A false-carrier state for the c.579G>A mutation in the NCF1 gene in Ashkenazi Jews.

BACKGROUND: Mutations in the NCF1 gene that encodes p47phox, a subunit of the NADPH oxidase complex, cause chronic granulomatous disease (CGD). In Kavkazi Jews, a c.579G>A (p.Trp193Ter) mutation in NCF1 is frequently found, leading to CGD. The same mutation is found in about 1% of Ashkenazi Jews, although Ashkenazi CGD patients with this mutation have never been described. METHODS: We used Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA), gene scan analysis and Ion Torrent Next Generation Sequencing for genetic analysis, and measured NADPH oxidase activity and p47phox expression. RESULTS: In an Ashkenazi couple expecting a baby, both parents were found to be heterozygotes for this mutation, as was the fetus. However, segregation analysis in the extended family was consistent with the fetus inheriting both carrier alleles from the parents. MLPA indicated four complete NCF1 genes in the fetus and three in each parent. Gene sequencing confirmed these results. Analysis of fetal leucocytes obtained by cordocentesis revealed substantial oxidase activity with three different assays, which was confirmed after birth. In six additional Ashkenazi carriers of the NCF1 c.579G>A mutation, we found five individuals with three complete NCF1 genes of which one was mutated (like the parents), and one individual with in addition a fusion gene of NCF1 with a pseudogene. CONCLUSION: These results point to the existence of a 'false-carrier' state in Ashkenazi Jews and have wide implications regarding pre-pregnancy screening in this and other population groups.

Renal hypodysplasia associates with a WNT4 variant that causes aberrant canonical WNT signaling.

Abnormal differentiation of the renal stem/progenitor pool into kidney tissue can lead to renal hypodysplasia (RHD), but the underlying causes of RHD are not well understood. In this multicenter study, we identified 20 Israeli pedigrees with isolated familial, nonsyndromic RHD and screened for mutations in candidate genes involved in kidney development, including PAX2, HNF1B, EYA1, SIX1, SIX2, SALL1, GDNF, WNT4, and WT1. In addition to previously reported RHD-causing genes, we found that two affected brothers were heterozygous for a missense variant in the WNT4 gene. Functional analysis of this variant revealed both antagonistic and agonistic canonical WNT stimuli, dependent on cell type. In HEK293 cells, WNT4 inhibited WNT3A induced canonical activation, and the WNT4 variant significantly enhanced this inhibition of the canonical WNT pathway. In contrast, in primary cultures of human fetal kidney cells, which maintain WNT activation and more closely represent WNT signaling in renal progenitors during nephrogenesis, this mutation caused significant loss of function, resulting in diminished canonical WNT/ß-catenin signaling. In conclusion, heterozygous WNT4 variants are likely to play a causative role in renal hypodysplasia.

The D144E substitution in the VSX1 gene: a non-pathogenic variant or a disease causing mutation?

PURPOSE: To identify the genetic defect associated with keratoconus (KC) in an Ashkenazi Jewish family and to evaluate its nature and its phenotypic expression within carriers. METHODS: A three generation Ashkenazi Jewish family with KC was ascertained. Diagnosis was based on clinical examination and corneal topography. Segregation analysis was performed using micro-satellite polymorphic markers in close proximity to 7 previously associated KC loci and genes. Mutation analysis of the VSX1 gene was performed by direct sequencing of PCR-amplified exons, and a BseR1 restriction assay. In selected cases, where the genotype was consistent with KC, additional effort to detect subtle corneal changes was made by computerized Orbscan measurements. RESULTS: We found co-segregation between the KC phenotype and a polymorphic marker close to the VSX1. Sequencing revealed a previously described missense mutation (D144E). All of the mutation carriers manifested pathologic corneal findings; some had overt KC while others had subtle corneal alterations identifiable only by Orbscan. CONCLUSIONS: These findings support the pathogenic role of VSX1 gene in KC. The variable expression among the carriers, suggests the involvement of other factors in determining the final phenotype.