Comprehensive Prediction Model, Including Genetic Testing, for the Outcomes of Cochlear Implantation.

OBJECTIVES: Despite growing interest in the genetic contribution to cochlear implant (CI) outcomes, only a few studies with limited samples have examined the association of CI outcomes with genetic etiologies. We analyzed CI outcomes using known predictors and genetic testing results to obtain a comprehensive understanding of the impact of genetic etiologies. DESIGN: We retrospectively reviewed the medical records and images of patients who underwent cochlear implantation and genetic testing at a single tertiary medical institution, between May 2008 and December 2020. After excluding those whose speech test results were unavailable, and those in whom the implant was removed due to complications, such as infection or device failure, 203 patients were included in this study. The participants were categorized into adult (≥19 years), child (2-18 years), and infant (<24 months) groups. Outcomes were measured based on categories of auditory perception, monosyllable, disyllable, and sentence scores. For the infant group, the Infant-Toddler Meaningful Auditory Integration Scale score was used. RESULTS: Among the 203 participants, a causative genetic variant was identified in 117 (57.6%) individuals. The presence of a causative variant was significantly associated with better CI outcomes in the infant group (ß = 0.23; 95% confidence interval, 0.01 to 0.47; p = 0.044), but not in the child and adult groups. In the genetically confirmed patients without cochlear malformation, genetic variants involving the spiral ganglion was a poor prognostic factor in the child group (ß = -57.24; 95% confidence interval, -90.63 to -23.75; p = 0.004). CONCLUSIONS: The presence of known genetic etiology of hearing loss was associated with better CI outcomes in the infant group, but not in the child and adult groups. A neural-type genetic variant was a poor prognostic factor in the genetically diagnosed child subgroup without cochlear malformation. Careful genetic counseling should be performed before cochlear implantation.

Distinct roles of stereociliary links in the nonlinear sound processing and noise resistance of cochlear outer hair cells.

Outer hair cells (OHCs) play an essential role in hearing by acting as a nonlinear amplifier which helps the cochlea detect sounds with high sensitivity and accuracy. This nonlinear sound processing generates distortion products, which can be measured as distortion-product otoacoustic emissions (DPOAEs). The OHC stereocilia that respond to sound vibrations are connected by three kinds of extracellular links: tip links that connect the taller stereocilia to shorter ones and convey force to the mechanoelectrical transduction channels, tectorial membrane-attachment crowns (TM-ACs) that connect the tallest stereocilia to one another and to the overlying TM, and horizontal top connectors (HTCs) that link adjacent stereocilia. While the tip links have been extensively studied, the roles that the other two types of links play in hearing are much less clear, largely because of a lack of suitable animal models. Here, while analyzing genetic combinations of tubby mice, we encountered models missing both HTCs and TM-ACs or HTCs alone. We found that the tubby mutation causes loss of both HTCs and TM-ACs due to a mislocalization of stereocilin, which results in OHC dysfunction leading to severe hearing loss. Intriguingly, the addition of the modifier allele modifier of tubby hearing 1 in tubby mice selectively rescues the TM-ACs but not the HTCs. Hearing is significantly rescued in these mice with robust DPOAE production, indicating an essential role of the TM-ACs but not the HTCs in normal OHC function. In contrast, the HTCs are required for the resistance of hearing to damage caused by noise stress.

Prevalence and Clinical Characteristics of Mitochondrial DNA Mutations in Korean Patients With Sensorineural Hearing Loss.

BACKGROUND: Mutations in mitochondrial DNA (mtDNA) are associated with several genetic disorders, including sensorineural hearing loss. However, the prevalence of mtDNA mutations in a large cohort of Korean patients with hearing loss has not yet been investigated. Thus, this study aimed to investigate the frequency of mtDNA mutations in a cohort of with pre- or post-lingual hearing loss of varying severity. METHODS: A total of 711 Korean families involving 1,099 individuals were evaluated. Six mitochondrial variants associated with deafness (MTRNR1 m.1555A>G, MTTL1 m.3243A>G, MTCO1 m.7444G>A and m.7445A>G, and MTTS1 m.7471dupC and m.7511T>C) were screened using restriction fragment length polymorphism. The prevalence of the six variants was also analyzed in a large control dataset using whole-genome sequencing data from 4,534 Korean individuals with unknown hearing phenotype. RESULTS: Overall, 12 of the 711 (1.7%) patients with hearing loss had mtDNA variants, with 10 patients from independent families positive for the MTRNR1 m.1555A>G mutation and 2 patients positive for the MTCO1 m.7444G>A mutation. The clinical characteristics of patients with the mtDNA variants were characterized by post-lingual progressive hearing loss due to the m.1555A>G variant (9 of 472; 1.9%). In addition, 18/4,534 (0.4%) of the Korean population have mitochondrial variants associated with hearing loss, predominantly the m.1555A>G variant. CONCLUSION: A significant proportion of Korean patients with hearing loss is affected by the mtDNA variants, with the m.1555A>G variant being the most prevalent. These results clarify the genetic basis of hearing loss in the Korean population and emphasize the need for genetic testing for mtDNA variants.

Surgical and nonsurgical treatment outcomes in traumatic facial nerve palsy.

PURPOSE: Facial nerve decompression surgery is performed on patients with immediate, complete traumatic facial palsy. However, the clinical advantage of the surgical treatment has weak evidence because of lack of control groups in previous studies. Therefore, this study compared facial function outcomes between the patients who underwent surgery and those who did not. Furthermore, in cases of bilateral traumatic facial palsy, the outcomes of the surgical and nonsurgical sides were also discussed. METHODS: A retrospective medical chart review of immediate and severe (House-Brackman [HB] grade V and VI) traumatic facial palsy was conducted. Twenty-five ears from the surgical group and eight ears from the conservative treatment group were enrolled. Among the patients, three with immediate and severe bilateral facial palsy underwent unilateral surgery. RESULTS: The average HB grade after 1-year follow-up was 1.7 in the surgical group and 1.5 in the nonsurgical group. Four patients who have definite facial canal disruption in the imaging study have recovered to HB grades I-III without surgical intervention. In patients with bilateral facial palsy, the nonsurgical side showed the same or better facial functions than the surgical side. CONCLUSIONS: Compared with nonsurgical conservative treatment, facial nerve decompression surgery did not show superior outcomes in immediate HB grade V-VI traumatic facial palsy. The clinical advantage of facial nerve decompression is questionable and should be re-evaluated in a prospectively designed study.

COCH-related autosomal dominant nonsyndromic hearing loss: a phenotype-genotype study.

This phenotype-genotype study aimed to investigate the extent of audioprofile variability related to cochlin major domains and to identify potential ethnic-specific differences associated with COCH-related hearing loss. Eight Korean families (26 cases) were diagnosed with COCH-related hearing loss by exome sequencing. Audiometric test results were combined with those from nine published East Asian families (20 cases) and compared with those from 38 European-descent families (277 cases). Audioprofiles were created by grouping audiometric test results into age ranges by age at testing and then averaging hearing loss thresholds by frequency within age ranges. The functional impact of the identified variants was assessed in vitro by examining the intracellular trafficking, secretion, and cleavage of cochlin. In both East Asian and European-descent families segregating COCH-related hearing loss, deafness-associated variants in non-LCCL domains of cochlin were associated with hearing loss that was more severe earlier in life than hearing loss caused by variants in the LCCL domain. Consistent with this phenotypic difference, functional studies demonstrated distinct pathogenic mechanisms for COCH variants in a domain-dependent manner; specifically, a cytotoxic effect was observed for the p.Phe230Leu variant, which is located in the vWFA1 domain. No ethnic-specific differences in hearing loss progression were observed, except for those attributable to an overrepresentation of presymptomatic cases in the European-descent cohort.

Differential genetic diagnoses of adult post-lingual hearing loss according to the audiogram pattern and novel candidate gene evaluation.

Ski-slope hearing loss (HL), which refers to increased auditory threshold at high frequencies, is common in adults. However, genetic contributions to this post-lingual HL remain largely unknown. Here, we prospectively investigated deafness-associated and novel candidate genes causing ski-slope HL. We analyzed 192 families with post-lingual HL via gene panel and/or exome sequencing. With an overall molecular diagnostic rate of 35.4% (68/192) in post-lingual HL, ski-slope HL showed a lower diagnostic rate (30.7%) compared with other conditions (40.7%). In patients who showed HL onset before the age of 40, genetic diagnostic probability was significantly lower for ski-slope HL than for other conditions. Further analysis of 51 genetically undiagnosed patients in the ski-slope HL group identified three variants in delta-like ligand 1 (DLL1), a Notch ligand, which presented in vitro gain-of-function effects on Notch downstream signaling. In conclusion, genetic diagnostic rates in post-lingual HL varied according to audiogram patterns with age-of-onset as a confounding factor. DLL1 was identified as a candidate gene causing ski-slope HL.

The Effects of Preoperative Audiovisual Speech Perception on the Audiologic Outcomes of Cochlear Implantation in Patients with Postlingual Deafness.

INTRODUCTION: Patients with postlingual deafness usually depend on visual information for communication, and their lipreading ability could influence cochlear implantation (CI) outcomes. However, it is unclear whether preoperative visual dependency in postlingual deafness positively or negatively affects auditory rehabilitation after CI. Herein, we investigated the influence of preoperative audiovisual per-ception on CI outcomes. METHOD: In this retrospective case-comparison study, 118 patients with postlingual deafness who underwent unilateral CI were enrolled. Evaluation of speech perception was performed under both audiovisual (AV) and audio-only (AO) conditions before and after CI. Before CI, the speech perception test was performed under hearing aid (HA)-assisted conditions. After CI, the speech perception test was performed under the CI-only condition. Only patients with a 10% or less preoperative AO speech perception score were included. RESULTS: Multivariable regression analysis showed that age, gender, residual hearing, operation side, education level, and HA usage were not correlated with either postoperative AV (pAV) or AO (pAO) speech perception. However, duration of deafness showed a significant negative correlation with both pAO (p = 0.003) and pAV (p = 0.015) speech perceptions. Notably, the preoperative AV speech perception score was not correlated with pAO speech perception (R2 = 0.00134, p = 0.693) but was positively associated with pAV speech perception (R2 = 0.0731, p = 0.003). CONCLUSION: Preoperative dependency on audiovisual information may positively influence pAV speech perception in patients with postlingual deafness.

Effect of Cochlear Implantation on Hearing Fluctuation in Patients with Biallelic SLC26A4 Variants.

INTRODUCTION: Fluctuating hearing loss is a distinctive feature caused by SLC26A4 variants. We investigated whether cochlear implantation had protective or deleterious effect on hearing fluctuation in patients with biallelic SLC26A4 variants. METHODS: Patients with biallelic SLC26A4 variants (N = 16; age = 10.24 ± 9.20 years) who had unilateral cochlear implantation and consecutive postsurgical, bilateral pure-tone audiograms more than 3 times were selected. We retrospectively reviewed the patients' medical records from 2008 to 2019 obtained from a tertiary medical center and used the auditory threshold change (Shift) over time as a marker of hearing fluctuation. Fluctuation events were counted, and the Shift of the implanted and contralateral ears was compared using logistic regression with a generalized estimating equation and linear mixed model. A total of 178 values were included. RESULTS: The odds of fluctuating hearing frequency were 11.185-fold higher in the unimplanted ears than in the implanted ears postoperatively (p = 0.001). The extent of fluctuation at 250 and 500 Hz was also significantly lower in the implanted ears than in the unimplanted ears after adjusting for every other effect (p = 0.003 and p < 0.001, respectively). Notably, higher residual hearing was rather associated with lesser fluctuation in frequency and the extent of fluctuation at 500 Hz, indicating residual hearing function is not the positive predictor for hearing fluctuation. CONCLUSION: In patients with biallelic SLC26A4 variants, cochlear implantation may reduce the frequency and extent of hearing fluctuations.

Activation of KCNQ4 as a Therapeutic Strategy to Treat Hearing Loss.

Potassium voltage-gated channel subfamily q member 4 (KCNQ4) is a voltage-gated potassium channel that plays essential roles in maintaining ion homeostasis and regulating hair cell membrane potential. Reduction of the activity of the KCNQ4 channel owing to genetic mutations is responsible for nonsyndromic hearing loss, a typically late-onset, initially high-frequency loss progressing over time. In addition, variants of KCNQ4 have also been associated with noise-induced hearing loss and age-related hearing loss. Therefore, the discovery of small compounds activating or potentiating KCNQ4 is an important strategy for the curative treatment of hearing loss. In this review, we updated the current concept of the physiological role of KCNQ4 in the inner ear and the pathologic mechanism underlying the role of KCNQ4 variants with regard to hearing loss. Finally, we focused on currently developed KCNQ4 activators and their pros and cons, paving the way for the future development of specific KCNQ4 activators as a remedy for hearing loss.

Increased incidence of unilateral sudden sensorineural hearing loss in patients with hematological malignancies requiring hematopoietic stem cell transplantation.

Haematopoietic stem cell transplantation (HSCT) may dramatically alter the immunity of a recipient. Transient immunodeficiency that occurs before and after HSCT could be associated with the development of sudden sensorineural hearing loss (SSNHL), which is presumed to be often due to viral aetiology. We found an incidence of SSNHL of 29.4 per 10,000 person-years in patients receiving HSCT, 12-fold higher than reported for background population incidence. Development of SSNHL tended to cluster early after diagnosis of haematological malignancies, rather than around date of treatment with HSCT. Increased risk of unilateral SSNHL in patients with haematological malignancy may relate to underlying disease rather than treatment.

Bicarbonate permeation through anion channels: its role in health and disease.

Many anion channels, frequently referred as Cl- channels, are permeable to different anions in addition to Cl-. As the second-most abundant anion in the human body, HCO3- permeation via anion channels has many important physiological roles. In addition to its classical role as an intracellular pH regulator, HCO3- also controls the activity and stability of dissolved proteins in bodily fluids such as saliva, pancreatic juice, intestinal fluid, and airway surface liquid. Moreover, HCO3- permeation through these channels affects membrane potentials that are the driving forces for transmembrane transport of solutes and water in epithelia and affect neuronal excitability in nervous tissue. Consequently, aberrant HCO3- transport via anion channels causes a number of human diseases in respiratory, gastrointestinal, genitourinary, and neuronal systems. Notably, recent studies have shown that the HCO3- permeabilities of several anion channels are not fixed and can be altered by cellular stimuli, findings which may have both physiological and pathophysiological significance. In this review, we summarize recent progress in understanding the molecular mechanisms and the physiological roles of HCO3- permeation through anion channels. We hope that the present discussions can stimulate further research into this very important topic, which will provide the basis for human disorders associated with aberrant HCO3- transport.

Genetic Inheritance of Late-Onset, Down-Sloping Hearing Loss and Its Implications for Auditory Rehabilitation.

OBJECTIVES: Late-onset, down-sloping sensorineural hearing loss has many genetic and nongenetic etiologies, but the proportion of this commonly encountered type of hearing loss attributable to genetic causes is not well known. In this study, the authors performed genetic analysis using next-generation sequencing techniques in patients showing late-onset, down-sloping sensorineural hearing loss with preserved low-frequency hearing, and investigated the clinical implications of the variants identified. DESIGN: From a cohort of patients with hearing loss at a tertiary referral hospital, 18 unrelated probands with down-sloping sensorineural hearing loss of late onset were included in this study. Down-sloping hearing loss was defined as a mean low-frequency threshold at 250 Hz and 500 Hz less than or equal to 40 dB HL and a mean high-frequency threshold at 1, 2, and 4 kHz greater than 40 dB HL. The authors performed whole-exome sequencing and segregation analysis to identify the genetic causes and evaluated the outcomes of auditory rehabilitation in the patients. RESULTS: There were nine simplex and nine multiplex families included, in which the causative variants were found in six of 18 probands, demonstrating a detection rate of 33.3%. Various types of variants, including five novel and three known variants, were detected in the MYH14, MYH9, USH2A, COL11A2, and TMPRSS3 genes. The outcome of cochlear and middle ear implants in patients identified with pathogenic variants was satisfactory. There was no statistically significant difference between pathogenic variant-positive and pathogenic variant-negative groups in terms of onset age, family history of hearing loss, pure-tone threshold, or speech discrimination scores. CONCLUSIONS: The proportion of patients with late-onset, down-sloping hearing loss identified with potentially causative variants was unexpectedly high. Identification of the causative variants will offer insights on hearing loss progression and prognosis regarding various modes of auditory rehabilitation, as well as possible concomitant syndromic features.

A recurrent mutation in KCNQ4 in Korean families with nonsyndromic hearing loss and rescue of the channel activity by KCNQ activators.

Mutations in potassium voltage-gated channel subfamily Q member 4 (KCNQ4) are etiologically linked to nonsyndromic hearing loss (NSHL), deafness nonsyndromic autosomal dominant 2 (DFNA2). To identify causative mutations of hearing loss in 98 Korean families, we performed whole exome sequencing. In four independent families with NSHL, we identified a cosegregating heterozygous missense mutation, c.140T>C (p.Leu47Pro), in KCNQ4. Individuals with the c.140T>C KCNQ4 mutation shared a haplotype flanking the mutated nucleotide, suggesting that this mutation may have arisen from a common ancestor in Korea. The mutant KCNQ4 protein could reach the plasma membrane and interact with wild-type (WT) KCNQ4, excluding a trafficking defect; however, it exhibited significantly decreased voltage-gated potassium channel activity and fast deactivation kinetics compared with WT KCNQ4. In addition, when co-expressed with WT KCNQ4, mutant KCNQ4 protein exerted a dominant-negative effect. Interestingly, the channel activity of the p.Leu47Pro KCNQ4 protein was rescued by the KCNQ activators MaxiPost and zinc pyrithione. The c.140T>C (p.Leu47Pro) mutation in KCNQ4 causes progressive NSHL; however, the defective channel activity of the mutant protein can be rescued using channel activators. Hence, in individuals with the c.140T>C mutation, NSHL is potentially treatable, or its progression may be delayed by KCNQ activators.

The TECTA mutation R1890C is identified as one of the causes of genetic hearing loss: a case report.

BACKGROUND: Many mutations in the α-tectorin gene (TECTA) have been reported to cause non-syndromic hearing loss (NSHL) in either a dominant or recessive inheritance pattern. Among the identified TECTA mutations, H1400Y has been associated with NSHL in two independent studies. However, its exact role in contributing to genetic hearing loss remains elusive. CASE PRESENTATION: We herein report the whole-exome sequencing of a proband presenting with prelingual, non-progressive, mild-to-moderate hearing loss in a simplex family. By using trio-based whole-exome sequencing, we found two heterozygous mutations of R1890C and H1400Y in the ZP and ZA domains of TECTA, respectively. R1890C, previously reported as a pathogenic autosomal dominant mutation of genetic hearing loss, was found to be inherited in a de novo pattern, causing hearing loss in the proband. By contrast, H1400Y was not segregated in this family, and one family member with normal hearing also carried the H1400Y mutation. CONCLUSION: According to the hearing loss-specific American College of Medical Genetics and Genomics (ACMG) guidelines, we conclude that H1400Y should be disqualified as a cause of genetic hearing loss. True pathogenic variants causing genetic hearing loss should be more deliberately reported in accordance with ACMG guidelines.

ANO9/TMEM16J promotes tumourigenesis via EGFR and is a novel therapeutic target for pancreatic cancer.

BACKGROUND: Anoctamin (ANO)/transmembrane member 16 (TMEM16) proteins mediate diverse physiological and pathophysiological functions including cancer cell proliferation. The present study aimed to identify the role of ANOs in pancreatic cancer. METHODS: In an initial screen of ANOs, ANO9/TMEM16J was overexpressed in pancreatic cancer cells, and its role in the pathogenesis of pancreatic cancer was evaluated using an integrated in vitro and in vivo approach. To determine clinical relevance of the experimental findings, the prognostic value of ANO9 was evaluated in patients with pancreatic cancer. RESULTS: The ANO9 mRNA and protein levels were increased in pancreatic cancer-derived cells. Exogenous expression of ANO9 in PANC-1 cells significantly increased cell proliferation in cell cultures and in mice. In contrast, knockdown of ANO9 in AsPC-1, BxPC-3, and Capan-2 cells strongly inhibited cell proliferation. Mechanistic analysis suggested that physical association of ANO9 with epidermal growth factor receptor (EGFR) underlies ANO9-induced cell proliferation. Knockdown of ANO9 augmented the effects of the EGFR inhibitor and the cytotoxic agent on pancreatic cancer cell proliferation. In addition, high ANO9 expression is a poor prognostic factor in patients with pancreatic cancer. CONCLUSIONS: The ANO9/TMEM16J appears to be a clinically useful prognostic marker for pancreatic cancer and a potential therapeutic target.

Whole-exome sequencing identified a missense mutation in WFS1 causing low-frequency hearing loss: a case report.

BACKGROUND: Low-frequency nonsyndromic hearing loss (LF-NSHL) is a rare, inherited disorder. Here, we report a family with LF-NSHL in whom a missense mutation was found in the Wolfram syndrome 1 (WFS1) gene. CASE PRESENTATION: Family members underwent audiological and imaging evaluations, including pure tone audiometry and temporal bone computed tomography. Blood samples were collected from two affected and two unaffected subjects. To determine the genetic background of hearing loss in this family, genetic analysis was performed using whole-exome sequencing. Among 553 missense variants, c.2419A → C (p.Ser807Arg) in WFS1 remained after filtering and inspection of whole-exome sequencing data. This missense mutation segregated with affected status and demonstrated an alteration to an evolutionarily conserved amino acid residue. Audiological evaluation of the affected subjects revealed nonprogressive LF-NSHL, with early onset at 10 years of age, but not to a profound level. CONCLUSION: This is the second report to describe a pathological mutation in WFS1 among Korean patients and the second to describe the mutation in a different ethnic background. Given that the mutation was found in independent families, p.S807R possibly appears to be a "hot spot" in WFS1, which is associated with LF-NSHL.

Mechanisms of CFTR functional variants that impair regulated bicarbonate permeation and increase risk for pancreatitis but not for cystic fibrosis.

CFTR is a dynamically regulated anion channel. Intracellular WNK1-SPAK activation causes CFTR to change permeability and conductance characteristics from a chloride-preferring to bicarbonate-preferring channel through unknown mechanisms. Two severe CFTR mutations (CFTRsev) cause complete loss of CFTR function and result in cystic fibrosis (CF), a severe genetic disorder affecting sweat glands, nasal sinuses, lungs, pancreas, liver, intestines, and male reproductive system. We hypothesize that those CFTR mutations that disrupt the WNK1-SPAK activation mechanisms cause a selective, bicarbonate defect in channel function (CFTRBD) affecting organs that utilize CFTR for bicarbonate secretion (e.g. the pancreas, nasal sinus, vas deferens) but do not cause typical CF. To understand the structural and functional requirements of the CFTR bicarbonate-preferring channel, we (a) screened 984 well-phenotyped pancreatitis cases for candidate CFTRBD mutations from among 81 previously described CFTR variants; (b) conducted electrophysiology studies on clones of variants found in pancreatitis but not CF; (c) computationally constructed a new, complete structural model of CFTR for molecular dynamics simulation of wild-type and mutant variants; and (d) tested the newly defined CFTRBD variants for disease in non-pancreas organs utilizing CFTR for bicarbonate secretion. Nine variants (CFTR R74Q, R75Q, R117H, R170H, L967S, L997F, D1152H, S1235R, and D1270N) not associated with typical CF were associated with pancreatitis (OR 1.5, p = 0.002). Clones expressed in HEK 293T cells had normal chloride but not bicarbonate permeability and conductance with WNK1-SPAK activation. Molecular dynamics simulations suggest physical restriction of the CFTR channel and altered dynamic channel regulation. Comparing pancreatitis patients and controls, CFTRBD increased risk for rhinosinusitis (OR 2.3, p<0.005) and male infertility (OR 395, p<<0.0001). WNK1-SPAK pathway-activated increases in CFTR bicarbonate permeability are altered by CFTRBD variants through multiple mechanisms. CFTRBD variants are associated with clinically significant disorders of the pancreas, sinuses, and male reproductive system.

Pore dilatation increases the bicarbonate permeability of CFTR, ANO1 and glycine receptor anion channels.

KEY POINTS: Cellular stimuli can modulate the ion selectivity of some anion channels, such as CFTR, ANO1 and the glycine receptor (GlyR), by changing pore size. Ion selectivity of CFTR, ANO1 and GlyR is critically affected by the electric permittivity and diameter of the channel pore. Pore size change affects the energy barriers of ion dehydration as well as that of size-exclusion of anion permeation. Pore dilatation increases the bicarbonate permeability (P HC O3/ Cl ) of CFTR, ANO1 and GlyR. Dynamic change in P HC O3/ Cl may mediate many physiological and pathological processes. ABSTRACT: Chloride (Cl(-) ) and bicarbonate (HCO3 (-) ) are two major anions and their permeation through anion channels plays essential roles in our body. However, the mechanism of ion selection by the anion channels is largely unknown. Here, we provide evidence that pore dilatation increases the bicarbonate permeability (P HC O3/ Cl ) of anion channels by reducing energy barriers of size-exclusion and ion dehydration of HCO3 (-) permeation. Molecular, physiological and computational analyses of major anion channels, such as cystic fibrosis transmembrane conductance regulator (CFTR), anoctamin-1(ANO1/TMEM16A) and the glycine receptor (GlyR), revealed that the ion selectivity of anion channels is basically determined by the electric permittivity and diameter of the pore. Importantly, cellular stimuli dynamically modulate the anion selectivity of CFTR and ANO1 by changing the pore size. In addition, pore dilatation by a mutation in the pore-lining region alters the anion selectivity of GlyR. Changes in pore size affected not only the energy barriers of size exclusion but that of ion dehydration by altering the electric permittivity of water-filled cavity in the pore. The dynamic increase in P HC O3/ Cl by pore dilatation may have many physiological and pathophysiological implications ranging from epithelial HCO3 (-) secretion to neuronal excitation.

Dynamic modulation of ANO1/TMEM16A HCO3(-) permeability by Ca2+/calmodulin.

Anoctamin 1 (ANO1)/transmembrane protein 16A (TMEM16A) is a calcium-activated anion channel that may play a role in HCO(3)(-) secretion in epithelial cells. Here, we report that the anion selectivity of ANO1 is dynamically regulated by the Ca(2+)/calmodulin complex. Whole-cell current measurements in HEK 293T cells indicated that ANO1 becomes highly permeable to HCO(3)(-) at high [Ca(2+)](i). Interestingly, this result was not observed in excised patches, indicating the involvement of cytosolic factors in this process. Further studies revealed that the direct association between ANO1 and calmodulin at high [Ca(2+)](i) is responsible for changes in anion permeability. Calmodulin physically interacted with ANO1 in a [Ca(2+)](i)-dependent manner, and addition of recombinant calmodulin to the cytosolic side of excised patches reversibly increased P(HCO3)/P(Cl). In addition, the high [Ca(2+)](i)-induced increase in HCO(3)(-) permeability was reproduced in mouse submandibular gland acinar cells, in which ANO1 plays a critical role in fluid secretion. These results indicate that the HCO(3)(-) permeability of ANO1 can be dynamically modulated and that ANO1 may play an important role in cellular HCO(3)(-) transport, especially in transepithelial HCO(3)(-) secretion.

Ventilation tube insertion is not effective to the treatment of hearing impairment in pediatric patients with Cornelia de Lange syndrome.

OBJECTIVE: Cornelia de Lange syndrome (CdLS) is a multiple developmental disorder including hearing loss. The hearing impairment in CdLS patients is not only sensorineural but also conductive hearing loss (CHL). The aim of this study was to elucidate hearing loss causes in CdLS patients and evaluate the effect of ventilation tube (v-tube) insertion in the cases of CHL. METHODS: Thirty-two patients clinically diagnosed with CdLS were enrolled and analyzed with retrospective case review. Audiologic evaluations and imaging studies such as a temporal bone computed tomogram or brain magnetic resonance imaging (MRI) were performed for all patients. Hearing rehabilitation such as ventilation tube insertion, hearing aid fitting, or cochlear implantation was chosen depending on the audiological condition. RESULTS: Among 32 CdLS patients who underwent auditory brainstem response test, 81.2% presented hearing loss. Imaging studies showed that only middle ear lesions without inner ear anomalies were identified in 56.3%. Notably, the soft tissue lesion in middle ear was identified even in the neonatal MRI. When 7 patients were thought to have CHL due to otitis media with effusion, v-tube insertion was applied first. However, v-tube insertion rarely improved CHL postoperatively. Moreover, middle ear lesion was not fluid effusion but soft tissue lesion according to the intraoperative finding. These lesions were not eradicated even after revision surgery of v-tube insertion. CONCLUSION: V-tube insertion is not effective to improve hearing or eradicate otitis media with effusion in CdLS patients.