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Purpose: The aim of this study was to characterize the genetic, audiologic, and epidemiologic characteristics of unilateral hearing loss (HL) in a national hereditary deafness repository.Materials and Methods: This is a prospective clinical study involving 34 subjects identified in a national hereditary deafness repository. Clinical data and family history of HL were obtained on enrollment. Candidate deafness genes were screened by single-stranded conformation polymorphism, and mutations were confirmed with sequencing.Results: Thirty-four subjects (19 males, 15 females) with unilateral HL were identified, ranging in age from 2 months to 36 years. The mean age at diagnosis was 7 years, and the left ear was affected in 62% of the cases. The racial distribution of our sample was 62% white, 23% African American, and 15% Hispanic. Imaging results were available in 47%, and most (69%) were considered normal. Nineteen percent had enlarged vestibular aqueducts, 2 had ipsilateral Mondini dysplasia, and 1 had a common cavity deformity. Twenty subjects (59%) had a family history of HL, with 26% specifically reporting familial unilateral HL. Mutational screening revealed sequence variants in the GJB2 (connexin 26), GJB3 (connexin 31), TECTA, and COCH genes. Two novel mutations were detected in COCH and TECTA.Conclusions: Sequence variants in known deafness genes were detected in more than one-third of our study population, suggesting that gene/gene or gene/environmental interactions may indeed play a role in the etiology of some cases of unilateral deafness. Further prospective studies including congenital cytomegalovirus screening at birth and molecular screening of deafness genes in children with congenital unilateral HL will be required to establish the etiology of unilateral deafness with certainty. [ABSTRACT FROM AUTHOR]

Genetic services for deafness are being increasingly sought due to the introduction of early hearing detection and intervention programs, as well as the rapid progress in the identification of deafness genes. This study aimed to assess the motivations of consumers for pursuing genetic testing as well as their preferences for provision of these services. We conducted 5 focus groups consisting of hearing parents of deaf children, deaf parents, and unmarried deaf adults. Motivations for pursuing genetic testing included determining the etiology, helping to alleviate the guilt associated with the diagnosis of hearing loss in a child, and acquiring information to help them and other family members prepare for the future. Most participants thought that a genetic counselor/geneticist would be the most appropriate professional to provide genetics services. For culturally Deaf individuals, the communication method was seen as more important than the type of professional. Parents preferred that genetic evaluation, including testing, occur either immediately at or a few months after the audiologic diagnosis of hearing loss. [ABSTRACT FROM AUTHOR]

Background: Mutations involving the closely linked GJB2 and GJB6 at the DFNB1 locus are a common genetic cause of profound congenital hearing loss in many populations. In some deaf GJB2 heterozygotes, a 309 kb deletion involving the GJB6 has been found to be the cause for hearing loss when inherited in trans to a GJB2 mutation., Methods: We screened 2,376 probands from a National DNA Repository of deaf individuals., Results: Fifty-two of 318 heterozygous probands with pathogenic GJB2 sequence variants had a GJB6 deletion. Additionally, eight probands had an isolated heterozygous GJB6 deletion that did not explain their hearing loss. In two deaf subjects, including one proband, a homozygous GJB6 deletion was the cause for their hearing loss, a rare occurrence not reported to date., Conclusion: This study represents the largest US cohort of deaf individuals harboring GJB2 and GJB6 variants, including unique subsets of families with deaf parents. Testing additional members to clarify the phase of GJB2/GJB6 variants in multiplex families was crucial in interpreting clinical significance of the variants in the proband. It highlights the importance of determining the phase of GJB2/GJB6 variants when interpreting molecular test results especially in multiplex families with assortative mating., (© 2020 The Authors. Molecular Genetics & Genomic Medicine published by Wiley Periodicals, Inc.)

Great strides in gene discovery have been made using a multitude of methods to associate phenotypes with genetic variants, but there still remains a substantial gap between observed symptoms and identified genetic defects. Herein, we use the convergence of various genetic and genomic techniques to investigate the underpinnings of a constellation of phenotypes that include prostate cancer (PCa) and sensorineural hearing loss (SNHL) in a human subject. Through interrogation of the subject's de novo, germline, balanced chromosomal translocation, we first identify a correlation between his disorders and a poorly annotated gene known as lipid droplet associated hydrolase (LDAH). Using data repositories of both germline and somatic variants, we identify convergent genomic evidence that substantiates a correlation between loss of LDAH and PCa. This correlation is validated through both in vitro and in vivo models that show loss of LDAH results in increased risk of PCa and, to a lesser extent, SNHL. By leveraging convergent evidence in emerging genomic data, we hypothesize that loss of LDAH is involved in PCa and other phenotypes observed in support of a genotype-phenotype association in an n-of-one human subject.

Hearing loss is a common and complex condition that can occur at any age, can be inherited or acquired, and is associated with a remarkably wide array of etiologies. The diverse causes of hearing loss, combined with the highly variable and often overlapping presentations of different forms of hearing loss, challenge the ability of traditional clinical evaluations to arrive at an etiologic diagnosis for many deaf and hard-of-hearing individuals. However, identifying the etiology of a hearing loss may affect clinical management, improve prognostic accuracy, and refine genetic counseling and assessment of the likelihood of recurrence for relatives of deaf and hard-of-hearing individuals. Linguistic and cultural identities associated with being deaf or hard of hearing can complicate access to and the effectiveness of clinical care. These concerns can be minimized when genetic and other health-care services are provided in a linguistically and culturally sensitive manner. This guideline offers information about the frequency, causes, and presentations of hearing loss and suggests approaches to the clinical evaluation of deaf and hard-of-hearing individuals aimed at identifying an etiologic diagnosis and providing informative and effective patient education and genetic counseling.

Optic atrophy (OA) and sensorineural hearing loss (SNHL) are key abnormalities in several syndromes, including the recessively inherited Wolfram syndrome, caused by mutations in WFS1. In contrast, the association of autosomal dominant OA and SNHL without other phenotypic abnormalities is rare, and almost exclusively attributed to mutations in the Optic Atrophy-1 gene (OPA1), most commonly the p.R445H mutation. We present eight probands and their families from the US, Sweden, and UK with OA and SNHL, whom we analyzed for mutations in OPA1 and WFS1. Among these families, we found three heterozygous missense mutations in WFS1 segregating with OA and SNHL: p.A684V (six families), and two novel mutations, p.G780S and p.D797Y, all involving evolutionarily conserved amino acids and absent from 298 control chromosomes. Importantly, none of these families harbored the OPA1 p.R445H mutation. No mitochondrial DNA deletions were detected in muscle from one p.A684V patient analyzed. Finally, wolframin p.A684V mutant ectopically expressed in HEK cells showed reduced protein levels compared to wild-type wolframin, strongly indicating that the mutation is disease-causing. Our data support OA and SNHL as a phenotype caused by dominant mutations in WFS1 in these additional eight families. Importantly, our data provide the first evidence that a single, recurrent mutation in WFS1, p.A684V, may be a common cause of ADOA and SNHL, similar to the role played by the p.R445H mutation in OPA1. Our findings suggest that patients who are heterozygous for WFS1 missense mutations should be carefully clinically examined for OA and other manifestations of Wolfram syndrome., (Copyright © 2011 Wiley-Liss, Inc.)

Mutations of GJB2 and GJB6 (connexin-26 and 30) at the DFNB1 locus are the most common cause of autosomal recessive, nonsyndromic deafness. Despite their widespread expression throughout the vestibular system, vestibular dysfunction has not been widely recognized as a commonly associated clinical feature. The observations of vertigo accompanying DFNB1 deafness in several large families prompted our hypothesis that vestibular dysfunction may be an integral, but often overlooked, component of DFNB1 deafness. Our aim was to define the prevalence of vestibular dysfunction in Cases of DFNB1 deafness and Controls with other forms of deafness. We developed and used a survey to assess symptoms of vestibular dysfunction, medical, and family history was distributed to Cases with deafness due to pathogenic GJB2 and/or GJB6 mutations and deaf Controls without DFNB1 deafness. Our results showed: Surveys were returned by 235/515 Cases (46%) with DFNB1 mutations and 121/321 Controls (38%) without these mutations. The mean age of Cases (41) was younger than Controls (51; P < 0.001). Vestibular dysfunction was reported by 127 (54%) of Cases and was present at significantly higher rates in Cases than in deaf Controls without DFNB1 deafness (P < 0.03). Most (63%) had to lie down in order for vertigo to subside, and 48% reported that vertigo interfered with activities of daily living. Vertigo was reported by significantly more Cases with truncating than non-truncating mutations and was also associated with a family history of dizziness. We conclude that vestibular dysfunction appears to be more common in DFNB1 deafness than previously recognized and affects activities of daily living in many patients., (Copyright © 2011 Wiley-Liss, Inc.)

The genetic fitness of an individual is influenced by their phenotype, genotype and family and social structure of the population in which they live. It is likely that the fitness of deaf individuals was quite low in the Western European population during the Middle Ages. The establishment of residential schools for deaf individuals nearly 400 years ago resulted in relaxed genetic selection against deaf individuals which contributed to the improved fitness of deaf individuals in recent times. As part of a study of deaf probands from Gallaudet University, we collected pedigree data, including the mating type and the number and hearing status of the children of 686 deaf adults and 602 of their hearing siblings. Most of these individuals had an onset of severe to profound hearing loss by early childhood. Marital rates of deaf adults were similar to their hearing siblings (0.83 vs. 0.85). Among married individuals, the fertility of deaf individuals is lower than their hearing siblings (2.06 vs. 2.26, p = 0.005). The fitness of deaf individuals was reduced (p = 0.002). Analysis of fertility rates after stratification by mating type reveals that matings between two deaf individuals produced more children (2.11) than matings of a deaf and hearing individual (1.85), suggesting that fertility among deaf individuals is influenced by multiple factors.

Hearing loss is a common sensory deficit and more than 50% of affected individuals have a genetic etiology. The discovery of 40 genes and more than 100 loci involved in hearing loss has made genetic testing for some of these genes widely available. Genetic services for deafness are also being sought more often due to the early identification of hearing loss through newborn screening services. The motivations for pursuing genetic testing, and how genetic services are provided to the client may differ among individuals. Additionally, information obtained through genetic testing can be perceived and used in different ways by parents of deaf children and deaf adults. This study aimed to follow up on focus group studies published earlier with a quantitative survey instrument and assess the preference of consumers for provision of genetic services. We conducted a national survey of hearing and deaf parents of children with hearing loss and of deaf adults. Data was compared and analyzed by hearing status of the participant, their community affiliation and the genetic testing status using nominal logistic regression. Consistent with our focus group results, the survey participants thought that a genetic counselor/geneticist would be the most appropriate professional to provide genetics services. Statistically significant differences were noted in the preferred choice of provider based on the genetic testing status. Parents preferred that genetic evaluation, including testing, occur either immediately at or a few months after the audiologic diagnosis of hearing loss. This data should help providers in clinical genetics keep patient preferences at the helm and provide culturally competent services.

Hearing loss is a common neuro-sensory deficit; nearly 50% of children with hearing loss have a genetic etiology. With the discovery of 40 genes and more than 100 loci involved in hearing loss, genetic testing is becoming more widely available. The information obtained through genetic testing can be perceived and used in different ways by parents of deaf children and deaf adults, based on their prior knowledge and understanding of these advances. It is therefore important to clarify the feelings of these potential consumers towards genetic services for hearing loss and understand their goals for genetic testing. The present study evaluates the feelings of consumers towards the advances in the genetics of hearing loss, the motivations for pursuing testing, and the perceived impact testing may have on their lives. We surveyed 808 parents of children with hearing loss nationally and 156 young deaf adults at Gallaudet University. In this study, learning the etiology of the hearing loss was the most commonly cited motivation for pursuing genetic testing and for parents was the most commonly cited outcome that genetic testing may have on their children's lives. Culturally Deaf respondents were less likely to believe that genetic testing will impact their lives or their children's lives and were less likely to report positive feelings about advances in the genetics of hearing loss. Cultural affiliation and genetic testing status, rather than hearing status, contributed more to the participants' responses., ((c) 2009 Wiley-Liss, Inc.)

Hearing loss with enlargement of the vestibular aqueduct (EVA) can be associated with mutations of the SLC26A4 gene encoding pendrin, a transmembrane Cl(-)/I(-)/HCO(3)(-) exchanger. Pendrin's critical transport substrates are thought to be I(-) in the thyroid gland and HCO(3)(-) in the inner ear. We previously reported that bi-allelic SLC26A4 mutations are associated with Pendred syndromic EVA whereas one or zero mutant alleles are associated with nonsyndromic EVA. One study proposed a correlation of nonsyndromic EVA with SLC26A4 alleles encoding pendrin with residual transport activity. Here we describe the phenotypes and SLC26A4 genotypes of 47 EVA patients ascertained since our first report of 39 patients. We sought to determine the pathogenic potential of each variant in our full cohort of 86 patients. We evaluated the trafficking of 11 missense pendrin products expressed in COS-7 cells. Products that targeted to the plasma membrane were expressed in Xenopus oocytes for measurement of anion exchange activity. p.F335L, p.C565Y, p.L597S, p.M775T, and p.R776C had Cl(-)/I(-) and Cl(-)/HCO(3)(-) exchange rate constants that ranged from 13 to 93% of wild type values. p.F335L, p.L597S, p.M775T and p.R776C are typically found as mono-allelic variants in nonsyndromic EVA. The high normal control carrier rate for p.L597S indicates it is a coincidentally detected nonpathogenic variant in this context. We observed moderate differential effects of hypo-functional variants upon exchange of HCO(3)(-) versus I(-) but their magnitude does not support a causal association with nonsyndromic EVA. However, these alleles could be pathogenic in trans configuration with a mutant allele in Pendred syndrome., ((c) 2009 Wiley-Liss, Inc.)

In 1898, E.A. Fay published an analysis of nearly 5000 marriages among deaf individuals in America collected during the 19(th) century. Each pedigree included three-generation data on marriage partners that included at least one deaf proband, who were ascertained by complete selection. We recently proposed that the intense phenotypic assortative mating among the deaf might have greatly accelerated the normally slow response to relaxed genetic selection against deafness that began in many Western countries with the introduction of sign language and the establishment of residential schools. Simulation studies suggest that this mechanism might have doubled the frequency of the commonest forms of recessive deafness (DFNB1) in this country during the past 200 years. To test this prediction, we collected pedigree data on 311 contemporary marriages among deaf individuals that were comparable to those collected by Fay. Segregation analysis of the resulting data revealed that the estimated proportion of noncomplementary matings that can produce only deaf children has increased by a factor of more than five in the past 100 years. Additional analysis within our sample of contemporary pedigrees showed that there was a statistically significant linear increase in the prevalence of pathologic GJB2 mutations when the data on 441 probands were partitioned into three 20-year birth cohorts (1920 through 1980). These data are consistent with the increase in the frequency of DFNB1 predicted by our previous simulation studies and provide convincing evidence for the important influence that assortative mating can have on the frequency of common genes for deafness.

Mutations in GJB2 (which encodes the gap-junction protein connexin 26) are the most common cause of genetic deafness in many populations. To date, more than 100 deafness-causing mutations have been described in this gene. The majority of these mutations are inherited in an autosomal recessive manner, but approximately 19 GJB2 mutations have been associated with dominantly inherited hearing loss. One, W44C, was first identified in two families from France. We subsequently described a family in the United States with the same mutation. In these families, W44C segregates with a dominantly inherited, early-onset, progressive, sensorineural deafness that is worse in the high frequencies. Since that report, we have tested additional family members and identified two siblings who are compound heterozygous for the W44C and K15T mutations. Their father, the original proband, is heterozygous for the dominant W44C mutation, and their mother is compound heterozygous for two recessively inherited mutations, K15T and 35delG. Both children have a profound, sensorineural deafness and use manual communication, in contrast to their parents and other relatives whose hearing losses are less severe and who can communicate orally. The difference in phenotype may be a result of the disruption of different functions of the gap-junction protein by the two mutations, which have an additive effect., ((c) 2007 Wiley-Liss, Inc)

Purpose: Progress in identifying genes for deafness together with implementation of universal audiologic screening of newborns has provided the opportunity for more widespread use of molecular tests to detect genetic forms of hearing loss. Efforts to assess consumer attitudes toward these advances have lagged behind., Methods: Consumer focus groups were held to explore attitudes toward genetic advances and technologies for hearing loss, views about newborn hearing screening, and reactions to the idea of adding molecular screening for hearing loss at birth. Focus group discussions were recorded, transcribed and analyzed., Results: Five focus groups with 44 participants including hearing parents of deaf children, deaf parents and young deaf adults were held. Focus group participants supported the use of genetic tests to identify the etiology of hearing loss but were concerned that genetic information might influence reproductive decisions. Molecular newborn screening was advocated by some; however, others expressed concern about its effectiveness., Conclusion: Documenting the attitudes of parents and other consumers toward genetic technologies establishes the framework for discussions on the appropriateness of molecular newborn screening for hearing loss and informs specialists about potential areas of public education necessary prior to the implementation of such screening.

Purpose: Permanent hearing loss at birth or in early childhood is common and has many genetic and environmental causes. Advances in the identification and characterization of genetic forms, combined with the early identification of children through the implementation of state-based Early Hearing Detection and Intervention programs suggests the need for education about the causes of hearing loss among professionals who work in these programs., Methods: An online survey was directed to state program coordinators of Early Hearing Detection and Intervention programs to identify gaps in knowledge about the genetic causes of hearing loss and to assess interest in continuing education on this topic., Results: The study identified clear gaps in respondents' knowledge about genetic causes of hearing loss. Twenty percent of respondents indicated that they had received no training in genetics. When asked to rate their knowledge about the genetics of hearing loss, most rated their knowledge as "not adequate." Respondents expressed interest in genetics training through several modalities, including a distance learning format., Conclusion: This study provides documentation of the need for education of health care professionals involved in the early identification of hearing loss. Suggestions for suitable educational formats based on respondent needs and interests are provided.

Astounding progress has been made in the identification and characterization of genes for hearing loss, which has led to an increasing role of genetics evaluation and testing in the diagnostic process for children with hearing loss. The importance of health professionals such as audiologists gaining core competencies in genetics has been recognized. The current report describes a survey of academic programs in audiology designed to determine the extent to which genetics content is included in the curriculum. Responses from 56% of existing academic programs indicate that 95% include some genetics content in their programs, with the total number of classroom hours ranging from 2 to 65. Most programs included information on basic genetic mechanisms, syndromes, and interpreting family history information, while many fewer reported covering the molecular basis of hearing loss, genetic testing, or ethical or legal issues. The results of this survey demonstrate the need to incorporate more genetics content into audiology curricula and suggest strategies for assisting audiology faculty with this process.

Recent advances have made molecular genetic testing for several forms of deafness more widely available. Previous studies have examined the attitudes of the deaf towards genetic testing, including prenatal diagnosis. This study examines the attitudes of deaf college students towards universal newborn hearing screening, including molecular testing for specific forms of deafness, as well as the utilization of genetic test results for mate selection. We found that there may be differences in the attitudes of deaf individuals who associate closely with the deaf community (DC), and those who have equal involvement with both the deaf and hearing communities (EIC). The majority perceived newborn hearing screening for deafness to be helpful. However, more members of the EIC than the DC groups support newborn testing for genes for deafness. While there was reported interest in using genetic testing for partner selection, most participants reported they would not be interested in selecting a partner to have children with a specific hearing status. The results of this study point out important differences that genetic professionals should be aware of when counseling deaf individuals., (Copyright 2004 Wiley-Liss, Inc.)

Purpose: Profound hearing loss occurs with a frequency of 1 in 1000 live births, half of which is genetic in etiology. The past decade has witnessed rapid advances in determining the pathogenesis of both syndromic and nonsyndromic deafness. The most significant clinical finding to date has been the discovery that mutations of GJB2 at the DFNB1 locus are the major cause of profound prelingual deafness in many countries. 1 More recently, GJB2 mutations have been shown to cause deafness when present with a deletion of the GJB6 gene. We report on the prevalence of GJB2 and GJB6 mutations in a large North American Repository of DNA from deaf probands and document the profound effects of familial ethnicity and parental mating types on the frequency of these mutations in the population., Methods: Deaf probands were ascertained through the Annual Survey of Deaf and Hard of Hearing Children and Youth, conducted at the Research Institute of Gallaudet University. Educational, etiologic, and audiologic information was collected after obtaining informed consent. DNA studies were performed for the GJB2 and GJB6 loci by sequencing and PCR methods., Results: GJB2 mutations accounted for 22.2% of deafness in the overall sample but differed significantly among Asians, African-Americans and Hispanics and for probands from deaf by deaf and deaf by hearing matings, as well as probands from simplex and multiplex sibships of hearing parents. In our sample, the overall incidence of GJB2/GJB6 deafness was 2.57%., Conclusion: GJB2 mutations account for a large proportion of deafness in the US, with certain mutations having a high ethnic predilection. Heterozygotes at the GJB2 locus should be screened for the GJB6 deletion as a cause of deafness. Molecular testing for GJB2 and GJB6 should be offered to all patients with nonsyndromic hearing loss.

An educational slide set entitled "Early Childhood Hearing Loss: Clinical and Molecular Genetics" is offered by the American College of Medical Genetics (ACMG). The slide set is produced in Microsoft PowerPoint 2002. It is extensively illustrated and supported with teaching tools, explanations of each slide and figure, links to Internet resources, and a bibliography. The slide set is expected to be used as a resource for self-directed learning and in support of medical genetics teaching activities. The slide set is available through the ACMG (http://www.acmg.net) for $20, plus applicable tax and shipping. It is the first in a series of educational slide sets to be developed by the ACMG.

Chudley-McCullough syndrome is an autosomal recessive condition characterized by profound sensorineural deafness, hydrocephalus secondary to obstruction of the foramen of Monro, and other structural abnormalities of the brain. We describe a family including two brothers and a sister with this condition. Each has profound sensorineural deafness that was either congenital or rapidly progressive in infancy and asymmetric dilatation of the lateral ventricles secondary to obstruction of the foramen of Monro. They also have additional brain abnormalities, including arachnoid cyst, partial agenesis of the corpus callosum, and abnormalities in the migration of cerebellar cells. This report is the fourth description of this condition within four years, suggesting Chudley-McCullough may not be as rare as once assumed. We, therefore, recommend an audiological assessment for all children with hydrocephalus, especially those with obstruction of the foramen of Monro., (Copyright 2003 Wiley-Liss, Inc.)

Prestin, a membrane protein that is highly and almost exclusively expressed in the outer hair cells (OHCs) of the cochlea, is a motor protein which senses membrane potential and drives rapid length changes in OHCs. Surprisingly, prestin is a member of a gene family, solute carrier (SLC) family 26, that encodes anion transporters and related proteins. Of nine known human genes in this family, three (SLC26A2, SLC26A3 and SLC26A4) are associated with different human hereditary diseases. The restricted expression of prestin in OHCs, and its proposed function as a mechanical amplifier, make it a strong candidate gene for human deafness. Here we report the cloning and characterization of four splicing isoforms for the human prestin gene (SLC26A5a, b, c and d). SLC26A5a is the predominant form of prestin whereas the others showed limited distribution associated with certain developmental stages. Based on the functional importance of prestin we screened for possible mutations involving the prestin gene in a group of deaf probands. We have identified a 5'-UTR splice acceptor mutation (IVS2-2A>G) in exon 3 of the prestin gene, which is responsible for recessive non-syndromic deafness in two unrelated families. In addition, a high frequency of heterozygosity for the same mutation was observed in these subjects, suggesting the possibility of semi-dominant influence of the mutation in causing hearing loss. Finally, the observation of this mutation only in the Caucasian probands indicated an association with a specific ethnic background. This study thereby reveals an essential function of prestin in human auditory processing.

Mutations in four members of the connexin gene family have been shown to underlie distinct genetic forms of deafness, including GJB2 [connexin 26 (Cx26)], GJB3 (Cx31), GJB6 (Cx30) and GJB1 (Cx32). We have found that alterations in a fifth member of this family, GJA1 (Cx43), appear to cause a common form of deafness in African Americans. We identified two different GJA1 mutations in four of 26 African American probands. Three were homozygous for a Leu-->Phe substitution in the absolutely conserved codon 11, whereas the other was homozygous for a Val-->Ala transversion at the highly conserved codon 24. Neither mutation was detected in DNA from 100 control subjects without deafness. Cx43 is expressed in the cochlea, as is demonstrated by PCR amplification from human fetal cochlear cDNA and by RT-PCR of mouse cochlear tissues. Immunohistochemical staining of mouse cochlear preparations showed immunostaining for Cx43 in non-sensory epithelial cells and in fibrocytes of the spiral ligament and the spiral limbus. To our knowledge this is the first alpha connexin gene to be associated with non-syndromic deafness. Cx43 must also play a critical role in the physiology of hearing, presumably by participating in the recycling of potassium to the cochlear endolymph.

Waardenburg syndrome (WS) type 1 is an autosomal dominant disorder characterized by sensorineural hearing loss, pigmentary abnormalities of the eye, hair, and skin, and dystopia canthorum. The phenotype is variable and affected individuals may exhibit only one or a combination of several of the associated features. To assess the relationship between phenotype and gene defect, clinical and genotype data on 48 families (271 WS individuals) collected by members of the Waardenburg Consortium were pooled. Forty-two unique mutations in the PAX3 gene, previously identified in these families, were grouped in five mutation categories: amino acid (AA) substitution in the paired domain, AA substitution in the homeodomain, deletion of the Ser-Thr-Pro-rich region, deletion of the homeodomain and the Ser-Thr-Pro-rich region, and deletion of the entire gene. These mutation classes are based on the structure of the PAX3 gene and were chosen to group mutations predicted to have similar defects in the gene product. Association between mutation class and the presence of hearing loss, eye pigment abnormality, skin hypopigmentation, or white forelock was evaluated using generalized estimating equations, which allowed for incorporation of a correlation structure that accounts for potential similarity among members of the same family. Odds for the presence of eye pigment abnormality, white forelock, and skin hypopigmentation were 2, 8, and 5 times greater, respectively, for individuals with deletions of the homeodomain and the Pro-Ser-Thr-rich region compared to individuals with an AA substitution in the homeodomain. Odds ratios that differ significantly from 1.0 for these traits may indicate that the gene products resulting from different classes of mutations act differently in the expression of WS. Although a suggestive association was detected for hearing loss with an odds ratio of 2.6 for AA substitution in the paired domain compared with AA substitution in the homeodomain, this odds ratio did not differ significantly from 1.0.

Purpose: Aminoglycoside-induced deafness caused by mutations in the mitochondrial 12S ribosomal RNA gene has been described in a number of Asian patients. The purpose of the current study is to analyze ethnically diverse patients in the United States with hearing loss after aminoglycoside exposure for presence or absence of these mitochondrial DNA mutations, and establish the frequency and clinical presentation associated with them., Patients and Methods: Clinical histories, medical records, and blood samples were obtained from 41 unrelated American individuals with hearing loss after aminoglycoside exposure. DNA was extracted from the blood of these individuals, amplified by the polymerase chain reaction, and analyzed for mitochondrial ribosomal RNA gene mutations by allele-specific oligonucleotide hybridization, restriction fragment length polymorphism analysis, and sequencing., Results: The nucleotide 1555 A-->G mutation was identified in 7 of 41 individuals (17%). None of the other known mutations was found. The ethnic origin of the individuals with predisposing mutations included Caucasians, Hispanics, and Asians. Four of the 7 patients with the 1555 A-->G mutation had a family history of aminoglycoside-induced ototoxicity. Particularly unexpected was the late onset of hearing loss in 3 of these patients, years after the aminoglycoside exposure. The 12S ribosomal RNA gene was sequenced in these patients, and a second sequence change that could be responsible for the milder phenotype was detected in 1 of the 3 patients., Conclusion: These findings imply that a significant proportion of patients with aminoglycoside-induced ototoxicity harbor mutations in the 12S rRNA gene, which can be detected by DNA screening. Also, the majority of these hearing losses could have been easily prevented by the simple taking of a clinical history. In these individuals, a genetic susceptibility to the ototoxic effects of aminoglycosides can be diagnosed, and deafness can be prevented in maternal relatives by avoidance of these antibiotics.

We have identified 11 mutational changes in the PAX3 gene in patients with type 1 Waardenburg syndrome (WS1) including three in the paired domain, six within or immediately adjacent to the homeodomain and two previously described polymorphic variants in exons 2 and 6. The affected members of one family carried substitutions involving two base pairs separated by one unaltered codon. Two of the deleterious mutations were identical and three others were identical to previously reported mutations. A comparison of clinical findings in families carrying substitutions in the same codon failed to reveal conspicuous similarities. Although subtle mutation-specific effects may well exist, allelic heterogeneity clearly cannot account for within family variation. However, the striking concordance of a pair of monozygotic twins with Waardenburg syndrome (WS) and previous reports of similar pairs indicate that phenotypic variation in WS has a genetic basis. If the genetic effects are mediated by oligogenic epistasis, as studies in the mouse suggest, it may ultimately be possible to predict clinically relevant aspects of the Waardenburg phenotype.

We used segregation analysis to investigate the genetic basis of variation in dystopia canthorum, one of the key diagnostic features of Waardenburg syndrome type 1 (WS1). We sought to determine whether the W-index, a quantitative measure of this craniofacial feature, is influenced primarily either by allelic variation in the PAX3 disease gene or other major loci, by polygenic background effects, or by all of these potential sources of genetic variation. We studied both WS1-affected individuals and their WS1-unaffected relatives. After adjustment of the W-index for WS1 disease status, segregation analyses by the regression approach indicated major-locus control of this variation, although residual parent-offspring and sib-sib correlations are consistent with additional (possibly polygenic) effects. Separate analyses of WS1-affected and WS1-unaffected individuals suggest that epistatic interactions between disease alleles at the PAX3 WS1 locus and a second major locus influence variation in dystopia canthorum. Our approach should be applicable for assessing the genetic architecture of variation associated with other genetic diseases.

We performed linkage and locus heterogeneity analyses of Waardenburg syndrome (WS) types 1 and 2 using 9 DNA markers from 2q35-q37, including two highly polymorphic microsatellites very closely linked to the PAX3 candidate gene. None of 5 WS type 2 (WS2) families showed linkage to the PAX3 candidate region. We localized the marker D2S102 to less than 1 cM from PAX3 (lod = 33.7, theta = 0), but a complete absence of crossovers prevented determining whether it maps distal or proximal to PAX3. Study of 14 WS type 1 (WS1) families yielded a maximum lod score of 27.81 at PAX3, theta f = 0.010, theta = 0.007 assuming homogeneity. However, we found significant evidence of locus heterogeneity, with one family initially classified as WS1 unlinked to the PAX3 region. Reevaluation of the clinical features of this family revealed atypical morphology of inner canthi. This produced the appearance of dystopia canthorum and high W-index scores. While our one unlinked WS1 family exhibits atypical canthal morphology, our type 1 families with classic dystopia appear to be homogeneously linked to PAX3. These and other findings identify precautions that need to be addressed before using PAX3-linked markers for diagnostic purposes.

Expression of clinical findings of Waardenburg syndrome type 1 (WS1) and type 2 (WS2) is extremely variable. Using our collection of 26 WS1 and 8 WS2 families, we analyzed the occurrence, severity, and symmetry of clinical manifestations associated with WS. We found significant differences between WS1 and WS2 in deafness, and in pigmentary and craniofacial anomalies. Factor analysis was used to identify manifestations which covaried, resulting in 2 orthogonal factors. Since mean factor scores were found to differ when compared between WS1 and WS2, we suggest that these factors could be useful in distinguishing WS types. We found that the WS gene was transmitted from mothers more often than from fathers. We also extensively examined the W-Index, a continuous measure of dystopia canthorum. Our data suggest that use of the W-Index to discriminate between affected WS1 and WS2 individuals may be problematic since 1) ranges of W-Index scores of affected and unaffected individuals overlapped considerably within both WS1 and WS2, and 2) a considerable number of both affected and unaffected WS2 individuals exhibited W-index scores consistent with dystopia canthorum. Misclassification of families may have implications for risk assessment of deafness, since WS2 families have been reported to have greater incidence of deafness, as confirmed in our study.

Waardenburg syndrome (WS) is a dominantly inherited and clinically variable syndrome of deafness, pigmentary changes, and distinctive facial features. Clinically, WS type I (WS1) is differentiated from WS type II (WS2) by the high frequency of dystopia canthorum in the family. In some families, WS is caused by mutations in the PAX3 gene on chromosome 2q. We have typed microsatellite markers within and flanking PAX3 in 41 WS1 kindreds and 26 WS2 kindreds in order to estimate the proportion of families with probable mutations in PAX3 and to study the relationship between phenotypic and genotypic heterogeneity. Evaluation of heterogeneity in location scores obtained by multilocus analysis indicated that WS is linked to PAX3 in 60% of all WS families and in 100% of WS1 families. None of the WS2 families were linked. In those families in which equivocal lod scores (between -2 and +1) were found, PAX3 mutations have been identified in 5 of the 15 WS1 families but in none of the 4 WS2 families. Although preliminary studies do not suggest any association between the phenotype and the molecular pathology in 20 families with known PAX3 mutations and in four patients with chromosomal abnormalities in the vicinity of PAX3, the presence of dystopia in multiple family members is a reliable indicator for identifying families likely to have a defect in PAX3.

Previous population studies of hearing loss have been limited to children with moderate to profound impairment, and have reported that heritability accounts for at least 50% of congenital or early-onset cases. The present study was designed to assess genetic factors associated with late-onset hearing impairment in an adult population. A brief family history and audiologic questionnaire was sent to approximately 11,200 members of the consumer organization, Self Help for the Hard of Hearing, Inc., and 4,039 questionnaires were returned. All respondents reported having at least one previous audiologic exam. Reported data were verified against audiograms when available. Regardless of the reported causes, 49% of early-onset cases (< or = 20 years of age) had one or two parent(s) with some form of hearing loss compared with 62% in later-onset cases. As expected, mean age at onset was substantially younger for cases with positive family histories than cases with negative family histories. Results from nuclear segregation analysis showed that fully recessive and dominant models failed to explain the early- or late-onset hearing loss data. In this nationwide survey, the large proportion of cases with positive family histories clearly indicates the importance of genetic factors in adult-onset forms of hearing loss. Comparison with younger-onset cases will permit further delineation of differences in inheritance patterns. This study should identify more homogeneous groups of adult-onset families for further genetic study, and provide empiric information for use in genetic counselling.

Maternally transmitted non-syndromic deafness was described recently both in pedigrees with susceptibility to aminoglycoside ototoxicity and in a large Arab-Israeli pedigree. Because of the known action of aminoglycosides on bacterial ribosomes, we analysed the sequence of the mitochondrial rRNA genes of three unrelated patients with familial aminoglycoside-induced deafness. We also sequenced the complete mitochondrial genome of the Arab-Israeli pedigree. All four families shared a nucleotide 1555 A to G substitution in the 12S rRNA gene, a site implicated in aminoglycoside activity. Our study offers the first description of a mitochondrial rRNA mutation leading to disease, the first cases of non-syndromic deafness caused by a mitochondrial DNA mutation and the first molecular genetic study of antibiotic-induced ototoxicity.

Profound, early-onset deafness is present in 4-11 per 10,000 children, and is attributable to genetic causes in at least 50% of cases. Family history questionnaires were sent to 26,152 families of children with profound, early-onset deafness not known to be related to an environmental cause. The probands were ascertained through the 1988-89 Gallaudet University Annual Survey of Hearing Impaired Children and Youth. The analysis is based on the responses that were received from 8,756 families. Classical segregation analysis was used to analyze the family data, and to estimate the proportions of sporadic, recessive and dominant causes of deafness in the families. These data were consistent with 37.2% of the cases due to sporadic causes, and 62.8% due to genetic causes (47.1% recessive, and 15.7% dominant). An earlier study using the 1969-70 Annual Survey found 49.3% sporadic cases and 50.6% genetic, demonstrating that the proportion of sporadic cases of early-onset deafness has significantly decreased since 1970.

Genetic service providers have stressed the importance of genetic counseling that is nondirective and specific to the personal needs of consultants. Successful genetic counseling for deaf persons often requires special provisions for complex family histories, syndromic conditions, and diversity in communication methods and cultural orientation. The Gallaudet University Genetic Services Center (GSC) was established in 1984 to provide genetic education and counseling services to the deaf community. The GSC staff developed and implemented a standardized system of data collection (family and medical history), clinical evaluation by consultant clinical geneticists, and counseling in sign language. In addition to clinical services, an in-depth educational program for professionals and consumers was developed and carried out. During a 6-year period, over 220 educational presentations were made and 659 deaf persons were seen for genetic evaluation and counseling. Most of these persons were self-referred. Sign language was the preferred means of communication of more than 90% of these individuals. A genetic cause of deafness was diagnosed in over 50% of the deaf consultants and was confirmed by segregation analysis, which had results similar to those reported for other studies of students in schools for the deaf. Special materials and strategies were developed in order to provide genetic services that were sensitive to the cultural and linguistic differences of the deaf population. These included written and visual materials that contained culturally neutral terminology and training of all staff members in sign language and the culture of the deaf.

Genetic counseling is a process that emphasizes accurate diagnosis of hereditary conditions and communication of information to families. Genetic counseling involves systematic collection of family and medical history, a physical examination by a certified clinical geneticist, sharing of information with the family, and follow-up and support services. The issues that arise in genetic counseling can differ for every family and are often dependent on the degree of deafness present in the family, age of onset, and linguistic and cultural orientation. It is important for the genetic counselor to consider these factors in the provision of genetic services. With the increasing application of molecular genetics to the diagnosis and management of hereditary deafness and the increasing participation of families with deafness in research studies, the involvement of genetic counselors to provide information and education to consumers as well as medical professionals and researchers is becoming even more critical. The success of genetic counseling for the provision of information to families and the delineation of types of hereditary deafness through clinical and laboratory research is dependent on appropriate referrals by medical professionals, including otolaryngologists. A working relationship between otolaryngologists and clinical geneticists for the referral and evaluation of patients with hereditary deafness or deafness of "unknown" etiology is important.