Maija Suvanto1, Jaakko Patrakka2, Timo Jahnukainen3,2, Pia-Maria Sjöström4, Matti Nuutinen5, Pekka Arikoski6, Janne Kataja7, Marjo Kestilä8, Hannu Jalanko3. 1. Children's Hospital, University of Helsinki and Helsinki University Hospital, Biomedicum 2U, Tukholmankatu 8, 00290, Helsinki, Finland. maija.suvanto@helsinki.fi. 2. Department of Medical Biochemistry and Biophysics, Division of Matrix Biology, Karolinska Institute, Stockholm, Sweden. 3. Children's Hospital, University of Helsinki and Helsinki University Hospital, Biomedicum 2U, Tukholmankatu 8, 00290, Helsinki, Finland. 4. Department of Pediatrics, District Hospital of Pietarsaari, Pietarsaari, Finland. 5. Department of Pediatrics, University Hospital of Oulu, Oulu, Finland. 6. Department of Pediatrics, Kuopio University Hospital and University of Eastern Finland, Kuopio, Finland. 7. Department of Pediatrics, University Hospital of Turku, Turku, Finland. 8. Department of Chronic Disease Prevention, National Institute for Health and Welfare, Helsinki, Finland.
Abstract
BACKGROUND: Steroid-resistant nephrotic syndrome (SRNS) is a common cause of end-stage renal disease in children but also occurs as an adult-onset condition. In a subset of SRNS patients, pathogenic variants are found in genes coding for podocyte foot process proteins. The aim of this study was to define the role of pathogenic variants in Finnish patients with familial and sporadic SRNS. METHODS: We analyzed SRNS-related genes NPHS1, NPHS2, NEPH1, ACTN4, TRPC6, INF2, WT1, CD2AP, LAMB2, and PLCE1 for disease-causing variants using direct sequencing of exons and intron/exon boundaries in all members of a family with dominant SRNS with early onset and slow progression to end-stage renal disease. We carried out a whole genome sequencing in two affected and two healthy family members. The function of found podocin variant was studied using co-immunoprecipitation and immunohistochemistry. Podocyte gene sequences were analyzed in a cohort of Finnish non-familial SRNS patients. RESULTS: A heterozygous de novo deletion, c.988_989delCT in NPHS2, was found in all affected family members and in none of their healthy relatives, non-familial patients or controls. No other SRNS-related gene variant, coding or non-coding co-segregated with the disease phenotype in the family. While the truncated podocin remained able to bind nephrin, the expression of nephrin was fragmented and podocin expression reduced. The gene analysis of the non-familial SRNS patients revealed few variants. CONCLUSION: The role of podocin variants in nephrotic syndrome may be more varied than previously thought.
BACKGROUND:Steroid-resistant nephrotic syndrome (SRNS) is a common cause of end-stage renal disease in children but also occurs as an adult-onset condition. In a subset of SRNS patients, pathogenic variants are found in genes coding for podocyte foot process proteins. The aim of this study was to define the role of pathogenic variants in Finnish patients with familial and sporadic SRNS. METHODS: We analyzed SRNS-related genes NPHS1, NPHS2, NEPH1, ACTN4, TRPC6, INF2, WT1, CD2AP, LAMB2, and PLCE1 for disease-causing variants using direct sequencing of exons and intron/exon boundaries in all members of a family with dominant SRNS with early onset and slow progression to end-stage renal disease. We carried out a whole genome sequencing in two affected and two healthy family members. The function of found podocin variant was studied using co-immunoprecipitation and immunohistochemistry. Podocyte gene sequences were analyzed in a cohort of Finnish non-familial SRNS patients. RESULTS: A heterozygous de novo deletion, c.988_989delCT in NPHS2, was found in all affected family members and in none of their healthy relatives, non-familial patients or controls. No other SRNS-related gene variant, coding or non-coding co-segregated with the disease phenotype in the family. While the truncated podocin remained able to bind nephrin, the expression of nephrin was fragmented and podocin expression reduced. The gene analysis of the non-familial SRNS patients revealed few variants. CONCLUSION: The role of podocin variants in nephrotic syndrome may be more varied than previously thought.
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