Transcriptome analysis of sheep follicular development during prerecruitment, dominant, and mature stages after FSH superstimulation.

Sheep is usually a monovular animal; superovulation technology is used to increase the number of offspring per individual and shorten generation intervals. To date, mature FSH superstimulatory treatments have been successfully used in sheep breeding, but much remains unknown about genes, pathways, and biological functions involved in follicular development. Therefore, in this study, we performed transcriptome profiling of small follicles (SFs; 2-2.5 mm), medium follicles (MFs; 3.5-4.5 mm), and large follicles (LFs; > 6 mm) in Mongolian ewes after FSH superstimulation. Furthermore, we identified differentially expressed genes and performed Kyoto Encyclopedia of Genes and Genomes pathway and Gene Ontology enrichment analyses in 3 separate pairwise comparisons. We found that ovarian steroidogenesis was significantly enriched in the SFs versus MFs analysis; the associated genes, cytochrome P450 family 19 (CYP19) and Hydroxy-delta-5-steroid dehydrogenase 3 beta- and steroid delta-isomerase 1 (HSD3B1), were significantly upregulated. Moreover, proline metabolism, glutathione metabolism, and PPAR signaling pathways were significantly enriched in the LFs versus SFs analysis; the associated genes, glutamate-cysteine ligase modifier subunit (GCLM) and cystathionine gamma-lyase (CTH), were significantly upregulated, whereas peroxisome proliferator-activated receptor gamma (PPARγ) was significantly downregulated. In summary, our study provides basic data and possible biological direction to further explore the molecular mechanism of sheep follicular development after FSH superstimulation.