Molecular analysis of NPHS2 and ACTN4 genes in a series of 33 Italian patients affected by adult-onset nonfamilial focal segmental glomerulosclerosis.
BACKGROUND
Mutations in the NPHS2 gene, encoding podocin, and in the ACTN4 gene, encoding alpha-actinin-4, have been identified in familial childhood-onset forms of focal and segmental glomerulosclerosis (FSGS). NPHS2 may be also responsible for some sporadic cases. The role of NPHS2 and ACTN4 in the adult sporadic form of the disease is being clarifying.


METHODS
Thirty-three adult subjects affected by sporadic FSGS were studied at molecular level. At biopsy, 12 patients had nephrotic syndrome, 5 patients had isolated proteinuria and 16 patients showed proteinuria and hematuria. Glomerular filtration rate (GFR) was in the normal range in 19 subjects and 14 patients had a variable degree of renal failure. Multiplex families presenting with a clear familial inheritance for proteinuria or other congenital nephrotic syndrome were excluded. The whole coding region, all intron/exon boundaries and flanking intronic regions of NPHS2 gene and the exon 8, i.e. hot-spot mutations of the ACTN4 gene, were analyzed in all patients by denaturing high-performance liquid chromatography (DHPLC) to search disease-causing defects.


RESULTS
The analysis identified four already described and two new polymorphisms, IVS3-21C>T and IVS3-46C>T, on the NPHS2 gene. Moreover, the R229Q allele was identified in 3/33 patients and in 7/124 controls, accounting for an allelic frequency of 0.045 and 0.028, respectively. The new intronic polymorphism IVS7-54C>T was also found in the exon 8 of the ACTN4 gene.


CONCLUSIONS
In this study, we exhaustively analyzed the NPHS2 and the exon 8 of the ACTN4 genes in a series of sporadic 'adult-onset' FSGS patients. No causative mutations were found while the R229Q allele was identified in 3 patients confirming its possible role as a 'disease-associated NPHS2 allele' although its pathogenetic involvement needs to be further clarified. Moreover, the description of new intronic polymorphisms in both genes is reported.
Aucella
Filippo
F
Department of Nephrology and Dialysis, Casa Sollievo della Sofferenza Hospital, IRCCS, San Giovanni Rotondo, Italy.
De Bonis
Patrizia
P
Gatta
Giuseppe
G
Muscarella
Lucia Anna
LA
Vigilante
Mimmo
M
di Giorgio
Giuseppe
G
D'Errico
Michele
M
Zelante
Leopoldo
L
Stallone
Carmine
C
Bisceglia
Luigi
L
D000185:Actinin / Q000235:genetics*; D002648:Child; D002851:Chromatography, High Pressure Liquid; D005091:Exons; D005260:Female; D005923:Glomerulosclerosis, Focal Segmental / Q000235:genetics*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008840:Microfilament Proteins / Q000235:genetics*; D009154:Mutation
C111453:ACTN4 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; C407223:NPHS2 protein; D000185:Actinin