Molecular Genetics and Functional Laboratory, Faculty of Science of Sfax, University of Sfax, Sfax 3000, Tunisia.
Department of Pediatrics, University Hospital Farhat Hached, Sousse, Tunisia.
Gene. 2024 Jul 1;914:148388. doi: 10.1016/j.gene.2024.148388. Epub 2024 Mar 16.
Congenital scoliosis (CS) is a spinal disorder caused by genetic-congenital vertebral malformations and may be associated with other congenital defects or may occur alone. It is genetically heterogeneous and numerous genes contributing to this disease have been identified. In addition, CS has a wide range of phenotypic and genotypic variability, which has been explained by the intervention of genetic factors like modifiers and environment genes. The aim of the present study was to determine the possible cause of CS in a Tunisian patient and to examine the association between mtDNA mutations and mtDNA content and CS.
Here we performed Whole-Exome Sequencing (WES) in a patient presenting clinical features suggestive of severe congenital scoliosis syndrome. Direct sequencing of the whole mitochondrial DNA (mtDNA) was also performed in addition to copy number quantification in the blood of the indexed case. In silico prediction tools, 3D modeling and molecular docking approaches were used.
The WES revealed the homozygous missense mutation c.512A > G (p.H171R) in the TBXT gene. Bioinformatic analysis demonstrated that the p.H171R variant was highly deleterious and caused the TBXT structure instability. Molecular docking revealed that the p.H171R mutation disrupted the monomer stability which seemed to be crucial for maintaining the stability of the homodimer and consequently to the destabilization of the homodimer-DNA complex. On the other hand, we hypothesized that mtDNA can be a modifier factor, so, the screening of the whole mtDNA showed a novel heteroplasmic m.10150T > A (p.M31K) variation in the MT-ND3 gene. Further, qPCR analyses of the patient's blood excluded mtDNA depletion. Bioinformatic investigation revealed that the p.M31K mutation in the ND3 protein was highly deleterious and may cause the ND3 protein structure destabilization and could disturb the interaction between complex I subunits.
We described the possible role of mtDNA genetics on the pathogenesis of congenital scoliosis by hypothesizing that the presence of the homozygous variant in TBXT accounts for the CS phenotype in our patient and the MT-ND3 gene may act as a modifier gene.
先天性脊柱侧凸（CS）是一种由遗传-先天性椎体畸形引起的脊柱疾病，可能与其他先天性缺陷有关，也可能单独发生。它具有遗传异质性，已经确定了许多导致这种疾病的基因。此外，CS 的表型和基因型具有广泛的可变性，这可以通过遗传因素（如修饰因子和环境基因）的干预来解释。本研究的目的是确定一名突尼斯患者 CS 的可能病因，并研究 mtDNA 突变和 mtDNA 含量与 CS 之间的关系。
我们对一名具有严重先天性脊柱侧凸综合征临床特征的患者进行了全外显子组测序（WES）。除了对索引病例的血液进行拷贝数定量外，还对整个线粒体 DNA（mtDNA）进行了直接测序。使用了计算机预测工具、3D 建模和分子对接方法。
WES 显示 TBXT 基因的纯合错义突变 c.512A>G（p.H171R）。生物信息学分析表明，p.H171R 变体高度有害，导致 TBXT 结构不稳定。分子对接显示，p.H171R 突变破坏了单体稳定性，这似乎对维持同源二聚体的稳定性至关重要，进而导致同源二聚体-DNA 复合物的不稳定。另一方面，我们假设 mtDNA 可以是一个修饰因子，因此，对整个 mtDNA 的筛选显示 MT-ND3 基因中存在一个新的异质体 m.10150T>A（p.M31K）变异。此外，对患者血液的 qPCR 分析排除了 mtDNA 耗竭。生物信息学研究表明，ND3 蛋白中的 p.M31K 突变高度有害，可能导致 ND3 蛋白结构不稳定，并可能干扰复合物 I 亚基之间的相互作用。
我们通过假设 TBXT 中的纯合变体导致我们患者的 CS 表型，以及 MT-ND3 基因可能作为修饰基因，描述了 mtDNA 遗传学在先天性脊柱侧凸发病机制中的可能作用。
