Variants of the LOXHD1 gene, which are expressed in hair cells of the cochlea and vestibule, have been reported to cause a progressive form of autosomal recessive non-syndromic hereditary hearing loss, DFNB77. In this study, genetic screening was conducted on 8074 Japanese hearing loss patients utilizing massively parallel DNA sequencing to identify individuals with LOXHD1 variants and to assess their phenotypes. A total of 28 affected individuals and 21 LOXHD1 variants were identified, among which 13 were novel variants. A recurrent variant c.4212 + 1G > A, only reported in Japanese patients, was detected in 18 individuals. Haplotype analysis implied that this variation occurred in a mutational hot spot, and that multiple ancestors of Japanese population had this variation. Patients with LOXHD1 variations mostly showed early onset hearing loss and presented different progression rates. We speculated that the varying severities and progression rates of hearing loss are the result of environmental and/or other genetic factors. No accompanying symptoms, including vestibular dysfunction, with hearing loss were detected in this study. Few studies have reported the clinical features of LOXHD1-gene associated hearing loss, and this study is by far the largest study focused on the evaluation of this gene.

Background/Objectives: Hearing loss is one of the most common sensorineural impairments, and approximately 60% of early-onset cases are due to genetic variations. The otogelin-like protein, encoded by the OTOGL gene, is a component of the acellular membranes of the inner ear, such as the tectorial membrane, and is thought to play an important role in cochlear amplification. OTOGL gene variants are a rare cause of hearing loss such as DFNB84B, a mild-to-moderate sensorineural hearing loss presenting in early childhood with autosomal recessive inheritance. In this study, we aim to enhance our comprehension of the phenotypes of hearing loss caused by OTOGL variants. Methods: A total of 7056 Japanese patients with hearing loss were recruited, and based on massively parallel DNA sequencing on 158 target genes, we selected patients with biallelic OTOGL variants. Results: Ten affected individuals with OTOGL gene variants were detected, the largest group of patients yet to be reported, and eight of the eleven variants were novel. Our results showed that variations in this gene led to mild-to-moderate non-progressive hearing loss, and the accompanying symptoms, mainly vestibular symptoms, were speculated to present in adulthood. Conclusions: Determination of the phenotypes of genes causative of hearing loss is expected to greatly benefit patients with hearing loss as it can assist in predicting outcomes and lead to appropriate intervention, which, in OTOGL-associated hearing loss cases, is based around the fact that the patients need not be concerned with deterioration in hearing, but require careful follow-up for vestibular symptoms.

Background/Objectives: MYO3A belongs to the unconventional myosin superfamily, and the myosin IIIa protein localizes on the tip of the stereocilia of vestibular and cochlear hair cells. Deficiencies in MYO3A have been reported to cause the deformation of hair cells into abnormally long stereocilia with an increase in spacing. MYO3A is a rare causative gene of autosomal recessive sensorineural hearing loss (DFNB30), with only 13 cases reported to date. In this study, we aimed to elucidate the phenotypes caused by MYO3A variations. Methods: Massively parallel DNA sequencing was performed on 15,684 Japanese hearing loss patients (mean age 27.5 ± 23.1 years old, 6574 male, 8612 female and 498 patients for whom information was unavailable), identifying nine candidate patients with MYO3A variants. Results: We identified eight causative MYO3A variants by massively parallel DNA sequencing, including six novel variants, and reported nine individuals possessing MYO3A gene variants, which is the largest group of non-related patients yet to be detected. Our findings confirmed that MYO3A variants cause progressive hearing loss, with its onset varying from birth to the second decade, eventually leading to severe-to-profound hearing loss. Conclusions: We clarified that patients with MYO3A gene variants present with late-onset, progressive hearing loss. Our findings have enabled us to predict the outcomes of hearing loss in patients with candidate MYO3A gene variants and to provide intervention in a timely manner.