A functional variant in the promoter region of IGF1 gene is associated with chicken abdominal fat deposition.

Insulin-like growth factor 1 (IGF1) plays an important role in the regulation of cell growth, proliferation, differentiation, and apoptosis. Previously several studies revealed that genotypes of chicken IGF1 c.-366A > C were significantly associated with abdominal fat weight and body weight in chickens. But the underlying mechanism is still unknown. To investigate the mechanism underlying the association, herein, we performed IGF1 gene mRNA expression profiling, a dual-luciferase reporter assay and electrophoretic mobility shift assay (EMSA). Quantitative real-time PCR results showed that IGF1 gene was widely expressed in 14 tissues. The mRNA expression levels of IGF1 gene in both abdominal fat and jejunum were significantly higher in fat broilers than in lean broilers. However, the opposite results were observed in the pancreas. The reporter gene assay showed that the promoter luciferase activity of allele A was significantly higher than that of allele C (P < 0.05). In addition, the luciferase activity of allele A promoted by the transcription factor AP1 and OCT1 was higher than that of allele C (P < 0.05). Electrophoretic mobility shift assay result showed that allele A binding to the transcription factor AP1 and OCT1 was stronger than that of allele C. All in all, our data indicated that the IGF1 gene c.-366A > C is a functional SNP responsible for chicken adipose deposition.