Genetic Architecture of Dilated Cardiomyopathy in Individuals of African and European Ancestry.

Importance: Black patients with dilated cardiomyopathy (DCM) have increased familial risk and worse outcomes than White patients, but most DCM genetic data are from White patients. Objective: To compare the rare variant genetic architecture of DCM by genomic ancestry within a diverse population of patients with DCM. Design: Cross-sectional study enrolling patients with DCM who self-identified as non-Hispanic Black, Hispanic, or non-Hispanic White from June 7, 2016, to March 15, 2020, at 25 US advanced heart failure programs. Variants in 36 DCM genes were adjudicated as pathogenic, likely pathogenic, or of uncertain significance. Exposure: Presence of DCM. Main Outcomes and Measures: Variants in DCM genes classified as pathogenic/likely pathogenic/uncertain significance and clinically actionable (pathogenic/likely pathogenic). Results: A total of 505, 667, and 26 patients with DCM of predominantly African, European, or Native American genomic ancestry, respectively, were included. Compared with patients of European ancestry, a lower percentage of patients of African ancestry had clinically actionable variants (8.2% [95% CI, 5.2%-11.1%] vs 25.5% [95% CI, 21.3%-29.6%]), reflecting the lower odds of a clinically actionable variant for those with any pathogenic variant/likely pathogenic variant/variant of uncertain significance (odds ratio, 0.25 [95% CI, 0.17-0.37]). On average, patients of African ancestry had fewer clinically actionable variants in TTN (difference, -0.09 [95% CI, -0.14 to -0.05]) and other genes with predicted loss of function as a disease-causing mechanism (difference, -0.06 [95% CI, -0.11 to -0.02]). However, the number of pathogenic variants/likely pathogenic variants/variants of uncertain significance was more comparable between ancestry groups (difference, -0.07 [95% CI, -0.22 to 0.09]) due to a larger number of non-TTN non-predicted loss of function variants of uncertain significance, mostly missense, in patients of African ancestry (difference, 0.15 [95% CI, 0.00-0.30]). Published clinical case-based evidence supporting pathogenicity was less available for variants found only in patients of African ancestry (P < .001). Conclusion and Relevance: Patients of African ancestry with DCM were less likely to have clinically actionable variants in DCM genes than those of European ancestry due to differences in genetic architecture and a lack of representation of African ancestry in clinical data sets.

Rare Variant Genetics and Dilated Cardiomyopathy Severity: The DCM Precision Medicine Study.

BACKGROUND: Dilated cardiomyopathy (DCM) can lead to advanced disease, defined herein as necessitating a durable left ventricular assist device or a heart transplant (LVAD/HT). DCM is known to have a genetic basis, but the association of rare variant genetics with advanced DCM has not been studied. METHODS: We analyzed clinical and genetic sequence data from patients enrolled between 2016 and 2021 in the US multisite DCM Precision Medicine Study, which was a geographically diverse, multiracial, multiethnic cohort. Clinical evaluation included standardized patient interview and medical record query forms. DCM severity was classified into 3 groups: patients with advanced disease with LVAD/HT; patients with an implantable cardioverter defibrillator (ICD) only; or patients with no ICD or LVAD/HT. Rare variants in 36 DCM genes were classified as pathogenic or likely pathogenic or variants of uncertain significance. Confounding factors we considered included demographic characteristics, lifestyle factors, access to care, DCM duration, and comorbidities. Crude and adjusted associations between DCM severity and rare variant genetic findings were assessed using multinomial models with generalized logit link. RESULTS: Patients' mean (SD) age was 51.9 (13.6) years; 42% were of African ancestry, 56% were of European ancestry, and 44% were female. Of 1198 patients, 347 had LVAD/HT, 511 had an ICD, and 340 had no LVAD/HT or ICD. The percentage of patients with pathogenic or likely pathogenic variants was 26.2%, 15.9%, and 15.0% for those with LVAD/HT, ICD only, or neither, respectively. After controlling for sociodemographic characteristics and comorbidities, patients with DCM with LVAD/HT were more likely than those without LVAD/HT or ICD to have DCM-related pathogenic or likely pathogenic rare variants (odds ratio, 2.3 [95% CI, 1.5-3.6]). The association did not differ by ancestry. Rare variant genetic findings were similar between patients with DCM with an ICD and those without LVAD/HT or ICD. CONCLUSIONS: Advanced DCM was associated with higher odds of rare variants in DCM genes adjudicated as pathogenic or likely pathogenic, compared with individuals with less severe DCM. This finding may help assess the risk of outcomes in management of patients with DCM and their at-risk family members. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT03037632.

Differences in Cardiac Mechanics among Genetically At-Risk First-Degree Relatives: The DCM Precision Medicine Study.

Aims: Among genetically at-risk first-degree relatives (FDRs) of probands with dilated cardiomyopathy (DCM), the ability to detect changes in left ventricular (LV) mechanics with normal LV size and ejection fraction (LVEF) remains incompletely explored. We sought to define a pre-DCM phenotype among at-risk FDRs, including those with variants of uncertain significance (VUSs), using echocardiographic measures of cardiac mechanics. Methods and Results: LV structure and function, including speckle-tracking analysis for LV global longitudinal strain (GLS), were evaluated in 124 FDRs (65% female; median age 44.9 [IQR: 30.6-60.3] years) of 66 DCM probands of European ancestry sequenced for rare variants in 35 DCM genes. FDRs had normal LV size and LVEF. Negative FDRs of probands with pathogenic or likely pathogenic (P/LP) variants (n=28) were a reference group to which negative FDRs of probands without P/LP variants (n=30), FDRs with only VUSs (n=27), and FDRs with P/LP variants (n=39) were compared. In an analysis accounting for age-dependent penetrance, FDRs below the median age showed minimal differences in LV GLS across groups while those above it with P/LP variants or VUSs had lower absolute values than the reference group (-3.9 [95% CI: -5.7, -2.1] or -3.1 [-4.8, -1.4] %-units) and negative FDRs of probands without P/LP variants (-2.6 [-4.0, -1.2] or -1.8 [-3.1, -0.6]). Conclusions: Older FDRs with normal LV size and LVEF who harbored P/LP variants or VUSs had lower absolute LV GLS values, indicating that some DCM-related VUSs are clinically relevant. LV GLS may have utility for defining a pre-DCM phenotype. Clinical Trial Registration: clinicaltrials.gov, NCT03037632.

Screening for Dilated Cardiomyopathy in At-Risk First-Degree Relatives.

BACKGROUND: Cardiovascular screening is recommended for first-degree relatives (FDRs) of patients with dilated cardiomyopathy (DCM), but the yield of FDR screening is uncertain for DCM patients without known familial DCM, for non-White FDRs, or for DCM partial phenotypes of left ventricular enlargement (LVE) or left ventricular systolic dysfunction (LVSD). OBJECTIVES: This study examined the yield of clinical screening among reportedly unaffected FDRs of DCM patients. METHODS: Adult FDRs of DCM patients at 25 sites completed screening echocardiograms and ECGs. Mixed models accounting for site heterogeneity and intrafamilial correlation were used to compare screen-based percentages of DCM, LVSD, or LVE by FDR demographics, cardiovascular risk factors, and proband genetics results. RESULTS: A total of 1,365 FDRs were included, with a mean age of 44.8 ± 16.9 years, 27.5% non-Hispanic Black, 9.8% Hispanic, and 61.7% women. Among screened FDRs, 14.1% had new diagnoses of DCM (2.1%), LVSD (3.6%), or LVE (8.4%). The percentage of FDRs with new diagnoses was higher for those aged 45 to 64 years than 18 to 44 years. The age-adjusted percentage of any finding was higher among FDRs with hypertension and obesity but did not differ statistically by race and ethnicity (16.2% for Hispanic, 15.2% for non-Hispanic Black, and 13.1% for non-Hispanic White) or sex (14.6% for women and 12.8% for men). FDRs whose probands carried clinically reportable variants were more likely to be identified with DCM. CONCLUSIONS: Cardiovascular screening identified new DCM-related findings among 1 in 7 reportedly unaffected FDRs regardless of race and ethnicity, underscoring the value of clinical screening in all FDRs.

Effectiveness of the Family Heart Talk Communication Tool in Improving Family Member Screening for Dilated Cardiomyopathy: Results of a Randomized Trial.

BACKGROUND: Managing disease risk among first-degree relatives of probands diagnosed with a heritable disease is central to precision medicine. A critical component is often clinical screening, which is particularly important for conditions like dilated cardiomyopathy (DCM) that remain asymptomatic until severe disease develops. Nonetheless, probands are frequently ill-equipped to disseminate genetic risk information that motivates at-risk relatives to complete recommended clinical screening. An easily implemented remedy for this key issue has been elusive. METHODS: The DCM Precision Medicine Study developed Family Heart Talk, a booklet designed to help probands with DCM communicate genetic risk and the need for cardiovascular screening to their relatives. The effectiveness of the Family Heart Talk booklet in increasing cardiovascular clinical screening uptake among first-degree relatives was assessed in a multicenter, open-label, cluster-randomized, controlled trial. The primary outcome measured in eligible first-degree relatives was completion of screening initiated within 12 months after proband enrollment. Because probands randomized to the intervention received the booklet at the enrollment visit, eligible first-degree relatives were limited to those who were alive the day after proband enrollment and not enrolled on the same day as the proband. RESULTS: Between June 2016 and March 2020, 1241 probands were randomized (1:1) to receive Family Heart Talk (n=621) or not (n=620) within strata defined by site and self-identified race/ethnicity (non-Hispanic Black, non-Hispanic White, or Hispanic). Final analyses included 550 families (n=2230 eligible first-degree relatives) in the Family Heart Talk arm and 561 (n=2416) in the control arm. A higher percentage of eligible first-degree relatives completed screening in the Family Heart Talk arm (19.5% versus 16.0%), and the odds of screening completion among these first-degree relatives were higher in the Family Heart Talk arm after adjustment for proband randomization stratum, sex, and age quartile (odds ratio, 1.30 [1-sided 95% CI, 1.08-∞]). A prespecified subgroup analysis did not find evidence of heterogeneity in the adjusted intervention odds ratio across race/ethnicity strata (P=0.90). CONCLUSIONS: Family Heart Talk, a booklet that can be provided to patients with DCM by clinicians with minimal additional time investment, was effective in increasing cardiovascular clinical screening among first-degree relatives of these patients. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT03037632.

Knowledge of Genome Sequencing and Trust in Medical Researchers Among Patients of Different Racial and Ethnic Groups With Idiopathic Dilated Cardiomyopathy.

Importance: Cardiovascular disease contributes outsized mortality in patients from underrepresented racial and ethnic groups. Understanding levels of trust in medical researchers and knowledge of genome sequencing may help identify barriers to research participation and develop strategies to educate patients about the role of genetics in cardiovascular disease. Objective: To assess racial and ethnic differences in trust in medical researchers and genome-sequencing knowledge among patients with idiopathic dilated cardiomyopathy and determine the association between trust in medical researchers and genome-sequencing knowledge. Design, Setting, and Participants: This cross-sectional study conducted by a consortium of 25 US heart failure programs included patients with idiopathic dilated cardiomyopathy defined as left ventricular systolic dysfunction and left ventricular enlargement after excluding usual clinical causes. Enrollment occurred from June 7, 2016, to March 15, 2020. Main Outcomes and Measures: Percent distributions, means, and associations of genome-sequencing knowledge scores and research trust scores for Hispanic, non-Hispanic Black (hereafter referred to as Black), and non-Hispanic White participants (hereafter referred to as White). Results: Among 1121 participants, mean (SD) age was 51.6 (13.6) years with 41.4% Black, 8.5% Hispanic, and 43.4% female. After accounting for site effects, the level of genome-sequencing knowledge was lower in Hispanic and Black participants compared with White participants (mean score difference, -2.6; 95% CI, -3.9 to -1.2 and mean score difference, -2.9; 95% CI, -3.6 to -2.2, respectively). The level of trust in researchers was lowest in Black participants (mean score, 27.7), followed by Hispanic participants (mean score, 29.4) and White participants (mean score, 33.9). Racial and ethnic differences remained after adjusting for education, age at enrollment, duration of dilated cardiomyopathy, and health status. A higher level of trust was associated with a higher level of genome-sequencing knowledge within different racial and ethnic groups. Conclusions and Relevance: In this cross-sectional study, large racial and ethnic differences in levels of genome-sequencing knowledge and trust in medical researchers were observed among patients with dilated cardiomyopathy. Findings from this study can inform future studies that aim to enhance the uptake of genomic knowledge and level of trust in medical researchers.

Communal Coping as a Strategy to Enhance Family Engagement in Dilated Cardiomyopathy.

BACKGROUND: Assuring that relatives are informed about a genetic diagnosis and have appropriate medical follow-up can be challenging. We hypothesize that communal coping (CC)-an approach in which a group views a stressor (such as a new genetic diagnosis) as our problem, versus my or your problem, and takes joint action to address it-can help families to address this challenge. A better understanding of CC could also inform counseling interventions to promote CC and family follow-up. METHODS: In the Dilated Cardiomyopathy (DCM) PM study (Precision Medicine), living first-degree relatives of DCM probands were invited to undergo clinical screening; 31% of these did so. This research program offers the opportunity to determine the frequency of CC in DCM families, assess whether CC attitudes and actions occurred more commonly among families in which family members participated, and conduct prospective follow-up to evaluate family coping and counseling needs over time. RESULTS: The proposed studies will provide evidence about the frequency of CC attitudes and actions among DCM families, assess the association of CC with increased family follow-up, and identify counseling needs related to family follow-up. CONCLUSIONS: The DCM PM study offers an opportunity to test the hypothesis that CC contributes to increased family follow-up and generate evidence to inform counseling interventions to encourage such follow-up.

TTR variants in patients with dilated cardiomyopathy: An investigation of the DCM Precision Medicine Study.

PURPOSE: The cardiac phenotype of hereditary transthyretin amyloidosis (hTTR) usually presents as a restrictive or hypertrophic cardiomyopathy, and, although rarely observed as dilated cardiomyopathy (DCM), TTR is routinely included in DCM genetic testing panels. However, the prevalence and phenotypes of TTR variants in patients with DCM have not been reported. METHODS: Exome sequences of 729 probands with idiopathic DCM were analyzed for TTR and 35 DCM genes. RESULTS: Rare TTR variants were identified in 2 (0.5%; 95% CI = 0.1%-1.8%) of 404 non-Hispanic White DCM probands; neither of them had features of hTTR. In 1 proband, a TTR His110Asn variant and a variant of uncertain significance in DSP were identified, and in the other proband, a TTR Val50Met variant known to cause hTTR and a likely pathogenic variant in FLNC were identified. The TTR Val142Ile variant was identified in 8 (3.0%) non-Hispanic Black probands, comparable with African/African American Genome Aggregation Database controls (OR = 1.01; 95% CI = 0.46-1.99). CONCLUSION: Among the 729 DCM probands, 2 had rare TTR variants identified without the features of hTTR, and both had other plausible genetic causes of DCM. Moreover, the frequency of TTR Val142Ile was comparable to a control sample. These findings suggest that hTTR variants may have a limited role in patients with DCM without TTR-specific findings.

Prevalence and Cumulative Risk of Familial Idiopathic Dilated Cardiomyopathy.

Importance: Idiopathic dilated cardiomyopathy (DCM) aggregates in families, and early detection in at-risk family members can provide opportunity to initiate treatment prior to late-phase disease. Most studies have included only White patients, yet Black patients with DCM have higher risk of heart failure-related hospitalization and death. Objective: To estimate the prevalence of familial DCM among DCM probands and the age-specific cumulative risk of DCM in first-degree relatives across race and ethnicity groups. Design, Setting, and Participants: A family-based, cross-sectional study conducted by a multisite consortium of 25 US heart failure programs. Participants included patients with DCM (probands), defined as left ventricular systolic dysfunction and left ventricular enlargement after excluding usual clinical causes, and their first-degree relatives. Enrollment commenced June 7, 2016; proband and family member enrollment concluded March 15, 2020, and April 1, 2021, respectively. Exposures: The presence of DCM in a proband. Main Outcomes and Measures: Familial DCM defined by DCM in at least 1 first-degree relative; expanded familial DCM defined by the presence of DCM or either left ventricular enlargement or left ventricular systolic dysfunction without known cause in at least 1 first-degree relative. Results: The study enrolled 1220 probands (median age, 52.8 years [IQR, 42.4-61.8]; 43.8% female; 43.1% Black and 8.3% Hispanic) and screened 1693 first-degree relatives for DCM. A median of 28% (IQR, 0%-60%) of living first-degree relatives were screened per family. The crude prevalence of familial DCM among probands was 11.6% overall. The model-based estimate of the prevalence of familial DCM among probands at a typical US advanced heart failure program if all living first-degree relatives were screened was 29.7% (95% CI, 23.5% to 36.0%) overall. The estimated prevalence of familial DCM was higher in Black probands than in White probands (difference, 11.3% [95% CI, 1.9% to 20.8%]) but did not differ significantly between Hispanic probands and non-Hispanic probands (difference, -1.4% [95% CI, -15.9% to 13.1%]). The estimated prevalence of expanded familial DCM was 56.9% (95% CI, 50.8% to 63.0%) overall. Based on age-specific disease status at enrollment, estimated cumulative risks in first-degree relatives at a typical US advanced heart failure program reached 19% (95% CI, 13% to 24%) by age 80 years for DCM and 33% (95% CI, 27% to 40%) for expanded DCM inclusive of partial phenotypes. The DCM hazard was higher in first-degree relatives of non-Hispanic Black probands than non-Hispanic White probands (hazard ratio, 1.89 [95% CI, 1.26 to 2.83]). Conclusions and Relevance: In a US cross-sectional study, there was substantial estimated prevalence of familial DCM among probands and modeled cumulative risk of DCM among their first-degree relatives. Trial Registration: ClinicalTrials.gov Identifier: NCT03037632.

The Complex and Diverse Genetic Architecture of Dilated Cardiomyopathy.

Our insight into the diverse and complex nature of dilated cardiomyopathy (DCM) genetic architecture continues to evolve rapidly. The foundations of DCM genetics rest on marked locus and allelic heterogeneity. While DCM exhibits a Mendelian, monogenic architecture in some families, preliminary data from our studies and others suggests that at least 20% to 30% of DCM may have an oligogenic basis, meaning that multiple rare variants from different, unlinked loci, determine the DCM phenotype. It is also likely that low-frequency and common genetic variation contribute to DCM complexity, but neither has been examined within a rare variant context. Other types of genetic variation are also likely relevant for DCM, along with gene-by-environment interaction, now established for alcohol- and chemotherapy-related DCM. Collectively, this suggests that the genetic architecture of DCM is broader in scope and more complex than previously understood. All of this elevates the impact of DCM genetics research, as greater insight into the causes of DCM can lead to interventions to mitigate or even prevent it and thus avoid the morbid and mortal scourge of human heart failure.

Attitudes of Dilated Cardiomyopathy Patients and Investigators Toward Genomic Study Enrollment, Consent Process, and Return of Genetic Results.

Precision medicine genetics study design requires large, diverse cohorts and thoughtful use of electronic technologies. Involving patients in research design may increase enrollment and engagement, thereby enabling a means to relevant patient outcomes in clinical practice. Few data, however, illustrate attitudes of patients with dilated cardiomyopathy (DCM) and their family members toward genetic study design. This study assessed attitudes of 16 enrolled patients and their family members (P/FM), and 18 investigators or researchers (I/R) of the ongoing DCM Precision Medicine Study during a conjoint patient and investigator meeting using structured, self-administered surveys examining direct-to-participant enrollment and web-based consent, return of genetic results, and other aspects of genetic study design. Survey respondents were half women and largely identified as white. Web-based consent was supported by 93% of P/FM and 88% of I/R. Most respondents believed that return of genetic results would motivate study enrollment, but also indicated a desire to opt out. Ideal study design preferences included a 1-hour visit per year, along with the ability to complete study aspects by telephone or web and possibility of prophylactic medication. This study supports partnership of patients and clinical researchers to inform research priorities and study design to attain the promise of precision medicine for DCM.

SOS1 Gain-of-Function Variants in Dilated Cardiomyopathy.

BACKGROUND: Dilated cardiomyopathy (DCM) is a genetically heterogeneous cardiac disease characterized by progressive ventricular enlargement and reduced systolic function. Here, we report genetic and functional analyses implicating the rat sarcoma signaling protein, SOS1 (Son of sevenless homolog 1), in DCM pathogenesis. METHODS: Exome sequencing was performed on 412 probands and family members from our DCM cohort, identifying several SOS1 variants with potential disease involvement. As several lines of evidence have implicated dysregulated rat sarcoma signaling in the pathogenesis of DCM, we assessed functional impact of each variant on the activation of ERK (extracellular signal-regulated kinase), AKT (protein kinase B), and JNK (c-Jun N-terminal kinase) pathways. Relative expression levels were determined by Western blot in HEK293T cells transfected with variant or wild-type human SOS1 expression constructs. RESULTS: A rare SOS1 variant [c.571G>A, p.(Glu191Lys)] was found to segregate alongside an A-band TTN truncating variant in a pedigree with aggressive, early-onset DCM. Reduced disease severity in the absence of the SOS1 variant suggested its potential involvement as a genetic risk factor for DCM in this family. Exome sequencing identified 5 additional SOS1 variants with potential disease involvement in 4 other families [c.1820T>C, p.(Ile607Thr); c.2156G>C, p.(Gly719Ala); c.2230A>G, p.(Arg744Gly); c.2728G>C, p.(Asp910His); c.3601C>T, p.(Arg1201Trp)]. Impacted amino acids occupied a number of functional domains relevant to SOS1 activity, including the N-terminal histone fold, as well as the C-terminal REM (rat sarcoma exchange motif), CDC25 (cell division cycle 25), and PR (proline-rich) tail domains. Increased phosphorylated ERK expression relative to wild-type levels was seen for all 6 SOS1 variants, paralleling known disease-relevant SOS1 signaling profiles. CONCLUSIONS: These data support gain-of-function variation in SOS1 as a contributing factor to isolated DCM.

Variant Interpretation for Dilated Cardiomyopathy: Refinement of the American College of Medical Genetics and Genomics/ClinGen Guidelines for the DCM Precision Medicine Study.

BACKGROUND: The hypothesis of the Dilated Cardiomyopathy Precision Medicine Study is that most dilated cardiomyopathy has a genetic basis. The study returns results to probands and, when indicated, to relatives. While both the American College of Medical Genetics and Genomics/Association for Molecular Pathology and ClinGen's MYH7-cardiomyopathy specifications provide relevant guidance for variant interpretation, further gene- and disease-specific considerations were required for dilated cardiomyopathy. To this end, we tailored the ClinGen MYH7-cardiomyopathy variant interpretation framework; the specifications implemented for the study are presented here. METHODS: Modifications were created and approved by an external Variant Adjudication Oversight Committee. After a pilot using 81 probands, further adjustments were made, resulting in 27 criteria (9 modifications of the ClinGen MYH7 framework and reintroduction of 2 American College of Medical Genetics and Genomics/Association of Molecular Pathology criteria that were deemed not applicable by the ClinGen MYH7 working group). RESULTS: These criteria were applied to 2059 variants in a test set of 97 probands. Variants were classified as benign (n=1702), likely benign (n=33), uncertain significance (n=71), likely pathogenic (likely pathogenic; n=12), and pathogenic (P; n=3). Only 2/15 likely pathogenic/P variants were identified in Non-Hispanic African ancestry probands. CONCLUSIONS: We tailored the ClinGen MYH7 criteria for our study. Our preliminary data show that 15/97 (15.5%) probands have likely pathogenic/P variants, most of which were identified in probands of Non-Hispanic European ancestry. We anticipate continued evolution of our approach, one that will be informed by new insights on variant interpretation and a greater understanding of the genetic architecture of dilated cardiomyopathy. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03037632.

Understanding BRCA Mutation Carriers' Preferences for Communication of Genetic Modifiers of Breast Cancer Risk.

Refined estimates of risk based on genetic risk modifiers could assist BRCA mutation carriers in understanding their risk, but it is not clear whether carriers are interested in receiving these estimates or how they might benefit from them. Using qualitative interviews, we investigated female BRCA1 and BRCA2 mutation carriers' (N = 20) reactions to numerical and verbal presentations of breast cancer risk based on risk modifiers and assessed women's preferences regarding visual formats for communicating risk. Our results show carriers are interested in receiving refined risk estimates and suggest the estimates may influence decision-making regarding cancer prevention, depending on the nature of the risk assessment. Although accurate and precise estimates of breast cancer risk are most important to women, they preferred quantitative risk estimates expressed as a proportion with or without a population comparison; however, women noted that comparisons to other BRCA mutation carriers were less useful given their high risk. Participants also preferred communication of a risk as a specific percentage versus a range of risk, but a clear preference regarding visual displays was not expressed. Results support many existing recommendations for genetic risk communication and provide guidance for the development of tools incorporating genetic risk modifiers.

Multigenic Disease and Bilineal Inheritance in Dilated Cardiomyopathy Is Illustrated in Nonsegregating LMNA Pedigrees.

BACKGROUND: We have previously described 19 pedigrees with apparent lamin (LMNA)-related dilated cardiomyopathy (DCM) manifesting in affected family members across multiple generations. In 6 of 19 families, at least 1 individual with idiopathic DCM did not carry the family's LMNA variant. We hypothesized that additional genetic cause may underlie DCM in these families. METHODS: Affected family members underwent exome sequencing to identify additional genetic cause of DCM in the 6 families with nonsegregating LMNA variants. RESULTS: In 5 of 6 pedigrees, we identified at least 1 additional rare variant in a known DCM gene that could plausibly contribute to disease in the LMNA variant-negative individuals. Bilineal inheritance was clear or presumed to be present in 3 of 5 families and was possible in the remaining 2. At least 1 individual with a LMNA variant also carried a variant in an additional identified DCM gene in each family. Using a multivariate linear mixed model for quantitative traits, we demonstrated that the presence of these additional variants was associated with a more severe phenotype after adjusting for sex, age, and the presence/absence of the family's nonsegregating LMNA variant. CONCLUSIONS: Our data support DCM as a genetically heterogeneous disease with, at times, multigene causation. Although the frequency of DCM resulting from multigenic cause is uncertain, our data suggest it may be higher than previously anticipated.

Toward Genetics-Driven Early Intervention in Dilated Cardiomyopathy: Design and Implementation of the DCM Precision Medicine Study.

BACKGROUND: The cause of idiopathic dilated cardiomyopathy (DCM) is unknown by definition, but its familial subtype is considered to have a genetic component. We hypothesize that most idiopathic DCM, whether familial or nonfamilial, has a genetic basis, in which case a genetics-driven approach to identifying at-risk family members for clinical screening and early intervention could reduce morbidity and mortality. METHODS: On the basis of this hypothesis, we have launched the National Heart, Lung, and Blood Institute- and National Human Genome Research Institute-funded DCM Precision Medicine Study, which aims to enroll 1300 individuals (600 non-Hispanic African ancestry, 600 non-Hispanic European ancestry, and 100 Hispanic) who meet rigorous clinical criteria for idiopathic DCM along with 2600 of their relatives. Enrolled relatives will undergo clinical cardiovascular screening to identify asymptomatic disease, and all individuals with idiopathic DCM will undergo exome sequencing to identify relevant variants in genes previously implicated in DCM. Results will be returned by genetic counselors 12 to 14 months after enrollment. The data obtained will be used to describe the prevalence of familial DCM among idiopathic DCM cases and the genetic architecture of idiopathic DCM in multiple ethnicity-ancestry groups. We will also conduct a randomized controlled trial to test the effectiveness of Family Heart Talk, an intervention to aid family communication, for improving uptake of preventive screening and surveillance in at-risk first-degree relatives. CONCLUSIONS: We anticipate that this study will demonstrate that idiopathic DCM has a genetic basis and guide best practices for a genetics-driven approach to early intervention in at-risk relatives. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT03037632.

Single Marker Family-Based Association Analysis Conditional on Parental Information.

Family-based designs have been commonly used in association studies. Different family structures such as extended pedigrees and nuclear families, including parent-offspring triads and families with multiple affected siblings (multiplex families), can be ascertained for family-based association analysis. Flexible association tests that can accommodate different family structures have been proposed. The pedigree disequilibrium test (PDT) (Martin et al., Am J Hum Genet 67:146-154, 2000) can use full genotype information from general (possibly extended) pedigrees with one or multiple affected siblings but requires parental genotypes or genotypes of unaffected siblings. On the other hand, the association in the presence of linkage (APL) test (Martin et al., Am J Hum Genet 73:1016-1026, 2003) is restricted to nuclear families with one or more affected siblings but can infer missing parental genotypes properly by accounting for identity-by-descent (IBD) parameters. Both the PDT and APL test are powerful association tests in the presence of linkage and can be used as complementary tools for association analysis. This chapter introduces these two tests and compares their properties. Recommendations and notes for performing the tests in practice are provided.

Valid Monte Carlo permutation tests for genetic case-control studies with missing genotypes.

Monte Carlo permutation tests can be formally constructed by choosing a set of permutations of individual indices and a real-valued test statistic measuring the association between genotypes and affection status. In this paper, we develop a rigorous theoretical framework for verifying the validity of these tests when there are missing genotypes. We begin by specifying a nonparametric probability model for the observed genotype data in a genetic case-control study with unrelated subjects. Under this model and some minimal assumptions about the test statistic, we establish that the resulting Monte Carlo permutation test is exact level α if (1) the chosen set of permutations of individual indices is a group under composition and (2) the distribution of the observed genotype score matrix under the null hypothesis does not change if the assignment of individuals to rows is shuffled according to an arbitrary permutation in this set. We apply these conditions to show that frequently used Monte Carlo permutation tests based on the set of all permutations of individual indices are guaranteed to be exact level α only for missing data processes satisfying a rather restrictive additional assumption. However, if the missing data process depends on covariates that are all identified and recorded, we also show that Monte Carlo permutation tests based on the set of permutations within strata of individuals with identical covariate values are exact level α. Our theoretical results are verified and supplemented by simulations for a variety of missing data processes and test statistics.

Whole exome sequencing of rare variants in EIF4G1 and VPS35 in Parkinson disease.

OBJECTIVE: Recently, vacuolar protein sorting 35 (VPS35) and eukaryotic translation initiation factor 4 gamma 1 (EIF4G1) have been identified as 2 causal Parkinson disease (PD) genes. We used whole exome sequencing for rapid, parallel analysis of variations in these 2 genes. METHODS: We performed whole exome sequencing in 213 patients with PD and 272 control individuals. Those rare variants (RVs) with <5% frequency in the exome variant server database and our own control data were considered for analysis. We performed joint gene-based tests for association using RVASSOC and SKAT (Sequence Kernel Association Test) as well as single-variant test statistics. RESULTS: We identified 3 novel VPS35 variations that changed the coded amino acid (nonsynonymous) in 3 cases. Two variations were in multiplex families and neither segregated with PD. In EIF4G1, we identified 11 (9 nonsynonymous and 2 small indels) RVs including the reported pathogenic mutation p.R1205H, which segregated in all affected members of a large family, but also in 1 unaffected 86-year-old family member. Two additional RVs were found in isolated patients only. Whereas initial association studies suggested an association (p = 0.04) with all RVs in EIF4G1, subsequent testing in a second dataset for the driving variant (p.F1461) suggested no association between RVs in the gene and PD. CONCLUSIONS: We confirm that the specific EIF4G1 variation p.R1205H seems to be a strong PD risk factor, but is nonpenetrant in at least one 86-year-old. A few other select RVs in both genes could not be ruled out as causal. However, there was no evidence for an overall contribution of genetic variability in VPS35 or EIF4G1 to PD development in our dataset.