Variants in CDH23 cause a broad spectrum of hearing loss: from non-syndromic to syndromic hearing loss as well as from congenital to age-related hearing loss.

Variants in the CDH23 gene are known to be responsible for both syndromic hearing loss (Usher syndrome type ID: USH1D) and non-syndromic hearing loss (DFNB12). Our series of studies demonstrated that CDH23 variants cause a broad range of phenotypes of non-syndromic hearing loss (DFNB12); from congenital profound hearing loss to late-onset high-frequency-involved progressive hearing loss. In this study, based on the genetic and clinical data from more than 10,000 patients, the mutational spectrum, clinical characteristics and genotype/phenotype correlations were evaluated. The present results reconfirmed that the variants in CDH23 are an important cause of non-syndromic sensorineural hearing loss. In addition, we showed that the mutational spectrum in the Japanese population, which is probably representative of the East Asian population in general, as well as frequent CDH23 variants that might be due to some founder effects. The present study demonstrated CDH23 variants cause a broad range of phenotypes, from non-syndromic to syndromic hearing loss as well as from congenital to age-related hearing loss. Genotype (variant combinations) and phenotype (association with retinal pigmentosa, onset age) are shown to be well correlated and are thought to be related to the residual function defined by the CDH23 variants.

A nationwide epidemiologic, clinical, genetic study of Usher syndrome in Japan.

BACKGROUND: Usher syndrome (USH) typically leads to deaf-blindness, requiring the provision of extensive education and rehabilitation services. Therefore, investigating the prevalence is crucial to requests for proper government support for USH patients. OBJECTIVE: The aim was to perform a nationwide epidemiologic survey of USH in Japan to estimate the prevalence of USH and reveal the relative frequency and characteristics of the three USH subtypes. METHODS: To estimate the number of USH patients visiting hospitals over a 1-year period, 1,628 hospitals were randomly selected from all Departments of Otorhinolaryngology and Ophthalmology in Japan. Subsequently, we collected data regarding the clinical characteristics of each patient treated and the results of genetic testing, if performed. RESULTS: We found that the prevalence of USH was at least 0.4 per 100,000 population. The frequency of clinical subtypes and causal genes for USH were consistent with previous reports. Also, we demonstrated the feasibility of genetic counseling for USH patients based on the results of genetic testing. CONCLUSION: USH is a rare disease, but requires social support due to the severity of symptoms. To minimize these issues, understanding the clinical characteristics and performing comprehensive genetic testing could allow early and accurate diagnosis as well as medical intervention.

Improvement of a Rapid and Highly Sensitive Method for the Diagnosis of the Mitochondrial m.1555A>G Mutation Based on a Single-Stranded Tag Hybridization Chromatographic Printed-Array Strip.

Aims: Pathogenic variants in mitochondrial DNA are known to be associated with sensorineural hearing loss (SNHL) and aminoglycoside-induced HL. Among them, the m.1555A>G mutation is the most common. Thus, a rapid and easy companion diagnostic method for this mutation would be desirable to prevent HL caused by aminoglycoside therapy. In this study, we report an improved protocol for the single-stranded tag hybridization chromatographic printed-array strip (STH-PAS) method for identifying the m.1555A>G mutation. Methods: To evaluate the accuracy of a novel diagnostic for the m.1555A>G mutation we analyzed 378 DNA samples with or without the m.1555A>G mutation, as determined by Invader assay, and calculated the sensitivity, specificity, and false negative and false positive ratios of this new method. Results: The newly developed protocol was robust; we, obtained the same results using multiple DNA concentrations, differing annealing temperatures, and different polymerase chain reaction thermal cyclers. The diagnostic sensitivity based on the STH-PAS method was 0.99, and the specificity was 1.00. The false negative and false positive ratios were 0 and 0.01, respectively. Conclusion: We improved the genotyping method for m.1555A>G mutations. This assays will be useful as a rapid companion diagnostic before aminoglycoside use.

A rational approach to identifying newborns with hearing loss caused by congenital cytomegalovirus infection by dried blood spot screening.

OBJECTIVE: Congenital cytomegalovirus (cCMV) infection is the most common congenital infection, with the majority of infected newborns having no detectable signs. The aim of this study was to examine the accuracy of our newly developed DBS-based assay as an appropriate mass screening method for cCMV infection. METHODS: Between May 2011 and October 2016, newborns delivered at six hospitals in Nagano Prefecture, Japan were enrolled prospectively. We employed dried blood spot (DBS)-based assays with real-time quantitative PCR (qPCR). RESULTS: Prior to the clinical study, confirmation analysis was carried out using positive and negative controls. The sensitivity and specificity of this DBS-based qPCR assay for the detection of CMV DNA were 83 and 97%, respectively. During the study period, 9675 newborns were enrolled. The total recovery rate of DBS was 99.92% (9,667/9,675). From our analysis of the 9,667 samples, 47 DBS samples were found positive by the qPCR test (0.48%), and 9620 (99.5%) DBS samples were CMV-negative. CONCLUSIONS: The risk of neural disorders associated with cCMV infection is thought likely to increase with CMV viral load in the blood. DBS screening for cCMV may be sufficient in a clinical setting, and offers a realistic and feasible option for universal mass screening.