High-throughput sequencing for the molecular diagnosis of Usher syndrome reveals 42 novel mutations and consolidates CEP250 as Usher-like disease causative

Abstract

Usher syndrome is a rare disorder causing retinitis pigmentosa, together with sensorineural hearing loss. Due to the phenotypic and genetic heterogeneity of this disease, the best method to screen the causative mutations is by high-throughput sequencing. In this study, we tested a semiconductor chip based sequencing approach with 77 unrelated patients, as a molecular diagnosis routine. In addition, Multiplex Ligation-dependent Probe Amplification and microarray-based Comparative Genomic Hybridization techniques were applied to detect large rearrangements, and minigene assays were performed to confirm the mRNA processing aberrations caused by splice-site mutations. The designed panel included all the USH causative genes (MYO7A, USH1C, CDH23, PCDH15, USH1G, CIB2, USH2A, ADGRV1, WHRN and CLRN1) as well as four uncertainly associated genes (HARS, PDZD7, CEP250 and C2orf71). The outcome showed an overall mutation detection ratio of 82.8% and allowed the identification of 42 novel putatively pathogenic mutations. Furthermore, we detected two novel nonsense mutations in CEP250 in a patient with a disease mimicking Usher syndrome that associates visual impairment due to cone-rod dystrophy and progressive hearing loss. Therefore, this approach proved reliable results for the molecular diagnosis of the disease and also allowed the consolidation of the CEP250 gene as disease causative for an Usher-like phenotype.

Ataluren for the Treatment of Usher Syndrome 2A Caused by Nonsense Mutations

“…As mutations in USH2A account for 12%-25% of non-syndromic RP patients and for 55%-90% of USH2 patients, it is one of the most important genes in these rare diseases [9,[39][40][41]. Moreover, 14%-29% of the disease-causing mutations in USH2A are nonsense mutations [42,43]; thus, targeting those mutations would be beneficial for a large cohort of affected individuals.…”

Expanding the Genetic Landscape of Usher-Like Phenotypes

“…For this purpose, we performed whole exome sequencing (WES) in probands from nine unrelated families that had been screened previously through our implemented targeted panel. 11…”

Therapeutic approaches and development of genomic diagnostic tools for Usher syndrome

“…Consequently, the gold standard to date for the molecular diagnosis of USH patients is by means of targeted exome sequencing (Oishi et al 2014, Eandi et al 2017, Fuster-García et al 2018). However, not all USH cases are explained by mutations in the coding regions of any of the USH genes, implying that there remain other unknown genes causing the disease or pathogenic variants in the non-coding regions of the USH genes.…”

“…2015, Neuhaus et al 2017), or due to other syndromes that also associate a retinal dystrophy (RD) and HL, such as polyneuropathy, hearing loss, ataxia, retinitis pigmentosa and cataracts (PHARC) or Heimler syndrome (Raas-Rothschild et al 2002, Eisenberger et al 2012, Fuster-García et al 2018. Taking this prospect into account, the genes responsible for nonsyndromic RP (nsRP) and HL independently should be considered, as well as those associated with more complex diseases with those symptoms among its spectrum.…”

“…We unveil the genetic landscape underlying cases with an USH-like phenotype yet negative for the USH genes, and unveil new insights of either new candidate genes or to resolve the genetic puzzle. For this purpose, we performed whole exome sequencing (WES) in probands from nine unrelated families that had been screened previously through our implemented targeted panel (Fuster-García et al 2018).…”