A point mutation in the gene for asparagine-linked glycosylation 10B (Alg10b) causes nonsyndromic hearing impairment in mice (Mus musculus)

Genome-wide DNA methylation analysis of middle-aged and elderly monozygotic twins with age-related hearing loss in Qingdao, China

OBJECTIVE

To explore the differences in DNA methylation associated with age-related hearing loss in a study of 57 twin pairs from China.

DESIGN

Monozygotic twins were identified through the Qingdao Twin Registration system. The median age of participants was >50 years. Their hearing thresholds were measured using a multilevel pure-tone audiometry assessment. The pure-tone audiometry was calculated at low frequencies (0.5, 1.0, and 2.0 kHz), speech frequencies (0.5, 1.0, 2.0, and 4.0kHz), and high frequencies (4.0 and 8 kHz). The CpG sites were tested using a linear mixed-effects model, and the function of the cis-regulatory regions and ontological enrichments were predicted using the online Genomic Regions Enrichment of Annotations Tool. The differentially methylated regions were identified using a comb-p python library approach.

RESULTS

In each of the PTA categories (low-, speech-, high-frequency), age-related hearing loss was detected in 25.9%, 19.3%, and 52.8% of participants. In the low-, speech- and high-frequency categories we identified 18, 42, and 12 individual CpG sites and 6, 11, and 6 differentially methylated regions. The CpG site located near DUSP4 had the strongest association with low- and speech-frequency, while the strongest association with high-frequency was near C21orf58. We identified associations of ALG10 with high-frequency hearing, C3 and LCK with low- and speech-frequency hearing, and GBX2 with low-frequency hearing. Top pathways that may be related to hearing, such as the Notch signaling pathway, were also identified.

CONCLUSION

Our study is the first of its kind to identify these genes and their associated with DNA methylation may play essential roles in the hearing process. The results of our epigenome-wide association study on twins clarify the complex mechanisms underlying age-related hearing loss.

Prenatal Diagnosis and Molecular Cytogenetic Characterization of Copy Number Variations on 4p15.2p16.3, Xp22.31, and 12p11.1q11 in a Fetus with Ultrasound Anomalies: A Case Report and Literature Review

Chromosomal rearrangements, such as duplications/deletions, can lead to a variety of genetic disorders. Herein, we reported a prenatal case with right aortic arch and aberrant left subclavian artery, consisting of a complex chromosomal copy number variations. Routine cytogenetic analysis described the chromosomal karyotype as 46,XY, add (2)(q37) for the fetus. However, the chromosomal microarray analysis (CMA) identified a 22.4 Mb duplication in chromosome 4p16.3p15.2, a 3.96 Mb microduplication in 12p11.1q11, and a 1.68 Mb microdeletion in Xp22.31. Fluorescence in situ hybridization (FISH) using a chromosome 4 painting probe was found to hybridize to the terminal of chromosome 2q on the fetus, thus confirming that the extra genetic materials of chromosome 2 was actually trisomy 4p detected through CMA. Meanwhile, the parental karyotypes were normal, which proved that the add (2) was de novo for fetus. The duplication of Wolf-Hirschhorn syndrome critical region (WHSCR) and X-linked recessive ichthyosis associated with Xp22.31 deletion separately were considered potentially pathogenic causes although other abnormalities involving these syndromes were not observed. For prenatal cases, the combined utilization of ultrasonography, traditional cytogenetic, and molecular diagnosis technology will enhance better diagnostic benefits, offer more detailed genetic counselling, and assess the prognosis of the fetuses.

Functional implications of Cav 2.3 R-type voltage-gated calcium channels in the murine auditory system - novel vistas from brainstem-evoked response audiometry

Voltage-gated Ca²⁺ channels (VGCCs) are considered to play a key role in auditory perception and information processing within the murine inner ear and brainstem. In the past, Ca_v 1.3 L-type VGCCs gathered most attention as their ablation causes congenital deafness. However, isolated patch-clamp investigation and localization studies repetitively suggested that Ca_v 2.3 R-type VGCCs are also expressed in the cochlea and further components of the ascending auditory tract, pointing to a potential functional role of Ca_v 2.3 in hearing physiology. Thus, we performed auditory profiling of Ca_v 2.3^+/+ controls, heterozygous Ca_v 2.3^+/- mice and Ca_v 2.3 null mutants (Ca_v 2.3^-/- ) using brainstem-evoked response audiometry. Interestingly, click-evoked auditory brainstem responses (ABRs) revealed increased hearing thresholds in Ca_v 2.3^+/- mice from both genders, whereas no alterations were observed in Ca_v 2.3^-/- mice. Similar observations were made for tone burst-related ABRs in both genders. However, Ca_v 2.3 ablation seemed to prevent mutant mice from total hearing loss particularly in the higher frequency range (36-42 kHz). Amplitude growth function analysis revealed, i.a., significant reduction in ABR wave W_I and W_III amplitude in mutant animals. In addition, alterations in W_I -W_IV interwave interval were observed in female Ca_v 2.3^+/- mice whereas absolute latencies remained unchanged. In summary, our results demonstrate that Ca_v 2.3 VGCCs are mandatory for physiological auditory information processing in the ascending auditory tract.

Cav3.2 T-Type Calcium Channels Are Physiologically Mandatory for the Auditory System

Voltage-gated Ca²⁺ channels (VGCCs) play key roles in auditory perception and information processing within the inner ear and brainstem. Pharmacological inhibition of low voltage-activated (LVA) T-type Ca²⁺ channels is related to both age- and noise induced hearing loss in experimental animals and may represent a promising approach to the treatment of auditory impairment of various etiologies. Within the LVA Ca²⁺ channel subgroup, Ca_v3.2 is the most prominently expressed T-type channel entity in the cochlea and auditory brainstem. Thus, we performed a complete gender specific click and tone burst based auditory brainstem response (ABR) analysis of Ca_v3.2^+/- and Ca_v3.2^-/- mice, including i.a. temporal progression in hearing loss, amplitude growth function and wave latency analysis as well as a cochlear qPCR based evaluation of other VGCCs transcripts. Our results, based on a self-programmed automated wavelet approach, demonstrate that both heterozygous and Ca_v3.2 null mutant mice exhibit age-dependent increases in hearing thresholds at 5 months of age. In addition, complex alterations in W_I-IV amplitudes and latencies were detected that were not attributable to alterations in the expression of other VGCCs in the auditory tract. Our results clearly demonstrate the important physiological role of Ca_v3.2 VGCCs in the spatiotemporal organization of auditory processing in young adult mice and suggest potential pharmacological targets for interventions in the future.

The role of post-translational modifications in hearing and deafness

Post-translational modifications (PTMs) are key molecular events that modify proteins after their synthesis and modulate their ultimate functional properties by affecting their stability, localisation, interaction potential or activity. These chemical changes expand the size of the proteome adding diversity to the molecular pathways governing the biological outcome of cells. PTMs are, thus, crucial in regulating a variety of cellular processes such as apoptosis, proliferation and differentiation and have been shown to be instrumental during embryonic development. In addition, alterations in protein PTMs have been implicated in the pathogenesis of many human diseases, including deafness. In this review, we summarize the recent progress made in understanding the roles of PTMs during cochlear development, with particular emphasis on the enzymes driving protein phosphorylation, acetylation, methylation, glycosylation, ubiquitination and SUMOylation. We also discuss how these enzymes may contribute to hearing impairment and deafness.