Jung H H, Lieber R L, Ryan A F
Department of Surgery/Otolaryngology, University of California at San Diego School of Medicine and Veterans Affairs Medical Center, La Jolla, California 92093, USA.
Am J Physiol. 1998 Jul;275(1):C68-74. doi: 10.1152/ajpcell.1998.275.1.C68.
The purpose of this study was to quantify the type and amount of myosin heavy chain (MHC) mRNA within muscles of different developmental origins to determine whether the regulation of gene expression is comparable. Seven MHC isoforms were analyzed in rat adult limb (extensor digitorum longus, tibialis anterior, and soleus) and nonlimb (extraocular, thyroarytenoid, diaphragm, and masseter) muscles using a competitive PCR assay. An exogenous template that included oligonucleotide sequences specific for seven rat sarcomeric MHC isoforms (beta-cardiac, 2A, 2X, 2B, extraocular, embryonic, and neonatal) as well as beta-actin was constructed and used as the competitor. Only the extraocular muscle contained all seven isoforms. All seven muscles contained type 2A and type 2X MHC transcripts in varying percentages. As expected, the soleus muscle contained primarily beta-cardiac MHC (87.8 +/- 2.6%). Extraocular MHC was found only in the extraocular and thyroarytenoid muscles and in relatively small proportions (7.4 +/- 1.5% and 4.0 +/- 0.7%, respectively). Neonatal MHC was identified in extraocular (7.9 +/- 0. 3%), thyroarytenoid (4.4 +/- 0.4%), and masseter (1.0 +/- 0.2%) muscles, and embryonic MHC was identified both in extraocular (1.2 +/- 0.5%) and, unexpectedly, in soleus (0.6 +/- 0.1%) muscles. Absolute MHC mRNA mass was greatest in the masseter (106 pg/0.5 microg RNA) and least for the tibialis anterior (64 pg/0.5 microg RNA). These values suggest that MHC mRNA represents from 4 to 17% of the total mRNA pool in various skeletal muscles. Differences in MHC profile between somatic and branchial arch muscles suggest that the developmental origin of a muscle may, at least in part, be responsible for the MHC expression program that is implemented in the adult. An inverse relationship between the expression of beta-cardiac and type 2B MHC transcripts across muscles was noted, suggesting that the expression of these two isoforms may be reciprocally regulated.
本研究的目的是量化不同发育起源肌肉中肌球蛋白重链（MHC）mRNA的类型和数量，以确定基因表达的调控是否具有可比性。使用竞争性PCR分析法在大鼠成年肢体肌肉（趾长伸肌、胫骨前肌和比目鱼肌）和非肢体肌肉（眼外肌、甲杓肌、膈肌和咬肌）中分析了七种MHC亚型。构建了一种外源模板，其包含针对七种大鼠肌节MHC亚型（β-心脏型、2A型、2X型、2B型、眼外肌型、胚胎型和新生儿型）以及β-肌动蛋白的寡核苷酸序列，并用作竞争物。只有眼外肌包含所有七种亚型。所有七种肌肉都含有不同百分比的2A型和2X型MHC转录本。正如预期的那样，比目鱼肌主要含有β-心脏型MHC（87.8±2.6%）。眼外肌型MHC仅在眼外肌和甲杓肌中发现，且比例相对较小（分别为7.4±1.5%和4.0±0.7%）。新生儿型MHC在眼外肌（7.9±0.3%）、甲杓肌（4.4±0.4%）和咬肌（1.0±0.2%）中被鉴定出来，胚胎型MHC在眼外肌（1.2±0.5%）中被鉴定出来，出乎意料的是，在比目鱼肌（0.6±0.1%）中也被鉴定出来。MHC mRNA的绝对质量在咬肌中最大（106 pg/0.5 μg RNA），在胫骨前肌中最小（6 μg/0.5 μg RNA）。这些值表明，MHC mRNA在各种骨骼肌的总mRNA库中占4%至17%。体肌和鳃弓肌之间MHC谱的差异表明，肌肉的发育起源可能至少部分负责成年期实施的MHC表达程序。注意到肌肉中β-心脏型和2B型MHC转录本的表达呈负相关，表明这两种亚型的表达可能相互调节。
