Juvenile nephronophthisis associated with retinal pigmentary dystrophy, cerebellar ataxia, and skeletal abnormalities.
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A boy aged 9 3/4 years with interstitial nephritis, retinal pigmentary dystrophy, cerebellar ataxia, and skeletal abnormalities is described. The association may be due to a new genetic disorder, since 2 similar cases have been reported. (+info)
Kappa light chain-associated Fanconi's syndrome: molecular analysis of monoclonal immunoglobulin light chains from patients with and without intracellular crystals.
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Plasma cell dyscrasias may be responsible for Fanconi's syndrome, due to the toxicity of a free monoclonal kappa light chain toward kidney proximal tubules. Eight cases of Fanconi's syndrome were analyzed. We compared the structures of VkappaI variability subgroup V domains from five cases of Fanconi's syndrome and one myeloma without renal involvement. Among Fanconi cases, four putative structures were obtained after molecular modeling by homology, and the other had previously been refined by X-ray crystallography. The complete sequences of one VkappaI, one VkappaIII and N-terminal sequences of two VkappaI light chains, from patients with different forms of Fanconi's syndrome, were compared with four previously studied sequences. All three kappa chains responsible for a 'classical' form with intralysosomal crystals and a low mass myeloma, were encoded by the LCO2/O12 germline gene and had an unusual non-polar residue exposed to the solvent in the CDR-L1 loop. Of both VkappaI light chains from patients with Fanconi's syndrome without intracellular crystals, one derived from LCO2/O12 and the other from LCO8/O18 gene. Another feature that could be related to non-crystallization was the absence of accessible side chains in the CDR-L3 loop which is known to be implicated in dimer formation. (+info)
Megalin knockout mice as an animal model of low molecular weight proteinuria.
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Megalin is an endocytic receptor expressed on the luminal surface of the renal proximal tubules. The receptor is believed to play an important role in the tubular uptake of macromolecules filtered through the glomerulus. To elucidate the role of megalin in vivo and to identify its endogenous ligands, we analyzed the proximal tubular function in mice genetically deficient for the receptor. We demonstrate that megalin-deficient mice exhibit a tubular resorption deficiency and excrete low molecular weight plasma proteins in the urine (low molecular weight proteinuria). Proteins excreted include small plasma proteins that carry lipophilic compounds including vitamin D-binding protein, retinol-binding protein, alpha(1)-microglobulin and odorant-binding protein. Megalin binds these proteins and mediates their cellular uptake. Urinary loss of carrier proteins in megalin-deficient mice results in concomitant loss of lipophilic vitamins bound to the carriers. Similar to megalin knockout mice, patients with low molecular weight proteinuria as in Fanconi syndrome are also shown to excrete vitamin/carrier complexes. Thus, these results identify a crucial role of the proximal tubule in retrieval of filtered vitamin/carrier complexes and the central role played by megalin in this process. (+info)
Neonatal diabetes mellitus with hypergalactosemia.
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We report the case of a male, small-for-gestational-age newborn who presented with failure to thrive, severe fluctuation of blood glucose concentrations, and increased serum concentrations of galactose. The infant responded well to a lactose-free diet supplemented with fructose, inulin and corn starch. The metabolic disorder disappeared within 6 months. The transient course, and results of a molecular analysis of the glucose transporter 2 (Glut2) gene seem to rule out Fanconi-Bickel syndrome. (+info)
Mutational analysis in murine models for myeloma-associated Fanconi's syndrome or cast myeloma nephropathy.
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We have designed an in vivo model in which murine hybridoma cell clones producing human Ig light chains (LC) are administered to mice. Depending on which monoclonal LC is expressed, this model mimics either cast myeloma nephropathy or the pathological condition defined as myeloma-associated Fanconi's syndrome (FS) with LC crystallization. Morphological alterations of the kidney cells are thus obtained in mice. All studied LC are closely related human monoclonal VkappaI proteins, which differ by a limited number of substitutions within the variable region. In the case of an FS monoclonal LC, we show that limited changes introduced through site-directed mutagenesis in the variable domain may suppress formation of intracellular crystals within tubular cells. We also show that multiple peculiarities of the variable region are simultaneously needed to allow LC crystallization; this property thus likely results from a unique LC tridimensional conformation imposed by concomitant somatic mutations of a specific germinally encoded framework. (+info)
A mouse model of renal tubular injury of tyrosinemia type 1: development of de Toni Fanconi syndrome and apoptosis of renal tubular cells in Fah/Hpd double mutant mice.
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Hereditary tyrosinemia type 1 (HT1) (McKusick 276700), a severe autosomal recessive disorder of tyrosine metabolism, is caused by mutations in the fumarylacetoacetate hydrolase gene Fah (EC 3.7.1.2), which encodes the last enzyme in the tyrosine catabolic pathway. HT1 is characterized by severe progressive liver disease and renal tubular dysfunction. Homozygous disruption of the gene encoding Fah in mice causes neonatal lethality (e.g., lethal Albino deletion c14CoS mice), an event that limits use of this animal as a model for HT1. A new mouse model was developed with two genetic defects, Fah and 4-hydroxyphenylpyruvate dioxygenase (Hpd). The Fah-/- Hpd-/- mice grew normally without evidence of liver and renal disease, and the phenotype is similar to that in Fah+/+ Hpd-/- mice. The renal tubular cells of Fah-/- Hpd-/- mice, particularly proximal tubular cells, underwent rapid apoptosis when homogentisate, the intermediate metabolite between HPD and FAH, was administered to the Fah-/- Hpd-/- mice. Simultaneously, renal tubular function was impaired and Fanconi syndrome occurred. Apoptotic death of renal tubular cells, but not renal dysfunction, was prevented by pretreatment of the animals with YVAD, a specific inhibitor of caspases. In the homogentisate-treated Fah-/- Hpd-/- mice, massive amounts of succinylacetone were excreted into the urine, regardless of treatment with inhibitors. It is suggested that apoptotic death of renal tubular cells, as induced by administration of homogentisate to Fah-/- Hpd-/- mice, was caused by an intrinsic process, and that renal apoptosis and tubular dysfunctions in tubular cells occurred through different pathways. These observations shed light on the pathogenesis of renal tubular injury in subjects with FAH deficiency. These Fah-/- Hpd-/- mice can serve as a model in experiments related to renal tubular damage. (+info)
An infant with severe combined immunodeficiency syndrome, an alpha-thalassemia trait and renal Fanconi syndrome.
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We describe an infant with severe combined immunodeficiency syndrome and an alpha-thalassemia trait who developed a renal Fanconi syndrome after his first stem cell transplantation. This syndrome consists of a generalized failure of proximal tubular reabsorption, which leads to a large number of metabolic disturbances. The etiology varies from inherited causes, including an idiopathic form, to acquired causes such as intoxications, immunological disorders and hemoglobinopathies. In this case report we discuss possible explanations of the Fanconi syndrome in our patient. (+info)
Genetic and physical mapping of the locus for autosomal dominant renal Fanconi syndrome, on chromosome 15q15.3.
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Autosomal dominant renal Fanconi syndrome is a genetic model for the study of proximal renal tubular transport pathology. We were able to map the locus for this disease to human chromosome 15q15.3 by genotyping a central Wisconsin pedigree with 10 affected individuals. After a whole-genome scan with highly polymorphic simple sequence repeat markers, a maximum LOD score of 3.01 was calculated for marker D15S659 on chromosome 15q15.3. Linkage and haplotype analysis for an additional 24 markers flanking D15S659 narrowed the interval to approximately 3 cM, with the two highest single-point LOD scores observed being 4.44 and 4.68 (for D15S182 and D15S537, respectively). Subsequently, a complete bacterial artificial chromosome contig was constructed, from the High Throughput Genomic Sequence Database, for the region bounded by D15S182 and D15S143. The identification of the gene and gene product altered in autosomal dominant renal Fanconi syndrome will allow the study of the physiology of proximal renal tubular transport. (+info)