Long non-coding RNA (LncRNA) have been identified as important regulators in the hypothalamic-pituitary-ovarian axis associated with sheep prolificacy. However, their expression pattern and potential roles in the pituitary are yet unclear. To explore the potential mRNAs and lncRNAs that regulate the expression of the genes involved in sheep prolificacy, we used stranded specific RNA-seq to profile the pituitary transcriptome (lncRNA and mRNA) in high prolificacy (genotype FecB BB, litter size = 3; H) and low prolificacy sheep (genotype FecB B+; litter size = 1; L). Our results showed that 57 differentially expressed (DE) lncRNAs and 298 DE mRNAs were found in the pituitary between the two groups. The qRT-PCR results correlated well with the RNA-seq results. Moreover, functional annotation analysis showed that the target genes of the DE lncRNAs were significantly enriched in pituitary function, hormone-related pathways as well as response to stimulus and some other terms related to reproduction. Furthermore, a co-expression network of lncRNAs and target genes was constructed and reproduction related genes such as SMAD2, NMB and EFNB3 were included. Lastly, the interaction of candidate lncRNA MSTRG.259847.2 and its target gene SMAD2 were validated in vitro of sheep pituitary cells. These differential mRNA and lncRNA expression profiles provide a valuable resource for understanding the molecular mechanisms underlying Hu sheep prolificacy.

Toll-like receptors (TLRs) play crucial roles in innate immunity, but their function in reproduction remains poorly understood. This study investigated the expression patterns and localization of TLR1-9 in the reproductive system of Hu sheep and their potential association with prolificacy. All TLRs were expressed in the oviduct, uterus, and ovary, with TLR6 showing significantly higher expression in the oviduct, while TLR3, TLR6, and TLR7 were predominantly expressed in the ovary. Following this initial screening, we focused on TLR2, TLR6, and TLR7 for detailed analysis. Immunohistochemical analysis revealed that TLR2, TLR6, and TLR7 were localized in the luminal epithelium and circular muscle of the oviduct, the luminal and superficial glandular epithelium of the uterus, and in ovarian follicles at all developmental stages. A comparative analysis between high-prolificacy (HP) and low-prolificacy (LP) Hu sheep demonstrated significantly lower TLR2 expression in the reproductive organs of HP sheep, while TLR6 expression was higher and TLR7 expression was lower in HP ovaries compared to LP ovaries. Notably, TLR7 was observed around apoptotic bodies of granulosa cells, suggesting a potential role in follicular development through the regulation of granulosa cell apoptosis. These findings establish a novel link between innate immunity and reproductive function in sheep, suggesting that TLRs, particularly TLR2, TLR6, and TLR7, may serve dual roles as immune sentinels and reproductive regulators influencing ovine fertility.