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BACKGROUNDAccurate penetrance of monogenic disorders is often unknown due to a phenotype-first approach to genetic testing. Here, we use a genotype-first approach in four large cohorts with different ascertainment contexts to accurately estimate penetrance of the three commonest causes of monogenic diabetes, Maturity Onset Diabetes of the Young (MODY). We contrast HNF1A-MODY / HNF4A-MODY which causes an age-related progressive diabetes and GCK-MODY, which causes life-long mild hyperglycaemia.METHODSWe analysed clinical and genetic sequencing data from four different cohorts: 1742 probands referred for clinical MODY testing; 2194 family members of the MODY probands; 132,194 individuals from an American hospital-based cohort; and 198,748 individuals from a UK population-based cohort.RESULTSAge-related penetrance of diabetes for pathogenic variants in HNF1A and HNF4A was substantially lower in the clinically unselected cohorts compared to clinically referred probands (ranging from 32% to 98% at age 40yrs for HNF1A, and 21% to 99% for HNF4A). The background rate of diabetes, but not clinical features or variant type, explained the reduced penetrance in the unselected cohorts. In contrast, penetrance of mild hyperglycaemia for pathogenic GCK variants was similarly high across cohorts (ranging from 89 to 97%) despite substantial variation in the background rates of diabetes.CONCLUSIONSAscertainment context is crucial when interpreting the consequences of monogenic variants for age-related variably penetrant disorders. This finding has important implications for opportunistic screening during genomic testing.

Genetic testing for monogenic diabetes, essential for accurate diagnosis and appropriate treatment is underutilized. Obstacles include clinical overlap with type 1 and type 2 diabetes and difficulty distinguishing clinically significant (pathogenic/likely pathogenic; P/LP) from normal (benign/likely benign; B/LB) variation. The ClinGen Monogenic Diabetes Expert Panel (MDEP) was formed to adapt American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) variant interpretation guidelines to monogenic diabetes genes and enable depositing of expert panel variant reviews into ClinVar, a public database relating gene variants to phenotypes. MDEP includes endocrinologists, laboratory directors, genetic counselors, medical geneticists, clinical scientists and researchers from 37 academic and commercial institutions, allowing the panel to benefit from multiple expert perspectives and pooling of case-level data. Currently, MDEP is focusing on the three most commonly implicated monogenic diabetes genes: GCK, HNF1A and HNF4A. MDEP generated gene-specific modifications and/or strength adjustments to existing rules to provide guidance for the use of evidence, including molecular, phenotypic, segregation, functional, and minor allele frequency data. Our guidelines have so far been tested on 98 HNF1A variants, 15 HNF4A variants and 22 GCK variants selected from ClinVar and the literature. Fourteen of 31 variants of uncertain significance (VUS) in ClinVar were re-classified: nine to P/LP (enabling diagnosis and treatment) and five to B/LB (reducing ambiguity). Six LP variants and one LB variant from ClinVar were re-classified to VUS (stimulating further surveillance). MDEP’s work will improve accuracy, standardization and concordance of variant interpretation for monogenic diabetes and support wider implementation of precision medicine in diabetes. Disclosure H. Zhang: None. K.A. Maloney: None. F. Barbetti: Consultant; Self; Amring. S.W. Greeley: None. J.L.T. Kettunen: None. J.P. Miranda: None. U.L. Mirshahi: None. J. Molnes: None. R. Murphy: None. R.N. Naylor: None. R.E. Pakyz: None. L.H. Philipson: None. S. Prudente: None. T. Tuomi: None. M. Udler: None. K. Colclough: None. L. Jeng: None. T.I. Pollin: None. Funding National Institutes of Health (5U24HD093486, R01DK104942, P30DK020595 )

Angiopoietin-like 4 (ANGPTL4) is an endogenous inhibitor of lipoprotein lipase that modulates lipid levels, coronary atherosclerosis risk, and nutrient partitioning. We hypothesize that loss of ANGPTL4 function might improve glucose homeostasis and decrease risk of type 2 diabetes (T2D). We investigate protein-altering variants in ANGPTL4 among 58,124 participants in the DiscovEHR human genetics study, with follow-up studies in 82,766 T2D cases and 498,761 controls. Carriers of p.E40K, a variant that abolishes ANGPTL4 ability to inhibit lipoprotein lipase, have lower odds of T2D (odds ratio 0.89, 95% confidence interval 0.85–0.92, p = 6.3 × 10−10), lower fasting glucose, and greater insulin sensitivity. Predicted loss-of-function variants are associated with lower odds of T2D among 32,015 cases and 84,006 controls (odds ratio 0.71, 95% confidence interval 0.49–0.99, p = 0.041). Functional studies in Angptl4-deficient mice confirm improved insulin sensitivity and glucose homeostasis. In conclusion, genetic inactivation of ANGPTL4 is associated with improved glucose homeostasis and reduced risk of T2D., Genetic variation in ANGPTL4 is associated with lipid traits. Here, the authors find that predicted loss-of-function variants in ANGPTL4 are associated with glucose homeostasis and reduced risk of type 2 diabetes and that Angptl4−/− mice on a high-fat diet show improved insulin sensitivity.

Doubts have been raised about the value of DNA-based screening for low-prevalence monogenic conditions following reports of testing this approach using available electronic health record (EHR) as the sole phenotyping source. We hypothesized that a better model for EHR-focused examination of DNA-based screening is Cystic Fibrosis (CF) since the diagnosis is proactively sought within the healthcare system. We reviewed CFTR variants in 50,778 exomes. In 24 cases with bi-allelic pathogenic CFTR variants, there were 21 true-positives. We considered three cases “potential” false-positives due to limitations in available EHR phenotype data. This genomic screening exhibited a positive predictive value of 87.5%, negative predictive value of 99.9%, sensitivity of 95.5%, and a specificity of 99.9%. Despite EHR-based phenotyping limitations in three cases, the presence or absence of pathogenic CFTR variants has strong predictive value for CF diagnosis when EHR data is used as the sole phenotyping source. Accurate ascertainment of the predictive value of DNA-based screening requires condition-specific phenotyping beyond available EHR data.

Maturity onset diabetes of the young (MODY) is a monogenic form of diabetes attributed to a highly penetrant variant in one of several genes, including GCK. GCK-MODY rarely requires pharmacotherapy, however, the clinical management of pregnant mothers depends on whether the fetus inherited the GCK variant. The classic GCK-MODY phenotype is young (diagnosed before 25 years), lean (BMI < 25 mg/kg2), with stable, mild hyperglycemia (Hba1c 5.8-7.6%). We hypothesized that strict application of these guidelines has led to under-reporting of GCK-MODY (prevalence 1.1 per 1000). In a cohort of 92,412 individuals from the DiscovEHR study, we identified 252 heterozygous carriers of 88 rare GCK variants (minor allele frequency < 0.02%). None had an existing diagnosis of monogenic diabetes. The median BMI of GCK carriers was 35 mg/kg2, compared to 31 mg/kg2 for nondiabetic noncarriers and 38 mg/kg2 for noncarriers with type 2 diabetes (T2D). Excluding variants with no evidence of hyperglycemia in 50% of the carriers resulted in 70 variants in 213 individuals. GCK-MODY variant carriers had mean HbA1c, fasting blood glucose (FBG), and random glucose measurements that were greater than nondiabetic non-carriers but less than those with T2D. Kaplan-Meier analysis adjusted for left-truncation bias showed that the age at which 50% of GCK-MODY subjects diagnosed with impaired fasting glucose and diabetes is 35 and 55 years, respectively, compared to 60 and 65 years in non-carriers with T2D (p< 2e-16). Within-individual variability of lifetime FBG measurements of GCK-MODY carriers was less than noncarriers with T2D (GCK-MODY, 7.9 ± 2.0 mg/dL; T2D, 17.6 ± 0.03 mg/dl, p Disclosure U.L. Mirshahi: None. J.M. Goehringer: None. Y. Hu: None. A.H. Wardeh: None. J. Williams: None. C.B. Manney: None. J.C. Staples: Employee; Self; Regeneron Pharmaceuticals. J.B. Leader: None. A.R. Shuldiner: Employee; Self; Regeneron Pharmaceuticals. Stock/Shareholder; Self; Rhythm Pharmaceuticals, Inc. T.I. Pollin: Other Relationship; Self; Regeneron Genetics Center. D.J. Carey: None.

Key Points Question What are the prevalence, risk, and phenotypic spectrum of individuals with a germline putative loss-of-function (pLOF) variant in DICER1 according to a genome-first approach in a population-scale cohort? Findings In this cohort study, DICER1 pLOF variants were more than twice as common (even after adjustment for relatedness) than previously observed. Malignant tumors were observed in 16% of participants with a DICER1 pLOF variant, which is comparable to the frequency of neoplasms in the largest phenotype-first DICER1 studies published to date. Meaning The genome-first approach complements more traditional approaches to syndrome delineation and may be an efficient approach for risk estimation in monogenic disorders., Importance Genetic disorders are historically defined through phenotype-first approaches. However, risk estimates derived from phenotype-linked ascertainment may overestimate severity and penetrance. Pathogenic variants in DICER1 are associated with increased risks of rare and common neoplasms and thyroid disease in adults and children. This study explored how effectively a genome-first approach could characterize the clinical traits associated with germline DICER1 putative loss-of-function (pLOF) variants in an unselected clinical cohort. Objective To examine the prevalence, penetrance, and phenotypic characteristics of carriers of germline DICER1 pLOF variants via genome-first ascertainment. Design, Setting, and Participants This cohort study classifies DICER1 variants in germline exome sequence data from 92 296 participants of the Geisinger MyCode Community Health Initiative. Data for each MyCode participant were used from the start of the Geisinger electronic health record to February 1, 2018. Main Outcomes and Measures Prevalence of germline DICER1 variation; penetrance of malignant tumors and thyroid disease in carriers of germline DICER1 variation; structured, manual review of electronic health records; and DICER1 sequencing of available tumors from an associated cancer registry. Results A total of 92 296 adults (mean [SD] age, 59 [18] years; 98% white; 60% female) participated in the study. Germline DICER1 pLOF variants were observed in 1 in 3700 to 1 in 4600 participants, more than double the expected prevalence. Malignant tumors (primarily thyroid carcinoma) were observed in 4 of 25 participants (16%) with DICER1 pLOF variants, which is comparable (by 50 years of age) to the frequency of neoplasms in the largest registry- and clinic-based (phenotype-first) DICER1 studies published to date. DICER1 pLOF variants were significantly associated with risks of thyroidectomy (odds ratio [OR], 6.0; 95% CI, 2.2-16.3; P = .007) and thyroid cancer (OR, 9.2; 95% CI, 2.1-34.7; P = .02) compared with controls, but there was not a significant increase in the risk of goiter (OR, 1.8; 95% CI, 0.7-4.9). A female patient in her 80s who was a carrier of a germline DICER1 hotspot variant was apparently healthy on electronic health record review. The term DICER1 did not appear in any of the medical records of the 25 participants with a pLOF DICER1 variant, even in those affected with a known DICER1-associated tumor or thyroid phenotype. Conclusions and Relevance This cohort study was able to ascertain individuals with germline DICER1 variants based on a genome-first approach rather than through a previously established DICER1-related phenotype. Use of the genome-first approach may complement more traditional approaches to syndrome delineation and may be an efficient approach for risk estimation., This cohort study examines the prevalence and penetrance of germline DICER1 putative loss-of-function variants via genome-first ascertainment.

Purpose Geisinger Health System (GHS) provides an ideal platform for Precision Medicine. Key elements are the integrated health system, stable patient population, and electronic health record (EHR) infrastructure. In 2007 Geisinger launched MyCode®, a system-wide biobanking program to link samples and EHR data for broad research use. Methods Patient-centered input into MyCode® was obtained using participant focus groups. Participation in MyCode® is based on opt-in informed consent and allows recontact, which facilitates collection of data not in the EHR, and, since 2013, the return of clinically actionable results to participants. MyCode® leverages Geisinger’s technology and clinical infrastructure for participant tracking and sample collection. Results MyCode® has a consent rate of >85% with more than 90,000 participants currently, with ongoing enrollment of ~4,000 per month. MyCode® samples have been used to generate molecular data, including high-density genotype and exome sequence data. Genotype and EHR-derived phenotype data replicate previously reported genetic associations. Conclusion The MyCode® project has created resources that enable a new model for translational research that is faster, more flexible, and more cost effective than traditional clinical research approaches. The new model is scalable, and will increase in value as these resources grow and are adopted across multiple research platforms.

Background: Heterologous functional validation studies of putative long-QT syndrome subtype 2–associated variants clarify their pathological potential and identify disease mechanism(s) for most variants studied. The purpose of this study is to clarify the pathological potential for rare nonsynonymous KCNH2 variants seemingly associated with sudden infant death syndrome. Methods: Genetic testing of 292 sudden infant death syndrome cases identified 9 KCNH2 variants: E90K, R181Q, A190T, G294V, R791W, P967L, R1005W, R1047L, and Q1068R. Previous studies show R181Q-, P967L-, and R1047L-Kv11.1 channels function similar to wild-type Kv11.1 channels, whereas Q1068R-Kv11.1 channels accelerate inactivation gating. We studied the biochemical and biophysical properties for E90K-, G294V-, R791W-, and R1005W-Kv11.1 channels expressed in human embryonic kidney 293 cells; examined the electronic health records of patients who were genotype positive for the sudden infant death syndrome–linked KCNH2 variants; and simulated their functional impact using computational models of the human ventricular action potential. RESULTS: Western blot and voltage-clamping analyses of cells expressing E90K-, G294V-, R791W-, and R1005W-Kv11.1 channels demonstrated these variants express and generate peak Kv11.1 current levels similar to cells expressing wild-type-Kv11.1 channels, but R791W- and R1005W-Kv11.1 channels accelerated deactivation and activation gating, respectively. Electronic health records of patients with the sudden infant death syndrome–linked KCNH2 variants showed that the patients had median heart rate–corrected QT intervals Conclusions: We conclude that these rare Kv11.1 missense variants are not long-QT syndrome subtype 2–causative variants and therefore do not represent the pathogenic substrate for sudden infant death syndrome in the variant-positive infants.

BACKGROUND: Elucidation of the genetic factors underlying chronic liver disease may reveal new therapeutic targets. METHODS: We used exome sequence data and electronic health records from 46,544 participants in the DiscovEHR human genetics study to identify genetic variants associated with serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Variants that were replicated in three additional cohorts (12,527 persons) were evaluated for association with clinical diagnoses of chronic liver disease in DiscovEHR study participants and two independent cohorts (total of 37,173 persons) and with histopathological severity of liver disease in 2391 human liver samples. RESULTS: A splice variant (rs72613567:TA) in HSD17B13, encoding the hepatic lipid droplet protein hydroxysteroid 17-beta dehydrogenase 13, was found to be associated with reduced levels of ALT (P=4.20×10(−12)) and AST (P=6.2×10(−10)). Among DiscovEHR study participants, this variant was found to be associated with a reduced risk of alcoholic liver disease (by 42% [95% confidence interval {CI}, 20 to 58] among heterozygotes and by 53% [95% CI, 3 to 77] among homozygotes), nonalcoholic liver disease (by 17% [95% CI, 8 to 25] among heterozygotes and by 30% [95% CI, 13 to 43] among homozygotes), alcoholic cirrhosis (by 42% [95% CI, 14 to 61] among heterozygotes and by 73% [95% CI, 15 to 91] among homozygotes), and nonalcoholic cirrhosis (by 26% [95% CI, 7 to 40] among heterozygotes and by 49% [95% CI, 15 to 69] among homozygotes). Associations were confirmed in two independent cohorts. The rs72613567:TA variant was associated with a reduced risk of nonalcoholic steatohepatitis, but not steatosis, in human liver samples. The rs72613567:TA variant mitigated liver injury associated with the risk-increasing PNPLA3 p.I148M allele and resulted in an unstable and truncated protein with reduced enzymatic activity. CONCLUSIONS: A loss-of-function variant in HSD17B13 is associated with a reduced risk of chronic liver disease and of progression from steatosis to steatohepatitis. (Funded by Regeneron Pharmaceuticals and others.)

Genome-wide association and linkage studies have identified multiple susceptibility loci for obesity. We hypothesized that such loci may affect weight loss outcomes following dietary or surgical weight loss interventions. A total of 1,001 white individuals with extreme obesity (BMI >35 kg/m(2)) who underwent a preoperative diet/behavioral weight loss intervention and Roux-en-Y gastric bypass surgery were genotyped for single-nucleotide polymorphisms (SNPs) in or near the fat mass and obesity-associated (FTO), insulin induced gene 2 (INSIG2), melanocortin 4 receptor (MC4R), and proprotein convertase subtilisin/kexin type 1 (PCSK1) obesity genes. Association analysis was performed using recessive and additive models with pre- and postoperative weight loss data. An increasing number of obesity SNP alleles or homozygous SNP genotypes was associated with increased BMI (P < 0.0006) and excess body weight (P < 0.0004). No association between the amounts of weight lost from a short-term dietary intervention and any individual obesity SNP or cumulative number of obesity SNP alleles or homozygous SNP genotypes was observed. Linear mixed regression analysis revealed significant differences in postoperative weight loss trajectories across groups with low, intermediate, and high numbers of obesity SNP alleles or numbers of homozygous SNP genotypes (P < 0.0001). Initial BMI interacted with genotype to influence weight loss with initial BMI