Xuan Dan, Qiang Fuyong, Xu Hui, Wang Li, Xia Yonghui
Department of Rheumatism and Immunology, The First Affiliated Hospital of Wannan Medical College, Wuhu, China.
Department of Respiratory and Critical Care Medicine, The Second Affiliated Hospital of Wannan Medical College, Wuhu, China.
Hum Hered. 2024;89(1):84-97. doi: 10.1159/000542357. Epub 2024 Nov 13.
Systemic lupus erythematosus (SLE) is a common autoimmune disease with unknown etiology. Recently, a growing number of evidence suggested that mitochondrial dysfunctions played active roles in the pathogenesis of SLE, but its detailed mechanism remains largely undetermined. The aim of this study was to analyze the frequencies of mitochondrial tRNA (mt-tRNA) variants in Chinese individuals with SLE.
We carried out a mutational screening of mt-tRNA variants in a cohort of 200 patients with SLE and 200 control subjects by PCR-Sanger sequencing. The potential pathogenicity of mt-tRNA variants was evaluated by phylogenetic conservation and haplogroup analyses. In addition, trans-mitochondrial cybrid cell lines were established, and mitochondrial functions including ATP, reactive oxygen species (ROS), mitochondrial DNA (mtDNA) copy number, mitochondrial membrane potential (MMP), superoxide dismutase (SOD), and mt-RNA transcription were analyzed in cybrids with and without these putative pathogenic mt-tRNA variants.
We identified five possible pathogenic variants: tRNAVal G1606A, tRNALeu(UUR) A3243G, tRNAIle A4295G, tRNAGly T9997C, and tRNAThr A15924G that only found in SLE patients but were absent in controls. Interestingly, these variants were located at extremely conserved nucleotides of the corresponding tRNAs and may alter tRNAs' structure and function. Furthermore, cells carrying these tRNA variants had much lower levels of ATP, mtDNA copy number, MMP, and SOD than controls; by contrast, the levels of ROS increased significantly (p < 0.05 for all). Furthermore, a significant reduction in mt-ND1, ND2, ND3, ND5, and A6 mRNA expression was observed in cells with these mt-tRNA variants, while compared with controls. Thus, failures in tRNA metabolism caused by these variants would impair mitochondrial translation and subsequently lead to mitochondrial dysfunction that was involved in the progression and pathogenesis of SLE.
Our study suggested that mt-tRNA variants were important causes for SLE, and screening for mt-tRNA pathogenic variants was recommended for early detection and prevention for this disorder.
系统性红斑狼疮（SLE）是一种病因不明的常见自身免疫性疾病。最近，越来越多的证据表明线粒体功能障碍在SLE的发病机制中起积极作用，但其详细机制仍 largely 未确定。本研究的目的是分析中国SLE患者中线粒体 tRNA（mt-tRNA）变体的频率。
我们通过 PCR-Sanger 测序对 200 例SLE患者和 200 例对照受试者进行了 mt-tRNA 变体的突变筛查。通过系统发育保守性和单倍群分析评估 mt-tRNA 变体的潜在致病性。此外，建立了转线粒体杂交细胞系，并分析了有和没有这些假定致病 mt-tRNA 变体的杂交细胞中线粒体功能，包括 ATP、活性氧（ROS）、线粒体 DNA（mtDNA）拷贝数、线粒体膜电位（MMP）、超氧化物歧化酶（SOD）和 mt-RNA 转录。
我们鉴定出五个可能的致病变体：tRNAVal G1606A、tRNALeu(UUR) A3243G、tRNAIle A4295G、tRNAGly T9997C 和 tRNAThr A15924G，这些变体仅在SLE患者中发现，而在对照中不存在。有趣的是，这些变体位于相应 tRNA 的极端保守核苷酸处，可能改变 tRNA 的结构和功能。此外，携带这些 tRNA 变体的细胞的 ATP、mtDNA 拷贝数、MMP 和 SOD 水平远低于对照；相比之下，ROS 水平显著升高（所有 p < 0.05）。此外，与对照相比，在具有这些 mt-tRNA 变体的细胞中观察到 mt-ND1、ND2、ND3、ND5 和 A6 mRNA 表达显著降低。因此，这些变体引起的 tRNA 代谢失败会损害线粒体翻译，进而导致参与SLE进展和发病机制的线粒体功能障碍。
我们的研究表明 mt-tRNA 变体是SLE的重要病因，建议筛查 mt-tRNA 致病变体以早期检测和预防这种疾病。
