Myostatin (MSTN) is a negative regulator of skeletal muscle growth and development. The skeletal muscle in MSTN-/- mice is significantly hypertrophied, with muscle fiber type Ⅱ increasing significantly while muscle fiber type I decreasing. However, it is still not clear how the skeletal muscle types change in MSTN-/- pigs, and how the mechanism for MSTN regulates fiber types, especially in large animals like pigs. This study conducted a comprehensive analysis of the composition of skeletal muscle fibers in MSTN-/- pigs produced in our laboratory. It was observed that, compared with wild-type (WT) pigs, both the total mass of skeletal muscle and type Ⅱb muscle fibers increased significantly (P<0.01), while the type I and type Ⅱa muscle fibers decreased significantly (P<0.01), in MSTN-/- Meishan pigs. In addition, to explore the influence of MSTN on muscle fiber type and its regulation mechanism in the embryonic stage, this study selected a few genes (Myf5, Mef2d, MyoD and Six1) associated with muscle fiber type and validated their expression by quantitative RT-PCR. Herein, it was found that Myh7, Myh2, Myh4 and Myh1 can be detected in the skeletal muscle of pigs at 65 days of gestation (dg). Compared with WT pigs, in MSTN-/- Meishan pigs, Myh7 decreased significantly (P<0.01), while Myh4 (P<0.001) and Myh1 (P<0.05) increased significantly. Meanwhile, the increased expression of Myf5 (P<0.05), Mef2d (P<0.01) and Six1 (P<0.05) in MSTN-/- Meishan pigs suggested that MSTN should regulate the directional development of muscle fiber types in the early stage of embryonic development. Thus, at the embryonic stage, the type Ⅱ muscle fibers began to increase in MSTN-/- pigs. These results can provide valuable information not only for pig meat quality improvement, but also for the study of human skeletal muscle development and disease treatment.

QIAN Li-li;XIE Jing-yi;GAO Ting;CAI Chun-bo;JIANG Sheng-wang;BI Han-fang;XIE Shan-shan;CUI Wen-tao

Institute for Translational Medicine,The Affiliated Hospital of Qingdao University,Qingdao University,Qingdao 266021,P.R.China;Institute of Animal Sciences,Chinese Academy of Agricultural Sciences,Beijing 100193,P.R.China;College of Animal Medicine,China Agricultural University,Beijing 100193,P.R.China

农业科学学报（英文）

[1]QIAN Li-li;XIE Jing-yi;GAO Ting;CAI Chun-bo;JIANG Sheng-wang;BI Han-fang;XIE Shan-shan;CUI Wen-tao-.Targeted myostatin loss-of-function mutation increases type Ⅱ muscle fibers in Meishan pigs)[J].农业科学学报（英文）,2022(01):188-198

Meishan,hypertrophied,Mef2d,Myh2,Myh4,Myh1,dg

Targeted,myostatin,loss,function,mutation,increases,muscle,fibers,pigs,Myostatin,MSTN,negative,regulator,skeletal,growth,development,mice,significantly,increasing,decreasing,However,still,not,clear,how,types,change,mechanism,regulates,especially,large,animals,like,This,study,conducted,comprehensive,analysis,composition,produced,our,laboratory,It,was,observed,that,compared,wild,WT,both,total,mass,increased,decreased,In,addition,explore,influence,its,regulation,embryonic,stage,this,selected,few,genes,Myf5,MyoD,Six1,associated,validated,their,expression,by,quantitative,Herein,found,Myh7,detected,days,gestation,Compared,Meanwhile,suggested,should,directional,early,Thus,began,These,results,provide,valuable,information,only,meat,quality,improvement,but,also,human,disease,treatment

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