Investigation of high fecundity genes by nanopore sequencing in sheep (Ovis aries) pituitary.

Background: Reproduction is a complex process, which is influenced by the inheritance of many minor genes and some major genes. The pituitary gland is an important endocrine organ that regulates estrus and reproduction in sheep mainly through hormone synthesis and secretion. Previous studies on reproduction traits have focused mainly on folliculogenesis and ovulation in sheep with different fecundities, and few systematic analyses of the mRNAs expressed in the pituitary have been performed. To explore the intrinsic molecular regulatory mechanisms and gene regulatory network of sheep reproductive traits, key genes affecting multiple fetal traits, such as ovulation number and litter size, were screened to provide a new reference for the study of reproduction traits in sheep.

Result: In this study, three healthy small-tailed Han sheep and three healthy Wadi sheep were selected respectively to form a high-reproduction group (small-tailed Han sheep, HP group) and a low-reproduction group (Wadi sheep, LP group). ONT full-length transcriptome sequencing technology was used for mRNA identification, screening, and functional analysis. A total of 7,123 DEGs were found between the two groups of sheep, including 3,551 genes that were upregulated and 3,572 genes that were downregulated in the HP group. The expression of screened genes PRKACB, MAPK1, CAMK2D, PIK3CB, GNAI3, RAC1, PTK2, ITGB1, PRKCB, MAPK10, and MAPK13 significantly differed between the HP and LP groups. GO and KEGG terms related to pituitary function and reproduction were enriched, including reproductive processes, responses to stimuli, and synapses, as well as the mTOR signaling pathway, PI3K-Akt signaling pathway, cAMP signaling pathway, ERK1/2 signaling pathways and MAPK signaling pathways.

Conclusions: Our results clearly indicate that the DEGs detected were involved in the development of morphology and structure of tissues and organs, as well as the secretion of hormones in the endocrine system, which could provide a scientific basis for elucidating the genetic mechanisms of high reproduction in sheep.