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.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 Pediatr+Nephrol
2017 ; 32
(3
): 467-476
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Evaluating Mendelian nephrotic syndrome genes for evidence for risk alleles or
oligogenicity that explain heritability
#MMPMID27766458
Crawford BD
; Gillies CE
; Robertson CC
; Kretzler M
; Otto EA
; Vega-Warner V
; Sampson MG
Pediatr Nephrol
2017[Mar]; 32
(3
): 467-476
PMID27766458
show ga
BACKGROUND: More than 30 genes can harbor rare exonic variants sufficient to
cause nephrotic syndrome (NS), and the number of genes implicated in monogenic NS
continues to grow. However, outside the first year of life, the majority of
affected patients, particularly in ancestrally mixed populations, do not have a
known monogenic form of NS. Even in those children classified with a monogenic
form of NS, there is phenotypic heterogeneity. Thus, we have only discovered a
fraction of the heritability of NS-the underlying genetic factors contributing to
phenotypic variation. Part of the "missing heritability" for NS has been posited
to be explained by patients harboring coding variants across one or more
previously implicated NS genes, insufficient to cause NS in a classical Mendelian
manner, but that nonetheless have a sufficient impact on protein function to
cause disease. However, systematic evaluation in patients with NS for rare or
low-frequency risk alleles within single genes, or in combination across genes
("oligogenicity"), has not been reported. To determine whether, compared with a
reference population, patients with NS have either a significantly increased
burden of protein-altering variants ("risk-alleles"), or a unique combination of
them ("oligogenicity"), in a set of 21 genes implicated in Mendelian forms of NS.
METHODS: In 303 patients with NS enrolled in the Nephrotic Syndrome Study Network
(NEPTUNE), we performed targeted amplification paired with next-generation
sequencing of 21 genes implicated in monogenic NS. We created a high-quality
variant call set and compared it with a variant call set of the same genes in a
reference population composed of 2,535 individuals from phase 3 of the 1000
Genomes Project. We created both a "stringent" and a "relaxed"
pathogenicity-filtering pipeline, applied them to both cohorts, and computed the
burden of variants in the entire gene set per cohort, the burden of variants in
the entire gene set per individual, the burden of variants within a single gene
per cohort, and unique combinations of variants across two or more genes per
cohort. RESULTS: With few exceptions when using the relaxed filter, and which are
likely the result of confounding by population stratification, NS patients did
not have a significantly increased burden of variants in Mendelian NS genes in
comparison to a reference cohort, nor was there any evidence for oligogenicity.
This was true when using both the relaxed and the stringent variant pathogenicity
filter. CONCLUSION: In our study, there were no significant differences in the
burden or particular combinations of low-frequency or rare protein-altering
variants in a previously implicated Mendelian NS genes cohort between North
American patients with NS and a reference population. Studies in larger
independent cohorts or meta-analyses are needed to assess the generalizability of
our discoveries and also address whether there is in fact small but significant
enrichment of risk alleles or oligogenicity in NS cases that was undetectable
with this current sample size. It is still possible that rare protein-altering
variants in these genes, insufficient to cause Mendelian disease, still
contribute to NS as risk alleles and/or via oligogenicity. However, we suggest
that more accurate bioinformatic analyses and the incorporation of functional
assays would be necessary to identify bona fide instances of this form of genetic
architecture as a contributor to the heritability of NS.