Next-generation sequencing of a 40 Mb linkage interval reveals TSPAN12 mutations in patients with familial exudative vitreoretinopathy.

Familial exudative vitreoretinopathy (FEVR) is a genetically heterogeneous retinal disorder characterized by abnormal vascularisation of the peripheral retina, often accompanied by retinal detachment. To date, mutations in three genes (FZD4, LRP5, and NDP) have been shown to be causative for FEVR. In two large Dutch pedigrees segregating autosomal-dominant FEVR, genome-wide SNP analysis identified an FEVR locus of approximately 40 Mb on chromosome 7. Microsatellite marker analysis suggested similar at risk haplotypes in patients of both families. To identify the causative gene, we applied next-generation sequencing in the proband of one of the families, by analyzing all exons and intron-exon boundaries of 338 genes, in addition to microRNAs, noncoding RNAs, and other highly conserved genomic regions in the 40 Mb linkage interval. After detailed bioinformatic analysis of the sequence data, prioritization of all detected sequence variants led to three candidates to be considered as the causative genetic defect in this family. One of these variants was an alanine-to-proline substitution in the transmembrane 4 superfamily member 12 protein, encoded by TSPAN12. This protein has very recently been implicated in regulating the development of retinal vasculature, together with the proteins encoded by FZD4, LRP5, and NDP. Sequence analysis of TSPAN12 revealed two mutations segregating in five of 11 FEVR families, indicating that mutations in TSPAN12 are a relatively frequent cause of FEVR. Furthermore, we demonstrate the power of targeted next-generation sequencing technology to identify disease genes in linkage intervals.

Overview of the mutation spectrum in familial exudative vitreoretinopathy and Norrie disease with identification of 21 novel variants in FZD4, LRP5, and NDP.

Wnt signaling is a crucial component of the cell machinery orchestrating a series of physiological processes such as cell survival, proliferation, and migration. Among the plethora of roles that Wnt signaling plays, its canonical branch regulates eye organogenesis and angiogenesis. Mutations in the genes encoding the low density lipoprotein receptor protein 5 (LRP5) and frizzled 4 (FZD4), acting as coreceptors for Wnt ligands, cause familial exudative vitreoretinopathy (FEVR). Moreover, mutations in the gene encoding NDP, a ligand for these Wnt receptors, cause Norrie disease and FEVR. Both FEVR and Norrie disease share similar phenotypic characteristics, including abnormal vascularization of the peripheral retina and formation of fibrovascular masses in the eye that can lead to blindness. In this mutation update, we report 21 novel variants for FZD4, LRP5, and NDP, and discuss the putative functional consequences of missense mutations. In addition, we provide a comprehensive overview of all previously published variants in the aforementioned genes and summarize the phenotypic characteristics in mouse models carrying mutations in the orthologous genes. The increasing molecular understanding of Wnt signaling, related to ocular development and blood supply, offers more tools for accurate disease diagnosis that may be important in the development of therapeutic interventions.

Endogenous endophthalmitis after otitis media.

PURPOSE: To report a case of bacterial endophthalmitis after otitis media in a healthy adult. DESIGN: Interventional case report. METHODS: A healthy 49-year-old Caucasian woman developed acute otitis media of the right ear. Three weeks after the first onset there was a recurrence of the otitis media, with perforation of the tympanic membrane. Two days after this, the woman presented at our clinic with endophthalmitis of the right eye. RESULTS: A culture of vitreous material grew Streptococcus pyogenes (Streptococcus Lancefield group A). The same strain was found in a smear from the perforated ear. Despite aggressive treatment, the affected eye had to be eviscerated. CONCLUSIONS: Otitis media can result in a bacteremia. This may, even in a healthy adult, lead to a devastating endogenous bacterial endophthalmitis.

Clinical and molecular evaluation of probands and family members with familial exudative vitreoretinopathy.

PURPOSE: To describe the ophthalmic characteristics and to identify the molecular cause of FEVR in a cohort of Dutch probands and their family members. METHODS: Twenty families with familial exudative vitreoretinopathy (FEVR) comprising 83 affected and nonaffected individuals were studied. Based on the presence of an avascular zone, the clinical diagnosis was made and biometric data of the posterior pole of 57 patients and family members were obtained by the analysis of fundus photographs and compared with the data of 40 controls. The FZD4, LRP5, and NDP genes were screened for mutations in one affected individual per family. The segregation of the gene variants was studied in the corresponding families. RESULTS: Forty of 83 individuals showed an avascular zone, the most evident clinical sign of FEVR, five showed major signs of FEVR, and 38 persons were not clinically affected. Compared with the control subjects the patients with FEVR had a significantly larger disc-to-macula distance and a significantly smaller optic disc. In 8 of 20 families, a FZD4 mutation was identified, in 2 a mutation in the LRP5 gene, and in 2 a mutation in the NDP gene. Three known and five novel mutations were identified. Nonpenetrance was observed in 26% of the mutation carriers. CONCLUSIONS: Significant anatomic differences were identified between the eyes of patients with FEVR with an avascular zone, when compared with those of the control subjects. In patients with an avascular zone, the optic disc was smaller and the disc-to-macula distance larger than in the control subjects. In 60% of the probands, mutations were identified in one of the three known FEVR genes.