Mitsuru Hattori

Ethnic-Specific Spectrum of GJB2 and SLC26A4 Mutations: Their Origin and a Literature Review

Objective: The mutation spectrum of the GJB2 and SLC26A4 genes, the 2 most common genes causing deafness, are known to be ethnic specific. In this study, the spectrum of the reported GJB2 and SLC26A4 mutations in different populations are reviewed and considered from a human migration perspective. Methods: Fifty-two and 17 articles on GJB2 and SLC26A4 mutations, respectively, were reviewed through the PubMed database from April 1996 to September 2014. The 4 most prevalent mutations were selected and compared. A cluster analysis was subsequently performed for these selected mutations. Results: The present review of frequent mutations shows the ethnic-specific GJB2 and SLC26A4 gene mutation spectrum. A cluster analysis of the GJB2 and SLC26A4 genes revealed similarities between ethnic populations. Conclusion: The mutation spectrum reviewed in this study clearly indicated that the frequent mutations in the GJB2 and SLC26A4 genes are consistent with the founder mutation hypothesis. A comparison with the Y-chromosome phylogenetic tree indicated that these mutations may have occurred during human migration.

Changes in pollinator fauna affect altitudinal variation of floral size in a bumblebee-pollinated herb.

Geographic trait variations are often caused by locally different selection regimes. As a steep environmental cline along altitude strongly influences adaptive traits, mountain ecosystems are ideal for exploring adaptive differentiation over short distances. We investigated altitudinal floral size variation of Campanula punctata var. hondoensis in 12 populations in three mountain regions of central Japan to test whether the altitudinal floral size variation was correlated with the size of the local bumblebee pollinator and to assess whether floral size was selected for by pollinator size. We found apparent geographic variations in pollinator assemblages along altitude, which consequently produced a geographic change in pollinator size. Similarly, we found altitudinal changes in floral size, which proved to be correlated with the local pollinator size, but not with altitude itself. Furthermore, pollen removal from flower styles onto bees (plants male fitness) was strongly influenced by the size match between flower style length and pollinator mouthpart length. These results strongly suggest that C. punctata floral size is under pollinator-mediated selection and that a geographic mosaic of locally adapted C. punctata exists at fine spatial scale.

Gene Expression Profiles of the Cochlea and Vestibular Endorgans: Localization and Function of Genes Causing Deafness

Objectives: We sought to elucidate the gene expression profiles of the causative genes as well as the localization of the encoded proteins involved in hereditary hearing loss. Methods: Relevant articles (as of September 2014) were searched in PubMed databases, and the gene symbols of the genes reported to be associated with deafness were located on the Hereditary Hearing Loss Homepage using localization, expression, and distribution as keywords. Results: Our review of the literature allowed us to systematize the gene expression profiles for genetic deafness in the inner ear, clarifying the unique functions and specific expression patterns of these genes in the cochlea and vestibular endorgans. Conclusions: The coordinated actions of various encoded molecules are essential for the normal development and maintenance of auditory and vestibular function.

The Patients Associated With TMPRSS3 Mutations Are Good Candidates for Electric Acoustic Stimulation

Objectives: To clarify the frequency of TMPRSS3 mutations in the hearing loss population, genetic analysis was performed, and detailed clinical characteristics were collected. Optical intervention for patients with TMPRSS3 mutations was also discussed. Methods: Massively parallel DNA sequencing (MPS) was applied for the target exon-sequencing of 63 deafness genes in a population of 1120 Japanese hearing loss patients. Results: Hearing loss in 5 patients was found to be caused by compound heterozygous TMPRSS3 mutations, and their detailed clinical features were collected and analyzed. Typically, all of the patients showed ski slope type audiograms and progressive hearing loss. Three of the 5 patients received electric acoustic stimulation (EAS), which showed good results. Further, the onset age was found to vary, and there were some correlations between genotype and phenotype (onset age). Conclusions: MPS is a powerful tool for the identification of rare causative deafness genes, such as TMPRSS3. The present clinical characteristics not only confirmed the findings from previous studies but also provided clinical evidence that EAS is beneficial for patients possessing TMPRSS3 mutations.

Mutations in the MYO15A Gene Are a Significant Cause of Nonsyndromic Hearing Loss Massively Parallel DNA Sequencing–Based Analysis

Objectives: Screening for MYO15A mutations was carried out using a large cohort to clarify the frequency and clinical characteristics of patients with MYO15A (DFNB3) mutations in a hearing loss population. Methods: Genetic analysis of 63 previously reported deafness genes based on massively parallel DNA sequencing (MPS) in 1120 Japanese hearing loss patients from 53 otorhinolaryngology departments was performed. Detailed clinical features of the patients with MYO15A mutations were then collected and analyzed. Results: Eleven patients from 10 families were found to have compound heterozygosity for MYO15A. Audiograms showed profound or high frequency hearing loss, with some patients showing progressive hearing loss. Age at onset was found to vary from 0 to 14 years, which seemed to be associated with the mutation. Four children underwent bilateral cochlear implantation for congenital hearing loss, with all showing good results. Conclusion: Mutations in the MYO15A gene are a notable cause of nonsyndromic hearing loss. MPS technology successfully detected mutations in relatively rare deafness genes such as MYO15A.

Comprehensive genetic testing with ethnic-specific filtering by allele frequency in a Japanese hearing-loss population.

Recent advances in targeted genomic enrichment with massively parallel sequencing (TGE+MPS) have made comprehensive genetic testing for non‐syndromic hearing loss (NSHL) possible. After excluding NSHL subjects with causative mutations in GJB2 and the MT‐RNR1 (1555A>G) variant by Sanger sequencing, we completed TGE+MPS on 194 probands with presumed NSHL identified across Japan. We used both publicly available minor allele frequency (MAF) datasets and ethnic‐specific MAF filtering against an in‐house database of 200 normal‐hearing Japanese controls. Ethnic‐specific MAF filtering allowed us to re‐categorize as common 203 variants otherwise annotated as rare or novel in non‐Japanese ethnicities. This step minimizes false‐positive results and improves the annotation of identified variants. Causative variants were identified in 27% of probands with solve rates of 35%, 35% and 19% for dominant, recessive and sporadic NSHL, respectively. Mutations in MYO15A and CDH23 follow GJB2 as the frequent causes of recessive NSHL; copy number variations in STRC are a major cause of mild‐to‐moderate NSHL. Ethnic‐specific filtering by allele frequency is essential to optimize the interpretation of genetic data.

Detailed hearing and vestibular profiles in the patients with COCH mutations.

Objectives: To evaluate the clinical features of Japanese DFNA9 families with mutations of the COCH gene. Methods: Mutation screening was performed using targeted next-generation sequencing (NGS) for 63 previously reported deafness genes. The progression of hearing loss and vestibular dysfunction were evaluated by pure-tone audiometry, caloric testing, cVEMP, and computed dynamic posturography. Results: We detected 1 reported mutation of p.G88E and 2 novel mutations of p.I372T and p.C542R. The patients with the novel mutations of p.I372T and p.C542R within the vWFA2 domain showed early onset progressive hearing loss, and the patients with the p.G88E mutation showed late onset hearing loss and acute hearing deterioration over a short period. Vestibular symptoms were reported in the patients with p.G88E and p.C542R. Vestibular testing was performed for the family with the p.G88E mutation. Severe vestibular dysfunction was observed in the proband, and the proband’s son showed unilateral semicircular canal dysfunction with mild hearing loss. Conclusions: Targeted exon resequencing of selected genes using NGS successfully identified mutations in the relatively rare deafness gene, COCH, in the Japanese population. The phenotype is compatible with that described in previous reports. Additional supporting evidence concerning progressive hearing loss and deterioration of vestibular function was obtained from our study.

Altitudinal flower size variation correlates with local pollinator size in a bumblebee‐pollinated herb, Prunella vulgaris L. (Lamiaceae)

The influence of locally different species interactions on trait evolution is a focus of recent evolutionary studies. However, few studies have demonstrated that geographically different pollinator‐mediated selection influences geographic variation in floral traits, especially across a narrow geographic range. Here, we hypothesized that floral size variation in the Japanese herb Prunella vulgaris L. (Lamiaceae) is affected by geographically different pollinator sizes reflecting different pollinator assemblages. To evaluate this hypothesis, we posed two questions. (1) Is there a positive correlation between floral length and the proboscis length of pollinators (bumblebees) across altitude in a mountain range? (2) Does the flower–pollinator size match influence female and male plant fitness? We found geographic variation in the assemblage of pollinators of P. vulgaris along an altitudinal gradient, and, as a consequence, the mean pollinator proboscis length also changed altitudinally. The floral corolla length of P. vulgaris also varied along an altitudinal gradient, and this variation strongly correlated with the local pollinator size but did not correlate with altitude itself. Furthermore, we found that the size match between the floral corolla length and bee proboscis length affected female and male plant fitness and the optimal size match (associated with peak fitness) was similar for the female and male fitness. Collectively, these results suggest that pollinator‐mediated selection influences spatial variation in the size of P. vulgaris flowers at a fine spatial scale.

Hearing Loss Caused by a P2RX2 Mutation Identified in a MELAS Family With a Coexisting Mitochondrial 3243AG Mutation

Objectives: We present a family with a mitochondrial DNA 3243A>G mutation resulting in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), of which some members have hearing loss in which a novel mutation in the P2RX2 gene was identified. Methods: One hundred ninety-four (194) Japanese subjects from unrelated families were enrolled in the study. Targeted genomic enrichment and massively parallel sequencing of all known nonsyndromic hearing loss genes were performed to identify the genetic causes of hearing loss. Results: A novel mutation in the P2RX2 gene that corresponded to c.601G>A (p.Asp201Tyr) was identified. Two patients carried the mutation and had severe sensorineural hearing loss, while other members with MELAS (who did not carry the P2RX2 mutation) had normal hearing. Conclusion: This is the first case report of a diagnosis of hearing loss caused by P2RX2 mutation in patients with MELAS. A potential explanation is that a decrease in adenosine triphosphate (ATP) production due to MELAS with a mitochondrial 3243A>G mutation might suppress activation of P2X2 receptors. We also suggest that hearing loss caused by the P2RX2 mutation might be influenced by the decrease in ATP production due to MELAS.

Demonstration of pollinator-mediated competition between two native Impatiens species, Impatiens noli-tangere and I. textori (Balsaminaceae).

Plant–plant interspecific competition via pollinators occurs when the flowering seasons of two or more plant species overlap and the pollinator fauna is shared. Negative sexual interactions between species (reproductive interference) through improper heterospecific pollen transfer have recently been reported between native and invasive species demonstrating pollination-driven competition. We focused on two native Impatiens species (I. noli-tangere and I. textori) found in Japan and examined whether pollinator-mediated plant competition occurs between them. We demonstrate that I. noli-tangere and I. textori share the same pollination niche (i.e., flowering season, pollinator fauna, and position of pollen on the pollinators body). In addition, heterospecific pollen grains were deposited on most stigmas of both I. noli-tangere and I. textori flowers that were situated within 2 m of flowers of the other species resulting in depressed fruit set. Further, by hand-pollination experiments, we show that when as few as 10% of the pollen grains are heterospecific, fruit set is decreased to less than half in both species. These results show that intensive pollinator-mediated competition occurs between I. noli-tangere and I. textori. This study suggests that intensive pollinator-mediated competition occurs in the wild even when interacting species are both native and not invasive.