Molecular cloning of the duck MyoG and MRF4 genes coding region sequence and their differential expression patterns in the breast and leg muscle during fetal development

The MyoG and MRF4 genes encode for transcription factors that play key roles in muscle formation during embryonic and fetal development. Due to the unique functions of these two genes, they have a specific expression pattern in the same muscle tissues. In order to investigate the different developmental expression patterns of the two genes, the coding region sequences of duck MyoG and MRF4 were cloned and their mRNA expression patterns in the duck breast and leg muscles were measured using real-time quantitative polymerase chain reaction (qPCR). The duck MyoG and MRF4 both have a basic helix-loop-helix (bHLH) domain with high homology to several other species. In addition, there is a low homology region at the carboxy-terminus of these two proteins. The mRNA expression of MyoG reaches a peak at embryonic day 14 (E14d) in both the breast muscle and the leg muscle of duck. The peak mRNA expression of MRF4 appears at E14d in the breast muscle and at E18d in the leg muscle. The expression patterns of MyoG and MRF4 were different between the breast muscle and the leg muscle of duck. In the fetal duck, the leg muscle develops earlier than the breast muscle, which may better accommodate the newborn duck to a new environment postnatally.