Effects Of Dexamethasone On The Expressions Of Myomaker And MyoD Genes In Mice Skeletal Muscle

Myomaker is a muscle-specific transmembrane protein that is essential for myocyte fusion.MyoD is an important regulatory factor during the process of muscle development and formation.In severe and persistent stress state,the organism will produce excessive glucocorticoids,which cause muscle atrophy and have adverse effects on the body's normal growth.In order to investigate the functions of myomaker and MyoD on the muscle repair and regeneration process after the excess glucocorticoids act on the body,in this study,the dexamethasone(Dex,artificially synthesized glucocorticoids)was injected intraperitoneally into mice at a dose of 20 mg/kg/d.And saline was injected with the same way as control group.After continuous intraperitoneal injection for one week,the quadriceps femoris were sampled on the first day,the fourth day,the seventh day and the fourteenth day after the last injection,and the expressions of myomaker and MyoD genes were detected by immunohistochemistry,qRT-PCR and Western blotting methods.The results showed that:(1)By using PCR method,we amplified the full-length CDS of myomaker gene in adult mice skeletal muscle,and the electrophoresis test showed that the stripe was bright.Moreover,the sequencing test result of the amplified fragment coincided with the registered sequence of myomaker gene published at NCBI.In addition,it was further confirmed that the myomaker protein was expressed in heathy adult mice skeletal muscle by immunohistochemistry and Western blotting tests.(2)By using immunohistochemistry method,we found that the myomaker protein was mainly expressed on the myocyte membrane,and the MyoD protein was mainly in the nucleus.The results of optical density analysis showed that the expression of myomaker protein was weaker on the first day after the last injection,and MyoD protein expression was stronger.And both of them are increased significantly on the fourth day after the last injection,and then maintained at normal level.(3)By using qRT-PCR and Western blotting methods,we found that the expressions of myomaker mRNA and protein decreased significantly on the first day after the last treatment,and MyoD mRNA and protein expressions had rising trend.On the fourth day after treatment,the expressions of mRNA and protein of myomaker and MyoD increased significantly,and then maintained at normal level.Conclusion:Myomaker gene was expressed in healthy adult mice.And the expressions of myomaker and MyoD increased significantly on the fourth day after dexamethasone treatment,indicating that dexamethasone could promote the expressions of myomaker and MyoD gene to make adaptive preparation for possible muscle regeneration.