Coagulation Factor C Homology Research Articles

A Novel COCH p.D544Vfs*3 Variant Associated with DFNA9 Sensorineural Hearing Loss Causes Pathological Multimeric Cochlin Formation.

COCH (coagulation factor C homology) is one of the most frequently mutated genes of autosomal dominant non-syndromic hearing loss. Variants in COCH could cause DFNA9, which is characterized by late-onset hearing loss with variable degrees of vestibular dysfunction. In this study, we report a Chinese family with a novel COCH variant (c.1687delA) causing p.D544Vfs*3 in the cochlin. Comprehensive audiometric tests and vestibular function assessments were taken to acquire the phenotypic profile of the subjects. Next-generation sequencing was conducted and segregation analysis was carried out using Sanger sequencing. The proband presented mild vestibular symptoms and normal functional assessment results in almost every test, while the variant co-segregated with hearing impairment in the pedigree. The variant was located beyond the vWFA2 domain, which was predicted to affect the post-translational cleavage of the cochlin via molecular modeling analysis. Notably, in the overexpressing study, by transient transfecting the HEK 293T cells, we found that the p.D544Vfs*3 variant increased the formation of multimeric cochlin. Our result enriched the spectrum of DFNA9-linked pathological COCH variants and suggested that variants, causative of cochlin multimerization, could be related to DFNA9 with sensorineural hearing loss rather than serious vestibular symptoms.

Massively Parallel Sequencing of a Chinese Family with DFNA9 Identified a Novel Missense Mutation in the LCCL Domain of COCH.

DFNA9 is a late-onset, progressive, autosomal dominantly inherited sensorineural hearing loss with vestibular dysfunction, which is caused by mutations in the COCH (coagulation factor C homology) gene. In this study, we investigated a Chinese family segregating autosomal dominant nonsyndromic sensorineural hearing loss. We identified a missense mutation c.T275A p.V92D in the LCCL domain of COCH cosegregating with the disease and absent in 100 normal hearing controls. This mutation leads to substitution of the hydrophobic valine to an acidic amino acid aspartic acid. Our data enriched the mutation spectrum of DFNA9 and implied the importance for mutation screening of COCH in age related hearing loss with vestibular dysfunctions.

A novel frameshift variant of COCH supports the hypothesis that haploinsufficiency is not a cause of autosomal dominant nonsyndromic deafness 9

COCH (coagulation factor C homology) encodes cochlin, and certain mutations of COCH cause autosomal dominant nonsyndromic deafness 9 (DFNA9). Hearing loss due to COCH mutation begins in adulthood, and 17 missense mutations and two in-frame mutations have been reported. Studies with animal and cellular models have suggested that the underlying biological mechanism of DFNA9 is the dominant-negative effect of mutated COCH and not haploinsufficiency. However, no human cases of DFNA9 that support this hypothesis have been reported. The proband of the present case was an 18-year-old male with congenital or infantile hearing loss. Targeted next-generation sequencing analysis detected a heterozygous novel frameshift mutation of COCH (c.146dupT, p.C50LfsX8) in the proband, whose hearing loss began earlier than what is typical for DFNA9. His mother also carried the mutation but had normal hearing. Consequently, the mutation was not considered to be the cause of the proband's hearing loss. This family is the first case of a truncating COCH variant and supports the hypothesis that COCH haploinsufficiency is not the cause of hearing loss in humans.

Novel COCH p.V123E Mutation, Causative of DFNA9 Sensorineural Hearing Loss and Vestibular Disorder, Shows Impaired Cochlin Post-Translational Cleavage and Secretion.

DFNA9 is an autosomal dominant disorder characterized by late-onset, non-syndromic hearing loss, and vestibular dysfunction. Mutations in the COCH (coagulation factor C homology) gene encoding cochlin are etiologically linked to DFNA9. Previous studies have shown that cochlin is cleaved by aggrecanase-1 during inflammation in the spleen and that the cleaved LCCL domain functions as an innate immune mediator. However, the physiological role of cochlin in the inner ear is not completely understood. Here, we report that cochlins containing DFNA9-linked mutations (p.P51S, p.V66G, p.G88E, p.I109T, p.W117R, p.V123E, and p.C162Y) demonstrate reduced cleavage by aggrecanase. Notably, in families affected with DFNA9, we found a novel COCH mutation causing p.V123E substitution in cochlin, which significantly reduced protein susceptibility to cleavage by aggrecanase (to about 20.5% of the wild-type). These results suggest that the impaired post-translational cleavage of cochlin mutants may be associated with pathological mechanisms underlying DFNA9-related sensorineural hearing loss.

Phenotype predictions of the pathogenic nonsynonymous single nucleotide polymorphisms in deafness-causing gene COCH

The COCH (Coagulation factor C homology) gene, located in human chromosome 14q12-q13, is the first gene identified to cause vestibular dysfunction. COCH encodes cochlin, which contains an N-terminal LCCL (Limulus factor C, cochlin, and late gestation lung protein Lgl1) domain and a C-temimal vWFA (Von Willebrand factor type A) domain. Recently, functional research of COCH mutations and cochlin have come under the spotlight in the field of hereditary deafness. Approximately 16 mutations in COCH have been confirmed to date, among which 13 non-synonymous single nucleotide polymorphisms (nsSNPs) are the most common form of genetic variations. Nonetheless, there is poor knowledge on the relationship between the genotype and the phenotype of the other nsSNPs in COCH. Here we analyzed deleterious nsSNPs from all SNPs in the COCH gene in the vWFA domain based on different computational methods and identified eight potential pathogenic nsSNPs (I176T, R180Q, G265E, V269L, I368N, I372T, R416C and Y424D) after combining literatures with 3D structures. Meanwhile, the protein structures of six reported pathogenic nsSNPs (P51S, G87W, I109N, I109T, W117R and F121S) in the LCCL domain have been constructed, and we identified aberrant structural changes in loops and chains. The prediction of pathogenic mutations for COCH nsSNPs will provide a blueprint for screening pathogenic mutations, and it will be beneficial to the functional research of COCH and cochlin in this field.

Identification of pathogenic mechanisms of COCH mutations, abolished cochlin secretion, and intracellular aggregate formation: genotype-phenotype correlations in DFNA9 deafness and vestibular disorder.

Mutations in COCH (coagulation factor C homology) cause autosomal-dominant nonsyndromic hearing loss with variable degrees of clinical onset and vestibular malfunction. We selected eight uncharacterized mutations and performed immunocytochemical and Western blot analyses to track cochlin through the secretory pathway. We then performed a comprehensive analysis of clinical information from DFNA9 patients with all 21 known COCH mutations in conjunction with cellular and molecular findings to identify genotype-phenotype correlations. Our studies revealed that five mutants were not secreted into the media: two von Willebrand factor A (vWFA) domain mutants, which were not transported from the endoplasmic reticulum to Golgi complex and formed high-molecular-weight aggregates in cell lysates, and three LCCL domain mutants, which were detected as intracellular dimeric cochlins. Mutant cochlins that were not secreted and accumulated in cells result in earlier age of onset of hearing defects. In addition, individuals with LCCL domain mutations show accompanying vestibular dysfunction, whereas those with vWFA domain mutations exhibit predominantly hearing loss. This is the first report showing failure of mutant cochlin transport through the secretory pathway, abolishment of cochlin secretion, and formation and retention of dimers and large multimeric intracellular aggregates, and high correlation with earlier onset and progression of hearing loss in individuals with these DFNA9-causing mutations.

Hearing and vestibular deficits in the Coch −/− null mouse model: Comparison to the Coch G88E/G88E mouse and to DFNA9 hearing and balance disorder

Two mouse models, the Coch G88E/G88E or “knock-in” and the Coch −/− or “knock-out” ( Coch null), have been developed to study the human late-onset, progressive, sensorineural hearing loss and vestibular dysfunction known as DFNA9. This disorder results from missense and in-frame deletion mutations in COCH ( coagulation factor C homology), encoding cochlin, the most abundantly detected protein in the inner ear. We have performed hearing and vestibular analyses by auditory brainstem response (ABR) and vestibular evoked potential (VsEP) testing of the Coch −/− and Coch G88E/G88E mouse models. Both Coch −/− and Coch G88E/G88E mice show substantially elevated ABRs at 21 months of age, but only at the highest frequency tested for the former and all frequencies for the latter. At 21 months, 9 of 11 Coch −/− mice and 4 of 8 Coch G88E/G88E mice have absent ABRs. Interestingly Coch −/+ mice do not show hearing deficits, in contrast to Coch G88E/+ , which demonstrate elevated ABR thresholds similar to homozyotes. These results corroborate the DFNA9 autosomal dominant mode of inheritance, in addition to the observation that haploinsufficiency of Coch does not result in impaired hearing. Vestibular evoked potential (VsEP) thresholds were analyzed using a two factor ANOVA (Age X Genotype). Elevated VsEP thresholds are detected in Coch −/− mice at 13 and 21 months, the two ages tested, and as early as seven months in the Coch G88E/G88E mice. These results indicate that in both mouse models, vestibular function is compromised before cochlear function. Analysis and comparison of hearing and vestibular function in these two DFNA9 mouse models, where deficits occur at such an advanced age, provide insight into the pathology of DFNA9 and age-related hearing loss and vestibular dysfunction as well as an opportunity to investigate potential interventional therapies.

A Case of Cochlear Implantation in a Patient with Mutation in the Coagulation Factor C Homology Gene(W117R)

The autosomal dominant deafness disorder at the DFNA9 locus has been described and the clinical aspects extensively characterized, showing adult-onset, progressive sensorineural hearing loss and vestibular dysfunction. DFNA9 is caused by mutations of the human Coagulation factor C homology (COCH)gene. COCH encodes cochlin, a highly abundant secreted protein of unk-nown function in the inner ear. Several mutations have been identified so far: P51S, V66G, G87W, G88E, V104del, I109T, I109N, W117R, A119T, M512T, C542F, C542T. We hereby report a case of cochlear implantation in a 55-year-old man with bilateral sensorineural hearing loss, which is caused by a mutation in COCH gene (W117R).

A targeted Coch missense mutation: a knock-in mouse model for DFNA9 late-onset hearing loss and vestibular dysfunction

Mutations in COCH (coagulation factor C homology) are etiologic for the late-onset, progressive, sensorineural hearing loss and vestibular dysfunction known as DFNA9. We introduced the G88E mutation by gene targeting into the mouse and have created a Coch(G88E/G88E) mouse model for the study of DFNA9 pathogenesis and cochlin function. Vestibular-evoked potential (VsEP) thresholds of Coch(G88E/G88E) mice were elevated at all ages tested compared with wild-type littermates. At the oldest ages, two out of eight Coch(G88E/G88E) mice had no measurable VsEP. Auditory brainstem response (ABR) thresholds of Coch(G88E/G88E) mice were substantially elevated at 21 months but not at younger ages tested. At 21 months, four of eight Coch(G88E/G88E) mice had absent ABRs at all frequencies tested and two of three Coch(G88E)(/+) mice had absent ABRs at three of four frequencies tested. Distortion product otoacoustic emission amplitudes of Coch(G88E/G88E) mice were substantially lower than Coch(+/+) mice and absent in the same Coch(G88E/G88E) mice with absent ABRs. These results suggest that vestibular function is affected beginning as early as 11 months when cochlear function appears to be normal, and dysfunction increases with age. Hearing loss declines substantially at 21 months of age and progresses to profound hearing loss at some to all frequencies tested. This is the only mouse model developed to date where hearing loss begins at such an advanced age, providing an opportunity to study both progressive age-related hearing loss and possible interventional therapies.

Mutation screening of the COCH gene in familial and sporadic patients with late onset nonsyndromic sensorineural hearing loss among Chinese population

To investigate the mutational of the coagulation factor C homology (COCH) gene related to autosomal dominant sensorineural nonsyndromic hearing loss (DFNA) with late onset in Chinese population. Peripheral blood samples were collected from he members of 26 DFNA families, members of 19 small DFNA families with un recognized inheritance pattern, and 22 sporadic patients with sensorineural nonsyndromic late onset hearing loss, the hearing loss of all of which occurred during the age range 10 - 40, and 100 normal controls. From different parts of China, these subjects underwent questionnaire survey too. Genomic DNA was isolated, COCH mutation was screened by PCR and sequencing, and restriction endonuclease analysis was used to detect the mutation sites of the COCH gene. The conservation in evolution of the target amino acid sequences was analyzed using CluatalX1.82 software. DNA sequencing of coding regions and exon/intron boundaries of COCH 2 - 12 exons identified a heterozygous G-to-A substitution at position 1625 in exon 12 in a large DFNA family, leading to a C542Y substitution, and a heterozygous T-to-C substitution at position 1535 in exon 12 in a small family, leading to a M512T substitutions. Both the residues of Cys542 and M512 were conserved across human, mouse, chicken, and zebrafish. These mutations were not detected in the 100 control subjects. The C542Y and the M512T mutations cause hearing loss in Chinese DFNA families.

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.

Absence of COCH mutations in patients with Meniere disease.

Missense mutations in the coagulation factor C homology (COCH) gene (14q12-q13) cause the autosomal dominant sensorineural hearing loss and vestibular disorder DFNA9 (OMIM 603196), and a high prevalence of symptoms of Meniere disease (MD) has been described in families with a mutation in the COCH gene. In this study, we search for mutations in the COCH gene in peripheral blood from patients with definite MD. DNA was extracted from peripheral blood cells of 30 individuals with MD and 30 controls. Exons 4 and 5 of the COCH gene were amplified by PCR reaction, using primer pairs flanking both exons. Sequences were analysed by a DNA sequencing system and compared with the published COCH cDNA sequence. No differences were found in the nucleotide sequences of exons 4 and 5 in the COCH gene in patients with definite sporadic MD when they were compared with the control group. Patients with definite MD have a low prevalence of mutations in exons 4 and 5 of the COCH gene.