Kyoko Nagai

Clinical features of patients with GJB2 (connexin 26) mutations: severity of hearing loss is correlated with genotypes and protein expression patterns.

AbstractMutations in the GJB2 (connexin 26, Cx26) gene are the major cause of nonsyndromic hearing impairment in many populations. Genetic testing offers opportunities to determine the cause of deafness and predict the course of hearing, enabling the prognostication of language development. In the current study, we compared severity of hearing impairment in 60 patients associated with biallelic GJB2 mutations and assessed the correlation of genotypes and phenotypes. Within a spectrum of GJB2 mutations found in the Japanese population, the phenotype of the most prevalent mutation, 235delC, was found to show more severe hearing impairment than that of V37I, which is the second most frequent mutation. The results of the present study, taken together with phenotypes caused by other types of mutations, support the general rule that phenotypes caused by the truncating GJB2 mutations are more severe than those caused by missense mutations. The present in vitro study further confirmed that differences in phenotypes could be explained by the protein expression pattern.

Clinical characteristics and genotype–phenotype correlation of hearing loss patients with SLC26A4 mutations

Conclusions. The present study confirmed the clinical characteristics of patients with SLC26A4 mutations: congenital, fluctuating, and progressive hearing loss usually associated with vertigo and/or goiter during long-term follow-up. This clarification should help to facilitate appropriate genetic counseling and proper medical management for patients with these mutations, but there was no particular genotype–phenotype correlation among them, suggesting that other factors may contribute to such variability. Objectives. Due to the wide range of phenotypes caused by SLC26A4 mutations, there is controversy with regard to genotype–phenotype correlation. The present study was performed: (1) to determine phenotypic range in patients with biallelic SLC26A4 mutations, and (2) to evaluate whether possible genotype–phenotype correlation exists. Subjects and methods. Phenotypes in 39 hearing loss patients with SLC26A4 mutations were summarized and genotype–phenotype correlation was analyzed. Results. Hearing level varied in the individuals from mild to profound severity. Most of the patients had fluctuating and progressive hearing loss that may have been of prelingual onset. Twenty-four (70.6%) patients had episodes of vertigo, and 10 (27.8%) patients had goiter, which had appeared at age 12 or older. In contrast to such phenotypic variabilities, no apparent correlation was found between these phenotypes and their genotypes.

Massively Parallel DNA Sequencing Facilitates Diagnosis of Patients with Usher Syndrome Type 1

Usher syndrome is an autosomal recessive disorder manifesting hearing loss, retinitis pigmentosa and vestibular dysfunction, and having three clinical subtypes. Usher syndrome type 1 is the most severe subtype due to its profound hearing loss, lack of vestibular responses, and retinitis pigmentosa that appears in prepuberty. Six of the corresponding genes have been identified, making early diagnosis through DNA testing possible, with many immediate and several long-term advantages for patients and their families. However, the conventional genetic techniques, such as direct sequence analysis, are both time-consuming and expensive. Targeted exon sequencing of selected genes using the massively parallel DNA sequencing technology will potentially enable us to systematically tackle previously intractable monogenic disorders and improve molecular diagnosis. Using this technique combined with direct sequence analysis, we screened 17 unrelated Usher syndrome type 1 patients and detected probable pathogenic variants in the 16 of them (94.1%) who carried at least one mutation. Seven patients had the MYO7A mutation (41.2%), which is the most common type in Japanese. Most of the mutations were detected by only the massively parallel DNA sequencing. We report here four patients, who had probable pathogenic mutations in two different Usher syndrome type 1 genes, and one case of MYO7A/PCDH15 digenic inheritance. This is the first report of Usher syndrome mutation analysis using massively parallel DNA sequencing and the frequency of Usher syndrome type 1 genes in Japanese. Mutation screening using this technique has the power to quickly identify mutations of many causative genes while maintaining cost-benefit performance. In addition, the simultaneous mutation analysis of large numbers of genes is useful for detecting mutations in different genes that are possibly disease modifiers or of digenic inheritance.

Congenital Arhinia: A Case Report and Functional Evaluation

Objectives: Congenital arhinia is rare clinical entity. An unusual case of congenital arhinia with no surgical treatment is presented.

Deletion mapping of split hand/split foot malformation with hearing impairment: a case report

Split hand/split foot malformation (SHFM), which typically appears as lobster-like limb malformation, is a rare clinical condition caused by a partial deletion of chromosome 7q. Hearing impairment sometimes accompanies syndromic SHFM cases; a case of inner and middle ear malformation with SHFM is described in this report. We conducted a genetic evaluation of this patient and found a deleted region that overlaps a previously reported locus of SHFM as well as a DFNB14 locus that can cause nonsyndromic hearing impairment by autosomal recessive inheritance.

OTOF mutation screening in Japanese severe to profound recessive hearing loss patients

BackgroundAuditory neuropathy spectrum disorder (ANSD) is a unique form of hearing loss that involves absence or severe abnormality of auditory brainstem response (ABR), but also the presence of otoacoustic emissions (OAEs). However, with age, the OAEs disappear, making it difficult to distinguish this condition from other nonsyndromic hearing loss. Therefore, the frequency of ANSD may be underestimated. The aim of this study was to determine what portion of nonsyndromic hearing loss is caused by mutations of OTOF, the major responsible gene for nonsyndromic ANSD.MethodsWe screened 160 unrelated Japanese with severe to profound recessive nonsyndromic hearing loss (ARNSHL) without GJB2 or SLC26A4 mutations, and 192 controls with normal hearing.ResultsWe identified five pathogenic OTOF mutations (p.D398E, p.Y474X, p.N727S, p.R1856Q and p.R1939Q) and six novel, possibly pathogenic variants (p.D450E, p.W717X, p.S1368X, p.R1583H, p.V1778I, and p.E1803A).ConclusionsThe present study showed that OTOF mutations accounted for 3.2–7.3% of severe to profound ARNSHL patients in Japan. OTOF mutations are thus a frequent cause in the Japanese deafness population and mutation screening should be considered regardless of the presence/absence of OAEs.