From the Centre for Nephrology (E.D.K., H.C.S., D.B., G.J., H.C., A.M.H., R.J.U., R.K.) and Institute of Child Health (D.B., R.K.), University College London, and Biomolecular Medicine, Imperial College London (S.L.R., A.D.W., E.H., J.K.N.) - both in London; the Departments of Medical Cell Biology (M.R., C.B., D.P., C.S., R. Warth), Internal Medicine III (K.R.), Internal Medicine II (S.W.R.), and Molecular and Cellular Anatomy (R. Witzgall) and the Institutes of Functional Genomics (J.R., K.E., N.A., P.J.O., K.D.) and Pathology (J.S.), University of Regensburg, and the Department of Radiology, Barmherzige Brueder Hospital (N.Z.) - all in Regensburg, Germany; the National Human Genome Research Institute (A.H.-W., S.L.R., H.C.S., K.O., I.B., D.M.K., W.A.G., R.K.) and National Heart, Lung, and Blood Institute (Y.I.), National Institutes of Health, Bethesda, MD; the Division of Pediatric Nephrology, University of Florida, Jacksonville (A.T., M.I.); the Genome Biology Department, Australian National University, Canberra, ACT, Australia (M.A.-B.); Kitasato University Medical Center, Saitama, Japan (H.N.); and the Department of Pathology, Northwestern University, Chicago (Y.J., J.K.R.).
N Engl J Med. 2014 Jan 9;370(2):129-38. doi: 10.1056/NEJMoa1307581.
In 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.
We 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 ((1)H-NMR) spectroscopy.
We 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. Immunocytofluorescence 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. (1)H-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.
Mistargeting 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.).
在肾性范可尼综合征中，近端肾小管细胞功能障碍导致水、电解质和低分子量营养物质的肾脏丢失。对于大多数类型的孤立性范可尼综合征，其遗传原因和潜在缺陷仍然未知。
我们对一个五代黑人家族的成员进行了临床和基因特征分析，他们患有孤立性常染色体显性范可尼综合征。我们进行了全基因组连锁分析、基因测序、肾近端小管细胞的生化和细胞生物学研究、敲除小鼠研究以及线粒体功能评估。使用质子磁共振波谱（1H-NMR）对尿液进行了研究。
我们将这个家族范可尼综合征的表型与染色体 3q27 上的一个单一基因座联系起来，该基因座上 EHHADH 的杂合错义突变与疾病共分离。p.E3K 突变在 EHHADH 的 N 端部分创建了一个新的线粒体靶向基序，EHHADH 是一种参与脂肪酸过氧化物体氧化的酶，在近端小管中表达。免疫细胞荧光研究表明，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，以及液体和葡萄糖类似物穿过上皮的转运缺陷。1H-NMR 波谱显示，受影响家族成员尿液中的线粒体代谢物水平升高。Ehhadh 敲除小鼠的肾小管细胞无异常，这表明该突变具有显性负效应，而不是杂合不足。
过氧化物体 EHHADH 的错误定位破坏了线粒体代谢，导致肾性范可尼综合征；这表明线粒体在近端肾小管功能中起核心作用。错误定位蛋白的显性负效应增加了范可尼综合征的单基因机制谱。（由欧盟第七框架计划和其他机构资助）。
