Downregulation of GJB2 and SLC26A4 Genes Induced by Noise Exposure is Associated with Cochlear Damage

Noise can change the pattern of gene expression inducing sensorineural hearing impairment. There is no investigation on effects of noise frequency on the expression of GJB2 and SLC26A4 genes involved in congenital hearing impairment in cochlear tissue. This study investigated impacts of white and purple noise on gene expression and pathologic changes of cochlear tissue. In this study, 32 adult male Westar rats were selected and divided into experimental groups WN (animals exposed to white noise with a frequency range of 100-20000 Hz), PN (animals exposed to purple noise with a frequency range of 4-20 kHz) and control groups. All experimental groups were exposed to a sound pressure level of 118-120 dB for 8 hours per day. Cochlear tissue sampling was performed for tissue pathology studies, also RNA was extracted at 1 hour & 1 week after cessation of noise exposure. The results showed that Both white and purple noises caused permanent damage to the cortical, estrosilica systems of hair cells and ganglion of the hearing nerve. GJB2 and SLC26A4 were downregulated in both groups exposed with white and purple noise. However, differences are notably more significant in 1 weak post-exposure than 1 hour. Our Findings suggest GJB2 and SLC26A4 can be considered as biomarkers of response to noise frequency which is associated with the pathological response of cochlear tissue, leading to sensorineural hearing impairment. It would be suggested the demand for a more conventional approach to assessment of noise-induced hearing loss and subsequently the practice of hearing protection programs.

A novel variant in DXML2 gene is associated with autosomal dominant non-syndromic hearing impairment (DFNA71) in a Cameroonian family

Approximately half of congenital hearing impairment cases are inherited, with non-syndromic hearing impairment (NSHI) being the most frequent clinical entity of genetic hearing impairment cases. A family from Cameroon with NSHI was investigated by performing exome sequencing using DNA samples obtained from three family members, followed by direct Sanger sequencing in additional family members and controls participants. We identified an autosomal dominantly inherited novel missense variant [NM_001174116.2:c.918G>T; p.(Q306H)] in DMXL2 gene (MIM:612186) that co-segregates with mild to profound non-syndromic sensorineural hearing impairment . The p.(Q306H) variant which substitutes a highly conserved glutamine residue is predicted deleterious by various bioinformatics tools and is absent from several genome databases. This variant was also neither found in 121 apparently healthy controls without a family history of hearing impairment , nor 112 sporadic NSHI cases from Cameroon. There is one previous report of a large Han Chinese NSHI family that segregates a missense variant in DMXL2. The present study provides additional evidence that DMXL2 is involved in hearing impairment etiology, and we suggest DMXL2 should be considered in diagnostic hearing impairment panels.

Mutation analysis of the SLC26A4 gene in patients in Yakutia with inner ear abnormalities: IP-I, IP-II (Mondini) and / or EVA

В работе представлены результаты обследований 165 пациентов с врожденными нарушениями слуха из Якутии, проведенных с использованием аудиологических, рентгенологических и молекулярно-генетических методов с целью изучения аутосомно-рецессивной формы глухоты, связанной с аномалиями внутреннего уха (IP-I, IP-II и/или EVA) и мутациями гена SLC26A4 (DFNB4, MIM 600791). We presents the results of audiological, radiological and molecular genetic studies of 165 patients with congenital hearing impairment in Yakutia to investigate of autosomal recessive form of deafness associated with anomalies of the inner ear (IP-I, IP-II and / or EVA) and mutations in the SLC26A4 gene (DFNB4, MIM 600791).

The Spectrum and Frequency of Inner Ear Anomalies in Patients with Congenital Hearing Impairment in Yakutia

Objective. To analyze the spectrum and frequency of inner ear anomalies in patients with congenital hearing impairment in Yakutia.Material and methods. A total of 165 patients with congenital hearing impairment were surveyed. All the patients were examined by an audiologist, an educational audiologist, and a neuropsychiatrist. All the patients underwent X-ray computed tomography (X-ray CT) of temporal bone structures (which was supplemented by magnetic resonance imaging (MRI) in some cases).Results. Based on modern ideas about inner ear anomalies and their classification, the authors first analyzed the spectrum and frequency of inner ear anomalies in patients with congenital hearing impairment in Yakutia. Inner ear malformations were identified in 16 (9.7%) of the 165 patients with hearing impairment, which corresponds to that in the previously studied samples of deaf people in different countries (from 3% to 35%). Of the inner ear structures, the cochlea and vestibule were more commonly affected. Abnormalities of the internal auditory meatus, semicircular canals, and vestibular aqueduct were less common. In general, the spectrum of anomalies was represented by 7 different malformations. Incomplete partition type II (IP-II) (34.3%) came first in incidence among all the abnormalities. Incomplete partition type III (IP-III) (18.7%) ranked second in incidence. The expansion of the internal auditory meatus (12.5%) and vestibular aqueduct (12.5%) occupied the third place. Inner ear anomalies occurred as concurrences that are difficult to interpret and classify in half (50%) of all the cases.Conclusion. Analysis of the spectrum and frequency of temporal bone abnormalities in Yakutia suggests that every 10 patients with congenital hearing impairment have one or another inner ear structural malformation (9.7%) and require accurate and timely diagnosis using up-to-date X-ray CT and MRI techniques.

Elucidating Biological Roles of Novel Murine Genes in Hearing Impairment in Africa

The prevalence of congenital hearing impairment (HI) is highest in Africa. Estimates evaluated genetic causes to account for 31% of HI cases in Africa, but the identification of associated causative genes mutations have been challenging. In this study, we reviewed the potential roles, in humans, of 38 novel genes identified in a murine study. We gathered information from various genomic annotation databases and performed functional enrichment analysis using online resources i.e. genemania and g.proflier. Results revealed that 27/38 genes are express mostly in the brain, suggesting additional cognitive roles. Indeed, HERC1- R3250X had been associated with intellectual disability in a Moroccan family. A homozygous 216-bp deletion in KLC2 was found in two siblings of Egyptian descent with spastic paraplegia. Up to 27/38 murine genes have link to at least a disease, and the commonest mode of inheritance is autosomal recessive (n=8). Network analysis indicates that 20 other genes have intermediate and biological links to the novel genes, suggesting their possible roles in HI. This study will contribute to advance our knowledge in unravelling the biological roles of novel murine HI genes in humans and could enhance the understanding of the genetic causes of HI in Africans.

Identification of hearing impairment

Universal newborn hearing screening has meant that babies with significant congenital hearing impairment can be identified soon after birth and management instituted to ameliorate resultant problems, that is, minimize disability and handicap and optimize life chances. Evidence for the value of school entry screening is lacking and there is some evidence it is neither effective nor cost-effective. Further research is needed on this. Otitis media with effusion can cause significant long-lasting effects and may need surgical intervention or the provision of hearing aids. Parents and professionals should be aware of the symptoms that are indicative of possible hearing loss. Parents’ concerns should always be taken seriously.