beta-MHC transgene expression in suspended and mechanically overloaded/suspended soleus muscle of transgenic mice.
beta-MHC transgene expression in suspended and mechanically overloaded/suspended soleus muscle of transgenic mice.
复制标题
转基因小鼠悬浮和机械超载/悬浮比目鱼肌中的 β-MHC 转基因表达。
DOI：
10.1152/ajpregu.1997.272.5.r1552
复制
发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Tsika,RW
中科院分区：
文献类型：
--
作者：
McCarthy,JJ;Fox,AM;Tsika,GL;Gao,L;Tsika,RW
非负重（NWB）活动[太空飞行和后肢悬吊（HS）]导致比目鱼肌质量损失、慢-快纤维类型转换以及β-肌球蛋白重链（β-MHC）蛋白和mRNA表达降低。为了确定β-MHC启动子序列所需的β-MHC表达减少响应HS，我们已经修改了现有的非侵入性后肢减重模型，以适应使用（转基因）小鼠。HS后2周，身体和肌肉（比目鱼肌>腓肠肌>跖肌）的重量下降，是HS比目鱼肌中的组织化学分类的I型纤维的比例。北方印迹分析显示，内源性mRNA代表β-MHC、慢肌球蛋白轻链1和2以及心脏/慢肌钙蛋白C减少，而代表骨骼肌钙蛋白C、肌肉肌酸激酶和甘油醛-3-磷酸脱氢酶的mRNA增加。从携带转基因的小鼠的HS比目鱼肌（SS）制备的蛋白质提取物，所述转基因包含野生型（wt）小鼠β-MHC启动子的5.6或0.6个酶（β 5.6 wt，β 0.6wt）和携带MCAT、富C和β e3亚区的同时突变（mut）的人（β 5.6mut3，β 0.6mut3）显示氯霉素乙酰转移酶（CAT）比活性相对于各自对照降低。对于转基因β 5.6mut3，品系85，观察到CAT mRNA降低。两周的同时施加的机械过载（电消融）和HS（MOV/HS）抵消了绝对和标准化SS重量的损失，但没有降低β 0.6wt转基因表达。这些转基因结果表明，600个碱基对的β-MHC启动子内的调节序列足以在HS 2周后指导β-MHC转基因的转录降低。
Non-weight-bearing (NWB) activity [space flight and hindlimb suspension (HS)] results in the loss of soleus muscle mass, a slow-to-fast fiber-type conversion, and decreased beta-myosin heavy chain (beta-MHC) protein and mRNA expression. To identify beta-MHC promoter sequences required for decreased beta-MHC expression in response to HS, we have modified an existing noninvasive hindlimb unweighting model to accommodate the use of (transgenic) mice. After 2 wk of HS, body and muscle (soleus > gastrocnemius > plantaris) weights were decreased as was the proportion of histochemically classified type I fibers in HS soleus muscle. Northern blot analysis revealed decreases in endogenous mRNA representing beta-MHC, slow myosin light chain 1 and 2, and cardiac/slow troponin C, whereas those representing skeletal troponin C, muscle creatine kinase, and glyceraldehyde-3-phosphate dehydrogenase increased. Protein extracts prepared from HS soleus (SS) muscle of mice harboring transgenes comprised of 5.6 or 0.6 kilobase of wild type (wt) mouse beta-MHC promoter (beta 5.6 wt, beta 0.6wt) and those carrying the simultaneous mutation (mut) of the MCAT, C-rich, and beta e3 subregions (beta 5.6mut3, beta 0.6mut3) revealed decreases in chloramphenicol acetyltransferase (CAT) specific activity relative to respective controls. Decreased CAT mRNA was observed for transgene beta 5.6mut3, line 85. Two weeks of the simultaneous imposition of mechanical overload (synergist ablation) and HS (MOV/HS) countermanded the loss in absolute and normalized SS weight but did not decrease beta 0.6wt transgene expression. These transgenic results demonstrate that regulatory sequences within a 600-base pair beta-MHC promoter are sufficient to direct decreased transcription of beta-MHC transgenes after 2 wk of HS.