Aims: To reveal the Usher syndrome type IIA (USH2A) gene variant profile in a large cohort of Chinese patients with non-syndromic retinitis pigmentosa (RP) or Usher syndrome type II (USH2) and to explore the genotype-phenotype correlation.
Methods: Targeted exome capture plus next-generation sequencing confirmed that 284 patients from 260 unrelated Chinese families carried USH2A disease-associated variants. Both personal medical history and family histories were reviewed. Ocular examinations were performed and audiograms were recorded if hearing loss was suspected. The genotype-phenotype correlation was evaluated by statistical analyses.
Results: A total of 230 variants in the USH2A gene were identified, of which 90 (39.13%) were novel. The most common variants in the RP and USH2 probands were p.Cys934Trp and p.Tyr2854_2894del, respectively, and 26.42% and 63.64% of the alleles in the RP and USH2 groups were truncating, respectively. Patients harbouring biallelic truncating variants had a younger age at the initial clinical visit and symptom onset than patients with missense variants; furthermore, the patients with USH2 had a younger age at the initial clinical visit and nyctalopia onset compared with the patients with RP (p<0.001). For the patients with USH2, the age of nyctalopia onset was positively correlated with that of hearing loss (p<0.05, r=0.219). In addition, three pseudo-dominant pedigrees were identified carrying biallelic USH2A variants.
Conclusions: This study enrolled the largest cohort of Chinese patients with USH2A and identified the most prevalent USH2A variants in USH2 and RP. We found that the patients with USH2 had more truncating variants and experienced an earlier decline in visual function. The findings enhance the current knowledge of USH2A heterogeneity and provide valuable information for future therapies.
Keywords: Degeneration; Electrophysiology; Eye (Globe); Genetics; Retina; Stem Cells.
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