Genetic polymorphism in core promoter sequence of ACTRIIB gene and association analysis with growth traits in chicken.

Molecular breeding exploiting candidate genes is burgeoning reproductive approach to improve growth traits in poultry. The activin type IIB receptor (ACTRIIB) is a negative growth regulator, modulating action of many muscle growth regulators. PCR-single-strand conformation polymorphism was employed to unravel polymorphism in promoter region of the ACTRIIB gene and delineate its association with growth traits in Aseel and control broiler (CB). Analysis of 5' promoter region (1122bp) of ACTRIIB gene identified five SNPs, that is g. [56 G > C (SNP1), 352A > C (SNP2), 580G > A (SNP3), 625C > T (SNP4) and 962C > T (SNP5)] at SMAD, paired box 7 homeodomain binding motif, GC box and bHLH-PAS type transcription factors in CB and Aseel. CB had significantly higher body weight (BW) and average daily gain (ADG) at all SNP sites, except at SNP 1. The haplotype construction resulted 8 haplotypes in CB and Aseel population. The BW and ADG differed significantly (p < .05) at all ages in CB and Aseel. The diplotypes H1H8 and H1H4 manifested higher BW and ADG, while diplotypes H3H8 and H3H7 displayed BW and ADG at each age in both lines (p < .05). Aseel exhibited higher expression of ACTRIIB gene than CB by 70.17, 4.83, 1.41, 2.38, 5.13, 1.20, 2.90, 6.53 and 11.75 times for h1h2, h1h3, h1h4, h1h6, h1h7, h1h8 h3h4, h3h7 and h3h8, respectively. The H3H8 and H3H7 diplotypes exhibited higher level of mRNA and protein than H1H8 and H1H4. The regulatory upstream region of ACTRIIB gene demonstrates high degree of genetic diversity and can be harnessed as potential marker in genetic selection programmes for increasing meat production.