Hereditary cochleovestibular dysfunction due to a COCH gene mutation (DFNA9): a follow-up study of a family

Interaural and sex differences in the natural evolution of hearing levels in pre-symptomatic and symptomatic carriers of the p.Pro51Ser variant in the COCH gene

Hearing impairment constitutes a significant health problem in developed countries. If hearing loss is slowly progressive, the first signs may not be noticed in time, or remain untreated until the moment the auditory dysfunction becomes more apparent. The present study will focus on DFNA9, an autosomal dominant disorder caused by pathogenic variants in the COCH gene. Although several cross-sectional studies on this topic have been conducted, a crucial need for longitudinal research has been reported by many authors. Longitudinal trajectories of individual hearing thresholds were established as function of age and superimposed lowess curves were generated for 101 female and male carriers of the p.Pro51Ser variant. The average number of times patients have been tested was 2.49 years with a minimum of 1 year and a maximum of 4 years. In addition, interaural and sex differences were studied, as they could modify the natural evolution of the hearing function. The current study demonstrates that, both in female carriers and male carriers, the first signs of hearing decline, i.e. hearing thresholds of 20 dB HL, become apparent as early as the 3rd decade in the highest frequencies. In addition, a rapid progression of SNHL occurs between 40 and 50 years of age. Differences between male and female carriers in the progression of hearing loss are most obvious between the age of 50 and 65 years. Furthermore, interaural discrepancies also manifest from the age of 50 years onwards. High-quality prospective data on the long-term natural evolution of hearing levels offer the opportunity to identify different disease stages in each cochlea and different types of evolution. This will provide more insights in the window of opportunity for future therapeutic intervention trials.

Efficient delivery of adeno-associated virus (AAV) into inner ear in vivo via trans-stapes route in adult guinea pig

Adeno-associated virus (AAV) are potent vectors to achieve treatment against hearing loss resulting from genetic defects. However, the effects of delivery routes and the corresponding transduction efficiencies for clinical applications remain elusive. Here, we screened AAV vectors of three serotypes (AAV 8, 9 and Anc80L65) into the inner ears of adult normal guinea pigs through trans-stapes (oval window) and trans-round window delivery routes in vivo. Trans-stapes route is akin to stape surgeries in humans. Then, auditory brainstem response (ABR) measurements were conducted to evaluate postoperative hearing, and inner ear tissues were harvested for transduction efficiency analysis. Results showed that AAV8 targeted partial inner hair cells (IHCs) in cochlear basal turn; AAV9 targeted IHCs in cochlear basal and second turn, also a part of vestibular hair cells (VHCs). In contrast, Anc80L65 contributed to GFP signals of 80%-95% IHCs and 67%-91% outer hair cells (OHCs), as well as 69% VHCs via the trans-round window route, with 15-20 dB ABR thresholds shifts. And, via trans-stapes (oval window) route, there were 71%-90% IHCs and 42%-81% OHCs, along with 64% VHCs demonstrating GFP positive, and the ABR thresholds shifts were within 10 dB. This study revealed AAV could be efficiently delivered into mammalian inner ear cells in vivo via trans-stapes (oval window) route with postoperative hearing preservation, and both delivery routes showed promise of virus-based clinical translation of hearing impairment treatment.

Genotype-Phenotype Correlations of Pathogenic COCH Variants in DFNA9: A HuGE Systematic Review and Audiometric Meta-Analysis

Pathogenic missense variants in COCH are associated with DFNA9, an autosomal dominantly inherited type of progressive sensorineural hearing loss with or without vestibular dysfunction. This study is a comprehensive overview of genotype-phenotype correlations using the PRISMA and HuGENet guidelines. Study characteristics, risk of bias, genotyping and data on the self-reported age of onset, symptoms of vestibular dysfunction, normative test results for vestibular function, and results of audiovestibular examinations were extracted for each underlying pathogenic COCH variant. The literature search yielded 48 studies describing the audiovestibular phenotypes of 27 DFNA9-associated variants in COCH. Subsequently, meta-analysis of audiometric data was performed by constructing age-related typical audiograms and by performing non-linear regression analyses on the age of onset and progression of hearing loss. Significant differences were found between the calculated ages of onset and progression of the audiovestibular phenotypes of subjects with pathogenic variants affecting either the LCCL domain of cochlin or the vWFA2 and Ivd1 domains. We conclude that the audiovestibular phenotypes associated with DFNA9 are highly variable. Variants affecting the LCCL domain of cochlin generally lead to more progression of hearing loss when compared to variants affecting the other domains. This review serves as a reference for prospective natural history studies in anticipation of mutation-specific therapeutic interventions.

A Novel COCH Mutation Affects the vWFA2 Domain and Leads to a Relatively Mild DFNA9 Phenotype

OBJECTIVE

To study the genotype and phenotype of a Dutch family with autosomal dominantly inherited hearing loss.

STUDY DESIGN

Genotype-phenotype correlation study. Genetic analysis consisted of linkage analysis, variable number of tandem repeats analysis, and Sanger sequencing. Audiovestibular function was examined. Regression analysis was performed on pure tone audiometry and speech recognition scores and correlated with the age and/or level of hearing loss.

SETTING

Tertiary referral center.

PATIENTS

A large Dutch family presenting with sensorineural hearing loss.

MAIN OUTCOME MEASURES

Identification of the underlying genetic defect of the hearing loss in this family. Results of pure tone and speech audiometry, onset age, progression of hearing loss and vestibular (dys)function.

RESULTS

A novel mutation in COCH, c.1312C > T p.(Arg438Cys), cosegregates with hearing loss and a variable degree of vestibular (dys)function in this family. The reported mean age of onset of hearing loss is 33 years (range, 18-49 yr). Hearing loss primarily affects higher frequencies and its progression is relatively mild (0.8 dB/yr). Speech perception is remarkably well preserved in affected family members when compared with other DFNA9 families with different COCH mutations.

CONCLUSION

These findings expand the genotypic and phenotypic spectrum of DFNA9. The c.1312C > T mutation, which affects the vWFA2 domain, causes a relatively mild audiovestibular phenotype when compared with other COCH mutations.

Does Otovestibular Loss in the Autosomal Dominant Disorder DFNA9 Have an Impact of on Cognition? A Systematic Review

Background and Purpose: Cognitive impairment has been observed in patients with bilateral vestibular loss (BVL) and in patients with sensorineural hearing loss (SNHL). DFNA9 is an autosomal dominant disorder that causes a combination of both sensory deficits by the 3rd to 5th decade. We therefore hypothesize a combined detrimental effect on cognition. The aim of this systematic review was to identify studies related to DFNA9 in general and its relationship with cognitive impairment more specifically.

Materials and Methods: Several databases including Medline, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, ISI Web of Knowledge, and Web of Science were searched to accumulate information about DFNA9-mutations, including phenotype, genotype, pathophysiology, quality of life (QOL), and imaging in general and cognitive function more specifically. A qualitative analysis was performed on the 55 articles that qualified.

Results: The clinical features of DFNA9 are different along the 24 COCH mutations, described up to now. Vestibular symptoms generally present themselves a few years after SNHL onset in mutations associated with the vWFA-domain although they can precede SNHL onset in other mutations associated with the LCCL-domain. QoL has not been studied extensively in DFNA9, although scarce work is available on the positive impact of cochlear implantation to rehabilitate hearing. No studies were found evaluating cognition in DFNA9 patients.

Conclusion: Although cognitive impairment has been demonstrated in patients with hearing loss as well as in patients with BVL, no studies have been reported on the combination of both sensory deficits, such as in DFNA9. Further research is warranted to correlate otovestibular status with cognition.

Phenotype Description of a Novel DFNA9/COCH Mutation, I109T

Objectives:

This is a report of the audiological and vestibular characteristics of a Dutch DFNA9 family with a novel mutation, I109T, in the LCCL domain of COCH.

Methods:

From the family with the novel I109T COCH mutation, audiometric data were collected and analyzed longitudinally. Results were compared to those obtained in previously identified P51S, G88E, and G87W COCH mutation carriers. Special attention was also given to a comparison of age-related features such as progressive hearing loss and vestibular impairment.

Results:

A novel mutation (I109T) in COCH segregates with hearing impairment and vestibular dysfunction in the present family. Pure tone thresholds, phoneme recognition scores, and vestibular responses of the I109T mutation carriers were essentially similar to those previously established in P51S, G87W, and G88E mutation carriers. Deterioration of hearing in the I109T mutation carriers started at 43 years of age, and vestibular function deteriorated at least 7 years later.

Conclusions:

The phenotype associated with the novel COCH (I109T) mutation is largely similar to that associated with P51S and G88E mutation carriers. However, subtle differences in terms of onset age and rate of progression seem to exist.

Phenotype analysis of an Australian DFNA9 family with the 1109N COCH mutation

OBJECTIVES

We studied the clinical characteristics of an Australian family with an autosomal dominant sensorineural hearing impairment (DFNA9) caused by an I109N mutation in COCH.

METHODS

Retrospective analyses of audiometric data from 8 mutation carriers of an Australian DFNA9 family with the I109N COCH mutation were performed. Cross-sectional hearing levels related to age, age-related typical audiograms, and speech recognition scores related to age and to the level of hearing impairment were investigated. Data were compared to those obtained in previously identified DFNA9 families with P51S, V66G, G87W, G88E, I109T, and C542F COCH mutations.

RESULTS

Deterioration of hearing in the I109N mutation carriers started before the age of 40 years. The audiometric characteristics of the I109N mutation carriers are essentially similar to those previously established in I109T mutation carriers and, to a lesser extent, in P51S, G87W, and G88E mutation carriers.

CONCLUSIONS

The phenotype associated with the I109N COCH mutation is largely similar to that associated with the I109T, P51S, G87W, and G88E mutation carriers. However, subtle differences seem to exist in terms of age of onset and rate of progression.

Contemporary perspectives on the pathophysiology of Meniere's disease: implications for treatment

PURPOSE OF REVIEW

Meniere's disease is characterized by episodic vertigo, fluctuating hearing loss, aural fullness and tinnitus. Endolymphatic hydrops, found on post-mortem examination, is the histologic hallmark. Recent research suggests that endolymphatic hydrops results from cytochemical perturbations of unknown etiology that lead to disturbance of the normal endolymphatic fluid homeostasis. This consequent hydropic state or the associated cytochemical perturbations appears to create a neurotoxic environment that ultimately leads to spiral ganglion cell death likely via the apoptotic mechanism. This review highlights some of the recent advances in the understanding of the pathophysiology of endolymphatic hydrops and progressive cochleovestibular deterioration, with emphasis placed on its potential therapeutic implications.

RECENT FINDINGS

Recent evidence supports that endolymphatic hydrops is possibly an epiphenomenon, and is preceded by perturbation of the normal ionic transport regulatory mechanisms. Furthermore, chronic cochleovestibular deterioration appears to be the result of an excitotoxic response to chronic hydrops. A recently described animal model, the Phex mouse, carrying a mutation in the Phex Hyp-Duk gene, provides a novel insight to genetically regulated postnatal endolymphatic hydrops and a useful tool to expand our understanding.

SUMMARY

Despite encouraging recent advances, there are considerable challenges that remain in the development of targeted therapeutic interventions that may offer new avenues of neuroprotection in known cases of Meniere's disease. These advances will hopefully provide pharmacotherapeutic interventions aimed at preventing progressive cochleovestibular dysfunction.

Vertical corneal striae in families with autosomal dominant hearing loss: DFNA9/COCH

PURPOSE

Investigation of a possible association between vertical corneal striae and mutations in the COCH gene, observed in four DFNA9 families with autosomal dominant hearing loss and vestibular dysfunction.

DESIGN

Prospective case series.

METHODS

Ophthalmologic examinations with photography of the cornea after instillation of fluorescein were performed in 98 family members with 61 mutation carriers of four DFNA9 families at the Radboud University Nijmegen Medical Centre. Families 1 and 2 harbor the Pro51Ser mutation, and families 3 and 4 harbor the Gly88Glu and the Gly87Trp mutation, respectively. Statistical analysis was performed to find an association between the vertical corneal striae and the COCH mutation for each family and to test whether the four families were different in this respect.

RESULTS

The vertical corneal striae were exclusively visible after instillation of fluorescein. They caused minor problems, as dry eye symptoms, and were not present in the general Dutch ophthalmologic population. The striae were present from an age of 47 years in 32 individuals, of whom 27 individuals had a COCH mutation. Statistical analysis on the striae and the COCH mutations showed a significant association in families 1, 2, and 3 (P = .0006), but not in family 4 (P = .63).

CONCLUSIONS

Data analysis demonstrated a significant association between vertical corneal striae and the Pro51Ser and Gly88Glu mutations in the COCH gene in DFNA9 families 1, 2, and 3 with cochleovestibular dysfunction. Our findings suggest that the vertical corneal striae and cochleovestibular dysfunction may be caused by the same COCH mutations.

Clinical Characteristics of a Dutch DFNA9 Family with a Novel COCH Mutation, G87W

The present study aims to report audiological and vestibular characteristics of a Dutch DFNA9 family with a novel mutation, G87W, in the LCCL domain of COCH. From the family with the novel G87W COCH mutation audiometric data were collected and analyzed longitudinally. Results were compared with those obtained in previously identified P51S COCH mutation carriers (n = 74) and with those obtained in G88E mutation carriers. Special attention was also given to a comparison of age-related features, such as progressive hearing loss and vestibular impairment. A novel mutation (G87W) in COCH is indicative of hearing impairment and vestibular dysfunction in the present family. Pure-tone thresholds, phoneme recognition scores, and vestibular responses of the G87W mutation carriers were essentially similar to those previously established in the P51S and G88E mutation carriers. Deterioration of hearing and vestibular function in the G87W mutation carriers started at the age of 43 years. Remarkably, similar to G88E mutation carriers, the proportion of patients over 40 years of age who developed complete vestibular areflexia was significantly lower for the G87W mutation carriers than for the P51S mutation carriers. In conclusion, the phenotype associated with the novel COCH (G87W) mutation is largely similar to that associated with the P51S and G88E mutation carriers. However, subtle differences in terms of onset age and rate of progression seem to exist.

Vestibular deterioration precedes hearing deterioration in the P51S COCH mutation (DFNA9): an analysis in 74 mutation carriers

OBJECTIVES

To analyze cochleovestibular impairment features in P51S COCH mutation carriers (n = 22) in a new, large Dutch family and to compare the results to those obtained in previously identified similar mutation carriers (n = 52). To evaluate age-related features between progressive hearing and vestibular impairment of all mutation carriers (n = 74).

STUDY DESIGN

Family study.

METHODS

Regression analysis was performed in relation to age to outline the development of hearing thresholds, speech recognition scores, and vestibulo-ocular reflex time constant as the key vestibular response parameter.

RESULTS

Pure tone thresholds, phoneme recognition scores, and vestibular responses of the mutation carriers in the new family were essentially similar to those previously established in all other mutation carriers. Hearing started to deteriorate in all mutation carriers from 43 years of age onwards, whereas deterioration of vestibular function started from age 34.

CONCLUSION

Vestibular impairment starts earlier, progresses more rapidly, and, eventually, is more complete than hearing impairment in P51S COCH mutation carriers.

Cochlin immunostaining of inner ear pathologic deposits and proteomic analysis in DFNA9 deafness and vestibular dysfunction

Seven missense mutations and one in-frame deletion mutation have been reported in the coagulation factor C homology (COCH) gene, causing the adult-onset, progressive sensorineural hearing loss and vestibular disorder at the DFNA9 locus. Prevalence of COCH mutations worldwide is unknown, as there is no systematic screening effort for late-onset hearing disorders; however, to date, COCH mutations have been found on four continents and the possibility of COCH playing an important role in presbycusis and disorders of imbalance has been considered. Cochlin (encoded by COCH) has also been shown as a major target antigen for autoimmune sensorineural hearing loss. In this report, we present histopathology, immunohistochemistry and proteomic analyses of inner ear tissues from post-mortem DFNA9 temporal bone samples of an individual from a large Dutch kindred segregating the P51S mutation and adult human unaffected controls, and wild-type (+/+) and Coch null (-/-) knock-out mice. DFNA9 is an inner ear disorder with a unique histopathology showing loss of cellularity and aggregation of abundant homogeneous acellular eosinophilic deposits in the cochlear and vestibular labyrinths, similar to protein aggregation in well-known neurodegenerative disorders. By immunohistochemistry on the DFNA9 temporal bone sections, we have shown cochlin staining of the characteristic cochlear and vestibular deposits, indicating aggregation of cochlin in the same structures in which it is normally expressed. Proteomic analysis identified cochlin as the most abundant protein in mouse and human cochleae. The high-level expression and stability of cochlin in the inner ear, even in the absence and severe atrophy of the fibrocytes that normally express COCH, are shown through these studies and further elucidate the pathobiologic events occurring in DFNA9 leading to hearing loss and vestibular dysfunction.

Personal factors involved in onset or progression of Ménière's disease and low-tone sensorineural hearing loss

PURPOSE

To identify personal causative factors for Ménière's disease.

PROCEDURES

Patterns of hearing loss progression were studied in patients with Ménière's disease and low-tone sensorineural hearing loss, and the involvement of stress and the relation of stressors to the onset or progression of the disease were analyzed.

RESULTS

Low-tone loss recurred in 40% of patients even after hearing was restored, and low-tone loss progressed to high-tone loss after frequent repetitions of recovery and recurrence. High-tone loss tended to proceed to all-tone loss. Eighty percent of patients reported that stress was involved or deeply involved in the onset or progression of the disease. Common causative stressors were business-related pressure, insufficient sleep, and troubles at the workplace or at home.

CONCLUSIONS

The present findings indicate that recovery and recurrence may be influenced by the strength and duration of stress that is produced when patients do not feel rewarded for engrossment in their work or for self-inhibiting behaviors.

A novelDFNA9mutation in the vWFA2 domain ofCOCHalters a conserved cysteine residue and intrachain disulfide bond formation resulting in progressive hearing loss and site-specific vestibular and central oculomotor dysfunction

Mutations within the COCH gene (encoding the cochlin protein) lead to auditory and vestibular impairment in the DFNA9 disorder. In this study, we describe the genetic mapping of progressive autosomal dominant sensorineural hearing loss first affecting high-frequency auditory thresholds within a human pedigree to the long arm of chromosome 14 in band q12. A maximal pairwise LOD score of 7.08 was obtained with marker D14S1021. We identified a c.1625G > T mutation in exon 12 of COCH that co-segregates with auditory dysfunction in the pedigree. The mutation results in a predicted p.C542F substitution at an evolutionarily conserved cysteine residue in the C-terminus of cochlin. The c.1625G > T transversion in COCH exon 12 represents the first reported mutation outside of the LCCL domain which is encoded by exons 4 and 5. The 542F mutant cochlin is translated and secreted by transfected mammalian cells. Western blot analysis under non-reducing and reducing conditions suggests that the 542F mutation alters intramolecular cochlin disulfide bond formation. In the vestibular system, a progressive horizontal canal hypofunction and a probable saccular otolith challenge were detected in family members with the c.1625G > T COCH alteration. Abnormal central oculomotor test results in family members with the c.1625G > T COCH alteration imply a possible central nervous system change not previously noted in DFNA9 pedigrees harboring mutations within the LCCL domain.

Audiometric, Vestibular, and Genetic Aspects of a DFNA9 Family with a G88E COCH Mutation

OBJECTIVES

To perform genetic analysis and to analyze cochleovestibular impairment features in a newly identified Dutch family with nonsyndromic autosomal dominant hearing impairment (DFNA9).

STUDY DESIGN

Genetic analysis was performed using microsatellite markers and single nucleotide polymorphisms. Audiometric data were collected and analyzed longitudinally. Results were compared with those obtained in previously identified P51S COCH mutation carriers (n = 74). Special attention was also given to a comparison of age-related features such as progressive hearing loss and vestibular impairment.

SETTING

Tertiary referral center.

PATIENTS

G88E COCH mutation carriers from a Dutch family.

MAIN OUTCOME MEASURES

The study of clinical features of a DFNA9 family carrying a G88E COCH mutation and to compare this to the symptoms of those carrying a P51S/COCH mutation.

RESULTS

Pure-tone thresholds, phoneme recognition scores, and vestibular responses of the G88E mutation carriers were essentially similar to those previously established in the P51S mutation carriers. Hearing started to deteriorate in G88E mutation carriers from age 46 to 49 years and onward, whereas deterioration of vestibular function started from approximately age 46 years. In the P51S mutation carriers, vestibular impairment started earlier, at approximately age 34 years. However, the difference in age of onset with the G88E mutation carriers was not significant. Remarkably, the proportion of patients who developed complete vestibular areflexia within the age range of 40 to 56 years was significantly lower for the G88E mutation carriers than for the P51S mutation carriers.

CONCLUSION

Apart from a significantly lower frequency of vestibular areflexia between the ages of 40 and 56 years, there are no phenotypic differences between carriers of the G88E and P51S mutations in the COCH gene.

Cochlin, a secreted von Willebrand factor type a domain-containing factor, is regulated by leukemia inhibitory factor in the uterus at the time of embryo implantation

Embryo implantation is a required step in the reproduction of all mammals. In mice, a transient rise in the uterine expression of leukemia inhibitory factor (LIF) occurs on d 4 of pregnancy and is essential for embryo implantation. However, which genes are regulated by LIF in the uterus at implantation has not been determined. We performed a subtractive hybridization assay between luminal epithelial (LE) mRNAs from d 3 and 4 of pregnancy to find genes up-regulated on d 4 and which would be potentially regulated by LIF. One candidate, Coch-5b2, was up-regulated on the day of implantation. Coch mRNA localized to the LE of wild-type mice and was not detected in uteri from Lif-deficient mice. Treatment of LE with LIF, both in vitro and in vivo, resulted in the up-regulation of Coch. Coch is also highly expressed in other tissues, including the spleen and inner ear, but only in the uterus is Coch expression regulated by LIF. Mice were derived in which Coch was either deleted or tagged with a LacZ reporter. In mice carrying the tagged Coch gene, expression of Coch was detected in the LE and also at the site of embryo implantation. However, mice in which the Coch gene was deleted were normal, showing no overt defects in their reproduction. Although loss of Coch expression is not essential to reproduction in mice, it may serve as a useful marker for assessing the state of uterine receptivity in response to LIF at the onset of implantation.

Mutations in COCH that result in non-syndromic autosomal dominant deafness (DFNA9) affect matrix deposition of cochlin

The COCH gene mutated in autosomal dominant sensorineural deafness (DFNA9) encodes cochlin, a major constituent of the inner ear extracellular matrix. Sequence analysis of cochlin from DFNA9 patients identified five distinct single-amino-acid mutations within a conserved region (the LCCL domain) of cochlin. To define the molecular basis of DFNA9, we have generated myc-tagged wild-type and mutant cochlins and explored their behavior in transient transfection systems. Western blotting of cell lysates and culture media indicates that wild-type and mutant cochlins are synthesized and secreted in similar amounts. Immunofluorescent staining confirms that all are detected within the endoplasmic reticulum and the Golgi complex of transfected cells. Our findings suggest that COCH mutations are unlikely to cause abnormalities in secretion and suggest that extracellular events might cause DFNA9 pathology. In agreement, we show that wild-type cochlin accumulates in extracellular deposits that closely parallel the matrix component fibronectin, whereas mutant cochlins vary in the amount and pattern of extracellular material. Whereas some mutants exhibit an almost normal deposition pattern, some show complete lack of deposition. Our results suggest that DFNA9 results from gene products that fail to integrate correctly into the extracellular matrix. The partial or complete penetrance of integration defects suggests that DFNA9 pathology may be caused by multiple molecular mechanisms, including compromised ability of cochlin to self-assemble or to form appropriate complexes with other matrix components.