Recessive NPHS2 (Podocin) mutations are rare in adult-onset idiopathic focal segmental glomerulosclerosis.
Recessive NPHS2 (podocin) mutations account for up to approximately 30% of steroid-resistant idiopathic FSGS in children and are associated with a reduced risk for disease recurrence after renal transplantation. R229Q, a missense variant that is present in 3.6% of the white population, has been implicated as a common disease-causing mutation. Given these clinical implications, we examined the role of NPHS2 mutations in a cohort of patients with adult-onset FSGS. We used denaturing HPLC to screen for heterozygous and homozygous gene variants in PCR-amplified DNA fragments that contained all exons and splice junctions of NPHS2. Bidirectional sequencing was performed to define all of the gene variants detected. With the use of the denaturing HPLC in a single-blind pilot study, 40 of 43 known NPHS2 mutations were detected from 22 pediatric patients with FSGS to establish a test sensitivity of 93%. This screen then was applied to 87 adult patients with idiopathic FSGS (15 steroid-sensitive, 63 steroid-resistant, and nine familial cases). In this latter cohort, compound heterozygous mutations were detected only in one patient with steroid-sensitive FSGS (R229Q and Q285fsX302) and no homozygous mutations. Overall, R229Q accounted for eight (80%) of ten of the putative mutant alleles that were detected in the study cohort. Contrary to the pediatric experience, recessive NPHS2 mutations are rare in this study population, suggesting that the pathogenesis of FSGS in adults may differ from that in children. These data do not support R229Q as a disease-causing mutation for steroid-resistant FSGS.
He
Ning
N
Division of Nephrology, Toronto General Hospital, University Health Network and University of Toronto, Toronto, Ontario, Canada.
Zahirieh
Alireza
A
Mei
Yan
Y
Lee
Brian
B
Senthilnathan
Sean
S
Wong
Betty
B
Mucha
Bettina
B
Hildebrandt
Friedhelm
F
Cole
David E
DE
Cattran
Daniel
D
Pei
York
Y
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D004252:DNA Mutational Analysis; D005260:Female; D005808:Genes, Recessive; D014644:Genetic Variation; D005923:Glomerulosclerosis, Focal Segmental / Q000235:genetics* / Q000503:physiopathology; D006579:Heterozygote; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008875:Middle Aged; D017354:Point Mutation; D044465:White People / Q000235:genetics
D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C407223:NPHS2 protein