Departamento de Bioquímica, Instituto de Investigaciones Biomédicas "Alberto Sols" UAM-CSIC and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Universidad Autónoma de Madrid 28029, Madrid, Spain ; Laboratorio de Enfermedades Mitocondriales, Instituto de Investigación Sanitaria Hospital 12 de Octubre (i+12) Madrid, Spain.
Departamento de Bioquímica, Instituto de Investigaciones Biomédicas "Alberto Sols" UAM-CSIC and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Universidad Autónoma de Madrid 28029, Madrid, Spain ; Servicio de Bioquímica, Instituto de Investigación Sanitaria Puerta de Hierro Majadahonda Madrid, Spain.
Mol Genet Genomic Med. 2014 Mar;2(2):107-14. doi: 10.1002/mgg3.47. Epub 2013 Nov 11.
Confirming the pathogenicity of mitochondrial tRNA point mutations is one of the classical challenges in the field of mitochondrial medicine. In addition to genetic and functional studies, the evaluation of a genetic change using a pathogenicity scoring system is extremely useful to discriminate between disease-causing mutations from neutral polymorphisms. The pathogenicity scoring system is very robust for confirming pathogenicity, especially of mutations that show impaired activity in functional studies. However, mutations giving normal results using the same functional approaches are disregarded, and this compromises the power of the system to rule out pathogenicity. We propose to include a new criterion in the pathogenicity scoring systems regarding mutations which fail to show any mitochondrial defect in functional studies. To evaluate this proposal we characterized two mutations, m.8296A>G and m.8347A>G, in the mitochondrial tRNA(L) (ys) gene (MT-TK) using trans-mitochondrial cybrid analysis. m.8347A>G mutation severely impairs oxidative phosphorylation, suggesting that it is highly pathogenic. By contrast, the behavior of cybrids homoplasmic for the m.8296A>G mutation is similar to cybrids containing wild-type mitochondrial DNA (mtDNA). The results indicate that including not only positive but also negative outcomes of functional studies in the scoring system is critical for facilitating the diagnosis of this complex group of diseases.
确认线粒体 tRNA 点突变的致病性是线粒体医学领域的经典挑战之一。除了遗传和功能研究外，使用致病性评分系统评估遗传变化对于区分致病突变与中性多态性非常有用。该致病性评分系统对于确认致病性非常有效，尤其是对于在功能研究中显示活性受损的突变。然而，使用相同的功能方法显示正常结果的突变会被忽略，这削弱了该系统排除致病性的能力。我们建议在致病性评分系统中纳入一个新的标准，即对于在功能研究中未显示任何线粒体缺陷的突变。为了评估这一建议，我们使用跨线粒体细胞杂种分析对线粒体 tRNA（L）（ys）基因（MT-TK）中的两个突变 m.8296A>G 和 m.8347A>G 进行了表征。m.8347A>G 突变严重损害氧化磷酸化，表明其高度致病性。相比之下，m.8296A>G 突变纯合的细胞杂种的行为与含有野生型线粒体 DNA（mtDNA）的细胞杂种相似。结果表明，在评分系统中不仅包括阳性结果，还包括功能研究的阴性结果，对于促进这组复杂疾病的诊断至关重要。
