Department of Clinical Laboratory, Quzhou People's Hospital, the Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou, China.
Department of Otolaryngology, Quzhou People's Hospital, the Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou, China.
J Clin Lab Anal. 2022 Apr;36(4):e24298. doi: 10.1002/jcla.24298. Epub 2022 Feb 26.
Sequence alternations in mitochondrial genomes, especially in genes encoding mitochondrial tRNA (mt-tRNA), were the important contributors to nonsyndromic hearing loss (NSHL); however, the molecular mechanisms remained largely undetermined.
A maternally transmitted Chinese pedigree with NSHL underwent clinical, genetic, and biochemical assessment. PCR and direct sequence analyses were performed to detect mitochondrial DNA (mtDNA), GJB2, and SLC26A4 gene mutations from matrilineal relatives of this family. Mitochondrial functions including mitochondrial membrane potential (MMP), ATP, and ROS were evaluated in polymononuclear leukocytes (PMNs) derived from three deaf patients and three controls from this pedigree.
Four of nine matrilineal relatives developed hearing loss at the variable age of onset. Two putative pathogenic mutations, m.5601C>T in tRNA and m.12311T>C in tRNA , were identified via PCR-Sanger sequencing, as well as 34 variants that belonged to mtDNA haplogroup G2b2. Intriguingly, m.5601C>T mutation resided at very conserved nucleotide in the TψC loop of tRNA (position 59), while the T-to-C substitution at position 12311 located at position 48 in the variable stem of tRNA and was believed to alter the aminoacylation and the steady-state level of tRNA. Biochemical analysis revealed the impairment of mitochondrial functions including the significant reductions of ATP and MMP, whereas markedly increased ROS levels were found in PMNs derived from NSHL patients with m.5601C>T and m.12311T>C mutations. However, we did not detect any mutations in GJB2 and SLC26A4 genes.
Our data indicated that mt-tRNA m.5601C>T and tRNA 12311T>C mutations were associated with NSHL.
线粒体基因组中的序列改变，特别是编码线粒体 tRNA（mt-tRNA）的基因，是导致非综合征性听力损失（NSHL）的重要因素；然而，其分子机制在很大程度上仍未确定。
对一个患有 NSHL 的中国母系遗传家系进行了临床、遗传和生化评估。对该家系母系亲属进行了 PCR 和直接测序分析，以检测线粒体 DNA（mtDNA）、GJB2 和 SLC26A4 基因突变。评估了来自该家系的 3 名耳聋患者和 3 名对照的多形核白细胞（PMNs）中的线粒体功能，包括线粒体膜电位（MMP）、ATP 和 ROS。
9 名母系亲属中有 4 名在不同年龄出现听力损失。通过 PCR-Sanger 测序发现了两个假定的致病性突变，即 tRNA 的 m.5601C>T 和 tRNA 的 m.12311T>C，以及属于 mtDNA 单倍群 G2b2 的 34 个变体。有趣的是，m.5601C>T 突变位于 tRNA 的 TψC 环非常保守的核苷酸（位置 59），而位于 tRNA 可变茎的位置 48 的 T 到 C 取代被认为会改变 tRNA 的氨酰化和稳态水平。生化分析显示，包括 ATP 和 MMP 在内的线粒体功能受损，而来自携带 m.5601C>T 和 m.12311T>C 突变的 NSHL 患者的 PMNs 中 ROS 水平显著升高。然而，我们没有在 GJB2 和 SLC26A4 基因中检测到任何突变。
我们的数据表明，mt-tRNA m.5601C>T 和 tRNA 12311T>C 突变与 NSHL 相关。
