Departments of Anaesthesia and Biomedicine, Basel University Hospital, Hebelstrasse, Basel, Switzerland.
Center for Transgenic Models, University of Basel, Mattenstrasse, Basel, Switzerland.
Hum Mol Genet. 2019 Jun 1;28(11):1872-1884. doi: 10.1093/hmg/ddz025.
Here we characterized a mouse model knocked-in for a frameshift mutation in RYR1 exon 36 (p.Gln1970fsX16) that is isogenic to that identified in one parent of a severely affected patient with recessively inherited multiminicore disease. This individual carrying the RYR1 frameshifting mutation complained of mild muscle weakness and fatigability. Analysis of the RyR1 protein content in a muscle biopsy from this individual showed a content of only 20% of that present in a control individual. The biochemical and physiological characteristics of skeletal muscles from RyR1Q1970fsX16 heterozygous mice recapitulates that of the heterozygous parent. RyR1 protein content in the muscles of mutant mice reached 38% and 58% of that present in total muscle homogenates of fast and slow muscles from wild-type (WT) littermates. The decrease of RyR1 protein content in total homogenates is not accompanied by a decrease of Cav1.1 content, whereby the Cav1.1/RyR1 stoichiometry ratio in skeletal muscles from RyR1Q1970fsX16 heterozygous mice is lower compared to that from WT mice. Electron microscopy (EM) revealed a 36% reduction in the number/area of calcium release units accompanied by a 2.5-fold increase of dyads (triads that have lost one junctional sarcoplasmic reticulum element); both results suggest a reduction of the RyR1 arrays. Compared to WT, muscle strength and depolarization-induced calcium transients in RyR1Q1970fsX16 heterozygous mice muscles were decreased by 20% and 15%, respectively. The RyR1Q1970fsX16 mouse model provides mechanistic insight concerning the phenotype of the parent carrying the RYR1 ex36 mutation and suggests that in skeletal muscle fibres there is a functional reserve of RyR1.
在这里，我们对一个在 RYR1 exon36 中发生移码突变（p.Gln1970fsX16）的小鼠模型进行了表征，该模型与一个患有隐性遗传性多核病的严重受累患者的一个亲本中发现的突变是同系的。该个体携带 RYR1 移码突变，主诉有轻度肌肉无力和易疲劳。对该个体肌肉活检中的 RyR1 蛋白含量进行分析显示，仅为对照个体的 20%。RYR1Q1970fsX16 杂合子小鼠的骨骼肌生化和生理学特征再现了杂合子亲本的特征。突变小鼠肌肉中的 RyR1 蛋白含量达到了野生型（WT）同窝仔鼠快肌和慢肌总肌肉匀浆中 RyR1 蛋白含量的 38%和 58%。在总匀浆中 RyR1 蛋白含量的减少并没有伴随着 Cav1.1 含量的减少，因此 RYR1Q1970fsX16 杂合子小鼠骨骼肌中的 Cav1.1/RyR1 化学计量比低于 WT 小鼠。电子显微镜（EM）显示，钙释放单位的数量/面积减少了 36%，同时二联体（失去一个连接的肌浆网元件的三联体）增加了 2.5 倍；这两个结果均表明 RyR1 阵列减少。与 WT 相比，RYR1Q1970fsX16 杂合子小鼠肌肉的肌肉力量和去极化诱导的钙瞬变分别降低了 20%和 15%。RYR1Q1970fsX16 小鼠模型提供了关于携带 RYR1 ex36 突变的亲本表型的机制见解，并表明在骨骼肌纤维中存在 RyR1 的功能储备。
