COL10A1 nonsense and frame-shift mutations have a gain-of-function effect on the growth plate in human and mouse metaphyseal chondrodysplasia type Schmid
COL10A1 nonsense and frame-shift mutations have a gain-of-function effect on the growth plate in human and mouse metaphyseal chondrodysplasia type Schmid
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DOI：
10.1093/hmg/ddm067
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发表时间：
2007-05-15
影响因子：
3.5
通讯作者：
Chan, Danny
中科院分区：
文献类型：
--
作者：
Ho, Matthew S. P.;Tsang, Kwok Yeung;Chan, Danny
胶原X基因（COL 10A 1）中的错义、无义和移码突变导致施密德型干骺端软骨发育不良（MCDS）。突变型COL 10A 1 mRNA在人MCDS软骨中通过无义介导的衰变完全降解暗示了体内无义突变发病机制中的单倍不足。然而，在突变mRNA持续存在的情况下，其机制尚不清楚。我们发现，无义/移码突变可以引起功能获得效应，影响生长板中的软骨细胞分化。在MCDS先证者中，p.Y663X无义突变杂合子，生长板软骨含有64%野生型和36%突变mRNA，肥大区紊乱和扩大。体外翻译的突变型胶原X链（截短）错误折叠，不能组装成三聚体，并干扰正常α 1（X）链组装成三聚体。与Col 10a 1无效突变体不同，携带相当于人MCDS p.P620fsX621突变的小鼠的转基因小鼠（FCdel）显示出MCDS的典型特征，具有不成比例的肢体缩短和早发性髋内翻。在FCdel小鼠中，肥大区的扩张程度是转基因剂量依赖性的，在转基因纯合子小鼠中最严重。在扩大的肥大区的下部区域的软骨细胞表达肥大软骨细胞的非特征性标志物，表明分化被破坏。错误折叠的FCdel α 1（X）链保留在肥大软骨细胞的内质网内，激活未折叠的蛋白质反应。我们的研究结果提供了强有力的体内证据的功能获得效应，这是与激活内质网应激反应和改变软骨细胞分化，作为一个可能的分子发病机制MCDS。
Missense, nonsense and frame-shift mutations in the collagen X gene (COL10A1) result in metaphyseal chondrodysplasia type Schmid (MCDS). Complete degradation of mutant COL10A1 mRNA by nonsense-mediated decay in human MCDS cartilage implicates haploinsufficiency in the pathogenesis for nonsense mutations in vivo. However, the mechanism is unclear in situations where the mutant mRNA persist. We show that non-sense/frame-shift mutations can elicit a gain-of-function effect, affecting chondrocyte differentiation in the growth plate. In an MCDS proband, heterozygous for a p.Y663X nonsense mutation, the growth plate cartilage contained 64% wild-type and 36% mutant mRNA and the hypertrophic zone was disorganized and expanded. The in vitro translated mutant collagen X chains, which are truncated, were misfolded, unable to assemble into trimers and interfered with the assembly of normal alpha 1(X) chains into trimers. Unlike Col10a1 null mutants, transgenic mice (FCdel) bearing the mouse equivalent of a human MCDS p.P620fsX621 mutation, displayed typical characteristics of MCDS with disproportionate shortening of limbs and early onset coxa vara. In FCdel mice, the degree of expansion of the hypertrophic zones was transgene-dosage dependent, being most severe in mice homozygous for the transgene. Chondrocytes in the lower region of the expanded hypertrophic zone expressed markers uncharacteristic of hypertrophic chondrocytes, indicating that differentiation was disrupted. Misfolded FCdel alpha 1(X) chains were retained within the endoplasmic reticulum of hypertrophic chondrocytes, activating the unfolded protein response. Our findings provide strong in vivo evidence for a gain-of-function effect that is linked to the activation of endoplasmic reticulum-stress response and altered chondrocyte differentiation, as a possible molecular pathogenesis for MCDS.