Gene Mapping for Familial Steroid Resistance Nephritic Syndrome

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Familial steroid-resistant nephrotic syndrome (SRN) is characterized by early onset of proteinuria with rapid progression of renal failure and renal histology of focal segmental glomerulosclerosis (FSGS). Defects in genes encoding components of glomerular silt diaphragm, e.g., NPHS1, 2, and NEPH1, have been implicated in the pathogenesis. Even though NPHS1 and 2 mutations have been significantly involved in Caucasian families, the relevance in Asian counterparts remains unclear. To explore the genetic basis of Asian patients, we tested linkage of the 3 known nephrotic syndrome loci (NPHS1, 2, and NEPH1) in 15 recessive SRN families originating from Japan and Korea. Linkage analysis excluded the contribution of 3 genes in 32 out of total 45 samples (3 loci in 15 families). The other 13 samples (6 families at NPHS1, 4 at NPHS2, and 3 at NEPH1) were inconclusive on linkage analysis but direct-sequencing revealed no alterations, thereby excluding the loci in all 15 families. Our data underscored genetic heterogeneity and ethnic differences in the pathogenesis of FSGS, and suggests the presence of as yet unidentified genes in Asian patients.