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GJB2-associated hearing loss (GJB2-HL) is the most common genetic cause of hearing loss in children. However, little is known about the clinical characteristics and early language outcomes in population-oriented samples including children with different degrees of hearing loss. Insight into these characteristics are relevant for the counselling of parents. Our sample consisted of 66 children at approximately 2 years of age (17–32 months) with bilateral hearing loss due to GJB2 from three population-based cohorts in Austria, Australia and the Netherlands. Predictors of early vocabulary, including demographic, audiological, genetic and intervention variables and the role of medical comorbidities and nonverbal cognition were examined. The vocabulary scores of children with GJB2-HL were approximately 0.7 standard deviations (SDs) below the norms of children with typical hearing. Age at access to family-centered early intervention and first-born position among siblings predicted language outcomes, whereas the degree of hearing loss and genetic subtype were not significantly correlated with expressive vocabulary. In children with GJB2-HL, early access to family-centered early intervention significantly affected language outcomes at the age of two.

Introduction An important accompaniment of Non-syndromic sensorineural hearing loss is family history and consanguinity. One of the widely studied single nucleotide polymorphism is the gap junction protein beta-2 (GJB2) gene which encodes the protein connexin26. This study aims to detect the frequency of W24X mutation in a population with non-syndromic sensorineural hearing loss concerning the degree of consanguinity. Materials and Methods The study includes 76 subjects with Non-syndromic sensorineural hearing loss. These subjects had congenital sensorineural hearing loss and other causes for the same had been ruled out. The SNP rs 104894396 was identified by the PCR-RFLP method. Results The frequency of the wild allele was 0.84% and the mutant allele was 0.15%. The frequency of wild allele and mutant allele did not differ much between patients with and without consanguinity. The association between consanguineous marriage and allele frequency was not significant. Gene polymorphism was not present in 77 percent of our NSHL subjects, though 79 percent of our study population were a result of consanguineous marriage. Conclusion Though the role of consanguineous marriages in congenital sensorineural hearing loss is well established, the association between allele frequency and consanguineous marriage was not seen. We assume that other genes responsible for deafness may be involved in the population.

Introduction An important accompaniment of Non-syndromic sensorineural hearing loss is family history and consanguinity. One of the widely studied single nucleotide polymorphism is the gap junction protein beta-2 (GJB2) gene which encodes the protein connexin26. This study aims to detect the frequency of W24X mutation in a population with non-syndromic sensorineural hearing loss concerning the degree of consanguinity. Materials and Methods The study includes 76 subjects with Non-syndromic sensorineural hearing loss. These subjects had congenital sensorineural hearing loss and other causes for the same had been ruled out. The SNP rs 104894396 was identified by the PCR-RFLP method. Results The frequency of the wild allele was 0.84% and the mutant allele was 0.15%. The frequency of wild allele and mutant allele did not differ much between patients with and without consanguinity. The association between consanguineous marriage and allele frequency was not significant. Gene polymorphism was not present in 77 percent of our NSHL subjects, though 79 percent of our study population were a result of consanguineous marriage. Conclusion Though the role of consanguineous marriages in congenital sensorineural hearing loss is well established, the association between allele frequency and consanguineous marriage was not seen. We assume that other genes responsible for deafness may be involved in the population.

Introduction An important accompaniment of Non-syndromic sensorineural hearing loss is family history and consanguinity. One of the widely studied single nucleotide polymorphism is the gap junction protein beta-2 (GJB2) gene which encodes the protein connexin26. This study aims to detect the frequency of W24X mutation in a population with non-syndromic sensorineural hearing loss concerning the degree of consanguinity. Materials and Methods The study includes 76 subjects with Non-syndromic sensorineural hearing loss. These subjects had congenital sensorineural hearing loss and other causes for the same had been ruled out. The SNP rs 104894396 was identified by the PCR-RFLP method. Results The frequency of the wild allele was 0.84% and the mutant allele was 0.15%. The frequency of wild allele and mutant allele did not differ much between patients with and without consanguinity. The association between consanguineous marriage and allele frequency was not significant. Gene polymorphism was not present in 77 percent of our NSHL subjects, though 79 percent of our study population were a result of consanguineous marriage. Conclusion Though the role of consanguineous marriages in congenital sensorineural hearing loss is well established, the association between allele frequency and consanguineous marriage was not seen. We assume that other genes responsible for deafness may be involved in the population.

Connexin (Cx) protein forms hemichannels and gap junctional channels, which play diverse and profound roles in human physiology and diseases. Gap junctions are arrays of intercellular channels formed by the docking of two hemichannels from adjacent cells. Each hexameric hemichannel contains the same or different Cx isoform. Although homomeric Cxs forms have been largely described functionally and structurally, the stoichiometry and arrangement of heteromeric Cx channels remain unknown. The latter, however, are widely expressed in human tissues and variation might have important implications on channel function. Investigating properties of heteromeric Cx channels is challenging considering the high number of potential subunit arrangements and stoichiometries, even when only combining two Cx isoforms. To tackle this problem, we engineered an HA tag onto Cx26 or Cx30 subunits and imaged hemichannels that were liganded by Fab-epitope antibody fragments via atomic force microscopy. For Cx26-HA/Cx30 or Cx30-HA/Cx26 heteromeric channels, the Fab-HA binding distribution was binomial with a maximum of three Fab-HA bound. Furthermore, imaged Cx26/Cx30-HA triple liganded by Fab-HA showed multiple arrangements that can be derived from the law of total probabilities. Atomic force microscopy imaging of ringlike structures of Cx26/Cx30-HA hemichannels confirmed these findings and also detected a polydisperse distribution of stoichiometries. Our results indicate a dominant subunit stoichiometry of 3Cx26:3Cx30 with the most abundant subunit arrangement of Cx26-Cx26-Cx30-Cx26-Cx30-Cx30. To our knowledge, this is the first time that the molecular architecture of heteromeric Cx channels has been revealed, thus providing the basis to explore the functional effect of these channels in biology.

Permanent hearing loss affects 1-3 per 1000 children in Australia. Universal hearing screening of neonates has facilitated early diagnosis and access to hearing devices and early intervention services. Despite this clinical management and investigation of newly diagnosed infants is highly variable. The aim is to provide consensus recommendations for the investigation and clinical management of children with hearing loss for geneticists, pediatricians, otolaryngolo-gists and general practitioners. The Childhood Hearing Australasian Medical Professionals (CHAMP) network was established in 2016 to improve care for hearing-impaired children in Australasia. A working group of 15 members held round-table discussions, examined existing guidelines and completed literature reviews to create a set of recommendations. Members votedonthe grade and strengthofrec-ommendations using NHMRC guidelines. Recommendations are presented in three tiers: (1) First line investigations for non-syndromic hearing loss, (2) Additional investigations based on clinical presentation, and (3) Investigations to consider if tier 1 and 2 investigations are negative. In addition to detailed history taking and examination, all children with congenital hearing loss should have CMV testing, brain MRI, ophthalmology assessment and family audiograms. Children with bilateral SNHL should be offered genetic testing after adequate genetic counseling, with connexin/GJB2 testing as first-line and chromosome microarray as second-line. Where available, genomic testing (exome or deafness panel) should be considered in children with bilateral SNHL, and may reduce the need for other investigations. The role of genetic testing in unilateral loss is limited and should be guided by clinical presentation.

Mutations in connexin 26 (Cx26) hemichannels can lead to syndromic deafness that affects the cochlea and skin. These mutations lead to gain-of-function hemichannel phenotypes by unknown molecular mechanisms. In this study, we investigate the biophysical properties of the syndromic mutant Cx26G12R (G12R). Unlike wild-type Cx26, G12R macroscopic hemichannel currents do not saturate upon depolarization, and deactivation is faster during hyperpolarization, suggesting that these channels have impaired fast and slow gating. Single G12R hemichannels show a large increase in open probability, and transitions to the subconductance state are rare and short-lived, demonstrating an inoperative fast gating mechanism. Molecular dynamics simulations indicate that G12R causes a displacement of the N terminus toward the cytoplasm, favoring an interaction between R12 in the N terminus and R99 in the intracellular loop. Disruption of this interaction recovers the fast and slow voltage-dependent gating mechanisms. These results suggest that the mechanisms of fast and slow gating in connexin hemichannels are coupled and provide a molecular mechanism for the gain-of-function phenotype displayed by the syndromic G12R mutation.

Mutations in GJB2, the gene that encodes connexin 26 (Cx26), are the most common cause of sensorineural hearing impairment. The truncating variant 35delG, which determines a complete loss of Cx26 protein function, is the prevalent GJB2 mutation in several populations. Here, we generated and analyzed Gjb2+/- mice as a model of heterozygous human carriers of 35delG. Compared to control mice, auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) worsened over time more rapidly in Gjb2+/- mice, indicating they were affected by accelerated age-related hearing loss (ARHL), or presbycusis. We linked causally the auditory phenotype of Gjb2+/- mice to apoptosis and oxidative damage in the cochlear duct, reduced release of glutathione from connexin hemichannels, decreased nutrient delivery to the sensory epithelium via cochlear gap junctions and deregulated expression of genes that are under transcriptional control of the nuclear factor erythroid 2-related factor 2 (Nrf2), a pivotal regulator of tolerance to redox stress. Moreover, a statistically significant genome-wide association with two genes (PRKCE and TGFB1) related to the Nrf2 pathway (p-value < 4 × 10-2) was detected in a very large cohort of 4091 individuals, originating from Europe, Caucasus and Central Asia, with hearing phenotype (including 1076 presbycusis patients and 1290 healthy matched controls). We conclude that (i) elements of the Nrf2 pathway are essential for hearing maintenance and (ii) their dysfunction may play an important role in the etiopathogenesis of human presbycusis.

Gap junction channels mediate intercellular signalling that is crucial in tissue development, homeostasis and pathologic states such as cardiac arrhythmias, cancer and trauma. To explore the mechanism by which Ca(2+) blocks intercellular communication during tissue injury, we determined the X-ray crystal structures of the human Cx26 gap junction channel with and without bound Ca(2+). The two structures were nearly identical, ruling out both a large-scale structural change and a local steric constriction of the pore. Ca(2+) coordination sites reside at the interfaces between adjacent subunits, near the entrance to the extracellular gap, where local, side chain conformational rearrangements enable Ca(2+)chelation. Computational analysis revealed that Ca(2+)-binding generates a positive electrostatic barrier that substantially inhibits permeation of cations such as K(+) into the pore. Our results provide structural evidence for a unique mechanism of channel regulation: ionic conduction block via an electrostatic barrier rather than steric occlusion of the channel pore.

Gap junction channels mediate intercellular signalling that is crucial in tissue development, homeostasis and pathologic states such as cardiac arrhythmias, cancer and trauma. To explore the mechanism by which Ca(2+) blocks intercellular communication during tissue injury, we determined the X-ray crystal structures of the human Cx26 gap junction channel with and without bound Ca(2+). The two structures were nearly identical, ruling out both a large-scale structural change and a local steric constriction of the pore. Ca(2+) coordination sites reside at the interfaces between adjacent subunits, near the entrance to the extracellular gap, where local, side chain conformational rearrangements enable Ca(2+)chelation. Computational analysis revealed that Ca(2+)-binding generates a positive electrostatic barrier that substantially inhibits permeation of cations such as K(+) into the pore. Our results provide structural evidence for a unique mechanism of channel regulation: ionic conduction block via an electrostatic barrier rather than steric occlusion of the channel pore.

The keratitis-ichthyosis-deafness (KID) syndrome is caused by mutations in the gap junctional channel protein connexin 26 (Cx26), among them the mutation Cx26S17F. Heterozygous Cx26S17F mice resemble the human KID syndrome, i.e. exhibiting epidermal hyperplasia and hearing impairments. Newborn Cx26S17F mice show a defective epidermal water barrier as well as altered epidermal lipid secretion and location. Linoleoyl ω-esterified ceramides are strongly decreased on the skin surface of Cx26S17F mice. Moreover, the epidermal calcium gradient is altered in the mutant mice. These alterations may be caused by an abnormal Cx26S17F channel function that leads to a defective epidermal water barrier, which in turn may trigger the hyperproliferation seen in the KID syndrome.

Cysteine-scanning mutagenesis combined with thiol reagent modification is a powerful method with which to define the pore-lining elements of channels and the changes in structure that accompany channel gating. Using the Xenopus laevis oocyte expression system and two-electrode voltage clamp, we performed cysteine-scanning mutagenesis of several pore-lining residues of connexin 26 (Cx26) hemichannels, followed by chemical modification using a methanethiosulfonate (MTS) reagent, to help identify the position of the gate. Unexpectedly, we observed that the effect of MTS modification on the currents was reversed within minutes of washout. Such a reversal should not occur unless reducing agents, which can break the disulfide thiol-MTS linkage, have access to the site of modification. Given the permeability to large metabolites of connexin channels, we tested whether cytosolic glutathione (GSH), the primary cell reducing agent, was reaching the modified sites through the connexin pore. Inhibition of gamma-glutamylcysteine synthetase by buthionine sulfoximine decreased the cytosolic GSH concentration in Xenopus oocytes and reduced reversibility of MTS modification, as did acute treatment with tert-butyl hydroperoxide, which oxidizes GSH. Cysteine modification based on thioether linkages (e.g., maleimides) cannot be reversed by reducing agents and did not reverse with washout. Using reconstituted hemichannels in a liposome-based transport-specific fractionation assay, we confirmed that homomeric Cx26 and Cx32 and heteromeric Cx26/Cx32 are permeable to GSH and other endogenous reductants. These results show that, for wide pores, accessibility of cytosolic reductants can lead to reversal of MTS-based thiol modifications. This potential for reversibility of thiol modification applies to on-cell accessibility studies of connexin channels and other channels that are permeable to large molecules, such as pannexin, CALHM, and VRAC.

Mutations in Cx26 gene are found in most cases of human genetic deafness. Some mutations produce syndromic deafness associated with skin disorders, like the Keratitis-Ichthyosis-Deafness syndrome (KID). Because in the human skin connexin 26 (Cx26) is co-expressed with other connexins, like Cx43 and Cx30, and as the KID syndrome is inherited as autosomal dominant condition, it is possible that KID mutations change the way Cx26 interacts with other co-expressed connexins. Indeed, some Cx26 syndromic mutations showed gap junction dominant negative effect when co-expressed with wild-type connexins, including Cx26 and Cx43. The nature of these interactions and the consequences on hemichannels and gap junction channel (GJC) functions remain unknown. In this study, we demonstrate that syndromic mutations, at the N terminus segment of Cx26, change connexin oligomerization compatibility, allowing aberrant interactions with Cx43. Strikingly, heteromeric oligomer formed by Cx43/Cx26 (syndromic mutants) shows exacerbated hemichannel activity but nonfunctional GJCs; this also occurs for those Cx26 KID mutants that do not show functional homomeric hemichannels. Heterologous expression of these hyperactive heteromeric hemichannels increases cell membrane permeability, favoring ATP release and Ca(2+) overload. The functional paradox produced by oligomerization of Cx43 and Cx26 KID mutants could underlie the severe syndromic phenotype in human skin.

Using a prospective, longitudinal study design, this paper addresses the impact of genetic counseling and testing for deafness on deaf adults and the Deaf community. This study specifically evaluated the effect of genetic counseling and Connexin-26 and Connexin-30 genetic test results on participants' deaf identity and understanding of their genetic test results. Connexin-26 and Connexin-30 genetic testing was offered to participants in the context of linguistically and culturally appropriate genetic counseling. Questionnaire data collected from 209 deaf adults at four time points (baseline, immediately following pre-test genetic counseling, 1-month following genetic test result disclosure, and 6-months after result disclosure) were analyzed. Four deaf identity orientations (hearing, marginal, immersion, bicultural) were evaluated using subscales of the Deaf Identity Development Scale-Revised. We found evidence that participants understood their specific genetic test results following genetic counseling, but found no evidence of change in deaf identity based on genetic counseling or their genetic test results. This study demonstrated that culturally and linguistically appropriate genetic counseling can improve deaf clients' understanding of genetic test results, and the formation of deaf identity was not directly related to genetic counseling or Connexin-26 and Connexin-30 genetic test results.

Connexin proteins form hexameric assemblies known as hemichannels. When docked to form gap junction (GJ) channels, hemichannels play a critical role in cell-cell communication and cellular homeostasis, but often are functional entities on their own in unapposed cell membranes. Defects in the Connexin26 (Cx26) gene are the major cause of hereditary deafness arising from dysfunctional hemichannels in the cochlea. Structural studies of Cx26 hemichannels properly trafficked and inserted in plasma membranes, including their clustering that forms a plaque-like feature in whole gap junctions, are limited. We used atomic force microscopy (AFM) to study the surface topography of Cx26 hemichannels using two different membrane preparations. Rat Cx26 containing appended carboxy terminal V5 and hexahistidine tags were expressed in baculovirus/Sf9 cell systems. The expressed Cx26 proteins form hemichannels in situ in Sf9 cells that were then purified either as (1) Sf9 membrane fragments containing Cx26 hemichannels or (2) solubilized hemichannels. The latter were subsequently reconstituted in liposomes. AFM images of purified membrane fragments showed clusters of protein macromolecular structures in the membrane that at higher magnification corresponded to Cx26 hemichannels. Hemichannels reconstituted into DOPC bilayers displayed two populations of channel heights likely resulting from differences in orientations of inserted hemichannels. Hemichannels in the protein rich portions of purified membranes also showed a reduced channel height above the bilayer compared to membranes with reconstituted hemichannels perhaps due to reduced AFM probe access to the lipid bilayer. These preparations of purified membranes enriched for connexin hemichannels that have been properly trafficked and inserted in membranes provide a platform for high-resolution AFM imaging of the structure, interconnexon interactions, and cooperativity of properly trafficked and inserted noncrystalline connexin hemi

Using a prospective, longitudinal study design, this paper addresses the impact of genetic counseling and testing for deafness on deaf adults and the Deaf community. This study specifically evaluated the effect of genetic counseling and Connexin-26 and Connexin-30 genetic test results on participants' deaf identity and understanding of their genetic test results. Connexin-26 and Connexin-30 genetic testing was offered to participants in the context of linguistically and culturally appropriate genetic counseling. Questionnaire data collected from 209 deaf adults at four time points (baseline, immediately following pre-test genetic counseling, 1-month following genetic test result disclosure, and 6-months after result disclosure) were analyzed. Four deaf identity orientations (hearing, marginal, immersion, bicultural) were evaluated using subscales of the Deaf Identity Development Scale-Revised. We found evidence that participants understood their specific genetic test results following genetic counseling, but found no evidence of change in deaf identity based on genetic counseling or their genetic test results. This study demonstrated that culturally and linguistically appropriate genetic counseling can improve deaf clients' understanding of genetic test results, and the formation of deaf identity was not directly related to genetic counseling or Connexin-26 and Connexin-30 genetic test results.

Connexin proteins form hexameric assemblies known as hemichannels. When docked to form gap junction (GJ) channels, hemichannels play a critical role in cell-cell communication and cellular homeostasis, but often are functional entities on their own in unapposed cell membranes. Defects in the Connexin26 (Cx26) gene are the major cause of hereditary deafness arising from dysfunctional hemichannels in the cochlea. Structural studies of Cx26 hemichannels properly trafficked and inserted in plasma membranes, including their clustering that forms a plaque-like feature in whole gap junctions, are limited. We used atomic force microscopy (AFM) to study the surface topography of Cx26 hemichannels using two different membrane preparations. Rat Cx26 containing appended carboxy terminal V5 and hexahistidine tags were expressed in baculovirus/Sf9 cell systems. The expressed Cx26 proteins form hemichannels in situ in Sf9 cells that were then purified either as (1) Sf9 membrane fragments containing Cx26 hemichannels or (2) solubilized hemichannels. The latter were subsequently reconstituted in liposomes. AFM images of purified membrane fragments showed clusters of protein macromolecular structures in the membrane that at higher magnification corresponded to Cx26 hemichannels. Hemichannels reconstituted into DOPC bilayers displayed two populations of channel heights likely resulting from differences in orientations of inserted hemichannels. Hemichannels in the protein rich portions of purified membranes also showed a reduced channel height above the bilayer compared to membranes with reconstituted hemichannels perhaps due to reduced AFM probe access to the lipid bilayer. These preparations of purified membranes enriched for connexin hemichannels that have been properly trafficked and inserted in membranes provide a platform for high-resolution AFM imaging of the structure, interconnexon interactions, and cooperativity of properly trafficked and inserted noncrystalline connexin hemi

Ethnic-specific differences in minor allele frequency impact variant categorization for genetic screening of nonsyndromic hearing loss (NSHL) and other genetic disorders. We sought to evaluate all previously reported pathogenic NSHL variants in the context of a large number of controls from ethnically distinct populations sequenced with orthogonal massively parallel sequencing methods. We used HGMD, ClinVar, and dbSNP to generate a comprehensive list of reported pathogenic NSHL variants and re-evaluated these variants in the context of 8,595 individuals from 12 populations and 6 ethnically distinct major human evolutionary phylogenetic groups from three sources (Exome Variant Server, 1000 Genomes project, and a control set of individuals created for this study, the OtoDB). Of the 2,197 reported pathogenic deafness variants, 325 (14.8%) were present in at least one of the 8,595 controls, indicating a minor allele frequency (MAF) > 0.00006. MAFs ranged as high as 0.72, a level incompatible with pathogenicity for a fully penetrant disease like NSHL. Based on these data, we established MAF thresholds of 0.005 for autosomal-recessive variants (excluding specific variants in GJB2) and 0.0005 for autosomal-dominant variants. Using these thresholds, we recategorized 93 (4.2%) of reported pathogenic variants as benign. Our data show that evaluation of reported pathogenic deafness variants using variant MAFs from multiple distinct ethnicities and sequenced by orthogonal methods provides a powerful filter for determining pathogenicity. The proposed MAF thresholds will facilitate clinical interpretation of variants identified in genetic testing for NSHL. All data are publicly available to facilitate interpretation of genetic variants causing deafness.

Control of plasma membrane connexin hemichannel opening is indispensable, and is achieved by physiological extracellular divalent ion concentrations. Here, we explore the differences between regulation by Ca(2+) and Mg(2+) of human connexin26 (hCx26) hemichannels and the role of a specific interaction in regulation by Ca (2+). To effect hemichannel closure, the apparent affinity of Ca(2+) (0.33 mM) is higher than for Mg(2+) (1.8 mM). Hemichannel closure is accelerated by physiological Ca(2+) concentrations, but non-physiological concentrations of extracellular Mg(2+) are required for this effect. Our recent report provided evidence that extracellular Ca(2+) facilitates hCx26 hemichannel closing by disrupting a salt bridge interaction between positions D50 and K61 that stabilizes the open state. New evidence from mutant cycle analysis indicates that D50 also interacts with Q48. We find that the D50-Q48 interaction contributes to stabilization of the open state, but that it is relatively insensitive to disruption by extracellular Ca(2+) compared with the D50-K61 interaction.

To explore the usefulness of protein profiling for characterization of ichthyoses, we here determined the profile of human epidermal stratum corneum by shotgun proteomics. Samples were analyzed after collection on tape circles from six anatomic sites (forearm, palm, lower leg, forehead, abdomen, upper back), demonstrating site-specific differences in profiles. Additional samples were collected from the forearms of subjects with ichthyosis vulgaris (filaggrin (FLG) deficiency), recessive X-linked ichthyosis (steroid sulfatase (STS) deficiency) and autosomal recessive congenital ichthyosis type lamellar ichthyosis (transglutaminase 1 (TGM1) deficiency). The ichthyosis protein expression patterns were readily distinguishable from each other and from phenotypically normal epidermis. In general, the degree of departure from normal was lower from ichthyosis vulgaris than from lamellar ichthyosis, parallel to the severity of the phenotype. Analysis of samples from families with ichthyosis vulgaris and concomitant modifying gene mutations (STS deficiency, GJB2 deficiency) permitted correlation of alterations in protein profile with more complex genetic constellations.

Limited data suggest that enhanced self-knowledge from genetic information related to non-medical traits can have a positive impact on psychological well-being. Deaf individuals undertake genetic testing for deaf genes to increase self-knowledge. Because deafness is considered a non-medical trait by many individuals, we hypothesized that deaf individuals receiving a genetic explanation for why they are deaf will experience increased psychological well-being. We report results from a prospective, longitudinal study to determine the impact of genetic testing (GJB2, Cx26; GJB6, Cx30) on perceived personal control (PPC), anxiety, and depression in deaf adults (N = 209) assessed following pre-test genetic counseling as well as 1-month and 6-months following test result disclosure. Participants were classified as Cx positive (n = 82) or Cx negative/inconclusive (n = 127). There was significant evidence for Cx group differences in PPC and anxiety over time (PPC: Cx group*time interaction p = 0.0007; anxiety: Cx group*time interaction p = 0.002), where PPC scores were significantly higher, and anxiety scores were significantly lower for the Cx positive group relative to the negative/inconclusive group following test result disclosure. Compared to pre-test, PPC scores increased at 1-month (p = 0.07) and anxiety scores decreased at 6-months (p = 0.03) for the Cx positive group. In contrast, PPC scores decreased (p = 0.009, p < 0.0001) and anxiety scores increased (p = 0.09, p = 0.02) for the Cx negative/inconclusive group at 1- and 6-months post test result disclosure. Genetic testing for deaf genes affects the psychological well-being of deaf individuals. Increasing deaf adults' access to genetic testing may potentially enhance self-knowledge and increase psychological well-being for those who receive a genetic explanation, which could offer downstream health benefits.

To explore the usefulness of protein profiling for characterization of ichthyoses, we here determined the profile of human epidermal stratum corneum by shotgun proteomics. Samples were analyzed after collection on tape circles from six anatomic sites (forearm, palm, lower leg, forehead, abdomen, upper back), demonstrating site-specific differences in profiles. Additional samples were collected from the forearms of subjects with ichthyosis vulgaris (filaggrin (FLG) deficiency), recessive X-linked ichthyosis (steroid sulfatase (STS) deficiency) and autosomal recessive congenital ichthyosis type lamellar ichthyosis (transglutaminase 1 (TGM1) deficiency). The ichthyosis protein expression patterns were readily distinguishable from each other and from phenotypically normal epidermis. In general, the degree of departure from normal was lower from ichthyosis vulgaris than from lamellar ichthyosis, parallel to the severity of the phenotype. Analysis of samples from families with ichthyosis vulgaris and concomitant modifying gene mutations (STS deficiency, GJB2 deficiency) permitted correlation of alterations in protein profile with more complex genetic constellations.

Empirical data on genetic counseling outcomes in the deaf population are needed to better serve this population. This study was an examination of genetics knowledge before and after culturally and linguistically appropriate pre-test genetic counseling in a diverse deaf adult sample. Individuals ≥18 years old with early-onset sensorineural deafness were offered connexin-26/30 testing and genetic counseling. Participants completed questionnaires containing 10 genetics knowledge items at baseline and following pre-test genetic counseling. The effects of genetic counseling, prior beliefs about etiology, and participant's preferred language on genetics knowledge scores were assessed (n = 244). Pre-test genetic counseling (p = .0007), language (p < .0001), prior beliefs (p < .0001), and the interaction between counseling and beliefs (p = .035) were predictors of genetics knowledge. American Sign Language (ASL)-users and participants with "non-genetic/unknown" prior beliefs had lower knowledge scores than English-users and participants with "genetic" prior beliefs, respectively. Genetics knowledge improved after genetic counseling regardless of participants' language; knowledge change was greater for the "non-genetic/unknown" beliefs group than the "genetic" beliefs group. ASL-users' lower knowledge scores are consistent with evidence that ethnic and cultural minority groups have less genetics knowledge, perhaps from exposure and access disparities. Culturally and linguistically appropriate pre-test genetic counseling significantly improved deaf individuals' genetics knowledge. Assessing deaf individuals' prior beliefs is important for enhancing genetics knowledge.

A fundamental feature of the mammalian neocortex is its columnar organization. In the visual cortex, functional columns consisting of neurons with similar orientation preferences have been characterized extensively, but how these columns are constructed during development remains unclear. The radial unit hypothesis posits that the ontogenetic columns formed by clonally related neurons migrating along the same radial glial fibre during corticogenesis provide the basis for functional columns in adult neocortex. However, a direct correspondence between the ontogenetic and functional columns has not been demonstrated. Here we show that, despite the lack of a discernible orientation map in mouse visual cortex, sister neurons in the same radial clone exhibit similar orientation preferences. Using a retroviral vector encoding green fluorescent protein to label radial clones of excitatory neurons, and in vivo two-photon calcium imaging to measure neuronal response properties, we found that sister neurons preferred similar orientations whereas nearby non-sister neurons showed no such relationship. Interestingly, disruption of gap junction coupling by viral expression of a dominant-negative mutant of Cx26 (also known as Gjb2) or by daily administration of a gap junction blocker, carbenoxolone, during the first postnatal week greatly diminished the functional similarity between sister neurons, suggesting that the maturation of ontogenetic into functional columns requires intercellular communication through gap junctions. Together with the recent finding of preferential excitatory connections among sister neurons, our results support the radial unit hypothesis and unify the ontogenetic and functional columns in the visual cortex.

A fundamental feature of the mammalian neocortex is its columnar organization. In the visual cortex, functional columns consisting of neurons with similar orientation preferences have been characterized extensively, but how these columns are constructed during development remains unclear. The radial unit hypothesis posits that the ontogenetic columns formed by clonally related neurons migrating along the same radial glial fibre during corticogenesis provide the basis for functional columns in adult neocortex. However, a direct correspondence between the ontogenetic and functional columns has not been demonstrated. Here we show that, despite the lack of a discernible orientation map in mouse visual cortex, sister neurons in the same radial clone exhibit similar orientation preferences. Using a retroviral vector encoding green fluorescent protein to label radial clones of excitatory neurons, and in vivo two-photon calcium imaging to measure neuronal response properties, we found that sister neurons preferred similar orientations whereas nearby non-sister neurons showed no such relationship. Interestingly, disruption of gap junction coupling by viral expression of a dominant-negative mutant of Cx26 (also known as Gjb2) or by daily administration of a gap junction blocker, carbenoxolone, during the first postnatal week greatly diminished the functional similarity between sister neurons, suggesting that the maturation of ontogenetic into functional columns requires intercellular communication through gap junctions. Together with the recent finding of preferential excitatory connections among sister neurons, our results support the radial unit hypothesis and unify the ontogenetic and functional columns in the visual cortex.

Empirical data on genetic counseling outcomes in the deaf population are needed to better serve this population. This study was an examination of genetics knowledge before and after culturally and linguistically appropriate pre-test genetic counseling in a diverse deaf adult sample. Individuals ≥18 years old with early-onset sensorineural deafness were offered connexin-26/30 testing and genetic counseling. Participants completed questionnaires containing 10 genetics knowledge items at baseline and following pre-test genetic counseling. The effects of genetic counseling, prior beliefs about etiology, and participant's preferred language on genetics knowledge scores were assessed (n = 244). Pre-test genetic counseling (p = .0007), language (p < .0001), prior beliefs (p < .0001), and the interaction between counseling and beliefs (p = .035) were predictors of genetics knowledge. American Sign Language (ASL)-users and participants with "non-genetic/unknown" prior beliefs had lower knowledge scores than English-users and participants with "genetic" prior beliefs, respectively. Genetics knowledge improved after genetic counseling regardless of participants' language; knowledge change was greater for the "non-genetic/unknown" beliefs group than the "genetic" beliefs group. ASL-users' lower knowledge scores are consistent with evidence that ethnic and cultural minority groups have less genetics knowledge, perhaps from exposure and access disparities. Culturally and linguistically appropriate pre-test genetic counseling significantly improved deaf individuals' genetics knowledge. Assessing deaf individuals' prior beliefs is important for enhancing genetics knowledge.

Severe to profound hearing impairment (HI) is estimated to affect around 1/2000 young children. Advances in genetics have made it possible to identify several genes related to HI. This information can cast light upon prognostic factors regarding the outcome in cochlear implantation, and provide information both for scientific and genetic counselling purposes. From 1992 to 2005, 273 children from 254 families (probands) were offered cochlear implants in Norway. An evaluation of the causes of HI, especially regarding the genes GJB2, GJB6, SLC26A4, KCNQ1, KCNE1, and the mutation A1555G in mitochondrial DNA was performed in 85% of the families. The number of probands with unknown cause of HI was thus reduced from 120 to 68 (43% reduction). Ninety-eight (46%) of the probands had an identified genetic etiology of their HI. A relatively high prevalence of Jervell and Lange-Nielsen syndrome was found. The main causes of severe and profound HI were similar to those found in other European countries. GJB2 mutations are a common cause of prelingual HI in Norwegian cochlear implanted children.

Mutations in GJB2 gene are the most common cause of genetic deafness. More than 100 mutations have been described. The aim of this work is to describe the personal experience in genetic hearing loss, investigating the audiological and genetical characteristics of Cx26 deafness and correlating genotype and phenotype. We performed audiological and genetical evaluation in 154 patients affected by non-syndromic deafness of different degree. All patients showed a bilateral symmetrical sensorineural hearing loss. From the genetical analysis 127 probands resulted as negatives while 27 as positives (51.8% homozygous for 35 delG, 14.8% compound heterozygosis and 33.3% single mutation); 7.5% of patients had a mild deafness, 37% moderate, 33.3% severe and 22.2% profound. The c.35 delG mutation was detected in 66.6% of patients. Three mutations were found in compound heterozygosis with 35 delG, six different single mutations already described, and a new mutation S138G were also found. Correlation between genotype and phenotype confirmed the high variability of hearing loss.

Noise has a metabolic and mechanical effect on the inner ear and may therefore interfere with gap junction channels, thus disrupting the interaction between cells in the cochlea. Studies have shown that carriers of connexin mutations in genes involved in HI may have some disturbance in auditory function and may be more susceptible to damage caused by, e.g. noises. Furthermore, hair cell damage in the cochlea as a result of noise exposure can also be mediated by reactive oxygen species. Smoking in combination with elevated diastolic blood pressure and presence of the Raynaud's disease (white finger disease) seems to aggravate noise induced hearing loss (NIHL). In the present study we investigated whether interaction between connexin mutations (C26 and C30) alone, or in combination with genetic variability in the cochlear antioxidant system (GSTM1 deletion, GSTT1 deletion), could explain differences in human noise susceptibility. Furthermore, smoking habits and cardiovascular factors (hypertension, heart disease and white finger diseases) were correlated with noise susceptibility and interactions between genetic factors. Smoking and cardiovascular factors were analysed and correlated with the differences in noise susceptibility found in a Swedish noise-exposed population. The results revealed that smoking alone seems to increase noise susceptibility, and that null-genotypes for the GSTM1 gene in the protective antioxidant system, who smoke/have ever smoked had an additional risk for NIHL compared to those who do not smoke/have never smoked.

IntroductionThe majority of hearing loss in children can be accounted for by genetic causes. Non-syndromic hearing loss accounts for 80% of genetic hearing loss in children, with mutations in DFNB1/GJB2 being by far the most common cause. Among the second tier genetic causes of hearing loss in children are mutations in the DFNB9/OTOF gene.MethodsIn total, 65 recessive non-syndromic hearing loss families were screened by genotyping for association with the DFNB9/OTOF gene. Families with genotypes consistent with linkage or uninformative for linkage to this gene region were further screened for mutations in the 48 known coding exons of otoferlin.ResultsEight OTOF pathological variants were discovered in six families. Of these, Q829X was found in two families. We also noted 23 other coding variant, believed to have no pathology. A previously published missense allele I515T was found in the heterozygous state in an individual who was observed to be temperature sensitive for the auditory neuropathy phenotype.ConclusionsMutations in OTOF cause both profound hearing loss and a type of hearing loss where otoacoustic emissions are spared called auditory neuropathy.

IntroductionThe majority of hearing loss in children can be accounted for by genetic causes. Non-syndromic hearing loss accounts for 80% of genetic hearing loss in children, with mutations in DFNB1/GJB2 being by far the most common cause. Among the second tier genetic causes of hearing loss in children are mutations in the DFNB9/OTOF gene.MethodsIn total, 65 recessive non-syndromic hearing loss families were screened by genotyping for association with the DFNB9/OTOF gene. Families with genotypes consistent with linkage or uninformative for linkage to this gene region were further screened for mutations in the 48 known coding exons of otoferlin.ResultsEight OTOF pathological variants were discovered in six families. Of these, Q829X was found in two families. We also noted 23 other coding variant, believed to have no pathology. A previously published missense allele I515T was found in the heterozygous state in an individual who was observed to be temperature sensitive for the auditory neuropathy phenotype.ConclusionsMutations in OTOF cause both profound hearing loss and a type of hearing loss where otoacoustic emissions are spared called auditory neuropathy.

Although it seems that genetic factors can influcence individual susceptiblity to noise, still very little is known about the genes or the mechanisms involved. The connexin 26 (cx26)(GJB2) gene is of particular interest to study in relation to noise, since the gene encodes a gap junction protein cx26. Noise has a metabolic and mechanical effect on the inner ear, and may therefore, interfere with gap junction channels. In order to investigate whether abnormally high susceptibility to noise induced hearing loss (NIHL) in humans is associated with the common 35delG mutation in the Cx26 gene, 1200 noise-exposed workers were investigated in Sweden. Using a selection procedure based on audiometric analysis, noise exposure data and questionnaires, noise-exposed workers were devided into two categories: noise susceptible and noise resistant. There was a correspondence in noise susceptibility between this noise-exposed population and the international reference ISO standard 1999. Blood samples were drawn from 245 highly selected male subjects (103 noise susceptible, 112 noise resistant and 30 randomized cases), and genomic DNA was analysed with respect to the Cx26 35delG mutation. The incidence of 35delG carriers among this cohort was determined by multiplex, allele-specific PCR. Two of the 245 subjects (0.8%-(95% confidence interval 0.1-2.9) were found to be heterozygous carriers of the 35delG mutation, while the remaining 243 individuals were all non-carriers. Both the heterozygous carriers were found in the noise susceptible group. Statistical evaluation of the results demonstrated no significant difference in carrier incidence between the noise susceptible and noise resistant individuals in our Swedish noise-exposed population. In conclusion, there was no support for a major role of Cx26 35delG mutation in explaining the variability in noise susceptibility in this Swedish population