Natural Mutations Affect Structure and Function of gC1q Domain of Otolin-1.

Otolin-1 is a scaffold protein of otoliths and otoconia, calcium carbonate biominerals from the inner ear. It contains a gC1q domain responsible for trimerization and binding of Ca2+. Knowledge of a structure-function relationship of gC1q domain of otolin-1 is crucial for understanding the biology of balance sensing. Here, we show how natural variants alter the structure of gC1q otolin-1 and how Ca2+ are able to revert some effects of the mutations. We discovered that natural substitutions: R339S, R342W and R402P negatively affect the stability of apo-gC1q otolin-1, and that Q426R has a stabilizing effect. In the presence of Ca2+, R342W and Q426R were stabilized at higher Ca2+ concentrations than the wild-type form, and R402P was completely insensitive to Ca2+. The mutations affected the self-association of gC1q otolin-1 by inducing detrimental aggregation (R342W) or disabling the trimerization (R402P) of the protein. Our results indicate that the natural variants of gC1q otolin-1 may have a potential to cause pathological changes in otoconia and otoconial membrane, which could affect sensing of balance and increase the probability of occurrence of benign paroxysmal positional vertigo (BPPV).

Inframe deletion of human ESPN is associated with deafness, vestibulopathy and vision impairment.

BACKGROUND: Usher syndrome (USH) is a neurosensory disorder characterised by deafness, variable vestibular areflexia and vision loss. The aim of the study was to identify the genetic defect in a Pakistani family (PKDF1051) segregating USH. METHODS: Genome-wide linkage analysis was performed by using an Illumina linkage array followed by Sanger and exome sequencing. Heterologous cells and mouse organ of Corti explant-based transfection assays were used for functional evaluations. Detailed clinical evaluations were performed to characterise the USH phenotype. RESULTS: Through homozygosity mapping, we genetically linked the USH phenotype segregating in family PKDF1051 to markers on chromosome 1p36.32-p36.22. The locus was designated USH1M. Using a combination of Sanger sequencing and exome sequencing, we identified a novel homozygous 18 base pair inframe deletion in ESPN. Variants of ESPN, encoding the actin-bundling protein espin, have been previously associated with deafness and vestibular areflexia in humans with no apparent visual deficits. Our functional studies in heterologous cells and in mouse organ of Corti explant cultures revealed that the six deleted residues in affected individuals of family PKDF1051 are essential for the actin bundling function of espin demonstrated by ultracentrifugation actin binding and bundling assays. Funduscopic examination of the affected individuals of family PKDF1051 revealed irregular retinal contour, temporal flecks and disc pallor in both eyes. ERG revealed diminished rod photoreceptor function among affected individuals. CONCLUSION: Our study uncovers an additional USH gene, assigns the USH1 phenotype to a variant of ESPN and provides a 12th molecular component to the USH proteome.

Correlations of Calcium Voltage-Gated Channel Subunit Alpha1 A (CACNA1A) Gene Polymorphisms with Benign Paroxysmal Positional Vertigo.

BACKGROUND The aim of this study was to investigate the correlations of calcium voltage-gated channel subunit alpha1 A (CACNA1A) gene polymorphisms with benign paroxysmal positional vertigo (BPPV). MATERIAL AND METHODS A total of 120 BPPV patients and 60 healthy controls were enrolled according to the diagnostic criteria in the Guideline of Diagnosis and Treatment of Benign Paroxysmal Positional Vertigo (2017). Clinical and biochemical data were collected, the rs2074880 (T/G) polymorphisms in the CACNA1A gene were detected using TaqMan-MGB probe method, and the correlations of BPPV with predisposing factors were analyzed through logistic analysis. RESULTS The BPPV group had higher levels of cholesterol and uric acid than in the control group (p<0.05). The cholesterol and uric acid levels were positively correlated with BPPV (p<0.05) [odds ratio (OR)=2.298 (1.252-4.350), 95% confidence interval (95% CI)=1.123 (0.987-1.987)]. The distribution frequency of TT genotype was higher than that of GG genotype (χ²=9.907, p=0.002, OR=0.279, 95% CI=0.123-0.633). In the BPPV group, cholesterol and uric acid levels of TT genotype were elevated compared with those in GG genotype (p<0.05). CONCLUSIONS The onset of BPPV is related to the increased levels of cholesterol and uric acid, as well as the dominant homozygous mutation of rs2074880 (T/G) in the CACNA1A gene.

A familial form of benign paroxysmal positional vertigo maps to chromosome 15.

AIM: Benign positional paroxysmal vertigo (BPPV) is characterized by short-lived episodes of vertigo in association with rapid changes in head position, most commonly extension and rotation of the neck while supine. It has been clinically observed that there is a subgroup of patients in whom the BPPV disease is inherited in an autosomal dominant fashion. However, little is known about the familial/genetic factors that may contribute to a predisposition to develop the disease. MATERIALS AND METHODS: We ascertained and performed a genome-wide scan on a three-generation family in which multiple family members developed BPPV. We performed whole genome mapping with 400 microsatellite repeat markers and analyzed this trait using both autosomal dominant and recessive models of inheritance. RESULTS: Two point linkage analysis showed LOD scores of one or greater than one on chromosomes 7, 15, 16 and 20. Independent of the model of inheritance, the highest two-point LOD scores localized to same marker on chromosome 15. Multipoint linkage analysis showed the highest LOD score of 2.84 to markers on chromosome 15 with the autosomal dominant model. Haplotype reconstruction indicates that the BPPV gene in this family maps to a critical chromosomal 15 interval between markers GATA151F03N and GATA85D02. CONCLUSIONS: Discovery of a BPPV gene (or genes) will facilitate a better understanding of not only BPPV, but also the vestibular system. In addition, with improved understanding of the pathophysiology the potential development of alternative therapies for BPPV may be possible.

Recurrent Benign Paroxysmal Positional Vertigo in DFNB16 Patients with Biallelic STRC Gene Deletions.

OBJECTIVE: Deletions of STRC gene (DFNB16) account for 12% of isolated congenital mild to moderate hearing loss (HL). In mice, the stereocilin protein, encoded by STRC , is present in the vestibular kinocilium embedded in the otoconial membrane of the utricular macula. Despite this, effects on vestibular function have not been widely investigated. The aim of this study was to investigate the prevalence of benign paroxysmal positional vertigo (BPPV) in a cohort of DFNB16 patients. STUDY DESIGN: Observational descriptive epidemiological study. SETTING: Single-center study, in a tertiary referral center. PATIENTS: Older than 5 years, with a genetic diagnosis of HL related to biallelic STRC gene deletions, diagnosed between 2015 and 2021. INTERVENTION: Patients or their parents were interviewed to determine whether they had experienced vertigo or episodes of BPPV. MAIN OUTCOME MEASURE: Criteria were at least five acute episodes of rotatory vertigo, each lasting less than 1 minute, episodes triggered by changes in specific head position, and an absence of neurological symptoms. RESULTS: Sixty-four patients having mild (33%) to moderate (66%) HL were included. Median age was 15 years (range, 6-48 yr). Prevalence of BPPV was 39% (25 of 64). Median age of first onset was 13 years (range, 3-18 yr). CONCLUSIONS: This study showed recurrent BPPV and early age of onset in patients with biallelic STRC gene deletions. BPPV may be associated with the HL phenotype in patients with STRC gene deletions. It is important to inform patients and families of this potential risk such that appropriate management can be proposed.

Recurrent benign paroxysmal positional vertigo in two DFNB16 siblings: A CARE case report.

INTRODUCTION: Deletions or variants of the STRC gene coding for stereocilin cause congenital bilateral mild-to-moderate sensorineural hearing loss without vestibular disorder: DFNB16. Stereocilin is a protein present in vestibular kinocilia embedded in the otoconial membrane of the utricular macula. Benign paroxysmal positional vertigo (BPPV) is a rare form of vertigo in children. The present study reports recurrent positional vertigo in two DFNB16 siblings. OBSERVATION: Two patients, 10 and 15 years old, presented with recurrent disabling positional vertigo episodes, triggered by turning over in bed, with a falling sensation. The diagnosis of right posterior canal BPPV was confirmed on Dix-Hallpike maneuvers in one of the patients. Variations in the response of ocular vestibular-evoked myogenic potentials were observed. Probable BPPV was diagnosed in the second patient. Their other two siblings did not have hearing loss or vertigo. CONCLUSION: The absence of stereocilin due to homozygous deletions of the STRC gene in DFNB16 patients can cause vestibular dysfunction, including BPPV.

Relationship between osteoporosis and benign paroxysmal positional vertigo based on evidence-based medicine and bioinformatics.

It has been reported that osteoporosis is a possible risk factor of benign paroxysmal positional vertigo (BPPV). PURPOSE: We analyzed the correlation between osteoporosis and BPPV and the possible mechanism by performing evidence-based medicine meta-analysis and bioinformatics analysis. METHODS: Initially, English articles related to osteoporosis and BPPV were obtained through PubMed and EMBASE databases. Stata12.0 software was used for meta-analysis to calculate the odd ratio (OR) and 95% confidence interval (CI) of outcome indicators, and the heterogeneity was evaluated by subgroup analysis, publication bias evaluation, and sensitivity analysis. In addition, microarray datasets related to BPPV and osteoporosis were obtained from gene expression omnibus (GEO) database to screen differentially expressed genes. At last, a mouse model of osteoporosis was established by bilateral oophorectomy for validation. RT-qPCR and Western blot analysis were performed to determine expression of related factors in mouse tissues. RESULTS: Osteoporosis was suggested as an important risk factor for BPPV through meta-analysis of these 12 articles. It was found that PPP2CA was upregulated in BPPV and low bone mineral density (BMD) samples. Moreover, PPP2CA induced dephosphorylation of BCL2, which may be involved in BPPV through regulation of BMD. Through this mechanism, silencing of PPP2CA could elevate the incidence of BPPV by promoting bone remodeling and reducing the density of otoconia around the macula. CONCLUSIONS: PPP2CA reduces BMD expression by inducing dephosphorylation of BCL2, which may be one of the mechanisms responsible for the onset of BPPV in osteoporosis.

Downregulation of VDR in benign paroxysmal positional vertigo patients inhibits otolith­associated protein expression levels.

Benign paroxysmal positional vertigo (BPPV) is the most common peripheral vertigo­associated disease. Vitamin D (VD) helps maintain normal otolith function and may be associated with BPPV. VD exerts its biological functions primarily via the VD receptor (VDR). The present study demonstrated that serum VD levels were significantly decreased in patients with BPPV compared with in controls. VDR, otolith­associated protein otoconin­90 (OC90) and NADPH oxidase 3 (NOX3) expression levels were also significantly decreased in patients with BPPV compared with in controls. Furthermore, a positive correlation was observed between VD levels and VDR expression. Receiver operating characteristic curve analysis identified VDR expression levels as a potential diagnostic marker for BPPV. OC90 and NOX3 expression levels were notably lower in the inner ear tissue of VDR knockout mice compared with in those of wild­type mice. In mice overexpressing VDR, OC90 and NOX3 were also overexpressed. Following intravenous injection of VD in VDR knockout mice, expression levels of OC90 and NOX3 were not significantly different from those in VDR knockout mice injected with saline. This indicated that VDR may be underexpressed in patients with BPPV and was associated with the expression levels of otolith­associated proteins. Moreover, VDR mediated VD activation, leading to otolith protein formation. The present study provided a novel theoretical basis for BPPV onset that may facilitate the development of more effective diagnostic and treatment options.

Identification of a genetic variant underlying familial cases of recurrent benign paroxysmal positional vertigo.

Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo in humans, yet the molecular etiology is currently unknown. Evidence suggests that genetic factors may play an important role in some cases of idiopathic BPPV, particularly in familial cases, but the responsible genetic variants have not been identified. In this study, we performed whole exome sequencing [including untranslated regions (UTRs)] of 12 families and Sanger sequencing of additional 30 families with recurrent BPPV in Caucasians from the United States (US) Midwest region, to identify the genetic variants responsible for heightened susceptibility to BPPV. Fifty non-BPPV families were included as controls. In silico and experimental analyses of candidate variants show that an insertion variant rs113784532 (frameshift causing truncation) in the neural cadherin gene PCDHGA10 (protocadherin-gamma A10) is an exceedingly strong candidate (p = 1.80x10-4 vs. sample controls; p = 5.85x10-19 vs. ExAC data; p = 4.9x10-3 vs. NHLBI exome data). The mutant protein forms large aggregates in BPPV samples even at young ages, and affected subjects carrying this variant have an earlier onset of the condition than those without [average 44.0±14.0 (n = 16) versus 54.4±16.1 (n = 36) years old, p = 0.054]. In both human and mouse inner ear tissues, PCDHGA10 is expressed in ganglia, hair cells and vestibular transitional epithelia. Fluorescent RNA in situ hybridization using mouse inner ear tissues shows that expression increases with age. In summary, our data show that a variant in the PCDHGA10 gene may be involved in causing or aggravating some familial cases of recurrent idiopathic BPPV.

A novel genetic variant associated with benign paroxysmal positional vertigo within the LOXL1.

BACKGROUND: Benign paroxysmal positional vertigo (BPPV) is a common, self-limited, and favorable prognostic peripheral vestibular disorder. BPPV is transmitted in an autosomal dominant fashion, but most cases occur sporadically. Little research has been reported regarding the mutation spectrum of sporadic BPPV in a large cohort. This study attempted to identify the causative candidate variants associated with BPPV in VDR, LOXL1, and LOXL1-AS1. METHODS: An amplicon-targeted next-generation sequencing (NGS) method for VDR, LOXL1, and LOXL1-AS1, was completed in 726 BPPV patients and 502 normal controls. A total of 30 variants (20 variants from VDR, nine variants from LOXL1, seven variants from LOXL1-AS1) were identified in these two groups. RESULTS: Three of 30 variants were nonsynonymous mutations, but no significant difference was found between the BPPV group and the control group via association analysis. A single nucleotide variant (SNV), rs1078967, was identified that is located in intron 1 of LOXL1. The allelic frequency distribution differed significantly between the BPPV group and the control group (p = 0.002). Genotypic frequency was also significantly different (p = 0.006), as determined by gene-based analyses. CONCLUSION: This report is the first to analyze the variant spectrum of BPPV in a large Chinese population.

A mouse model for benign paroxysmal positional vertigo with genetic predisposition for displaced otoconia.

Abnormal formation of otoconia, the biominerals of the inner ear, results in balance disorders. The inertial mass of otoconia activates the underlying mechanosensory hair cells in response to change in head position primarily during linear and rotational acceleration. Otoconia associate exclusively with the two gravity receptors, the utricle and saccule. The cristae sensory epithelium is associated with an extracellular gelatinous matrix known as cupula, equivalent to otoconia. During head rotation, the inertia of endolymphatic fluids within the semicircular canals deflects the cupula of the corresponding crista and activates the underlying mechanosensory hair cells. It is believed that detached free-floating otoconia particles travel ectopically to the semicircular canal and cristae and are the culprit for benign paroxysmal positional vertigo (BPPV). The Slc26a4 mouse mutant harbors a missense mutation in pendrin. This mutation leads to impaired transport activity of pendrin and to defects in otoconia composition and distribution. All Slc26a4 loop/loop homozygous mutant mice are profoundly deaf but show inconsistent vestibular deficiency. A panel of behavioral tests was utilized in order to generate a scoring method for vestibular function. A pathological finding of displaced otoconia was identified consistently in the inner ears of mutant mice with severe vestibular dysfunction. In this work, we present a mouse model with a genetic predisposition for ectopic otoconia with a clinical correlation to BPPV. This unique mouse model can serve as a platform for further investigation of BPPV pathophysiology, and for developing novel treatment approaches in a live animal model.

The potential role of epigenetic modulations in BPPV maneuver exercises.

Benign paroxysmal positional vertigo (BPPV) is one of the most common complaints encountered in clinics and is strongly correlated with advanced age or, possibly, degeneration. Redistribution exercises are the most effective approaches to treat BPPV, and canalith repositioning procedure (CRP) cure most BPPV cases. However, the mechanisms through which the treatment modulates systemic molecules in BPPV patients remain largely unknown. In this study, we report that the miR-34a and Sirtuin 1 (SIRT1) genes correlated with the treatment effects of CRP in BPPV subjects. We found that miR-34a expression was largely inhibited and SIRT1 expression was significantly reversed after BPPV maneuver treatment. We also confirmed that the PPAR-γ, PGC-1 and FoxO gene expressions were decreased immediately after canalith repositioning procedure (CRP) for BPPV, and were largely increased after a complete cure of BPPV. Moreover, we observed that after a complete recovery of BPPV, the ROS concentrations, pro-inflammatory cytokine concentrations and p53 expression levels were attenuated. We conclude that BPPV treatment might involve some epigenetic regulations through the mediation of miR-34a, SIRT1 functions and repression of redox status.

Gender-based comorbidity in benign paroxysmal positional vertigo.

It has been noted that benign paroxysmal positional vertigo (BPPV) may be associated with certain disorders and medical procedures. However, most studies to date were done in Europe, and epidemiological data on the United States (US) population are scarce. Gender-based information is even rarer. Furthermore, it is difficult to assess the relative prevalence of each type of association based solely on literature data, because different comorbidities were reported by various groups from different countries using different patient populations and possibly different inclusion/exclusion criteria. In this study, we surveyed and analyzed a large adult BPPV population (n = 1,360 surveyed, 227 completed, most of which were recurrent BPPV cases) from Omaha, NE, US, and its vicinity, all diagnosed at Boys Town National Research Hospital (BTNRH) over the past decade using established and consistent diagnostic criteria. In addition, we performed a retrospective analysis of patients' diagnostic records (n = 1,377, with 1,360 adults and 17 children). The following comorbidities were found to be significantly more prevalent in the BPPV population when compared to the age- and gender-matched general population: ear/hearing problems, head injury, thyroid problems, allergies, high cholesterol, headaches, and numbness/paralysis. There were gender differences in the comorbidities. In addition, familial predisposition was fairly common among the participants. Thus, the data confirm some previously reported comorbidities, identify new ones (hearing loss, thyroid problems, high cholesterol, and numbness/paralysis), and suggest possible predisposing and triggering factors and events for BPPV.