Gauthier G F
Department of Cell Biology, University of Massachusetts Medical School, Worcester 01655.
J Cell Biol. 1990 Mar;110(3):693-701. doi: 10.1083/jcb.110.3.693.
Myosin was localized in situ in the posthatch chicken pectoralis using isoform-specific mAbs. The distribution among myofibrils was demonstrated by immunofluorescence and by immunogold EM. Fluorescein- or rhodamine-labeled antibody (12C5) specific for the head region (S1) of myosin was used as a marker to identify "embryonic" myosin. In longitudinal semithin frozen sections, a minority population of myofibrils stained intensely with 12C5. All other myofibrils in the same cell stained only weakly. Similarly, in Lowicryl-embedded ultrathin sections prepared for EM, a minority population reacted preferentially with gold-labeled 12C5. An antibody (5B4) specific for the rod portion of "neonatal" myosin reacted strongly with nearly all myofibrils, and this was evident by light and electron microscopy. A few of the fibrils that reacted strongly with 12C5 reacted weakly with 5B4. These observations demonstrate that an epitope reacting with 12C5 is more abundant in some myofibrils than in others within the same cell. Three categories of myofibrils can be identified by their relative proportions of embryonic and neonatal forms of myosin: in nearly all fibrils, a neonatal isoform predominates; in a minority population, embryonic and neonatal isoforms are both abundant; and in a few fibrils, an embryonic isoform predominates. It is concluded that there are distinct populations of myofibrils in which specific isoforms are segregated within an individual cell.
使用同工型特异性单克隆抗体在孵化后鸡的胸肌中对肌球蛋白进行原位定位。通过免疫荧光和免疫金电子显微镜观察了其在肌原纤维中的分布。用针对肌球蛋白头部区域（S1）的荧光素或罗丹明标记抗体（12C5）作为标志物来鉴定“胚胎型”肌球蛋白。在纵向半薄冰冻切片中，少数肌原纤维被12C5强烈染色。同一细胞中的所有其他肌原纤维仅微弱染色。同样，在为电子显微镜制备的Lowicryl包埋超薄切片中，少数群体优先与金标记的12C5反应。一种针对“新生型”肌球蛋白杆部的抗体（5B4）与几乎所有肌原纤维强烈反应，这在光学显微镜和电子显微镜下都很明显。一些与12C5强烈反应的纤维与5B4反应较弱。这些观察结果表明，与12C5反应的表位在同一细胞内的某些肌原纤维中比在其他肌原纤维中更丰富。根据肌球蛋白胚胎型和新生型的相对比例，可以将三类肌原纤维区分开来：在几乎所有纤维中，新生型同工型占主导；在少数群体中，胚胎型和新生型同工型都很丰富；在少数纤维中，胚胎型同工型占主导。结论是，在单个细胞内存在不同的肌原纤维群体，其中特定的同工型是分开的。
