Karyotype–phenotype insights from 11q14.1‐q23.2 interstitial deletions:FZD4haploinsufficiency and exudative vitreoretinopathy in a patient with a complex chromosome rearrangement

Abstract

We detected a unique de novo complex chromosome rearrangement (CCR) in a patient with multiple abnormalities including growth retardation, facial anomalies, exudative vitreoretinopathy (EVR), cleft palate, and minor digital anomalies. Cytogenetic analysis, fluorescent in situ hybridization, and microsatellite genotyping showed a reciprocal translocation between chromosomes 5 and 8, and a complex translocation-deletion-inversion process in the formation of derivative chromosomes 11 and 16. High-density whole-genome oligonucleotide array comparative genomic hybridization (oaCGH) defined a 35-megabase interstitial deletion of 11q14.1-q23.2 and a 1 megabase deletion of 16q22.3-q23.1. The Frizzled-4 (FZD4) gene is located within this 11q deletion. Parental studies and sequencing analysis confirmed that the patient was hemizygous for FZD4 due to the loss of a paternal allele on the derivative chromosome 11. Mutations in FZD4 are known to cause autosomal dominant exudative vitreoretinopathy (EVR1). Our patient's findings suggest that haploinsufficiency of the FZD4 gene product can also be a disease-causing mechanism for EVR1. We reviewed the clinical manifestations of 23 cases with 11q14-q23 interstitial deletions, with particular scrutiny of the present case and four reported cases characterized by molecular cytogenetics. These findings were used to construct a regional deletion map consisting of a haplosufficient segment at 11q14.3, a flanking centromeric segment at 11q14.1-q14.2, and a flanking telomeric segment at 11q21-q23.3. We propose that deletions of the FZD4 gene located within the centromeric segment cause retinal dysgenesis, while deletions within the telomeric segment account for dysmorphic craniofacial features, growth and mental retardation, and mild digital anomalies. These results provide insight into karyotype-phenotype correlations and prompt a rational analytic approach to cases with interstitial deletions of the 11q14-q23 region.