Mutational screening of the USH2A gene in Spanish USH patients reveals 23 novel pathogenic mutations

García‐García, Gema; Aparisi, María José; Jaijo, Teresa; Rodrigo, Regina; Leon, Ana M.; Ávila-Fernández, Almudena; Blanco‐Kelly, Fiona; Bernal, Sara; Navarro, Rafael; Díaz-Llopis, M.; Baiget, Montserrat; Ayuso, Carmen; Millán, José María; Aller, Elena

doi:10.1186/1750-1172-6-65

Cited by 49 publications

(43 citation statements)

References 42 publications

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“…28 Participant 12 with late onset RP had two missense variants of unknown significance, c.7130A>G (p.Asn2377Ser) and c.11927C>T (p.Thr3976Met), which have both previously been reported. 28-30 …”

Section: Discussionmentioning

confidence: 99%

High Diagnostic Yield of Whole Exome Sequencing in Participants With Retinal Dystrophies in a Clinical Ophthalmology Setting

Lee

Berg

Milko

et al. 2015

American Journal of Ophthalmology

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Purpose To assess the diagnostic yield and the practicality of implementing whole exome sequencing within a clinical ophthalmology setting. Design Evaluation of a diagnostic protocol. Methods Setting Patient participants were enrolled during clinical appointments in a university based Ophthalmic Genetics clinic. Patient Population Twenty-six patients with a variety of presumed hereditary retinal dystrophies. Intervention: Participants were offered whole exome sequencing in addition to clinically available sequencing gene panels between July 2012 and January 2013 to determine the molecular etiology of their retinal dystrophy. Main Outcome Measures Diagnostic yield and acceptability of whole exome sequencing in patients with retinal disorders. Results Twenty-six of 29 (~90%) eligible patients who were approached opted to undergo molecular testing. Each participant chose whole exome sequencing in addition to, or in lieu of, clinically available sequencing gene panels. Time to obtain informed consent was manageable in the clinical context. Whole exome sequencing successfully identified known pathogenic mutations or suspected deleterious variants in 57.7% of participants. Additionally, one participant had 2 autosomal dominant medically actionable incidental findings (unrelated to retinopathy) that were reported to enable the participant to take preventive action and reduce risk for future disease. Conclusions In this study, we identified the molecular etiology for more than half of all participants. Additionally, we found that participants were widely accepting of whole exome sequencing and the possibility of being informed about medically actionable incidental findings.

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Section: Discussionmentioning

confidence: 99%

High Diagnostic Yield of Whole Exome Sequencing in Participants With Retinal Dystrophies in a Clinical Ophthalmology Setting

Lee

Berg

Milko

et al. 2015

American Journal of Ophthalmology

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“…It is often not possible to identify both pathogenic variants in USH2A [6-8]. In this study we identified eight mutations in 23 USH2 families (35%) who were known to have a monoallelic pathogenic/UV4/UV3 mutations in USH2A detected by Sanger sequencing.…”

Section: Discussionmentioning

confidence: 99%

“…Usher type 2 is the most prevalent form accounting for more than half of reported cases. There are three genes underlying USH2: USH2A, GPR98 and DFNB31 ( WHRN) , with USH2A accounting for 75-80% of cases [6-8]. The mutational spectrum of USH2A is diverse and includes nonsense, frameshift, missense and splice-affecting mutations, as well as deletions and small duplications [9].…”

Section: Introductionmentioning

confidence: 99%

“…Despite recent sequencing strategies that have analysed nine Usher Syndrome genes, and other studies involving thorough sequencing of USH2A , 8-19% of USH2 individuals have just one heterozygous likely disease-causing mutation in USH2A [6-8], and 13% of USH2 patients have no convincing disease-causing mutations [7]. Unidentified mutations in USH2 individuals could lie in the promoter, regulatory regions, and deep intronic areas, all of which are not usually analysed during conventional mutation screening.…”

Section: Introductionmentioning

confidence: 99%

“…Current investigations into the genetic basis of Usher syndrome have focused on Sanger sequencing to detect mutations [7,8]. It is not possible to robustly detect deletions and duplications by sequencing alone, as this method is not sensitive to relative changes in the copy number of exons.…”

Section: Introductionmentioning

confidence: 99%

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Screening for duplications, deletions and a common intronic mutation detects 35% of second mutations in patients with USH2A monoallelic mutations on Sanger sequencing

Steele-Stallard¹,

Stabej²,

Lenassi

et al. 2013

Orphanet J Rare Dis

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BackgroundUsher Syndrome is the leading cause of inherited deaf-blindness. It is divided into three subtypes, of which the most common is Usher type 2, and the USH2A gene accounts for 75-80% of cases. Despite recent sequencing strategies, in our cohort a significant proportion of individuals with Usher type 2 have just one heterozygous disease-causing mutation in USH2A, or no convincing disease-causing mutations across nine Usher genes. The purpose of this study was to improve the molecular diagnosis in these families by screening USH2A for duplications, heterozygous deletions and a common pathogenic deep intronic variant USH2A: c.7595-2144A>G.MethodsForty-nine Usher type 2 or atypical Usher families who had missing mutations (mono-allelic USH2A or no mutations following Sanger sequencing of nine Usher genes) were screened for duplications/deletions using the USH2A SALSA MLPA reagent kit (MRC-Holland). Identification of USH2A: c.7595-2144A>G was achieved by Sanger sequencing. Mutations were confirmed by a combination of reverse transcription PCR using RNA extracted from nasal epithelial cells or fibroblasts, and by array comparative genomic hybridisation with sequencing across the genomic breakpoints.ResultsEight mutations were identified in 23 Usher type 2 families (35%) with one previously identified heterozygous disease-causing mutation in USH2A. These consisted of five heterozygous deletions, one duplication, and two heterozygous instances of the pathogenic variant USH2A: c.7595-2144A>G. No variants were found in the 15 Usher type 2 families with no previously identified disease-causing mutations. In 11 atypical families, none of whom had any previously identified convincing disease-causing mutations, the mutation USH2A: c.7595-2144A>G was identified in a heterozygous state in one family. All five deletions and the heterozygous duplication we report here are novel. This is the first time that a duplication in USH2A has been reported as a cause of Usher syndrome.ConclusionsWe found that 8 of 23 (35%) of ‘missing’ mutations in Usher type 2 probands with only a single heterozygous USH2A mutation detected with Sanger sequencing could be attributed to deletions, duplications or a pathogenic deep intronic variant. Future mutation detection strategies and genetic counselling will need to take into account the prevalence of these types of mutations in order to provide a more comprehensive diagnostic service.

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Clinical Aspects of Usher Syndrome and theUSH2AGene in a Cohort of 433 Patients

et al. 2015

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IMPORTANCE A new statistical approach is needed to describe the clinical differences between type I and type II Usher syndrome and between the 2 most frequent mutations in the USH2A gene. OBJECTIVES To describe the primary phenotypic characteristics and differences between type I and type II Usher syndrome and to establish a phenotype-genotype correlation for the 2 most frequent mutations in the USH2A gene. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional study at a genetics department, in which clinical evaluations were performed for 433 patients (297 unrelated families) who were classified as having type I, II, III, atypical, or unclassified Usher syndrome according to their clinical history, pedigree data, results from ophthalmological studies, and audiological, neurophysiological, and vestibular test results. Molecular studies were performed for 304 patients (256 unrelated families). The Mann-Whitney U test or the χ 2 test was used for calculating the differences between mean values for the analyzed parameters. MAIN OUTCOMES AND MEASURES Age at diagnosis; age at onset of night blindness, visual field loss, visual acuity loss, and cataracts; and severity and age at diagnosis of hearing loss. RESULTS The comparison between patients with type I Usher syndrome and those with type II Usher syndrome revealed P < .001 for most items analyzed. The most frequent mutations in the USH2A gene were the p.Glu767Serfs*21 and p.Cys759Phe mutations, with an allelic frequency of 23.2% (63 of 272 alleles) and 8.1% (22 of 272 alleles), respectively. The phenotypic analysis for patients carrying p.Cys759Phe showed P < .001 for most items analyzed when compared with patients carrying p.Glu767Serfs*21 and when compared with patients carrying other mutations in the USH2A gene. None of the p.Cys759Phe patients exhibited a severe hearing loss phenotype, and more than 60% had only mild hearing loss. Most patients carrying the p.Glu767Serfs*21 mutation (72.1%) were moderately deaf. CONCLUSIONS AND RELEVANCE Our study presents the clinical differences between type I and type II Usher syndrome and between the 2 most frequent mutations in the USH2A gene. Detailed genotype-phenotype correlations, as presented in our study, allow for a better correlation of clinical signs with a known genotype and can improve the clinical management, genetic counseling, and risk assessment of patients with Usher syndrome because an estimated prognosis of their disease can be made.

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Mutational screening of the USH2A gene in Spanish USH patients reveals 23 novel pathogenic mutations

Cited by 49 publications

References 42 publications

High Diagnostic Yield of Whole Exome Sequencing in Participants With Retinal Dystrophies in a Clinical Ophthalmology Setting

High Diagnostic Yield of Whole Exome Sequencing in Participants With Retinal Dystrophies in a Clinical Ophthalmology Setting

Screening for duplications, deletions and a common intronic mutation detects 35% of second mutations in patients with USH2A monoallelic mutations on Sanger sequencing

Clinical Aspects of Usher Syndrome and theUSH2AGene in a Cohort of 433 Patients

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