Meat Protein Research Team, National Institute of Livestock and Grassland Science, Tsukuba, Ibaraki, Japan.
Anim Sci J. 2009 Dec;80(6):678-85. doi: 10.1111/j.1740-0929.2009.00684.x.
To clarify muscle type-specific effect of myostatin on myogenic regulatory factors (MRFs), we examined mRNA expression of MRFs in five skeletal muscles of normal (NM) and myostatin-deficient double-muscled (DM) adult Japanese Shorthorn cattle by quantitative reverse-transcribed PCR. Among the four MRFs, namely, Myf5, MyoD, myogenin, and MRF4, MyoD expression was different among the muscles of the DM cattle (P < 0.01) but not of the NM cattle. Meanwhile, MyoD expression was significantly elevated only in masseter (MS) muscle in the DM cattle due to the myostatin deficiency (P < 0.05). Myf5 and MRF4 expression in semitendinosus (ST) was higher in the DM than in the NM cattle (P < 0.05). According to analysis of myosin heavy chain (MyHC) isoform expression, more MyHC-2x and -2a and less -slow isoforms were expressed in the longissimus and ST muscles compared to the MS muscle in both cattle (P < 0.05), but no significant difference in MyHC expression was observed between the NM and DM cattle. Taken together, myostatin has influences on Myf5 and MRF4 expression in faster-type muscles and on MyoD expression in slower-type muscles, suggesting a possible muscle type-specific effect of myostatin in skeletal muscle growth and maintenance.
为了阐明肌肉生长抑制素（myostatin）对肌生成调节因子（MRFs）的肌肉类型特异性作用，我们通过定量逆转录 PCR 检测了正常（NM）和肌肉生长抑制素缺乏型双肌（DM）成年日本短角牛五种骨骼肌中的 MRFs mRNA 表达。在这四种 MRFs 中，Myf5、MyoD、myogenin 和 MRF4 中，DM 牛的肌肉之间 MyoD 表达存在差异（P < 0.01），而 NM 牛的肌肉之间则不存在差异。同时，由于肌肉生长抑制素缺乏，DM 牛的咬肌（MS）肌肉中 MyoD 表达显著升高（P < 0.05）。DM 牛的半腱肌（ST）中的 Myf5 和 MRF4 表达高于 NM 牛（P < 0.05）。根据肌球蛋白重链（MyHC）同工型表达分析，与 MS 肌肉相比，NM 和 DM 牛的背最长肌和 ST 肌肉中更多地表达了 MyHC-2x 和 -2a 以及更少的 -slow 同工型（P < 0.05），但 NM 和 DM 牛之间的 MyHC 表达没有明显差异。总之，肌肉生长抑制素对快肌型的 Myf5 和 MRF4 表达以及慢肌型的 MyoD 表达有影响，表明肌肉生长抑制素在骨骼肌生长和维持方面可能具有肌肉类型特异性作用。
