Discordant expression of utrophin and its transcript in human and mouse skeletal muscles
Discordant expression of utrophin and its transcript in human and mouse skeletal muscles
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DOI：
10.1097/00005072-199903000-00003
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发表时间：
1999-03-01
影响因子：
3.2
通讯作者：
Jasmin, BJ
中科院分区：
文献类型：
--
作者：
Gramolini, AO;Karpati, G;Jasmin, BJ
为了确定调节人类骨骼肌中肌营养不良蛋白表达的机制，我们检查了正常受试者以及杜氏肌营养不良症 (DMD) 和多发性肌炎 (PM) 患者活检组织中肌营养不良蛋白及其转录物的表达和分布。我们首先通过免疫印迹确定，与正常受试者的活检相比，DMD 和 PM 患者肌肉样本中的肌营养蛋白水平确实较高，如之前所示。相比之下，通过 RT-PCR 测定和原位杂交测定的肌营养蛋白 mRNA 水平，在正常受试者与 DMD 和 PM 患者的肌肉样本中是相同的。在这些实验中，我们还注意到，虽然肌营养不良蛋白转录物具有在正常人类肌肉纤维的突触后肌浆内积累的明显趋势，但突触积累的程度远小于我们最近在小鼠肌肉纤维中观察到的程度。从 DMD 和 PM 患者获得的肌纤维突触和突触外区室中肌营养蛋白转录物的分布与沿正常受试者肌纤维观察到的分布相似。最后，我们还监测了注射心脏毒素诱导退化的小鼠肌肉再生过程中肌营养不良蛋白及其转录物的表达。在这些再生的肌肉中，我们通过免疫印迹和免疫荧光观察到，utropin 水平大幅增加（4 至 7 倍）。与我们在人类肌肉中获得的结果一致，再生小鼠肌肉中肌营养蛋白水平的增加并不伴随肌营养蛋白转录物丰度的平行变化。综上所述，这些结果表明，在某些条件下，肌肉中肌营养蛋白及其转录物的水平受到不一致的调节，从而突出了转录后调节机制在控制骨骼肌纤维中肌营养蛋白水平方面的重要贡献。
In order to determine the mechanisms regulating utrophin expression in human skeletal muscle, we examined the expression and distribution of utrophin and its transcript in biopsies from normal subjects as well as from Duchenne muscular dystrophy (DMD) and polymyositis (PM) patients. We first determined by immunoblotting that in comparison to biopsies from normal subjects, utrophin levels were indeed higher in muscle samples from both DMD and PM patients as previously shown. By contrast, levels of utrophin mRNAs as determined by both RT-PCR assays and in situ hybridization, were identical in muscle samples obtained from normal subjects versus DMD and PM patients. In these experiments, we also noted that while utrophin transcripts had a clear tendency to accumulate within the postsynaptic sarcoplasm of normal human muscle fibers, the extent of synaptic accumulation was considerably less than that which we recently observed in mouse muscle fibers. The distribution of utrophin transcripts in synaptic and extrasynaptic compartments of muscle fibers obtained from DMD and PM patients was similar to that seen along muscle fibers from normal subjects. Finally, we also monitored expression of utrophin and its transcripts during regeneration of mouse muscle induced to degenerate by cardiotoxin injections. In these regenerating muscles, we observed by both immunoblotting and immunofluorescence, a large increase (4- to 7-fold) in the levels of utrophin. In agreement with our results obtained with human muscle, the increase in utrophin levels in regenerating mouse muscle was not accompanied by parallel changes in the abundance of utrophin transcripts. Taken together, these results indicate that the levels of utrophin and its transcript in muscle are discordantly regulated under certain conditions thereby highlighting the important contribution of post-transcriptional regulatory mechanisms in the control of utrophin levels in skeletal muscle fibers.