Highly variable hearing loss due to POU4F3 (c.37del) is revealed by longitudinal, frequency specific analyses.

Genotype-phenotype correlations add value to the management of families with hereditary hearing loss (HL), where age-related typical audiograms (ARTAs) are generated from cross-sectional regression equations and used to predict the audiogram phenotype across the lifespan. A seven-generation kindred with autosomal dominant sensorineural HL (ADSNHL) was recruited and a novel pathogenic variant in POU4F3 (c.37del) was identified by combining linkage analysis with whole exome sequencing (WES). POU4F3 is noted for large intrafamilial variation including the age of onset of HL, audiogram configuration and presence of vestibular impairment. Sequential audiograms and longitudinal analyses reveal highly variable audiogram features among POU4F3 (c.37del) carriers, limiting the utility of ARTAs for clinical prognosis and management of HL. Furthermore, a comparison of ARTAs against three previously published families (1 Israeli Jewish, 2 Dutch) reveals significant interfamilial differences, with earlier onset and slower deterioration. This is the first published report of a North American family with ADSNHL due to POU4F3, the first report of the pathogenic c.37del variant, and the first study to conduct longitudinal analysis, extending the phenotypic spectrum of DFNA15.

A pathogenic deletion in Forkhead Box L1 (FOXL1) identifies the first otosclerosis (OTSC) gene.

Otosclerosis is a bone disorder of the otic capsule and common form of late-onset hearing impairment. Considered a complex disease, little is known about its pathogenesis. Over the past 20 years, ten autosomal dominant loci (OTSC1-10) have been mapped but no genes identified. Herein, we map a new OTSC locus to a 9.96 Mb region within the FOX gene cluster on 16q24.1 and identify a 15 bp coding deletion in Forkhead Box L1 co-segregating with otosclerosis in a Caucasian family. Pre-operative phenotype ranges from moderate to severe hearing loss to profound sensorineural loss requiring a cochlear implant. Mutant FOXL1 is both transcribed and translated and correctly locates to the cell nucleus. However, the deletion of 5 residues in the C-terminus of mutant FOXL1 causes a complete loss of transcriptional activity due to loss of secondary (alpha helix) structure. FOXL1 (rs764026385) was identified in a second unrelated case on a shared background. We conclude that FOXL1 (rs764026385) is pathogenic and causes autosomal dominant otosclerosis and propose a key inhibitory role for wildtype Foxl1 in bone remodelling in the otic capsule. New insights into the molecular pathology of otosclerosis from this study provide molecular targets for non-invasive therapeutic interventions.

A randomized controlled trial comparing right and left lateral decubitus starting position on outcomes in colonoscopy.

BACKGROUND: Patient positioning in colonoscopy has been proposed as a simple and inexpensive technique to increase luminal distention and improve navigation through the large bowel. We sought to determine if the right lateral (RL) starting position compared to the standard left lateral (LL) starting position could improve outcomes in colonoscopy. METHODS: We conducted a randomized controlled trial of 185 patients who were undergoing an elective colonoscopy. Patients were randomized to either a right lateral decubitus starting position or a left lateral decubitus starting position and the primary outcome measure was cecal intubation time. Secondary outcome measures included cecal intubation rate, patient discomfort, and sedation dosage. All colonoscopists who had successfully completed a colonoscopy skills improvement course were included in the trial. A sample size was calculated prior to the start of the study and outcomes were analyzed using univariate and multiple regression analyses. RESULTS: A total of 94 patients were randomized to RL starting position and 91 patients were randomized to LL starting position. No difference was found in time to cecal intubation comparing the RL starting position (542.6 s, SD 360.7 s) to LL starting position (497.85 s, SD 288.3 s) (p = 0.354). Variables associated with prolonged cecal intubation time included female gender, General Surgery specialty, less than 5 years of endoscopist experience, a high patient discomfort score, amount of water used, and number of position changes required to reach the cecum. There was no difference in any of the secondary outcome measures aside from the amount of midazolam used, with more midazolam used for patients starting in the right lateral decubitus position. CONCLUSION: This study failed to show an association between cecal intubation time and patient position comparing right and left lateral starting position.

Cardiac arrest in a mother and daughter and the identification of a novel RYR2 variant, predisposing to low penetrant catecholaminergic polymorphic ventricular tachycardia in a four-generation Canadian family.

BACKGROUND: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited arrhythmia syndrome characterized by adrenergically driven ventricular arrhythmia predominantly caused by pathogenic variants in the cardiac ryanodine receptor (RyR2). We describe a novel variant associated with cardiac arrest in a mother and daughter. METHODS: Initial sequencing of the RYR2 gene identified a novel variant (c.527G > T, p.R176L) in the index case (the mother), and her daughter. Structural analysis demonstrated the variant was located within the N-terminal domain of RyR2, likely leading to a gain-of-function effect facilitating enhanced calcium ion release. Four generation cascade genetic and clinical screening was carried out. RESULTS: Thirty-eight p.R176L variant carriers were identified of 94 family members with genetic testing, and 108 family members had clinical evaluations. Twelve carriers were symptomatic with previous syncope and 2 additional survivors of cardiac arrest were identified. Thirty-two had clinical features suggestive of CPVT. Of 52 noncarriers, 11 had experienced previous syncope with none exhibiting any clinical features of CPVT. A documented arrhythmic event rate of 2.89/1000 person-years across all carriers was calculated. CONCLUSION: The substantial variability in phenotype and the lower than previously reported penetrance is illustrative of the importance of exploring family variants beyond first-degree relatives.

"There are days I wish it wasn't there, and there's days I realize I'm lucky": A qualitative study of psychological sequelae to the implantable cardioverter defibrillator as a treatment for the prevention of sudden cardiac death in arrhythmogenic right ventricular cardiomyopathy.

OBJECTIVES: Arrhythmogenic right ventricular cardiomyopathy caused by a TMEM43 p.S358L mutation is a fully penetrant autosomal dominant cause of sudden cardiac death where prophylactic implantable cardioverter defibrillator therapy significantly reduces mortality by returning lethal cardiac rhythms to normal. This qualitative study assessed the psychological ramifications of the implantable cardioverter defibrillator on recipients, their spouses and their mutation negative siblings. DESIGN: Qualitative interview study. PARTICIPANTS: Twenty-one individuals (nine mutation positive, eight mutation negative and four spouses) from 15 families completed semi-structured interviews. RESULTS: No theoretical assumptions about the data were made: inductive sub-coding was accomplished with the constant comparison method and cohesive themes across all respondent interviews were determined. All interviewees had a family history of sudden cardiac death and appropriate implantable cardioverter defibrillator therapy in themselves or family members. Average length of time with an implantable cardioverter defibrillator was 10 years. Major themes included: (1) acceptance and gratitude, (2) grudging acceptance, (3) psychological effects (on emotional and psychological well-being; functioning of the broader family unit; and relationships), and (4) practical concerns (on clothes, travel, loss of driving licence and the effects of an implantable cardioverter defibrillator discharge). These affected all family members, regardless of mutation status. CONCLUSIONS: Despite the survival advantage of implantable cardioverter defibrillator therapy, the intervention carries psychological and practical burdens for family members from kindreds manifesting p.S358L TMEM43 ARVC that does not appear to dissipate with time. A move towards integrating psychology services with the cardiac genetics clinic for the extended family may provide benefit.

Perceived economic burden associated with an inherited cardiac condition: a qualitative inquiry with families affected by arrhythmogenic right ventricular cardiomyopathy.

PURPOSE: Significant gaps remain in the literature on the economic burden of genetic illness. We explored perceived economic burden associated with one inherited cardiac condition, arrhythmogenic right ventricular cardiomyopathy (ARVC). METHODS: Semistructured interviews were held with individuals from families affected by ARVC. Data on the perceived financial and economic impacts of ARVC were used to identify emerging categories and themes using the method of constant comparison. RESULTS: Data analysis revealed four themes that described participants' perceptions of the economic impact ARVC had on them and their families: (i) economic impact during childhood, (ii) impact on current and future employment, (iii) impact on current and future financial well-being, and (iv) no perceived economic impact. CONCLUSIONS: This study is the first to explore the economic burden of ARVC from the perspective of affected families. It revealed a number of perceived burdens, from employment and career choices to worry about insurance for self and children, decreased household spending, and the need for childhood employment. Findings highlight potential areas of discussion for genetic counseling sessions, as well as areas for future research.Genet Med 18 6, 584-592.

The TMEM43 Newfoundland mutation p.S358L causing ARVC-5 was imported from Europe and increases the stiffness of the cell nucleus.

AIMS: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a rare genetic condition caused predominantly by mutations within desmosomal genes. The mutation leading to ARVC-5 was recently identified on the island of Newfoundland and caused by the fully penetrant missense mutation p.S358L in TMEM43. Although TMEM43-p.S358L mutation carriers were also found in the USA, Germany, and Denmark, the genetic relationship between North American and European patients and the disease mechanism of this mutation remained to be clarified. METHODS AND RESULTS: We screened 22 unrelated ARVC patients without mutations in desmosomal genes and identified the TMEM43-p.S358L mutation in a German ARVC family. We excluded TMEM43-p.S358L in 22 unrelated patients with dilated cardiomyopathy. The German family shares a common haplotype with those from Newfoundland, USA, and Denmark, suggesting that the mutation originated from a common founder. Examination of 40 control chromosomes revealed an estimated age of 1300-1500 years for the mutation, which proves the European origin of the Newfoundland mutation. Skin fibroblasts from a female and two male mutation carriers were analysed in cell culture using atomic force microscopy and revealed that the cell nuclei exhibit an increased stiffness compared with TMEM43 wild-type controls. CONCLUSION: The German family is not affected by a de novo TMEM43 mutation. It is therefore expected that an unknown number of European families may be affected by the TMEM43-p.S358L founder mutation. Due to its deleterious clinical phenotype, this mutation should be checked in any case of ARVC-related genotyping. It appears that the increased stiffness of the cell nucleus might be related to the massive loss of cardiomyocytes, which is typically found in ventricles of ARVC hearts.

Identification of a novel in-frame deletion in KCNQ4 (DFNA2A) and evidence of multiple phenocopies of unknown origin in a family with ADSNHL.

Autosomal dominant sensorineural hearing loss (ADSNHL) is extremely genetically heterogeneous, making it difficult to molecularly diagnose. We identified a multiplex (n=28 affected) family from the genetic isolate of Newfoundland, Canada with variable SNHL and used a targeted sequencing approach based on population-specific alleles in WFS1, TMPRSS3 and PCDH15; recurrent mutations in GJB2 and GJB6; and frequently mutated exons of KCNQ4, COCH and TECTA. We identified a novel, in-frame deletion (c.806_808delCCT: p.S269del) in the voltage-gated potassium channel KCNQ4 (DFNA2), which in silico modeling predicts to disrupt multimerization of KCNQ4 subunits. Surprisingly, 10/23 deaf relatives are non-carriers of p.S269del. Further molecular characterization of the DFNA2 locus in deletion carriers ruled out the possibility of a pathogenic mutation other than p.S269del at the DFNA2A/B locus and linkage analysis showed significant linkage to DFNA2 (maximum LOD=3.3). Further support of genetic heterogeneity in family 2071 was revealed by comparisons of audio profiles between p.S269del carriers and non-carriers suggesting additional and as yet unknown etiologies. We discuss the serious implications that genetic heterogeneity, in this case observed within a single family, has on molecular diagnostics and genetic counseling.

Privacy protection and public goods: building a genetic database for health research in Newfoundland and Labrador.

OBJECTIVE: To provide a legal and ethical analysis of some of the implementation challenges faced by the Population Therapeutics Research Group (PTRG) at Memorial University (Canada), in using genealogical information offered by individuals for its genetics research database. MATERIALS AND METHODS: This paper describes the unique historical and genetic characteristics of the Newfoundland and Labrador founder population, which gave rise to the opportunity for PTRG to build the Newfoundland Genealogy Database containing digitized records of all pre-confederation (1949) census records of the Newfoundland founder population. In addition to building the database, PTRG has developed the Heritability Analytics Infrastructure, a data management structure that stores genotype, phenotype, and pedigree information in a single database, and custom linkage software (KINNECT) to perform pedigree linkages on the genealogy database. DISCUSSION: A newly adopted legal regimen in Newfoundland and Labrador is discussed. It incorporates health privacy legislation with a unique research ethics statute governing the composition and activities of research ethics boards and, for the first time in Canada, elevating the status of national research ethics guidelines into law. The discussion looks at this integration of legal and ethical principles which provides a flexible and seamless framework for balancing the privacy rights and welfare interests of individuals, families, and larger societies in the creation and use of research data infrastructures as public goods. CONCLUSION: The complementary legal and ethical frameworks that now coexist in Newfoundland and Labrador provide the legislative authority, ethical legitimacy, and practical flexibility needed to find a workable balance between privacy interests and public goods. Such an approach may also be instructive for other jurisdictions as they seek to construct and use biobanks and related research platforms for genetic research.

Recurrent missense mutations in TMEM43 (ARVD5) due to founder effects cause arrhythmogenic cardiomyopathies in the UK and Canada.

AIMS: Autosomal dominant arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) (in the group of arrhythmogenic cardiomyopathies) is a common cause of sudden cardiac death in young adults. It is both clinically and genetically heterogeneous, with 12 loci (ARVC/D1-12) and eight genes identified, the majority of which encode structural proteins of cardiac desmosomes. The most recent gene identified, TMEM43, causes disease due to a missense mutation in a non-desmosomal gene (p.S358L) in 15 extended families from Newfoundland, Canada. To determine whether mutations in TMEM43 cause ARVC/D and arrhythmogenic cardiomyopathy in other populations, we fully re-sequenced TMEM43 on 143 ARVC/D probands (families) from the UK and 55 probands (from 55 families) from Newfoundland. METHODS AND RESULTS: Bidirectional sequencing of TMEM43 including intron-exon boundaries revealed 33 variants, the majority located in non-coding regions of TMEM43. For the purpose of validation, families of probands with rare, potentially deleterious coding variants were subjected to clinical and molecular follow-up. Three missense variants of uncertain significance (p.R28W, p.E142K, p.R312W) were located in highly conserved regions of the TMEM43 protein. One variant (p.R312W) also co-segregated with relatives showing clinical signs of disease. Genotyping and expansion of the disease-associated haplotype in subjects with the p.R312W variant from Newfoundland, Canada, and the UK suggest common ancestry. CONCLUSION: Although the p.R312W variant was found in controls (3/378), identification of an ancestral disease p R312W haplotype suggests that the p.R312W variant is a pathogenic founder mutation.

Duty to warn and genetic disease.

In this clinical column, we discuss the ambiguous distinction between genetic research and clinical genetics, particularly for Mendelian diseases with high recurrence risk, high morbidity and/or mortality and the possible amelioration of such diseases by screening or treatment. We use arrhythmogenic right ventricular cardiomyopathy as an example of a lethal Mendelian disorder, which prompted the discussion contained in this column. Working with such diseases may mean that genetic researchers have some responsibility for both immediate research subjects and their extended families, as they obtain molecular genetic information. For some diseases, therefore, a willingness to accept genetic research results should be an inclusion criterion, and it may be considered unethical for research ethics boards to approve genetic studies unless measures to ensure clinical follow-up have been established. We recommend managing the tensions between genetic research and clinical practice by using disease-based genetic registers, organized within a clinical genetic service.

Translation of research discoveries to clinical care in arrhythmogenic right ventricular cardiomyopathy in Newfoundland and Labrador: lessons for health policy in genetic disease.

Arrhythmogenic right ventricular cardiomyopathy, a lethal autosomal dominant cause of sudden cardiac death in young people, is prevalent in Newfoundland and Labrador (genetic subtype ARVD5). In the absence of implantable cardioverter defibrillator treatment, death rates are extremely high. Research into arrhythmogenic right ventricular cardiomyopathy (ARVD5) began in the 1980s and the causative gene and mutation were discovered in 2008. The decades of research highlighted major issues associated with the ethical management of genetic information and the translation of research findings to clinical care. We describe these issues and the strategies used in managing them. Effective knowledge transfer of the research information has resulted in systematic clinical and genetic screening coupled with genetic counseling and treatment for at-risk family members. Improved survival for patients has been one clear result of this strategy. Optimal care of families where individuals are at-high risk of inheriting a disease with high morbidity and mortality requires the full integration of both genetic research and clinical genetics programs. Although yet to be fully effected in our setting, our discussion highlights both the ethical necessity as well as some practical barriers in realizing this outcome.

Variable neurologic phenotype in a GEFS+ family with a novel mutation in SCN1A.

PURPOSE: To describe the spectrum of clinical disease in a mutliplex family with an autosomal dominant form of generalized epilepsy with febrile seizures plus (GEFS+) and determine its genetic etiology. METHODS: Medical and family history was obtained on 11 clinically affected individuals and their relatives across three generations through medical chart review and home visits. A candidate gene approach including haplotype analysis and direct sequencing was used. RESULTS: An epilepsy-associated haplotype was identified on 2q24. Direct sequencing of the entire SCN1A gene identified seven sequence variants. However, only one of these, c.1162 T>C, was not found in population controls. This transition in exon 8 of SCN1A predicts a substitution (Y388H) of a highly conserved tyrosine residue in the loop between transmembrane segments S5 and S6 of the sodium channel protein (Na(v)1.1). Clinical features in mutation carriers of this novel missense mutation were highly variable, ranging from febrile seizures to severe refractory epilepsy. CONCLUSION: A novel missense mutation in the pore-forming region of the sodium channel gene SCN1A causes GEFS+ with a variable phenotype that includes mood and anxiety disorders, as well as ataxia, expanding the GEFS+ spectrum to include neuropsychiatric disease.

Is gene discovery research or diagnosis?

The criteria that distinguish human genetic research from clinical molecular diagnosis are frequently practical rather than theoretical. They are driven by the availability and costs of the relevant technologies and the systemic level of scientific fluency in interpreting laboratory results. The guiding principle in the practice of medicine is the primacy of patient care. In the service of this overarching goal the defining characteristic of clinical diagnosis is the definition of the disease entity, even when no immediate treatment is possible. For heritable disorders caused by single-gene defects, identifying the putative causal variant is the goal of molecular diagnostics. Current technologies, costs, and standards of institutional infrastructure have not typically permitted novel gene discovery to be performed within the realm of the clinical laboratory. Discovery is usually funded by self-defined research organizations and carried out by self-defined research personnel with the primary intent of publishing findings in research journals. However, exponential improvements in technological capabilities and the concurrent decline in associated costs seem poised to recast this landscape, bringing to clinical medicine some activities now considered research. Even whole genome resequencing of individual patient DNA is within clinical reach in the foreseeable future.

Arrhythmogenic right ventricular cardiomyopathy type 5 is a fully penetrant, lethal arrhythmic disorder caused by a missense mutation in the TMEM43 gene.

Autosomal-dominant arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) causes sudden cardiac death and is characterized by clinical and genetic heterogeneity. Fifteen unrelated ARVC families with a disease-associated haplotype on chromosome 3p (ARVD5) were ascertained from a genetically isolated population. Identification of key recombination events reduced the disease region to a 2.36 Mb interval containing 20 annotated genes. Bidirectional resequencing showed one rare variant in transmembrane protein 43 (TMEM43 1073C-->T, S358L), was carried on all recombinant ARVD5 ancestral haplotypes from affected subjects and not found in population controls. The mutation occurs in a highly conserved transmembrane domain of TMEM43 and is predicted to be deleterious. Clinical outcomes in 257 affected and 151 unaffected subjects were compared, and penetrance was determined. We concluded that ARVC at locus ARVD5 is a lethal, fully penetrant, sex-influenced morbid disorder. Median life expectancy was 41 years in affected males compared to 71 years in affected females (relative risk 6.8, 95% CI 1.3-10.9). Heart failure was a late manifestation in survivors. Although little is known about the function of the TMEM43 gene, it contains a response element for PPAR gamma (an adipogenic transcription factor), which may explain the fibrofatty replacement of the myocardium, a characteristic pathological finding in ARVC.

The impact of implantable cardioverter-defibrillator therapy on survival in autosomal-dominant arrhythmogenic right ventricular cardiomyopathy (ARVD5).

OBJECTIVES: We sought to determine the impact of implantable cardioverter-defibrillator (ICD) therapy in patients with familial arrhythmogenic right ventricular cardiomyopathy (ARVC). BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy is a cause of sudden cardiac death, which may be prevented by ICD. METHODS: We studied 11 families in which a 3p25 deoxyribonucleic acid (DNA) haplotype at locus ARVD5 segregated with disease and compared mortality in subjects who received an ICD with that in control subjects who were matched for age, gender, ARVC status, and family. Subjects (n = 367) at 50% a priori risk of inheriting ARVC were classified as high risk (HR) (n = 197), low risk (n = 92), or unknown (n = 78) on the basis of clinical events, DNA haplotyping, and/or pedigree position. Forty-eight HR subjects (30 males, [median age 32 years] and 18 females [median age 41 years]) were followed after ICD (secondary to ventricular tachycardia [VT] in 27%). Survival was compared with 58 HR control subjects who were alive at the same age to-the-day at which the ICD subject received the device. RESULTS: In the HR group, 50% of males were dead by 39 years and females by 71 years: relative risk of death was 5.1 (95% confidence interval 3 to 8.5) for males. The five-year mortality rate after ICD in males was zero compared with 28% in control subjects (p = 0.009). Within five years, the ICD fired for VT in 70% and for VT >240 beats/min in 30%, with no difference in discharge rate when analyzed by ICD indication. CONCLUSIONS: The unknown mutation at the ARVD5 locus causing ARVC results in high mortality. Risk stratification using genetic haplotyping and ICD therapy produced improved survival for males.