A systematic approach to mapping recessive disease genes in individuals from outbred populations

The identification of recessive disease-causing genes by homozygosity mapping is often restricted by lack of suitable consanguineous families. To overcome these limitations, we apply homozygosity mapping to single affected individuals from outbred populations. In 72 individuals of 54 kindred ascertained worldwide with known homozygous mutations in 13 different recessive disease genes, we performed total genome homozygosity mapping using 250,000 SNP arrays. Likelihood ratio Z-scores (ZLR) were plotted across the genome to detect ZLR peaks that reflect segments of homozygosity by descent, which may harbor the mutated gene. In 93% of cases, the causative gene was positioned within a consistent ZLR peak of homozygosity. The number of peaks reflected the degree of inbreeding. We demonstrate that disease-causing homozygous mutations can be detected in single cases from outbred populations within a single ZLR peak of homozygosity as short as 2 Mb, containing an average of only 16 candidate genes. As many specialty clinics have access to cohorts of individuals from outbred populations, and as our approach will result in smaller genetic candidate regions, the new strategy of homozygosity mapping in single outbred individuals will strongly accelerate the discovery of novel recessive disease genes

Mutations In Plce1 Are A Major Cause Of Isolated Diffuse Mesangial Sclerosis (Idms)

Background and objectives. Diffuse mesangial sclerosis (DMS) is a histologically distinct variant of nephrotic syndrome (NS) that is characterized by early onset and by progression to end-stage kidney disease (ESKD). Besides syndromic DMS, isolated (non-syndromic) DMS (IDMS) has been described. The etiology and pathogenesis of DMS is not understood. We recently identified by positional cloning recessive mutations in the gene PLCE1/NPHS3 as a novel cause of IDMS. We demonstrated a role of PLCE1 in glomerulogenesis. Mutations in two other genes WT1 and LAMB2 may also cause IDMS. We therefore determine in this study the relative frequency of mutations in PLCE1, WT1 or LAMB2 as the cause of IDMS in a worldwide cohort. Methods. We identified 40 children from 35 families with IDMS from a worldwide cohort of 1368 children with NS. All the subjects were analyzed for mutations in all exons of PLCE1 by multiplex capillary heteroduplex analysis and direct sequencing, by direct sequencing of exons 8 and 9 of WT1, and all the exons of LAMB2. Results. The median ( range) age at onset of NS was 11 (1-72) months. We detected truncating mutations in PLCE1 in 10/35 (28.6%) families and WT1 mutations in 3/35 (8.5%) families. We found no mutations in LAMB2. Conclusions. PLCE1 mutation is the most common cause of IDMS in this cohort. We previously reported that one child with truncating mutation in PLCE1 responded to cyclosporine therapy. If this observation is confirmed in a larger study, mutations in PLCE1 may serve as a biomarker for selecting patients with IDMS who may benefit from treatment.WoSScopu

Positional cloning uncovers mutations in PLCE1 responsible for a nephrotic syndrome variant that may be reversible

Nephrotic syndrome, a malfunction of the kidney glomerular filter, leads to proteinuria, edema and, in steroid-resistant nephrotic syndrome, end-stage kidney disease. Using positional cloning, we identified mutations in the phospholipase C epsilon gene (PLCE1) as causing early-onset nephrotic syndrome with end-stage kidney disease. Kidney histology of affected individuals showed diffuse mesangial sclerosis (DMS). Using immunofluorescence, we found PLC epsilon 1 expression in developing and mature glomerular podocytes and showed that DMS represents an arrest of normal glomerular development. We identified IQ motif-containing GTPase-activating protein 1 as a new interaction partner of PLC epsilon 1. Two siblings with a missense mutation in an exon encoding the PLCe1 catalytic domain showed histology characteristic of focal segmental glomerulosclerosis. Notably, two other affected individuals responded to therapy, making this the first report of a molecular cause of nephrotic syndrome that may resolve after therapy. These findings, together with the zebrafish model of human nephrotic syndrome generated by plce1 knockdown, open new inroads into pathophysiology and treatment mechanisms of nephrotic syndrome

Positional cloning uncovers mutations in PLCE1 responsible for a nephrotic syndrome variant that may be reversible

Nephrotic syndrome, a malfunction of the kidney glomerular filter, leads to proteinuria, edema and, in steroid-resistant nephrotic syndrome, end-stage kidney disease. Using positional cloning, we identified mutations in the phospholipase C epsilon gene (PLCE1) as causing early-onset nephrotic syndrome with end-stage kidney disease. Kidney histology of affected individuals showed diffuse mesangial sclerosis (DMS). Using immunofluorescence, we found PLC epsilon 1 expression in developing and mature glomerular podocytes and showed that DMS represents an arrest of normal glomerular development. We identified IQ motif-containing GTPase-activating protein 1 as a new interaction partner of PLC epsilon 1. Two siblings with a missense mutation in an exon encoding the PLCe1 catalytic domain showed histology characteristic of focal segmental glomerulosclerosis. Notably, two other affected individuals responded to therapy, making this the first report of a molecular cause of nephrotic syndrome that may resolve after therapy. These findings, together with the zebrafish model of human nephrotic syndrome generated by plce1 knockdown, open new inroads into pathophysiology and treatment mechanisms of nephrotic syndrome