Transcriptomic analysis reveals stage-specific cholesterol metabolism and steroidogenic in theca layer cells during...

Ovarian follicle development is a critical factor affecting laying performance in poultry. Follicles are mainly composed of the granulosa layer cells and theca layer cells (TLs). However, the regulatory role of TLs remains inadequately understood. This study explored the abundance of differentially expressed genes (DEGs) in chicken TLs across small yellow follicles (SYFT), the smallest hierarchical follicle (F6T), and the largest hierarchical follicle (F1T) through transcriptome analysis. Results revealed that the top abundance DEGs were linked to cholesterol metabolism (MSMO1, NPC1) and steroid hormone synthesis (STAR, CYP11A1, CYP19A1, POR, NR0B1). Notably, genes involved in steroid hormone synthesis (STAR, CYP11A1, and CYP19A1) were highly expressed at the F6T stage. Up-regulated DEGs in F6T were primarily enriched in metabolism pathways, including one carbon pool by folate and citrate cycle, which contribute to elevated cholesterol synthesis (MSMO1) at this stage. While cholesterol metabolism (NPC1, NR0B1, and POR) were prominent at the SYFT stage, where up-regulated DEGs were linked to cell differentiation such as Wnt and mTOR signaling pathways. Key genes including CYP19A1, CYP17A1, POR, NPC1, VLDLR, and NR0B1 were predominantly found in profiles 3 and 1, which represented significant trends identified through trend analysis. The main KEGG pathways included cell cycle, homologous recombination, metabolism and transport. This study highlights that TLs shift their transcriptional program from cholesterol transport in small yellow follicles to cholesterol synthesis and steroidogenesis in hierarchical follicles, revealing a key transcriptional program governing follicle development in chickens.