Functional Variants in NOS1 and NOS2A Are Not Associated with Progressive Hearing Loss in Ménière's Disease in a European Caucasian Population

Genetic advances in Meniere Disease

Meniere Disease (MD) is an idiopathic inner ear disease with complex etiology and pathogenesis, which is still unclear. With the development in gene analysis technology, the genetic research of MD has attracted extensive attention, resulting in a large number of studies on the research of the relationship between human genes and MD. This paper aims to review the studies on this topic in recent years. The studies mainly focused on the genetics of familial MD and the correlation between MD and potentially related functional genes. The results of these studies have demonstrated the complexity and diversity of the pathogenesis of MD with both genetic and epigenetic alterations, suggesting that MD might be related to inflammation, immunity, aqua and ion balance in the lymphatic fluid, virus infection, metabolism, and abnormal function of nerve conduction. The finding of rare mutations in TECTA, MYO7A and OTOG genes and other genes such as CDH23, PCDH15 and ADGRV1 in the same families suggest that the integrity of the stereocilia and their interaction with the tectorial and otolithic membranes could be involved in the pathophysiology of familial MD.

Risk factors for Meniere disease: a systematic review and meta-analysis

PURPOSE

To summarized the latest evidence of risk factors for developing MD.

METHODS

We searched Medline, the Cochrane Central Register of Controlled Trials (CENTRAL), Embase, CBM, VIP, WanFANG, and CNKI, and ClinicalTrials.gov. till June 2021 for cohort and case-control studies investigating risk factors for MD. The exposure group was participants with a clinical diagnosis of MD which was made according to the diagnostic scale of the Equilibrium Committee of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), the control group was participants without MD. The outcome was determined by incidence or prognostic of MD. Paired reviewers independently screened citations, assessed bias risk of included studies using the Newcastle-Ottawa Scale. Odds ratios (OR), hazard ratios(HR), relative risk(RR) and 95% confidence interval (CI) were calculated for dichotomous data. The statistical analyses were carried out with the use of Review Manager 5.3. The level of statistical heterogeneity for pooled data were assessed by using I² statistics and Q-test.

RESULTS

768 abstracts and articles were identified by our search, of which 25 studies (n = 1, 471, 944) were included. There were 18 cohort studies, 7 case-control studies. Three distinct subgroups (age, sex, sleep) were identified. There were a total of two studies involving age, two studies involving gender and two studies involving sleep disorder. High to moderate methodological quality established that age [hazard ratios (HR) 2.21, 95% CI 1.85-2.65, I² = 0%] and sleep disorder[HR 1.68, 95% CI 1.47-1.93, I² = 0%] were risk factors for MD. While there was little evidence showing that sex was not a risk factor for MD [HR 1.61, 95% CI 0.91-2.84, I² = 74%].

CONCLUSION

The current evidence supports the suggestion that age and sleep disorder are risk factors for MD. Sex, gene, and hypothyroidism are tentative risk factors but conflicting/inconclusive results.

FUNDING

No external funding.

REGISTRATION

CRD42021248199 (Prospero).

A Drosophila model for Meniere's disease: Dystrobrevin is required for support cell function in hearing and proprioception

Meniere's disease (MD) is an inner ear disorder characterised by recurrent vertigo attacks associated with sensorineural hearing loss and tinnitus. Evidence from epidemiology and Whole Exome Sequencing (WES) suggests a genetic susceptibility involving multiple genes, including α-Dystrobrevin (DTNA). Here we investigate a Drosophila model. We show that mutation, or knockdown, of the DTNA orthologue in Drosophila, Dystrobrevin (Dyb), results in defective proprioception and impaired function of Johnston's Organ (JO), the fly's equivalent of the inner ear. Dyb and another component of the dystrophin-glycoprotein complex (DGC), Dystrophin (Dys), are expressed in support cells within JO. Their specific locations suggest that they form part of support cell contacts, thereby helping to maintain the integrity of the hemolymph-neuron diffusion barrier, which is equivalent to a blood-brain barrier. These results have important implications for the human condition, and notably, we note that DTNA is expressed in equivalent cells of the mammalian inner ear.

Association between polymorphisms in genes encoding methylenetetrahydrofolate reductase and the risk of Ménière's disease

Folate metabolism is essential for cellular functioning. Despite extensive research on the roles of folate-metabolism-related gene polymorphisms in the pathophysiology of many diseases, such as cardiovascular disease, cancers, and sudden sensorineural hearing loss, little is known about their association with Ménière's disease (MD). The aim of this study was to investigate the effect of methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms (C677T and A1298C) on the risk of MD in a Japanese population. We examined the C677T and A1298C (rs1801133 and rs1801131) polymorphisms in the MTHFR gene and compared them between 1946 adults (986 men and 960 women) participating in the National Institute for Longevity Sciences Longitudinal Study of Aging and 86 cases of MD. A multiple logistic regression was performed to obtain odds ratios (ORs) for the risk of MD regarding the MTHFR polymorphisms before (model 1) and after (model 2) adjustment for age and sex factors. The OR of MTHFR C677T for the risk of MD was 0.669 (95% confidence interval [CI], 0.479-0.934) in model 1 and 0.680 (95% CI, 0.484-0.954) in model 2. In contrast, the OR of MTHFR A1298C for the risk of MD was 1.503 (95% CI, 1.064-2.123) in model 1 and 1.505 (95% CI, 1.045-2.167) in model 2. Our results imply that the MTHFR C677T and A1298C polymorphisms are associated with the risk of MD.

A replication study on proposed candidate genes in Ménière's disease, and a review of the current status of genetic studies

OBJECTIVE

Multiple candidate genes have been presented for Ménière's disease (MD), but to date no positive replications have been reported. We review here all the previously proposed candidate genes for MD and report our results on the analysis of six such genes, AQP2, KCNE1, KCNE3, HCFC1, COCH, and ADD1.

STUDY SAMPLE

A well-defined sample set of 38 sporadic and 21 familial Finnish MD patients.

DESIGN

Mutation analysis, case-control study, and review of literature.

RESULTS

A polymorphism rs1805127 in the potassium channel gene, KCNE1, was associated with MD in sporadic (p = 0.011), but not familial patients (p = 0.62). In addition, we identified four novel unique variations in the KCNE1 gene. PolyPhen and Mutation Taster analyses indicated that at least one of the variations c.259T > C; p.Trp87Arg is probably damaging to the coded protein.

CONCLUSIONS

Our review of the reported candidate genes shows that the current understanding of the genetic factors contributing to the development of MD is limited, and that the study of its etiology would benefit greatly from more comprehensive genetic knowledge.

Genetics of recurrent vertigo and vestibular disorders

We present recent advances in the genetics of recurrent vertigo, including familial episodic ataxias, migraneous vertigo, bilateral vestibular hypofunction and Meniere's disease.Although several vestibular disorders are more common within families, the genetics of vestibulopathies is largely not known. Genetic loci and clinical features of familial episodic ataxias have been defined in linkage disequilibrium studies with mutations in neuronal genes KCNA1 and CACNA1A. Migrainous vertigo is a clinical disorder with a high comorbidity within families much more common in females with overlapping features with episodic ataxia and migraine. Bilateral vestibular hypofunction is a heterogeneous clinical group defined by episodes of vertigo leading to progressive loss of vestibular function which also can include migraine. Meniere's disease is a clinical syndrome characterized by spontaneous episodes of recurrent vertigo, sensorineural hearing loss, tinnitus and aural fullness and familial Meniere's disease in around 10-20% of cases. An international collaborative effort to define the clinical phenotype and recruiting patients with migrainous vertigo and Meniere's disease is ongoing for genome-wide association studies.

[Role of genomic medicine in middle and inner ear diseases]

INTRODUCTION AND OBJECTIVES

Genomic medicine investigates groups of genetic markers that determine susceptibility for complex diseases. The aim of this review was to introduce genomics to the clinical otorhinolaryngologist. Technological advances in genotyping and sequencing that have facilitated genome-wide association studies in common causes of hearing loss during the last years are summarised.

METHODS

A search strategy in PubMed was designed using the following keywords: (gene OR genomics OR GWAS OR high throughput) AND (hearing loss OR chronic otitis media OR age-related hearing loss OR otosclerosis OR Meniere's disease) during the last 5 years. A total of 1,846 references were obtained. After filtering by human studies and English as the language of publication, 1,295 summaries were evaluated, selecting 58 papers.

RESULTS

The impact of sequencing the human genome in the knowledge of genome architecture, DNA variability and the significance of structural variations in the sequence to cause diseases is presented. The evolution of sequencing technology has determined the design and performance of genetic association studies. Finally, we present genetic association studies performed in common causes of ear diseases.