Background: Myostatin gene (MSTN) and myogenic regulatory factors (MRFs) have an important role in muscle development. The aim of this study is investigate the expression level of MSTN gene and myogenic regulatory factors (MyoD and MyoG) at embryonic days 7, 13, and 16 and 3days post hatch in Cobb broiler chickens as well as the difference in their expression at the marketing age in higher and lower body weight birds. Also, to screen nucleotide polymorphism in a whole translated region of MSTN gene among the two different weights. Methods: Quantitative real-time PCR was used for assessment of the target genes expression at different embryonic stages of Cobb broiler and at marketing age. Cobb MSTN exons were sequenced for their characterization. Results: The expression profile of MSTN and MyoG at different embryonic stages showed the highest significant increase at day 7 (125±0.06, 25±0.99 fold), and their expression decrease at E13, 16 and 3 days post hatch. The relative expression level of MyoD was significantly high (p≤ 0.05) at E7 (42.79±2.03 fold) and reach its peak at E16 (54.95±2.92 fold) and decreased to 6.80±1.30 fold at three days post hatch. At marketing age, there were differences in expression level of MSTN, MyoD, and MyoG in Cobb broiler among high and low body weight birds. Concerning MSTN gene sequence data; high similarity in the sequences was detected among high and low body weights at the three exons of Cobb broiler. Conclusions: There is strong putative role for MSTN, MyoD, and MyoG gene expression at embryonic day 7 in Cobb broiler and this role were also found for these genes at the marketing age that influence bird's weights. Additionally, MyoD gene expressed at early and late embryonic life, 3 days post hatch and at marketing age, suggesting its role in muscle differentiation and development.
