Establishment of primary chicken embryo myoblast cell culture, antigenic epitopes prediction and production of anti activin receptor type IIB polyclonal antibody in chicken.

The detection of activin receptor typeIIB (ACTRIIB) protein, a prominent negative muscle growth regulator has paramount value in augmenting growth traits through molecular breeding schemes in chicken. The study was formulated to establish primary chicken embryo myoblast culture (CEM) using 9th and 18th day chick embryos and to develop antibodies for immunodetection of ACTRIIB protein. The physicochemical and structural attributes of the ACTRIIB sequence were evaluated to identify substantial antigenic regions. The ACTRIIB sequence was transfected into CEM and expressed protein was injected subcutaneously into rats to produce hyperimmune serum. The average propensity of protein sequence for beta turns, surface accessibility, chain flexibility, antigenicity, hydrophilicity and linear epitopes was 0.978, 1.000, 0.991, 1.038, 1.258 and 0.512, respectively. The 9th day CEM exhibited confluency (80-90%) earlier than the 18th day. The expression of myogenic regulatory factors in 9th day myoblasts was higher than the 18th day by 7.28, 5.16, 6.28 and 6.93 folds for MYF5, MRF4, MYOG and MYOD, respectively. The ACTRIIB mRNA was downregulated by 2.54 folds on the 9th day compared to the 18th day myoblasts and protein varied significantly between 9th and 18th day myoblasts. The CEM culture can be harnessed unequivocally to investigate molecular mechanisms underlying muscle growth besides raising antibodies.

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.

Expression Profiling of Activin type IIB Receptor During Ontogeny in Broiler and Indigenous Chicken.

Augmenting the meat production is among the primary breeding objective of genetic selection programs in poultry production. However, the knowledge about the expression of genes regulating muscle growth at the molecular level is inadequate. Activin type IIB receptor (ACTRIIB) has been reported to play vital role in the negative regulation of muscle growth by binding to multiple members of transforming growth factor-ß superfamily. The present investigation was carried out to comprehend the trend of ACTRIIB messenger RNA in pectoralis major muscle during embryonic (E5-20) and post embryonic age (days 1, 14, 28, and 42) in both Control Broiler (CB) and Aseel by using Real-time PCR. The expression profile of ACTRIIB gene displayed a similar trend in CB and Aseel, however Aseel showed significantly (P < 0.001) higher transcription throughout the period. The fold change in expression of ACTRIIB in Aseel relative to CB varied from 3.94 to 14.72 folds and 3.28 to 7.14 folds during embryonic and post embryonic age, respectively. ACTRIIB exhibited its peak on E7, E11, and E16 during embryonic age, which coincides with the formation of primary and secondary muscle fibers in both lines. While at the time of post-embryonic age, ACTRIIB showed highest transcription on day 1 and lowest transcription on day 28 in both CB and Aseel. Within each line, the expression of ACTRIIB differed significantly (P < 0.001) between days in the course of embryonic and post-embryonic period. ACTRIIB gene expression had significant (P < 0.05) effect on all carcass traits except neck weight. Our results suggest that Aseel expressed higher levels of ACTRIIB transcript than CB. The study inferred that expression pattern of ACTRIIB was analogous in both CB and Aseel, which might imply that molecular mechanisms underlying muscle development and regulation are comparable in nature.