Expression profile analysis of estrous-phased ovarian tissue of high and low prolific lines of inbred Swiss albino mice.

Abstract

Background: Litter size in mice is an important fitness and economic feature that is controlled by several genes and influenced by non-genetic factors too. High positive selection pressure in each generation for Litter size at birth (LSB), resulted in the development of high and low prolific lines of inbred Swiss albino mice (SAM). Despite uniform management conditions, these lines showed variability in LSB across the generation.

Methods and results: Variation in estrous-phased ovarian gene expression between high (LSB ≥ 12) and low prolific lines (LSB ≤ 3) of F₄ inbred SAM, was explored using RNA-Seq. Estrous phase assessment was done using vaginal cytology. A total of 870 differentially expressed genes (DEGs) were identified; among which, 287 genes were significantly up-regulated while 583 genes were down-regulated in HLS as compared to the LLS group. DEGs were assigned to 166 Gene Ontology (GO) terms and KEGG pathways. In HLS, the significantly up-regulated DEGs were involved in ovarian cell-cell signaling, regulation of biological activity and ovarian metabolic-associated pathways. Most down-regulated DEGs were expressed in immune-related pathways, indicating that immunological dampening is associated with a high ovulation rate and higher level of progesterone concentration leading to physiological changes responsible for higher fecundity.

Conclusions: The present study, based on bulk RNA-seq analysis reflects the aggregate gene expression of the whole ovarian tissue, and reveals 24 DEGs that could be used as candidates for litter size attributes in future polymorphism and functional studies to gain further insights into the mechanisms underlying litter size variations in animals.