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Background <p>Mitochondrial disorders are a group of heterogeneous diseases marked by deficiencies in oxidative phosphorylation (OXPHOS). A common subtype, MELAS (mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes [SLEs]), is primarily linked to variants in mitochondrial transfer RNA (mt-tRNA) genes, yet the molecular mechanisms underlying many of these variants remain poorly understood.</p> Methods <p>We performed a comprehensive assessment of a 14-year-old male patient, including clinical evaluation, genetic testing, histopathology, and functional biochemical analyses of muscle tissue. A systematic literature review was conducted to compare previously reported MT-TS2 variants and their associated phenotypes.</p> Results <p>We identified a rare m.12244G &gt; A variant in the tRNASer(AGY) gene associated with classical MELAS phenotype. Functional analysis demonstrated impaired mitochondrial translation and OXPHOS dysfunction. Histological findings revealed COX-negative and ragged red fibers, while western blotting indicated downregulation of key mitochondrial proteins. Literature review showed that MT-TS2 variants are associated with variable phenotypes including encephalopathy, myopathy, deafness, diabetes, and retinopathy.</p> Conclusion <p>Our study provides the first experimental validation of the pathogenicity of the m.12244G &gt; A variant, confirming its deleterious impact on mitochondrial function. This finding expands the genotype spectrum of MELAS and highlights the importance of functional validation for rare mtDNA variants.</p>

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A novel tRNASer(AGY) 12244G > a variant impairs mitochondrial function and presents with classical MELAS phenotype

  • 期刊论文

  • 发表日期：

    2026年2月16日

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  • Xingyu Zhuang,
  • Jiayin Wang,
  • Jianing Wang,
  • Yan Lin,
  • Chuanzhu Yan,
  • Kunqian Ji

摘要

Background

Mitochondrial disorders are a group of heterogeneous diseases marked by deficiencies in oxidative phosphorylation (OXPHOS). A common subtype, MELAS (mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes [SLEs]), is primarily linked to variants in mitochondrial transfer RNA (mt-tRNA) genes, yet the molecular mechanisms underlying many of these variants remain poorly understood.

Methods

We performed a comprehensive assessment of a 14-year-old male patient, including clinical evaluation, genetic testing, histopathology, and functional biochemical analyses of muscle tissue. A systematic literature review was conducted to compare previously reported MT-TS2 variants and their associated phenotypes.

Results

We identified a rare m.12244G > A variant in the tRNASer(AGY) gene associated with classical MELAS phenotype. Functional analysis demonstrated impaired mitochondrial translation and OXPHOS dysfunction. Histological findings revealed COX-negative and ragged red fibers, while western blotting indicated downregulation of key mitochondrial proteins. Literature review showed that MT-TS2 variants are associated with variable phenotypes including encephalopathy, myopathy, deafness, diabetes, and retinopathy.

Conclusion

Our study provides the first experimental validation of the pathogenicity of the m.12244G > A variant, confirming its deleterious impact on mitochondrial function. This finding expands the genotype spectrum of MELAS and highlights the importance of functional validation for rare mtDNA variants.