Poly(ADP-ribose) polymerase-1 (PARP-1) longer alleles spanning the promoter region may confer protection to bilateral Meniere's disease

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.

Rare Variants of Putative Candidate Genes Associated With Sporadic Meniere's Disease in East Asian Population

Objectives: The cause of Meniere's disease (MD) is unclear but likely involves genetic and environmental factors. The aim of this study was to investigate the genetic basis underlying MD by screening putative candidate genes for MD.

Methods: Sixty-eight patients who met the diagnostic criteria for MD of the Barany Society were included. We performed targeted gene sequencing using next generation sequencing (NGS) panel composed of 45 MD-associated genes. We identified the rare variants causing non-synonymous amino acid changes, stop codons, and insertions/deletions in the coding regions, and excluded the common variants with minor allele frequency >0.01 in public databases. The pathogenicity of the identified variants was analyzed by various predictive tools and protein structural modeling.

Results: The average read depth for the targeted regions was 1446.3-fold, and 99.4% of the targeted regions were covered by 20 or more reads, achieving the high quality of the sequencing. After variant filtering, annotation, and interpretation, we identified a total of 15 rare heterozygous variants in 12 (17.6%) sporadic patients. Among them, four variants were detected in familial MD genes (DTNA, FAM136A, DPT), and the remaining 11 in MD-associated genes (PTPN22, NFKB1, CXCL10, TLR2, MTHFR, SLC44A2, NOS3, NOTCH2). Three patients had the variants in two or more genes. All variants were not detected in our healthy controls (n = 100). No significant differences were observed between patients with and without a genetic variant in terms of sex, mean age of onset, bilaterality, the type of MD, and hearing threshold at diagnosis.

Conclusions: Our study identified rare variants of putative candidate genes in some of MD patients. The genes were related to the formation of inner ear structures, the immune-associated process, or systemic hemostasis derangement, suggesting the multiple genetic predispositions in the development of MD.

Variants in the KCNE1 or KCNE3 gene and risk of Ménière's disease: A meta-analysis

BACKGROUND

Ménière's disease (MD) is defined as an idiopathic disorder of the inner ear characterized by the triad of tinnitus, vertigo, and sensorineural hearing loss. Although many studies have evaluated the association between variants in the KCNE1 or KCNE3 gene and MD risk, debates still exist.

OBJECTIVE

Our aim is to evaluate the association between KCNE gene variants, including KCNE1 rs1805127 and KCNE3 rs2270676, and the risk of MD by a systematic review.

METHODS

We searched the literature in PubMed, SCOPUS and EMBASE through May 2015. We calculated pooled odds ratios (OR) and 95% confidence intervals (CIs) using a fixed-effects model or a random-effects model for the risk to MD associated with different KCNE gene variants. The heterogeneity assumption decided the effect model.

RESULTS

A total of three relevant studies, with 302 MD cases and 515 controls, were included in this meta-analysis. The results indicated that neither the KCNE1 rs1805127 variant (for G vs. A: OR = 0.724, 95%CI 0.320, 1.638, P= 0.438), nor the KCNE3 rs2270676 variant (for T vs. C: OR = 0.714, 95%CI 0.327, 1.559, P = 0.398) was associated with MD risk.

CONCLUSIONS

Based on current evidence from published studies, neither of the two variants from KCNE was significantly associated with the risk of MD. Larger studies with mixed ethnicity subjects and stratified by clinical and sub-clinical characteristics are needed to validate our findings.

The genetics of Ménière's disease

Our understanding of the genetic basis of Ménière’s disease (MD) is still limited. Although the familial clustering and the geographical and racial differences in incidence strongly suggest a certain role for genetic factors in the development of MD, no convincing evidence for an association with any gene exists, at present. In this review, starting from rational bases for a genetic approach to MD, we explored the numerous reports published in literature and summarize the recent advances in understanding of the genetic fundaments of the disease.

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.

Finnish familial Meniere disease is not linked to chromosome 12p12.3, and anticipation and cosegregation with migraine are not common findings

PURPOSE

To study the inheritance and characteristics of familial Meniere disease in Finland and genetic linkage to the previously proposed locus on chromosome 12p12.3.

METHODS

Sixteen Meniere families recruited from Kainuu Central Hospital and Helsinki and Oulu University Hospitals in the period 2001-2004 were reevaluated in 2009 using hospital records and mailed questionnaire forms. Ten highly polymorphic microsatellite markers were selected from the area of chromosome 12p12.3 and studied for linkage using the GENEHUNTER protocol.

RESULTS

The families showed autosomal dominant inheritance without cosegregation with migraine. Anticipation was seen only in one family, and in the rest of the families, the age of onset varied randomly among generations and individuals. The severity of the disease was not related to descending generations. None of the maximum logarithm of odds (LOD)/heterogeneity LOD scores in the analysis of chromosome 12p12.3 in Finnish Meniere families reached a significant value of 3.0 (maximum cumulative LOD score: -7.29, heterogeneity LOD: -0.95, α = 0.4).

CONCLUSIONS

Families affected by Meniere disease are highly heterogeneous. Migraine, age at onset, anticipation, or penetrance was not a shared feature. The findings support the multifactorial nature of the disease and indicate that genetic heterogeneity exists within familial Meniere disease.