Mutation ofPOC1Bin a Severe Syndromic Retinal Ciliopathy

We describe a consanguineous Iraqi family with Leber congenital amaurosis (LCA), Joubert syndrome (JBTS), and polycystic kidney disease (PKD). Targeted next-generation sequencing for excluding mutations in known LCA and JBTS genes, homozygosity mapping, and whole-exome sequencing identified a homozygous missense variant, c.317G>C (p.Arg106Pro), in POC1B, a gene essential for ciliogenesis, basal body, and centrosome integrity. In silico modeling suggested a requirement of p.Arg106 for the formation of the third WD40 repeat and a protein interaction interface. In human and mouse retina, POC1B localized to the basal body and centriole adjacent to the connecting cilium of photoreceptors and in …

The Role of Cadherins in Ca2+-Mediated Cell Adhesion and Inherited Photoreceptor Degeneration

Cadherins are Ca2+-binding, transmembrane proteins involved in cell adhesion. Recently, three cadherin molecules, cadherin-23, protocadherin-15, and cadherin-3, were found to be defective in various human diseases, many of them with photoreceptor degeneration and/or sensorineural hearing loss as major features such Usher syndrome type 1D (USH1D), USH1F, and hypotrichosis with juvenile macular dystrophy. The process, by which mutations lead to photoreceptor degeneration is still not fully understood. Data from the inner ear phenotype of USH1 mouse models suggest that loss of cell adhesion is a crucial event.

C21orf2 is mutated in recessive early-onset retinal dystrophy with macular staphyloma and encodes a protein that localises to the photoreceptor primary cilium.

Background/aim We have noted a phenotype of early-onset retinal dystrophy with macular staphyloma but without high myopia. The aim of this study is to report the underlying genetic mutations and the subcellular localisation of the gene product in the retina. Methods Retrospective case series (2012–2015); immunohistochemical analyses of mammalian retina for in situ protein localisation. Results All three probands were first noted to have decreased vision at 3–6 years old which worsened over time. At ages 39, 37 and 12 years old, all had similar retinal findings: dystrophic changes (retinal pigment epithelium mottling, vessel narrowing), macular staphyloma (despite only mild myopia or high hy…

Next‐generation sequencing reveals the mutational landscape of clinically diagnosed Usher syndrome: copy number variations, phenocopies, a predominant target for translational read‐through, and PEX26 mutated in Heimler syndrome

Background Combined retinal degeneration and sensorineural hearing impairment is mostly due to autosomal recessive Usher syndrome (USH1: congenital deafness, early retinitis pigmentosa (RP); USH2: progressive hearing impairment, RP). Methods Sanger sequencing and NGS of 112 genes (Usher syndrome, nonsyndromic deafness, overlapping conditions), MLPA, and array-CGH were conducted in 138 patients clinically diagnosed with Usher syndrome. Results A molecular diagnosis was achieved in 97% of both USH1 and USH2 patients, with biallelic mutations in 97% (USH1) and 90% (USH2), respectively. Quantitative readout reliably detected CNVs (confirmed by MLPA or array-CGH), qualifying targeted NGS as one …

PEX6 is Expressed in Photoreceptor Cilia and Mutated in Deafblindness with Enamel Dysplasia and Microcephaly

Deafblindness is part of several genetic disorders. We investigated a consanguineous Egyptian family with two siblings affected by congenital hearing loss and retinal degeneration, initially diagnosed as Usher syndrome type 1. At teenage, severe enamel dysplasia, developmental delay, and microcephaly became apparent. Genome-wide homozygosity mapping and whole-exome sequencing detected a homozygous missense mutation, c.1238G>T (p.Gly413Val), affecting a highly conserved residue of peroxisomal biogenesis factor 6, PEX6. Biochemical profiling of the siblings revealed abnormal and borderline plasma phytanic acid concentration, and cerebral imaging revealed white matter disease in both. We show …

TALPID3 controls centrosome and cell polarity and the human ortholog KIAA0586 is mutated in Joubert syndrome (JBTS23)

Joubert syndrome (JBTS) is a severe recessive neurodevelopmental ciliopathy which can affect several organ systems. Mutations in known JBTS genes account for approximately half of the cases. By homozygosity mapping and whole-exome sequencing, we identified a novel locus, JBTS23, with a homozygous splice site mutation in KIAA0586 (alias TALPID3), a known lethal ciliopathy locus in model organisms. Truncating KIAA0586 mutations were identified in two additional patients with JBTS. One mutation, c.428delG (p.Arg143Lysfs*4), is unexpectedly common in the general population and may be a major contributor to JBTS. We demonstrate KIAA0586 protein localization at the basal body in human and mouse p…

Author response: TALPID3 controls centrosome and cell polarity and the human ortholog KIAA0586 is mutated in Joubert syndrome (JBTS23)