Aigner S, Pette D
Faculty of Biology, University of Konstanz, Germany.
Symp Soc Exp Biol. 1992;46:311-7.
An in situ-hybridization assay using a digoxigenin-labeled cRNA probe specific for the slow myosin heavy chain (HCI) was established. Type I fibres of normal rabbit muscles were stained with this probe. The reaction product was confined to the perinuclear regions of the subsarcolemmal space and extended along the I-bands into the fibre core region. Myosin HCI mRNA was also detected in transforming fibres of low-frequency stimulated rabbit fast-twitch muscles. Its intracellular distribution resembled that of normal type I fibres, but higher amounts of the message were present in fibres undergoing a fast-to-slow transition. The number of HCI mRNA-positive fibres in stimulated muscles increased in a time-dependent manner and correlated with the amount of myosin HCI protein in these muscles. These findings support the notion that enhanced transcription of the slow myosin HC gene leads to an increased translation of HCI mRNA during the stimulation-induced fibre transformation. Finally, the progressive increase in fibres expressing myosin HCI mRNA indicates that the fast-to-slow fibre conversion occurs in a sequential manner. The pre-existing type IIA fibres appear to transform first, whereas fibre types IIB and IID have to first reach the IIA state. Adult muscle fibers represent versatile entities and may be transformed in response to altered functional demands. Although the majority of normal muscle fibers express only a single myosin HC isoform (for review see Pette and Staron, 1990), the coexistence of two or more myosin HC isoforms has been shown in transforming adult muscle fibers (Staron, Gohlsch, Pette, 1987; Termin, Staron, Pette, 1989).(ABSTRACT TRUNCATED AT 250 WORDS)
建立了一种使用地高辛标记的、对慢肌球蛋白重链（HCI）特异的cRNA探针的原位杂交检测方法。用该探针检测正常兔肌肉的I型纤维。反应产物局限于肌膜下间隙的核周区域，并沿I带延伸至纤维核心区域。在低频刺激的兔快肌转变纤维中也检测到肌球蛋白HCI mRNA。其细胞内分布与正常I型纤维相似，但在经历快到慢转变的纤维中存在更多的该信息分子。刺激肌肉中HCI mRNA阳性纤维的数量呈时间依赖性增加，且与这些肌肉中肌球蛋白HCI蛋白的量相关。这些发现支持这样的观点，即在刺激诱导的纤维转变过程中，慢肌球蛋白HC基因转录增强导致HCI mRNA翻译增加。最后，表达肌球蛋白HCI mRNA的纤维逐渐增加表明快到慢的纤维转变是按顺序发生的。先前存在的IIA型纤维似乎首先发生转变，而IIB型和IID型纤维必须首先达到IIA型状态。成年肌纤维具有多种特性，可能会因功能需求改变而发生转变。尽管大多数正常肌纤维仅表达单一的肌球蛋白HC同工型（综述见Pette和Staron，1990），但在成年转变肌纤维中已显示两种或更多种肌球蛋白HC同工型共存（Staron、Gohlsch、Pette，1987；Termin、Staron、Pette，1989）。（摘要截短于250字）
