Clone And Developmental Expression Of MyoG And MRF4 Genes In Duck Skeletal Muscle

MyoG and MRF4 factors belong to MyoD family,which play an important role in the the muscle fiber differentiation at the later stage of embryogenesis.MyoG play a key role in the fusion period of myoblast,and MRF4 is important for the muscle differentiation.Total RNA was extracted from breast muscle of duck at 14th day during embryonic period,then the complete CDS of MyoG and MRF4 genes was cloned.The characterization of expression of duck MyoG and MRF4 genes in breast muscle and leg muscle at the different time was detected by real-time fluorescent PCR.The developmental expression pattern of embryonic muscle by observing histological section of breast muscle and leg muscle.The main results are as follows:1.The sequence length of MyoG and MRF4 is 684bp and 723bp,which code 227 and 240 amino acid residues.The MyoG nucleotide and amino acid homology of duck and chicken is 90.9%and 92.1%,and the duck have high identity with other species.The homology of duck MRF4 with chick are 92.0%and 93.8%,respectively,and above 60% with other species.2.The duck MyoG and MRF4 gene both contain a bHLH domain,which have high identity at 100%with Mammals There are 2 and 6 amino acid variations compared to the sequences of the zebrafish MyoG and MRF4;there are 7 variations of the two genes at the bHLH domain.3.There are three kinds of secondary structure on duck MyoG and MRF4 gene.the rate of random coil proportion is about 65%as the highest one,the next one is the alpha helix about 30%,and the lowest one is 5%of extended strand.There are 10 phosphorylation sites on the MyoG peptide bond,Ser(7),Thr(2) and Tyr(1);and Ser (18),Thr(3),Tyr(0) for MRF4.The most of the phosphorylation sites distribute in the two sides of the peptide bond.4.The mRNA expression were detected in different level in breast muscle and leg muscle at E10d,E14d,E18d,E22d,E27d and p7d by real-time fluorescent PCR.In leg muscle,the peak time of MyoG and MRF4 mRNA come at 14d,18d,the time of lowest expression is 27d,then the mRNA level increased at a high level the 7^th days after born.The highest level of mRNA expression of the two genes in breast muscle is at 14d, then the mRNA level goes down.The mRNA expression of MyoG at 27d is obviously lower than it at 7d.5.The mRNA expression of MyoG in breast muscle and leg muscle reached the highest level on 14d and the lowest level on the 27d,the mRNA expression of MyoG was higher in breast muscle than that in leg muscle at the embryonic development stage,and it was contrary after born.The mRNA expression of MRF4 in breast muscle reached the peak on the 14d.The mRNA expression of MRF4 in leg muscle reached the peak on the 18d.Then they would decline at the difference degree.The mRNA expression of MRF4 in breast muscle is much higher than that in leg muscle.6.The result of histological section of breast muscle and leg muscle indicate that the form of leg muscle fiber was earlier than that of leg muscle fiber.