A 7-bp Insertion/Deletion Functional Variation in Fatty Acid Synthase Gene Is Associated with Abdominal Fat Accumulation

Reducing abdominal fat (AF) in broilers is a key objective in broiler breeding, as excessive AF deposition has an unfavorable effect on reproductive and growth traits. Fatty acid synthase gene (FASN) encodes the fatty acid synthase, which promotes fatty acid synthesis and lipid synthesis. Our previous study identified a 7-bp InDel variant (g.4944396_4944402delGACTTCA, rs1060467633) in intron 42 of chicken FASN, demonstrating a marked association with chicken AF. To investigate the underlying mechanism of this association, we conducted dual-luciferase reporter assay, bioinformatics analysis and electrophoretic mobility shift assay (EMSA). Luciferase reporter showed that the deletion allele had significantly higher activity than the insertion allele (p < 0.05), indicating its potential role in regulating gene expression. Bioinformatics analysis and EMSA indicated that the insertion allele created binding site for cAMP-responsive element-binding protein 1 (CREB1). Luciferase reporter confirmed that the insertion allele suppresses FASN expression through CREB1, with a stronger inhibitory effect than the deletion allele. In conclusion, rs1060467633, as a functional variant, regulates FASN expression and AF deposition by altering the binding to CREB1 in chickens.