Genetic sex validation for sample tracking in next-generation sequencing clinical testing.

OBJECTIVE: Data from DNA genotyping via a 96-SNP panel in a study of 25,015 clinical samples were utilized for quality control and tracking of sample identity in a clinical sequencing network. The study aimed to demonstrate the value of both the precise SNP tracking and the utility of the panel for predicting the sex-by-genotype of the participants, to identify possible sample mix-ups. RESULTS: Precise SNP tracking showed no sample swap errors within the clinical testing laboratories. In contrast, when comparing predicted sex-by-genotype to the provided sex on the test requisition, we identified 110 inconsistencies from 25,015 clinical samples (0.44%), that had occurred during sample collection or accessioning. The genetic sex predictions were confirmed using additional SNP sites in the sequencing data or high-density genotyping arrays. It was determined that discrepancies resulted from clerical errors (49.09%), samples from transgender participants (3.64%) and stem cell or bone marrow transplant patients (7.27%) along with undetermined sample mix-ups (40%) for which sample swaps occurred prior to arrival at genome centers, however the exact cause of the events at the sampling sites resulting in the mix-ups were not able to be determined.

Heterozygous loss-of-function variants in DOCK4 cause neurodevelopmental delay and microcephaly.

Neurons form the basic anatomical and functional structure of the nervous system, and defects in neuronal differentiation or formation of neurites are associated with various psychiatric and neurodevelopmental disorders. Dynamic changes in the cytoskeleton are essential for this process, which is, inter alia, controlled by the dedicator of cytokinesis 4 (DOCK4) through the activation of RAC1. Here, we clinically describe 7 individuals (6 males and one female) with variants in DOCK4 and overlapping phenotype of mild to severe global developmental delay. Additional symptoms include coordination or gait abnormalities, microcephaly, nonspecific brain malformations, hypotonia and seizures. Four individuals carry missense variants (three of them detected de novo) and three individuals carry null variants (two of them maternally inherited). Molecular modeling of the heterozygous missense variants suggests that the majority of them affect the globular structure of DOCK4. In vitro functional expression studies in transfected Neuro-2A cells showed that all missense variants impaired neurite outgrowth. Furthermore, Dock4 knockout Neuro-2A cells also exhibited defects in promoting neurite outgrowth. Our results, including clinical, molecular and functional data, suggest that loss-of-function variants in DOCK4 probable cause a variable spectrum of a novel neurodevelopmental disorder with microcephaly.

Evaluation of Malignant Hyperthermia Features in Patients with Pathogenic or Likely Pathogenic RYR1 Variants Disclosed through a Population Genomic Screening Program.

BACKGROUND: Malignant hyperthermia (MH) susceptibility is a heritable musculoskeletal disorder that can present as a potentially fatal hypermetabolic response to triggering anesthesia agents. Genomic screening for variants in MH-associated genes RYR1 and CACNA1S provides an opportunity to prevent morbidity and mortality. There are limited outcomes data from disclosing variants in RYR1, the most common MH susceptibility gene, in unselected populations. The authors sought to identify the rate of MH features or fulminant episodes after triggering agent exposure in an unselected population undergoing genomic screening including actionable RYR1 variants. METHODS: The MyCode Community Health Initiative by Geisinger (USA) is an electronic health record-linked biobank that discloses pathogenic and likely pathogenic variants in clinically actionable genes to patient-participants. Available electronic anesthesia and ambulatory records for participants with actionable RYR1 results returned through December 2020 were evaluated for pertinent findings via double-coded chart reviews and reconciliation. Descriptive statistics for observed phenotypes were calculated. RESULTS: One hundred fifty-two participants had an actionable RYR1 variant disclosed during the study period. None had previous documented genetic testing for MH susceptibility; one had previous contracture testing diagnosing MH susceptibility. Sixty-eight participants (44.7%) had anesthesia records documenting triggering agent exposure during at least one procedure. None received dantrolene treatment or had documented muscle rigidity, myoglobinuria, hyperkalemia, elevated creatine kinase, severe myalgia, or tea-colored urine. Of 120 possibly MH-related findings (postoperative intensive care unit admissions, hyperthermia, arterial blood gas evaluation, hypercapnia, or tachycardia), 112 (93.3%) were deemed unlikely to be MH events; 8 (6.7%) had insufficient records to determine etiology. CONCLUSIONS: Results demonstrate a low frequency of classic intraanesthetic hypermetabolic phenotypes in an unselected population with actionable RYR1 variants. Further research on the actionability of screening for MH susceptibility in unselected populations, including economic impact, predictors of MH episodes, and expanded clinical phenotypes, is necessary.

Genetic Sex Validation for Sample Tracking in Clinical Testing.

Objective: Data from DNA genotyping via a 96-SNP panel in a study of 25,015 clinical samples were utilized for quality control and tracking of sample identity in a clinical sequencing network. The study aimed to demonstrate the value of both the precise SNP tracking and the utility of the panel for predicting the sex-by-genotype of the participants, to identify possible sample mix-ups. Results: Precise SNP tracking showed no sample swap errors within the clinical testing laboratories. In contrast, when comparing predicted sex-by-genotype to the provided sex on the test requisition, we identified 110 inconsistencies from 25,015 clinical samples (0.44%), that had occurred during sample collection or accessioning. The genetic sex predictions were confirmed using additional SNP sites in the sequencing data or high-density genotyping arrays. It was determined that discrepancies resulted from clerical errors, samples from transgender participants and stem cell or bone marrow transplant patients along with undetermined sample mix-ups.

The landscape of reported VUS in multi-gene panel and genomic testing: Time for a change.

PURPOSE: Variants of uncertain significance (VUS) are a common result of diagnostic genetic testing and can be difficult to manage with potential misinterpretation and downstream costs, including time investment by clinicians. We investigated the rate of VUS reported on diagnostic testing via multi-gene panels (MGPs) and exome and genome sequencing (ES/GS) to measure the magnitude of uncertain results and explore ways to reduce their potentially detrimental impact. METHODS: Rates of inconclusive results due to VUS were collected from over 1.5 million sequencing test results from 19 clinical laboratories in North America from 2020 to 2021. RESULTS: We found a lower rate of inconclusive test results due to VUSs from ES/GS (22.5%) compared with MGPs (32.6%; P < .0001). For MGPs, the rate of inconclusive results correlated with panel size. The use of trios reduced inconclusive rates (18.9% vs 27.6%; P < .0001), whereas the use of GS compared with ES had no impact (22.2% vs 22.6%; P = ns). CONCLUSION: The high rate of VUS observed in diagnostic MGP testing warrants examining current variant reporting practices. We propose several approaches to reduce reported VUS rates, while directing clinician resources toward important VUS follow-up.

Low adenoma burden in unselected patients with a pathogenic APC variant.

PURPOSE: Genomic screening can improve clinical outcomes, but presentation of individuals with risk for polyposis identified via genomic screening is unknown. To inform assessment of clinical utility of genomic screening for polyposis risk, clinical presentation of individuals in an unselected health care system cohort with an APC pathogenic or likely pathogenic (P/LP) variant causative of familial adenomatous polyposis are described. METHODS: Electronic health records of individuals with an APC P/LP variant identified via the MyCode program (MyCode APC+) were reviewed to assess adenoma burden and compare it among individuals with a clinical diagnosis of familial adenomatous polyposis and matched variant-negative controls. RESULTS: The prevalence of APC P/LP variants in this health care cohort is estimated to be 1 in 2800. Twenty-four MyCode APC+ individuals were identified during the study period. Median age at result disclosure was 53 years. Rate of clinical polyposis was 8%. Two of six participants with a classic region variant and none of those with an attenuated region variant had polyposis. MyCode APC+ participants did not differ from controls in cumulative adenoma count. CONCLUSION: APC P/LP variant prevalence estimate in the MyCode cohort is higher than prior published prevalence rates. Individuals with APC P/LP variants identified via genomic screening had a low adenoma burden.

Yield of Familial Hypercholesterolemia Genetic and Phenotypic Diagnoses After Electronic Health Record and Genomic Data Screening.

Background Data mining of electronic health records to identify patients suspected of familial hypercholesterolemia (FH) has been limited by absence of both phenotypic and genomic data in the same cohort. Methods and Results Using the Geisinger MyCode Community Health Initiative cohort (n=130 257), we ran 2 screening algorithms (Mayo Clinic [Mayo] and flag, identify, network, deliver [FIND] FH) to determine FH genetic and phenotypic diagnostic yields. With 29 243 excluded by Mayo (for secondary causes of hypercholesterolemia, no lipid value in electronic health records), 52 034 excluded by FIND FH (insufficient data to run the model), and 187 excluded for prior FH diagnosis, a final cohort of 59 729 participants was created. Genetic diagnosis was based on presence of a pathogenic or likely pathogenic variant in FH genes. Charts from 180 variant-negative participants (60 controls, 120 identified by FIND FH and Mayo) were reviewed to calculate Dutch Lipid Clinic Network scores; a score ≥5 defined probable phenotypic FH. Mayo flagged 10 415 subjects; 194 (1.9%) had a pathogenic or likely pathogenic FH variant. FIND FH flagged 573; 34 (5.9%) had a pathogenic or likely pathogenic variant, giving a net yield from both of 197 out of 280 (70%). Confirmation of a phenotypic diagnosis was constrained by lack of electronic health record data on physical findings or family history. Phenotypic FH by chart review was present by Mayo and/or FIND FH in 13 out of 120 versus 2 out of 60 not flagged by either (P<0.09). Conclusions Applying 2 recognized FH screening algorithms to the Geisinger MyCode Community Health Initiative identified 70% of those with a pathogenic or likely pathogenic FH variant. Phenotypic diagnosis was rarely achievable due to missing data.

The Maryland (USA) Critical Care Coordination Center (C4): From Pandemic to Permanence.

INTRODUCTION: The 2019 coronavirus disease (COVID-19) pandemic created overwhelming demand for critical care services within Maryland's (USA) hospital systems. As intensive care units (ICUs) became full, critically ill patients were boarded in hospital emergency departments (EDs), a practice associated with increased mortality and costs. Allocation of critical care resources during the pandemic requires thoughtful and proactive management strategies. While various methodologies exist for addressing the issue of ED overcrowding, few systems have implemented a state-wide response using a public safety-based platform. The objective of this report is to describe the implementation of a state-wide Emergency Medical Services (EMS)-based coordination center designed to ensure timely and equitable access to critical care. METHODS: The state of Maryland designed and implemented a novel, state-wide Critical Care Coordination Center (C4) staffed with intensivist physicians and paramedics purposed to ensure appropriate critical care resource management and patient transfer assistance. A narrative description of the C4 is provided. A retrospective cohort study design was used to present requests to the C4 as a case series report to describe the results of implementation. RESULTS: Providing a centralized asset with regional situational awareness of hospital capability and bed status played an integral role for directing the triage process of critically ill patients to appropriate facilities during and after the COVID-19 pandemic. A total of 2,790 requests were received by the C4. The pairing of a paramedic with an intensivist physician resulted in the successful transfer of 67.4% of requests, while 27.8% were managed in place with medical direction. Overall, COVID-19 patients comprised 29.5% of the cohort. Data suggested increased C4 usage was predictive of state-wide ICU surges. The C4 usage volume resulted in the expansion to pediatric services to serve a broader age range. The C4 concept, which leverages the complimentary skills of EMS clinicians and intensivist physicians, is presented as a proposed public safety-based model for other regions to consider world-wide. CONCLUSION: The C4 has played an integral role in the State of Maryland's pledge to its citizens to deliver the right care to the right patient at the right time and can be considered as a model for adoption by other regions world-wide.

Poison exon annotations improve the yield of clinically relevant variants in genomic diagnostic testing.

PURPOSE: Neurodevelopmental disorders (NDDs) often result from rare genetic variation, but genomic testing yield for NDDs remains below 50%, suggesting that clinically relevant variants may be missed by standard analyses. Here, we analyze "poison exons" (PEs), which are evolutionarily conserved alternative exons often absent from standard gene annotations. Variants that alter PE inclusion can lead to loss of function and may be highly penetrant contributors to disease. METHODS: We curated published RNA sequencing data from developing mouse cortex to define 1937 conserved PE regions potentially relevant to NDDs, and we analyzed variants found by genome sequencing in multiple NDD cohorts. RESULTS: Across 2999 probands, we found 6 novel clinically relevant variants in PE regions. Five of these variants are in genes that are part of the sodium voltage-gated channel alpha subunit family (SCN1A, SCN2A, and SCN8A), which is associated with epilepsies. One variant is in SNRPB, associated with cerebrocostomandibular syndrome. These variants have moderate to high computational impact assessments, are absent from population variant databases, and in genes with gene-phenotype associations consistent with each probands reported features. CONCLUSION: With a very minimal increase in variant analysis burden (average of 0.77 variants per proband), annotation of PEs can improve diagnostic yield for NDDs and likely other congenital conditions.

Poison exon annotations improve the yield of clinically relevant variants in genomic diagnostic testing.

Purpose: Neurodevelopmental disorders (NDDs) often result from rare genetic variation, but genomic testing yield for NDDs remains around 50%, suggesting some clinically relevant rare variants may be missed by standard analyses. Here we analyze "poison exons" (PEs) which, while often absent from standard gene annotations, are alternative exons whose inclusion results in a premature termination codon. Variants that alter PE inclusion can lead to loss-of-function and may be highly penetrant contributors to disease. Methods: We curated published RNA-seq data from developing mouse cortex to define 1,937 PE regions conserved between humans and mice and potentially relevant to NDDs. We then analyzed variants found by genome sequencing in multiple NDD cohorts. Results: Across 2,999 probands, we found six clinically relevant variants in PE regions that were previously overlooked. Five of these variants are in genes that are part of the sodium voltage-gated channel alpha subunit family ( SCN1A, SCN2A , and SCN8A ), associated with epilepsies. One variant is in SNRPB , associated with Cerebrocostomandibular Syndrome. These variants have moderate to high computational impact assessments, are absent from population variant databases, and were observed in probands with features consistent with those reported for the associated gene. Conclusion: With only a minimal increase in variant analysis burden (most probands had zero or one candidate PE variants in a known NDD gene, with an average of 0.77 per proband), annotation of PEs can improve diagnostic yield for NDDs and likely other congenital conditions.

Deleterious, protein-altering variants in the transcriptional coregulator ZMYM3 in 27 individuals with a neurodevelopmental delay phenotype.

Neurodevelopmental disorders (NDDs) result from highly penetrant variation in hundreds of different genes, some of which have not yet been identified. Using the MatchMaker Exchange, we assembled a cohort of 27 individuals with rare, protein-altering variation in the transcriptional coregulator ZMYM3, located on the X chromosome. Most (n = 24) individuals were males, 17 of which have a maternally inherited variant; six individuals (4 male, 2 female) harbor de novo variants. Overlapping features included developmental delay, intellectual disability, behavioral abnormalities, and a specific facial gestalt in a subset of males. Variants in almost all individuals (n = 26) are missense, including six that recurrently affect two residues. Four unrelated probands were identified with inherited variation affecting Arg441, a site at which variation has been previously seen in NDD-affected siblings, and two individuals have de novo variation resulting in p.Arg1294Cys (c.3880C>T). All variants affect evolutionarily conserved sites, and most are predicted to damage protein structure or function. ZMYM3 is relatively intolerant to variation in the general population, is widely expressed across human tissues, and encodes a component of the KDM1A-RCOR1 chromatin-modifying complex. ChIP-seq experiments on one variant, p.Arg1274Trp, indicate dramatically reduced genomic occupancy, supporting a hypomorphic effect. While we are unable to perform statistical evaluations to definitively support a causative role for variation in ZMYM3, the totality of the evidence, including 27 affected individuals, recurrent variation at two codons, overlapping phenotypic features, protein-modeling data, evolutionary constraint, and experimentally confirmed functional effects strongly support ZMYM3 as an NDD-associated gene.

Return of non-ACMG recommended incidental genetic findings to pediatric patients: considerations and opportunities from experiences in genomic sequencing.

BACKGROUND: The uptake of exome/genome sequencing has introduced unexpected testing results (incidental findings) that have become a major challenge for both testing laboratories and providers. While the American College of Medical Genetics and Genomics has outlined guidelines for laboratory management of clinically actionable secondary findings, debate remains as to whether incidental findings should be returned to patients, especially those representing pediatric populations. METHODS: The Sequencing Analysis and Diagnostic Yield working group in the Clinical Sequencing Evidence-Generating Research Consortium has collected a cohort of pediatric patients found to harbor a genomic sequencing-identified non-ACMG-recommended incidental finding. The incidental variants were not thought to be associated with the indication for testing and were disclosed to patients and families. RESULTS: In total, 23 "non-ACMG-recommended incidental findings were identified in 21 pediatric patients included in the study. These findings span four different research studies/laboratories and demonstrate differences in incidental finding return rate across study sites. We summarize specific cases to highlight core considerations that surround identification and return of incidental findings (uncertainty of disease onset, disease severity, age of onset, clinical actionability, and personal utility), and suggest that interpretation of incidental findings in pediatric patients can be difficult given evolving phenotypes. Furthermore, return of incidental findings can benefit patients and providers, but do present challenges. CONCLUSIONS: While there may be considerable benefit to return of incidental genetic findings, these findings can be burdensome to providers and present risk to patients. It is important that laboratories conducting genomic testing establish internal guidelines in anticipation of detection. Moreover, cross-laboratory guidelines may aid in reducing the potential for policy heterogeneity across laboratories as it relates to incidental finding detection and return. However, future discussion is required to determine whether cohesive guidelines or policy statements are warranted.

The uptake and utility of genetic testing and genetic counseling for hypertrophic cardiomyopathy-A systematic review and meta-analysis.

Genetic testing and genetic counseling are routinely indicated for patients with hypertrophic cardiomyopathy (HCM); however, the uptake and utility of these services is not entirely understood. This systematic review and meta-analysis summarizes the uptake and utility of genetic counseling and genetic testing for patients with HCM and their at-risk family members, as well as the impact of genetic counseling/testing on patient-reported outcomes (PROs). A systematic search was performed through March 12, 2021. Meta-analyses were performed whenever possible; other findings were qualitatively summarized. Forty-eight studies met inclusion criteria (47 observational, 1 randomized). Uptake of genetic testing in probands was 57% (95% confidence interval [CI]: 40, 73). Uptake of cascade screening for at-risk relatives were as follows: 61% for cascade genetic testing (95% CI: 45, 75), 58% for cardiac screening (e.g. echocardiography) (95% CI: 40, 73), and 69% for either/both approaches (95% CI: 43, 87). In addition, relatives of probands with a positive genetic test result were significantly more likely to undergo cascade screening compared to relatives of probands with a negative result (odds ratio = 3.17, 95% CI: 2.12, 4.76). Overall, uptake of genetic counseling in both probands and relatives ranged from 37% to 84%. Multiple studies found little difference in PROs between individuals receiving positive versus negative genetic test results; however, other studies found that individuals with positive genetic test results experienced worse psychological outcomes. Genetic testing may also inform life choices, particularly decisions related to reproduction and insurance. Genetic counseling was associated with high satisfaction, increased perceived personal control and empowerment, and decreased anxiety. Approximately half to three-quarters of patients with HCM and their relatives undergo genetic testing or cascade screening. PROs after genetic testing varied and genetic counseling was associated with high satisfaction and improved PROs.

Observational study of population genomic screening for variants associated with endocrine tumor syndromes in a large, healthcare-based cohort.

BACKGROUND: In current care, patients' personal and self-reported family histories are primarily used to determine whether genetic testing for hereditary endocrine tumor syndromes (ETS) is indicated. Population genomic screening for other conditions has increased ascertainment of individuals with pathogenic/likely pathogenic (P/LP) variants, leading to improved management and earlier diagnoses. It is unknown whether such benefits occur when screening broader populations for P/LP ETS variants. This manuscript assesses clinical utility outcomes of a large, unselected, healthcare-based genomic screening program by describing personal and family history of syndrome-related features, risk management behaviors after result disclosure, and rates of relevant post-disclosure diagnoses in patient-participants with P/LP ETS variants. METHODS: Observational study of individuals informed of a P/LP variant in MEN1, RET, SDHAF2, SDHB, SDHC, SDHD, or VHL through Geisinger's MyCode Community Health Initiative between June 2016 and October 2019. Electronic health records (EHRs) of participants were evaluated for a report of pre-disclosure personal and self-reported family histories and post-disclosure risk management and diagnoses. RESULTS: P/LP variants in genes of interest were identified in 199 of 130,490 (1 in 656) adult Geisinger MyCode patient-participants, 80 of which were disclosed during the study period. Eighty-one percent (n = 65) did not have prior evidence of the result in their EHR and, because they were identified via MyCode, were included in further analyses. Five participants identified via MyCode (8%) had a personal history of syndrome-related features; 16 (25%) had a positive self-reported family history. Time from result disclosure to EHR review was a median of 0.7 years. Post-disclosure, 36 (55.4%) completed a recommended risk management behavior; 11 (17%) were diagnosed with a syndrome-related neoplasm after completing a risk management intervention. CONCLUSIONS: Broader screening for pathogenic/likely pathogenic variants associated with endocrine tumor syndromes enables detection of at-risk individuals, leads to the uptake of risk management, and facilitates relevant diagnoses. Further research will be necessary to continue to determine the clinical utility of screening diverse, unselected populations for such variants.

Loss-of-Function FLNC Variants Are Associated With Arrhythmogenic Cardiomyopathy Phenotypes When Identified Through Exome Sequencing of a General Clinical Population.

BACKGROUND: The FLNC gene has recently garnered attention as a likely cause of arrhythmogenic cardiomyopathy, which is considered an actionable genetic condition. However, the association with disease in an unselected clinical population is unknown. We hypothesized that individuals with loss-of-function variants in FLNC (FLNCLOF) would have increased odds for arrhythmogenic cardiomyopathy-associated phenotypes versus variant-negative controls in the Geisinger MyCode cohort. METHODS: We identified rare, putative FLNCLOF among 171 948 individuals with exome sequencing linked to health records. Associations with arrhythmogenic cardiomyopathy phenotypes from available diagnoses and cardiac evaluations were investigated. RESULTS: Sixty individuals (0.03%; median age 58 years [47-70 interquartile range], 43% male) harbored 27 unique FLNCLOF. These individuals had significantly increased odds ratios for dilated cardiomyopathy (odds ratio, 4.9 [95% CI, 2.6-7.6]; P<0.001), supraventricular tachycardia (odds ratio, 3.2 [95% CI, 1.1-5.6]; P=0.048), and left-dominant arrhythmogenic cardiomyopathy (odds ratio, 4.2 [95% CI, 1.4-7.9]; P=0.03). Echocardiography revealed reduced left ventricular ejection fraction (52±13% versus 57±9%; P=0.001) associated with FLNCLOF. Overall, at least 9% of FLNCLOF patients demonstrated evidence of penetrant disease. CONCLUSIONS: FLNCLOF variants are associated with increased odds of ventricular arrhythmia and dysfunction in an unselected clinical population. These findings support genomic screening of FLNC for actionable secondary findings.

Diagnostic validity and clinical utility of genetic testing for hypertrophic cardiomyopathy: a systematic review and meta-analysis.

OBJECTIVE: This study summarises the diagnostic validity and clinical utility of genetic testing for patients with hypertrophic cardiomyopathy (HCM) and their at-risk relatives. METHODS: A systematic search was performed in PubMed (MEDLINE), Embase, CINAHL and Cochrane Central Library databases from inception through 2 March 2020. Subgroup and sensitivity analyses were prespecified for individual sarcomere genes, presence/absence of pathogenic variants, paediatric and adult cohorts, family history, inclusion of probands, and variant classification method. Study quality was assessed using the Newcastle-Ottawa tool. RESULTS: A total of 132 articles met inclusion criteria. The detection rate based on pathogenic and likely pathogenic variants was significantly higher in paediatric cohorts compared with adults (56% vs 42%; p=0.01) and in adults with a family history compared with sporadic cases (59% vs 33%; p=0.005). When studies applied current, improved, variant interpretation standards, the adult detection rate significantly decreased from 42% to 33% (p=0.0001) because less variants met criteria to be considered pathogenic. The mean difference in age-of-onset in adults was significantly earlier for genotype-positive versus genotype-negative cohorts (8.3 years; p<0.0001), MYH7 versus MYBPC3 cohorts (8.2 years; p<0.0001) and individuals with multiple versus single variants (7.0 years; p<0.0002). Overall, disease penetrance in adult cohorts was 62%, but differed significantly depending on if probands were included or excluded (73% vs 55%; p=0.003). CONCLUSIONS: This systematic review and meta-analysis is the first, to our knowledge, to collectively quantify historical understandings of detection rate, genotype-phenotype associations and disease penetrance for HCM, while providing the answers to important routine clinical questions and highlighting key areas for future study.

Activating RAC1 variants in the switch II region cause a developmental syndrome and alter neuronal morphology.

RAC1 is a highly conserved Rho GTPase critical for many cellular and developmental processes. De novo missense RAC1 variants cause a highly variable neurodevelopmental disorder. Some of these variants have previously been shown to have a dominant negative effect. Most previously reported patients with this disorder have either severe microcephaly or severe macrocephaly. Here, we describe eight patients with pathogenic missense RAC1 variants affecting residues between Q61 and R68 within the switch II region of RAC1. These patients display variable combinations of developmental delay, intellectual disability, brain anomalies such as polymicrogyria and cardiovascular defects with normocephaly or relatively milder micro- or macrocephaly. Pulldown assays, NIH3T3 fibroblast spreading assays and staining for activated PAK1/2/3 and WAVE2 suggest that these variants increase RAC1 activity and over-activate downstream signalling targets. Axons of neurons isolated from Drosophila embryos expressing the most common of the activating variants are significantly shorter, with an increased density of filopodial protrusions. In vivo, these embryos exhibit frequent defects in axonal organization. Class IV dendritic arborization neurons expressing this variant exhibit a significant reduction in the total area of the dendritic arbour, increased branching and failure of self-avoidance. RNAi knock down of the WAVE regulatory complex component Cyfip significantly rescues these morphological defects. These results establish that activating substitutions affecting residues Q61-R68 within the switch II region of RAC1 cause a developmental syndrome. Our findings reveal that these variants cause altered downstream signalling, resulting in abnormal neuronal morphology and reveal the WAVE regulatory complex/Arp2/3 pathway as a possible therapeutic target for activating RAC1 variants. These insights also have the potential to inform the mechanism and therapy for other disorders caused by variants in genes encoding other Rho GTPases, their regulators and downstream effectors.

The Role of a Statewide Critical Care Coordination Center in the Coronavirus Disease 2019 Pandemic-and Beyond.

OBJECTIVE: Public health emergencies, like the coronavirus disease 2019 pandemic, can cause unprecedented demand for critical care services. We describe statewide implementation of a critical care coordination center designed to optimize ICU utilization. To describe a centralized critical care coordination center designed to ensure appropriate intensive care resource allocation. DESIGN: A descriptive case series of consecutive critically ill adult patients. SETTING: ICUs, emergency departments, freestanding medical facilities in the state of Maryland and adjacent states, serving a population of over 6,045,000 across a land area of 9,776 sq mi (25,314 km2). PATIENTS: Adults requiring intensive care. INTERVENTIONS: Consultation with a critical care physician and emergency medical services clinician. MEASUREMENTS AND MAIN RESULTS: Number of consults, number of patient movements to higher levels of critical care, and number of extracorporeal membrane oxygenation referrals for both patients with and without coronavirus disease 2019. Over a 6-month period, critical care coordination center provided 1,006 critical care consultations and directed 578 patient transfers for 58 hospitals in the state of Maryland and adjoining region. Extracorporeal membrane oxygenation referrals were requested for 58 patients. Four-hundred twenty-eight patients (42.5%) were managed with consultation only and did not require transfer. CONCLUSIONS: Critical care coordination center, staffed 24/7 by a critical care physician and emergency medical service clinician, may improve critical care resource use and patient flow. This serves as a model for a tiered regionalized system to ensure that the demand for critical care services may be met during a pandemic and beyond.

Genomic Screening for Pathogenic Transthyretin Variants Finds Evidence of Underdiagnosed Amyloid Cardiomyopathy From Health Records.

BACKGROUND: New treatments for transthyretin amyloidosis improve survival, but diagnosis remains challenging. Pathogenic or likely pathogenic (P/LP) variants in the transthyretin (TTR) gene are one cause of transthyretin amyloidosis, and genomic screening has been proposed to identify at-risk individuals. However, data on disease features and penetrance are lacking to inform the utility of such population-based genomic screening for TTR. OBJECTIVES: This study characterized the prevalence of P/LP variants in TTR identified through exome sequencing and the burden of associated disease from electronic health records for individuals with these variants from a large (N = 134,753), primarily European-ancestry cohort. METHODS: We compared frequencies of common disease features and cardiac imaging findings between individuals with and without P/LP TTR variants. RESULTS: We identified 157 of 134,753 (0.12%) individuals with P/LP TTR variants (43% male, median age 52 [Q1-Q3: 37-61] years). Seven P/LP variants accounted for all observations, the majority being V122I (p.V142I; 113, 0.08%). Approximately 60% (n = 91) of individuals with P/LP TTR variants (all V122I) had African ancestry. Diagnoses of amyloidosis were limited (2 of 157 patients), although related heart disease diagnoses, including cardiomyopathy and heart failure, were significantly increased in individuals with P/LP TTR variants who were aged >60 years. Fourteen percent (7 of 49) of individuals aged ≥60 or older with a P/LP TTR variant had heart disease and ventricular septal thickness >1.2 cm, only one of whom was diagnosed with amyloidosis. CONCLUSIONS: Individuals with P/LP TTR variants identified by genomic screening have increased odds of heart disease after age 60 years, although amyloidosis is likely underdiagnosed without knowledge of the genetic variant.