Mistargeting of Peroxisomal EHHADH and Inherited Renal Fanconi's Syndrome
Mistargeting of Peroxisomal EHHADH and Inherited Renal Fanconi's Syndrome
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DOI：
10.1056/nejmoa1307581
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发表时间：
2014-01-09
影响因子：
158.5
通讯作者：
Kleta, Robert
中科院分区：
文献类型：
--
作者：
Klootwijk, Enriko D.;Reichold, Markus;Kleta, Robert
在肾性Fanconi综合征中，近端肾小管细胞功能障碍导致肾脏水、电解质和低分子营养素的丢失。对于大多数类型的孤立性Fanconi综合征，其遗传原因和潜在缺陷尚不清楚。方法我们对一个5代黑人单纯性常染色体显性遗传性Fanconi综合征家族的成员进行了临床和遗传学特征分析。我们进行了全基因组连锁分析、基因测序、肾脏近端小管细胞的生化和细胞生物学研究、基因敲除小鼠的研究以及线粒体的功能评估。结果该家系Fanconi‘s综合征的表型与染色体3q27上的单基因座连锁，EHHADH杂合性错义突变与该病分离。E.E3K突变在EHHADH的N端部分产生了一个新的线粒体靶向基序，EHHADH是一种参与脂肪酸过氧体氧化的酶，在近端小管中表达。免疫细胞荧光研究显示突变的EHHADH错误定位于线粒体。对近端肾小管细胞的研究显示，线粒体氧化磷酸化受损，在液体和葡萄糖类似物跨上皮运输方面存在缺陷。H-1-核磁共振波谱显示，受影响的家庭成员尿液中线粒体代谢物水平升高。Ehhadh基因敲除小鼠肾小管上皮细胞未见异常，提示该突变为显性负性突变，而不是单倍体缺陷。结论Ehhadh基因敲除小鼠肾小管线粒体代谢紊乱，导致肾Fanconi综合征，提示线粒体在近端肾小管功能中起中心作用。错误定位蛋白的显性负效应增加了Fanconi综合征单基因机制的光谱。(由欧盟委员会第七框架方案和其他方案资助。)
BackgroundIn renal Fanconi's syndrome, dysfunction in proximal tubular cells leads to renal losses of water, electrolytes, and low-molecular-weight nutrients. For most types of isolated Fanconi's syndrome, the genetic cause and underlying defect remain unknown.MethodsWe clinically and genetically characterized members of a five-generation black family with isolated autosomal dominant Fanconi's syndrome. We performed genomewide linkage analysis, gene sequencing, biochemical and cell-biologic investigations of renal proximal tubular cells, studies in knockout mice, and functional evaluations of mitochondria. Urine was studied with the use of proton nuclear magnetic resonance (H-1-NMR) spectroscopy.ResultsWe linked the phenotype of this family's Fanconi's syndrome to a single locus on chromosome 3q27, where a heterozygous missense mutation in EHHADH segregated with the disease. The p.E3K mutation created a new mitochondrial targeting motif in the N-terminal portion of EHHADH, an enzyme that is involved in peroxisomal oxidation of fatty acids and is expressed in the proximal tubule. Immuno-cytofluorescence studies showed mistargeting of the mutant EHHADH to mitochondria. Studies of proximal tubular cells revealed impaired mitochondrial oxidative phosphorylation and defects in the transport of fluids and a glucose analogue across the epithelium. H-1-NMR spectroscopy showed elevated levels of mitochondrial metabolites in urine from affected family members. Ehhadh knockout mice showed no abnormalities in renal tubular cells, a finding that indicates a dominant negative nature of the mutation rather than haploinsufficiency.ConclusionsMistargeting of peroxisomal EHHADH disrupts mitochondrial metabolism and leads to renal Fanconi's syndrome; this indicates a central role of mitochondria in proximal tubular function. The dominant negative effect of the mistargeted protein adds to the spectrum of monogenic mechanisms of Fanconi's syndrome. (Funded by the European Commission Seventh Framework Programme and others.)