Molecular basis of steroid-resistant nephrotic syndrome.
The identification of the underlying gene defect in some cases of steroid resistant nephrotic syndrome (SRNS) has recently led to a critical breakthrough in the understanding of the pathogenesis of nephrotic syndromes. The more severe form of hereditary nephrotic syndromes is the congenital nephrotic syndrome of the Finnish type (CNF). The causative gene, NPHS1, encodes a novel protein, nephrin which is a transmembrane protein belonging to the immunoglobulin superfamily specifically expressed in the podocyte at the slit diaphragm. Using a positional cloning approach, our group identified a gene, NPHS2, involved in a specific entity of familial SRNS characterized by early onset, complete steroid-resistance, rapid progression to ESRD and no recurrence after renal transplantation. NPHS2 encodes a novel membrane protein named podocin localized at the cytoplasmic part of the slit diaphragm. Familial autosomal dominant cases of primary FSGS have been described in adulthood. Two corresponding genes have been mapped to date, one to 19q13 and the second to 11q21-22. The former has been identified as ACTN4, the gene encoding the actin-binding protein, a-actinin 4. Other genes involved in the slit-diaphragm or the nephrotic syndrome are CD2-associated protein (CD2AP), FAT1, WT1, LMX1B, SMARCAL1. Altogether, these data demonstrate the pivotal role of the podocyte in the development and the maintenance of the glomerular filtration barrier and the crucial role of the genetic factors in the development of SRNS.
Antignac
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Inserm U574 and Department of Genetics, Necker Hospital, Paris 5 University, Paris, France.
D000185:Actinin; D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D002648:Child; D003598:Cytoskeletal Proteins; D018450:Disease Progression; D004351:Drug Resistance; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007676:Kidney Failure, Chronic / Q000209:etiology; D016030:Kidney Transplantation; D008565:Membrane Proteins / Q000235:genetics; D008840:Microfilament Proteins; D009154:Mutation; D009404:Nephrotic Syndrome / Q000150:complications / Q000151:congenital / Q000188:drug therapy / Q000209:etiology / Q000235:genetics*; D011506:Proteins / Q000235:genetics; D013256:Steroids / Q000627:therapeutic use
C111453:ACTN4 protein, human; D048868:Adaptor Proteins, Signal Transducing; C114545:CD2-associated protein; D003598:Cytoskeletal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; C407223:NPHS2 protein; D011506:Proteins; D013256:Steroids; C113267:nephrin; D000185:Actinin