Emperador Sonia, Pacheu-Grau David, Bayona-Bafaluy M Pilar, Garrido-Pérez Nuria, Martín-Navarro Antonio, López-Pérez Manuel J, Montoya Julio, Ruiz-Pesini Eduardo
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza Zaragoza, Spain ; Instituto de Investigación Sanitaria de Aragón, Universidad de Zaragoza Zaragoza, Spain ; Centros de Investigación Biomédica en Red de Enfermedades Raras, Universidad de Zaragoza Zaragoza, Spain.
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza Zaragoza, Spain.
Front Genet. 2015 Jan 14;5:469. doi: 10.3389/fgene.2014.00469. eCollection 2014.
Several homoplasmic pathologic mutations in mitochondrial DNA, such as those causing Leber hereditary optic neuropathy or non-syndromic hearing loss, show incomplete penetrance. Therefore, other elements must modify their pathogenicity. Discovery of these modifying factors is not an easy task because in multifactorial diseases conventional genetic approaches may not always be informative. Here, we have taken an evolutionary approach to unmask putative modifying factors for a particular homoplasmic pathologic mutation causing aminoglycoside-induced and non-syndromic hearing loss, the m.1494C>T transition in the mitochondrial DNA. The mutation is located in the decoding site of the mitochondrial ribosomal RNA. We first looked at mammalian species that had fixed the human pathologic mutation. These mutations are called compensated pathogenic deviations because an organism carrying one must also have another that suppresses the deleterious effect of the first. We found that species from the primate family Cercopithecidae (old world monkeys) harbor the m.1494T allele even if their auditory function is normal. In humans the m.1494T allele increases the susceptibility to aminoglycosides. However, in primary fibroblasts from a Cercopithecidae species, aminoglycosides do not impair cell growth, respiratory complex IV activity and quantity or the mitochondrial protein synthesis. Interestingly, this species also carries a fixed mutation in the mitochondrial ribosomal protein S12. We show that the expression of this variant in a human m.1494T cell line reduces its susceptibility to aminoglycosides. Because several mutations in this human protein have been described, they may possibly explain the absence of pathologic phenotype in some pedigree members with the most frequent pathologic mutations in mitochondrial ribosomal RNA.
线粒体DNA中的几种同质性病理突变，如那些导致Leber遗传性视神经病变或非综合征性听力损失的突变，表现出不完全外显率。因此，其他因素必定会改变它们的致病性。发现这些修饰因子并非易事，因为在多因素疾病中，传统的遗传方法可能并不总是能提供有用信息。在这里，我们采用了一种进化方法来揭示一种特定的同质性病理突变的潜在修饰因子，该突变导致氨基糖苷类药物诱发的非综合征性听力损失，即线粒体DNA中的m.1494C>T转换。该突变位于线粒体核糖体RNA的解码位点。我们首先研究了已经固定了人类病理突变的哺乳动物物种。这些突变被称为补偿性致病偏差，因为携带一种突变的生物体必定还具有另一种能够抑制第一种突变有害效应的突变。我们发现，猕猴科（旧世界猴）的物种即使听觉功能正常也携带m.1494T等位基因。在人类中，m.1494T等位基因会增加对氨基糖苷类药物的易感性。然而，在一种猕猴科物种的原代成纤维细胞中，氨基糖苷类药物不会损害细胞生长、呼吸复合体IV活性及数量或线粒体蛋白质合成。有趣的是，该物种在线粒体核糖体蛋白S12中也携带一个固定突变。我们表明，这种变体在人类m.1494T细胞系中的表达降低了其对氨基糖苷类药物的易感性。由于已经描述了该人类蛋白质中的几种突变，它们可能解释了一些线粒体核糖体RNA中最常见病理突变的家系成员中没有病理表型的原因。
