Dataset Information

Cone-rod dystrophy and a frameshift mutation in the PROM1 gene.

ABSTRACT: To identify the genetic cause underlying autosomal recessive cone-rod dystrophy (CORD) and high myopia.Nine members of a consanguineous Arab family were clinically examined and were given fluorescein angiography (FA), biometry, and full field electroretinogram (ERG) testing. Blood samples were collected for DNA extraction. A homozygousity genome-wide scan was performed using >382 polymorphic microsatellite markers on genomic DNA from three affected family members. Regions of homozygosity were further analyzed in all members of the family. Mutation analysis of the PROM1 gene was performed by direct sequencing of PCR-amplified exons.The phenotype is characterized by severe visual impairment evident in the first decade of life. Affected family members have bull;s-eye macular appearance, peripheral retinal pigment clumps, and cone-rod type ERG changes. Additionally, they have high myopia with axial lengths exceeding 25.3 mm. A genome-wide scan detected a region of 2.1 Mb on chromosome 4p that fully segregates with the disease within the family. This region encompasses the PROML1 gene, mutations of which have been implicated in retinal dystrophies. PROML1 mutation analysis identified a novel single nucleotide insertion at position 1629 of the cDNA resulting in truncation of approximately one-third of the protein.The mutation described in this report further expands the clinical spectrum of PROM1 mutations.

SUBMITTER: Pras E

PROVIDER: S-EPMC2732717 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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Cone-rod dystrophy and a frameshift mutation in the PROM1 gene.

Pras Eran E Abu Almogit A Rotenstreich Ygal Y Avni Isaac I Reish Orit O Morad Yair Y Reznik-Wolf Haike H Pras Elon E

Molecular vision 20090828

<h4>Purpose</h4>To identify the genetic cause underlying autosomal recessive cone-rod dystrophy (CORD) and high myopia.<h4>Methods</h4>Nine members of a consanguineous Arab family were clinically examined and were given fluorescein angiography (FA), biometry, and full field electroretinogram (ERG) testing. Blood samples were collected for DNA extraction. A homozygousity genome-wide scan was performed using >382 polymorphic microsatellite markers on genomic DNA from three affected family members. ...[more]

PMID: 19718270

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Project description:To investigate the genetic basis for autosomal recessive cone-rod dystrophy (CRD) in a consanguineous Israeli Jewish family.Patients underwent a detailed ophthalmic evaluation, including eye examination, visual field testing, optical coherence tomography (OCT), and electrophysiological tests, electroretinography (ERG) and visual evoked potential (VEP). Genome-wide homozygosity mapping using a single nucleotide polymorphism (SNP) array was performed to identify homozygous regions shared among two of the affected individuals. Mutation screening of the underlying gene was performed with direct sequencing. In silico and in vitro analyses were used to predict the effect of the identified mutation on splicing.The affected family members are three siblings who have various degrees of progressive visual deterioration, glare, color vision abnormalities, and night vision difficulties. Visual field tests revealed central scotomas of different extension. Cone and rod ERG responses were reduced, with cones more severely affected. Homozygosity mapping revealed several homozygous intervals shared among two of the affected individuals. One included the PROM1 gene. Sequence analysis of the 26 coding exons of PROM1 in one affected individual revealed no mutations in the coding sequence or in intronic splice sites. However, in intron 21, proximate to the intron-exon junction, we observed a homozygous 10 bp deletion between positions -26 and -17 (c.2281-26_-17del). The deletion was linked to a known SNP, c.2281-6C>G. The deletion cosegregated with the disease in the family, and was not detected in public databases or in 101 ethnically-matched control individuals. In silico analysis predicted that this deletion would lead to altered intron 21 splicing. Bioinformatic analysis predicted that a recognition site for the SRSF2 splicing factor is located within the deleted sequence. The in vitro splicing assay demonstrated that c.2281-26_-17del leads to complete exon 22 skipping.A novel and unique intronic mutation of PROM1, underlying autosomal recessive CRD in a consanguineous Israeli family, was found. This report expands the spectrum of pathogenic mutations of PROM1 and further demonstrates the importance of intronic mutations.

Project description:UnlabelledMutations in RPGRIP1 are associated with early onset retinal degenerations in humans and dogs. Dogs homozygous for a 44 bp insertion including a polyA(29) tract potentially leading to premature truncation of the protein, show cone rod degeneration. This is rapid and blinding in a colony of dogs in which the mutation was characterised but in dogs with the same mutation in the pet population there is very variable disease severity and rate of progression.ObjectiveWe hypothesized that this variability must be associated with leakiness of the RPGRIP1 mutation, allowing continued RPGRIP1 production. The study was designed to discover mechanisms that might allow such leakiness.MethodsWe analysed alternate start sites and splicing of RPGRIP1 transcripts; variability of polyA(n) length in the insertion and slippage at polyA(n) during transcription/translation.Results and significanceWe observed a low rate of use of alternative start codons having potential to allow forms of transcript not including the insertion, with the possibility of encoding truncated functional RPGRIP1 protein isoforms. Complex alternative splicing was observed, but did not increase this potential. Variable polyA(n) length was confirmed in DNA from different RPGRIP1(-/-) dogs, yet polyA(n) variability did not correspond with the clinical phenotypes and no individual was found that carried a polyA(n) tract capable of encoding an in-frame variant. Remarkably though, in luciferase reporter gene assays, out-of-frame inserts still allowed downstream reporter gene expression at some 40% of the efficiency of in-frame controls. This indicates a major role of transcriptional or translational frameshifting in RPGRIP1 expression. The known slippage of reverse transcriptases as well as RNA polymerases and thermostable DNA polymerases on oligoA homopolymers meant that we could not distinguish whether the majority of slippage was transcriptional or translational. This leakiness at the mutation site may allow escape from severe effects of the mutation for some dogs.

Project description:To identify the causative mutation in a canine cone-rod dystrophy (crd3) that segregates as an adult onset disorder in the Glen of Imaal Terrier breed of dog.Glen of Imaal Terriers were ascertained for crd3 phenotype by clinical ophthalmoscopic examination, and in selected cases by electroretinography. Blood samples from affected cases and non-affected controls were collected and used, after DNA extraction, to undertake a genome-wide association study using Affymetrix Version 2 Canine single nucleotide polymorphism chips and 250K Sty Assay protocol. Positional candidate gene analysis was undertaken for genes identified within the peak-association signal region. Retinal morphology of selected crd3-affected dogs was evaluated by light and electron microscopy.A peak association signal exceeding genome-wide significance was identified on canine chromosome 16. Evaluation of genes in this region suggested A Disintegrin And Metalloprotease domain, family member 9 (ADAM9), identified concurrently elsewhere as the cause of human cone-rod dystrophy 9 (CORD9), as a strong positional candidate for canine crd3. Sequence analysis identified a large genomic deletion (over 20 kb) that removed exons 15 and 16 from the ADAM9 transcript, introduced a premature stop, and would remove critical domains from the encoded protein. Light and electron microscopy established that, as in ADAM9 knockout mice, the primary lesion in crd3 appears to be a failure of the apical microvilli of the retinal pigment epithelium to appropriately invest photoreceptor outer segments. By electroretinography, retinal function appears normal in very young crd3-affected dogs, but by 15 months of age, cone dysfunction is present. Subsequently, both rod and cone function degenerate.Identification of this ADAM9 deletion in crd3-affected dogs establishes this canine disease as orthologous to CORD9 in humans, and offers opportunities for further characterization of the disease process, and potential for genetic therapeutic intervention.

Dataset Information

Cone-rod dystrophy and a frameshift mutation in the PROM1 gene.

Publications

Cone-rod dystrophy and a frameshift mutation in the PROM1 gene.

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