Nephrotic syndrome: Genetic testing in steroid-resistant nephrotic syndrome

Novel variations in NPHS1 gene in children of South Indian population and its association with primary nephrotic syndrome

Mutations in NPHS1 can lead to disruption of the filtration barrier and cause proteinuria in nephrotic syndrome (NS). The aim of the study was to evaluate NPHS1 mutations, its susceptibility to the disease, and their association in children with steroid-resistant NS; mutation frequency of 9% was observed in patients with steroid-resistant NS, of which, six mutations and two single-nucleotide polymorphisms observed in the study population were found to be novel.

Steroid-resistant nephrotic syndrome caused by novel WT1 mutation inherited from a mosaic parent

Steroid-resistant nephrotic syndrome (SRNS) is a severe childhood disorder frequently progressing toward renal failure. Among its genetic causes are mutations in the Wilms tumor gene, WT1, which codes for a transcription factor with key role for the embryonic development of the genitourinary tract as well as for maintaining podocyte differentiation and slit diaphragm structure in adults. Defects in WT1 are associated with sporadic cases of both syndromic and isolated SRNS. We report here a novel WT1 mutation associated with SRNS in a female patient, which leads to a Cys428Ser substitution on protein level, affecting one of the cysteine residues responsible for zinc binding in the second zinc finger domain. Surprisingly, the mutation identified in the patient was found to be inherited from the healthy mosaic mother. The presence of mosaicism was confirmed using quantitative polymerase chain reaction (PCR) high-resolution melting. The clinical implications of this finding for the family are discussed.

A multicolor podocyte reporter highlights heterogeneous podocyte changes in focal segmental glomerulosclerosis

In contrast to most glomerular diseases, the injury pattern in focal segmental glomerulosclerosis (FSGS) is highly heterogeneous, even though podocytes are genetically identical and exposed to the same environmental factors. To understand changes in individual podocytes, we generated and analyzed a stochastic multicolor Cre-reporter, encoding four fluorescent proteins. In these animals podocytes were randomly labeled allowing individual cells and their foot processes to be distinguished. In healthy animals podocyte size and structure showed little cell to cell variability. In the doxorubicin-induced FSGS model, fluorescent-labeled glomerular podocyte numbers decreased and fluorescent cells could be recovered from the urine. The size of the remaining podocytes showed a high degree of heterogeneity, some cells remained small, while others enlarged. Both enlarged and non-enlarged podocytes showed alterations in their foot process morphology. Thus, by the virtue of a multicolor cre-reporter, individual podocytes could be viewed in real time at a cellular resolution indicating a heterogeneous podocyte injury response during the pathogenesis of FSGS.