Transcriptome analysis reveals steroid hormones biosynthesis pathway involved in abdominal fat deposition in broilers

Excessive abdominal fat deposition reduces the feed efficiency and increase the cost of production in broilers. Therefore, poultry breeders have the important of developing a breed with reduced abdominal fat deposition. Abdominal fat deposition is a highly complex biological process, and its molecular basis remains elusive. In this study, we performed transcriptome analysis to compare gene expression profiles at different stages of abdominal fat deposition to identify the key genes and pathways involved in abdominal fat accumulation. We found that abdominal fat weight (AFW) increased gradually from day 35 (D35) to 91 (D91), and then decreased at day 119 (D119). Accordingly, after detecting differentially expressed genes (DEGs) by comparing gene expression profiles at D35 vs. D63 and D35 vs. D91, and identifying gene modules associated with fat deposition by weighted gene co-expression network analysis (WGCNA), we performed intersection analysis of the detected DEGs and WGCNA gene modules and identified 394 and 435 intersecting genes, respectively. The results of the gene ontology (GO) functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses showed that the steroid hormone biosynthesis and insulin signaling pathways were co-enriched in all intersecting genes, steroid hormones have been shown that regulated insulin signaling pathway, indicating the importance of the steroid hormone biosynthesis pathway in the development of broiler abdominal fat. We then identified six hub genes (ACTB, SOX9, RHOBTB2, PDLIM3, NEDD9, and DOCK4) related to abdominal fat deposition. Further analysis also revealed that there were direct interactions between 6 hub genes. SOX9 has been shown to bind to proteins required for steroid hormone receptor binding, and RHOBTB2 indirectly regulates the steroid hormones biosynthesis through cyclin factor, and ultimately affect fat deposition. Our results suggest that the genes RHOBTB2 and SOX9 play an important role in fat deposition in broilers, by regulating steroid hormone synthesis. These findings provide new targets and directions for further studies on the the mechanisms of fat deposition in chicken.