. RNA extracted from the HPGA organs samples (n=4 per group) were sequenced through RNAseq. The raw files were subjected to a bioinformatic pipeline to determine differentially expressed genes (FDR<0.05) in IVP versus MOET samples and the KEGG pathways enriched by these genes (FDR < 0.1). Pathways related to the reproductive process (GnRH secretion in hypothalamus, GnRH signaling in pituitary and steroidogenesis in testicle) were stimulated in IVP calves, suggesting an early activation of the HPG axis in male IVP calves when compared to MOET counterparts. Samples were obtained from the hypothalamus, pituitary, testicle and adrenal from three-month-old IVP calves (n=4) and control MOET calves (n=4).