Clinical Characteristics and In Vitro Analysis of MYO6 Variants Causing Late-onset Progressive Hearing Loss

Abstract

MYO6 is known as a genetic cause of autosomal dominant and autosomal recessive inherited hearing loss. In this study, to clarify the frequency and clinical characteristics of hearing loss caused by MYO6 gene mutations, a large-scale genetic analysis of Japanese patients with hearing loss was performed. By means of massively parallel DNA sequencing (MPS) using next-generation sequencing for 8074 Japanese families, we found 27 MYO6 variants in 33 families, 22 of which are novel. In total, 2.40% of autosomal dominant sensorineural hearing loss (ADSNHL) in families in this study (32 out of 1336) was found to be caused by MYO6 mutations. The present study clarified that most cases showed juvenile-onset progressive hearing loss and their hearing deteriorated markedly after 40 years of age. The estimated hearing deterioration was found to be 0.57 dB per year; when restricted to change after 40 years of age, the deterioration speed was accelerated to 1.07 dB per year. To obtain supportive evidence for pathogenicity, variants identified in the patients were introduced to MYO6 cDNA by site-directed mutagenesis and overexpressed in epithelial cells. They were then assessed for their effects on espin1-induced microvilli formation. Cells with wildtype myosin 6 and espin1 co-expressed created long microvilli, while co-expression with mutant constructs resulted in severely shortened microvilli. In conclusion, the present data clearly showed that MYO6 is one of the Genes 2020, 11, 273 2 of 14 genes to keep in mind with regard to ADSNHL, and the molecular characteristics of the identified gene variants suggest that a possible pathology seems to result from malformed stereocilia of the cochlear hair cells.

The genetic etiology of hearing loss in Japan revealed by the social health insurance-based genetic testing of 10K patients

“…Etiological studies have shown that genetic causes are the most common etiology of deafness, and approximately two-thirds of congenital/early-onset sensorineural hearing loss in developed countries is estimated to be due to genetic causes (Morton and Nance 2006). Recent studies have indicated that a significant portion of late-onset hearing loss is also due to genetic causes (Kitano et al 2017;Kobayashi et al 2018;Shinagawa et al 2020a;Yasukawa et al 2019;Oka et al 2020;Miyajima et al 2020). A series of etiological studies has demonstrated genetic disorders to be a common cause of all types of sensorineural hearing loss, but there has been no detailed genetic epidemiological data covering a wide range of ages.…”

“…Meanwhile, both the number of DNA samples and detailed clinical data are increasing, and genetic and clinical data from over 10,000 patients has been collected from 102 collaborative centers. Based on this large-cohort data, we have published a series of studies demonstrating the mutational spectrum and clinical features caused by the representative deafness genes, including GJB2 (Tsukada et al 2010), CDH23 (Miyagawa et al 2012), KCNQ4 (Naito et al 2013), OTOF (Iwasa et al 2013(Iwasa et al , 2019, mitochondrial 1555A > G and 3243A > G (Yano et al 2014), SLC26A4 (Miyagawa et al 2014), LRTOMT (Ichinose et al 2015), GRXCR1 (Mori et al 2015a), PTPRQ (Sakuma et al 2015), COCH (Tsukada et al 2015a), TMPRSS3 (Miyagawa et al 2015d), STRC (Moteki et al 2016;Yokota et al 2019), LOXHD1 (Mori et al 2015b;Maekawa et al 2019), ACTG1 (Miyagawa et al 2015b;Miyajima et al 2020), MYO15A (Miyagawa et al 2015a), POU4F3 (Kitano et al 2017), WFS1 (Kobayashi et al 2018), CLDN14 (Kitano et al 2019), EYA4 (Shinagawa et al 2020a, b), TECTA (Yasukawa et al 2019), OTOA (Sugiyama et al 2019), and MYO6 (Miyagawa et al 2015c;Oka et al, 2020). These studies were performed between 2010 and 2020.…”

“…With regard to progression, in the case of the GJB2 and STRC , hearing is rather stable and progression of hearing loss is rarely observed (Tsukada et al 2010;Yokota et al 2019). On the other hand, hearing loss due to SLC26A4 (Suzuki et al 2007;Miyagawa et al 2014), CDH23 (Miyagawa et al 2012, TMPRSS3 (Miyagawa et al 2015c), LOXHD1 (Maekawa et al 2019), KCNQ4 (Naito et al 2013), ACTG1 (Miyajima et al 2020), POU4F3 (Kitano et al 2017), EYA4 (Shinagawa et al 2020a), MYO6 (Oka et al 2020), and mitochondrial m.1555A > G (Usami et al 1997) requires a good deal of attention as it is progressive. Figure 6 demonstrates the progressive or non-progressive nature of each gene, and supports our previous data regarding progressiveness.…”

Prevalence and Clinical Characteristics of Hearing Loss Caused by MYH14 Variants

“…Various genes have been reported to be causative in ADNSHL families [6,8]; however, at present, there is no particular major responsible deafness gene for ADNSHL. Our screening using the same cohort clarified the frequencies for the other causative genes in ADNSHL patients; KCNQ4: 6.6% [37], POU4F3: 4% [38], TECTA: 2.9% [39], WFS1: 2.5% [40], MYO6: 2.4% [41], ACTG1: 1.1% [42], and EYA4: 0.9% [43]. Although MYH14-associated HL is rare, the present results indicated that this gene should be included in HL screening, especially that for ADNSHL.…”

Predicting pathogenicity for novel hearing loss mutations based on genetic and protein structure approaches

“…Moreover, the structural change caused by the mutation in the alpha-helix of this highly motile region could potentially affect the contiguous actin binding region. In this regard, mutations in the MYO6 motor domain alter anchoring of the membrane of stereocilia to actin filaments, leading to disruption of hair bundle organization 36 , 37 .…”