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PURPOSE: Mendelian disease genomic research has undergone a massive transformation over the past decade. With increasing availability of exome and genome sequencing, the role of Mendelian research has expanded beyond data collection, sequencing, and analysis to worldwide data sharing and collaboration. METHODS: Over the past 10 years, the National Institutes of Health–supported Centers for Mendelian Genomics (CMGs) have played a major role in this research and clinical evolution. RESULTS: We highlight the cumulative gene discoveries facilitated by the program, biomedical research leveraged by the approach, and the larger impact on the research community. Beyond generating a list of gene-phenotype relationships and participating in widespread data sharing, the CMGs have created resources, tools, and training for the larger community to foster understanding of genes and genome variation. The CMGs have participated in a wide range of data sharing activities, including deposition of all eligible CMG data into the Analysis, Visualization, and Informatics Lab-space (AnVIL), sharing candidate genes through the Matchmaker Exchange and the CMG website, and sharing variants in Genotypes to Mendelian Phenotypes (Geno2MP) and VariantMatcher. CONCLUSION: The work is far from complete; strengthening communication between research and clinical realms, continued development and sharing of knowledge and tools, and improving access to richly characterized data sets are all required to diagnose the remaining molecularly undiagnosed patients.

BACKGROUND: Wolff-Parkinson-White (WPW) syndrome is a relatively common arrhythmia affecting ~1-3/1000 individuals. Mutations in PRKAG2 have been described in rare patients in association with cardiomyopathy. However, the genetic basis of WPW in individuals with a structurally normal heart remains poorly understood. Sudden death due to atrial fibrillation (AF) can also occur in these individuals. Several studies have indicated that despite ablation of an accessory pathway, the risk of AF remains high in patients compared to general population. METHODS: We applied exome sequencing in 305 subjects, including 65 trios, 80 singletons, and 6 multiple affected families. We used de novo analysis, candidate gene approach, and burden testing to explore the genetic contributions to WPW. RESULTS: A heterozygous deleterious variant in PRKAG2 was identified in one subject, accounting for 0.6% (1/151) of the genetic basis of WPW in this study. Another individual with WPW and left ventricular hypertrophy carried a known pathogenic variant in MYH7. We found rare de novo variants in genes associated with arrhythmia and cardiomyopathy (ANK2, NEBL, PITX2, and PRDM16) in this cohort. There was an increased burden of rare deleterious variants (MAF

Maternal diabetes is a known teratogen that can cause a wide spectrum of birth defects, collectively referred to as diabetic embryopathy (DE). However, the pathogenic mechanisms underlying DE remain uncertain and there are no definitive tests to establish the diagnosis. Here, we explore the potential of DNA methylation as a diagnostic biomarker for DE and to inform disease pathogenesis. Bisulfite sequencing was used to identify gene regions with differential methylation between DE neonates and healthy infants born with or without prenatal exposure to maternal diabetes, and to investigate the role of allele-specific methylation at implicated sites. We identified a methylation signature consisting of 237 differentially methylated loci that distinguished infants with DE from control infants. These loci were found proximal to genes associated with Mendelian syndromes that overlap the DE phenotype (e.g., CACNA1C, TRIO, ANKRD11) or genes known to influence embryonic development (e.g., BRAX1, RASA3). Further, we identified allele-specific methylation (ASM) at 11 of these loci, within which 61.5% of ASM single-nucleotide variants are known expression quantitative trait loci (eQTLs). Our study suggests a role for aberrant DNA methylation and cis-sequence variation in the pathogenesis of DE and highlights the diagnostic potential of DNA methylation for teratogenic birth defects.

In 2016, guidelines for diagnostic Next Generation Sequencing (NGS) have been published by EuroGentest in order to assist laboratories in the implementation and accreditation of NGS in a diagnostic setting. These guidelines mainly focused on Whole Exome Sequencing (WES) and targeted (gene panels) sequencing detecting small germline variants (Single Nucleotide Variants (SNVs) and insertions/deletions (indels)). Since then, Whole Genome Sequencing (WGS) has been increasingly introduced in the diagnosis of rare diseases as WGS allows the simultaneous detection of SNVs, Structural Variants (SVs) and other types of variants such as repeat expansions. The use of WGS in diagnostics warrants the re-evaluation and update of previously published guidelines. This work was jointly initiated by EuroGentest and the Horizon2020 project Solve-RD. Statements from the 2016 guidelines have been reviewed in the context of WGS and updated where necessary. The aim of these recommendations is primarily to list the points to consider for clinical (laboratory) geneticists, bioinformaticians, and (non-)geneticists, to provide technical advice, aid clinical decision-making and the reporting of the results. This work was supported by the Solve-RD project (European Union’s Horizon 2020 grant agreement No 779257) to MS, SB, OR and CG, and the National Centre for medical genomics (www.ncmg.cz, CZ.02.1.01/0.0/0.0/16_026/000844, LM2018132 (MSMT.cz) and 00064203/6003 (MZCR.cz) to MM). OR received financial support from Illumina for implementing whole genome sequencing into clinical diagnostics (Ge-Med project)

Whole genome sequencing (WGS) shows promise as a first-tier diagnostic test for patients with rare genetic disorders. However, standards addressing the definition and deployment practice of a best-in-class test are lacking. To address these gaps, the Medical Genome Initiative, a consortium of leading health care and research organizations in the US and Canada, was formed to expand access to high quality clinical WGS by convening experts and publishing best practices. Here, we present best practice recommendations for the interpretation and reporting of clinical diagnostic WGS, including discussion of challenges and emerging approaches that will be critical to harness the full potential of this comprehensive test.

To identify the economic impact of pediatric patients with clinical indications of genetic disease (GD) on the US health-care system. Using the 2012 Kids’ Inpatient Database, we identified pediatric inpatient discharges with International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes linked to genetic disease, including well-established genetic disorders, neurological diseases, birth defects, and other physiological or functional abnormalities with a genetic basis. Cohort characteristics and health-care utilization measures were analyzed. Discharges with a GD-associated primary diagnosis were used to estimate the minimum burden; discharges with GD-associated primary or secondary codes established the maximum burden. Of 5.85 million weighted discharges, 2.6–14% included GD-associated ICD-9-CM codes. For these discharges, mean total costs were $16,000–77,000 higher (P

Purpose Current diagnostic testing for genetic disorders involves serial use of specialized assays spanning multiple technologies. In principle, genome sequencing (GS) can detect all genomic pathogenic variant types on a single platform. Here we evaluate copy-number variant (CNV) calling as part of a clinically accredited GS test. Methods We performed analytical validation of CNV calling on 17 reference samples, compared the sensitivity of GS-based variants with those from a clinical microarray, and set a bound on precision using orthogonal technologies. We developed a protocol for family-based analysis of GS-based CNV calls, and deployed this across a clinical cohort of 79 rare and undiagnosed cases. Results We found that CNV calls from GS are at least as sensitive as those from microarrays, while only creating a modest increase in the number of variants interpreted (~10 CNVs per case). We identified clinically significant CNVs in 15% of the first 79 cases analyzed, all of which were confirmed by an orthogonal approach. The pipeline also enabled discovery of a uniparental disomy (UPD) and a 50% mosaic trisomy 14. Directed analysis of select CNVs enabled breakpoint level resolution of genomic rearrangements and phasing of de novo CNVs. Conclusion Robust identification of CNVs by GS is possible within a clinical testing environment.

Background Intrachromosomal triplications (TRP) can contribute to disease etiology via gene dosage effects, gene disruption, position effects, or fusion gene formation. Recently, post-zygotic de novo triplications adjacent to copy-number neutral genomic intervals with runs of homozygosity (ROH) have been shown to result in uniparental isodisomy (UPD). The genomic structure of these complex genomic rearrangements (CGRs) shows a consistent pattern of an inverted triplication flanked by duplications (DUP-TRP/INV-DUP) formed by an iterative DNA replisome template-switching mechanism during replicative repair of a single-ended, double-stranded DNA (seDNA), the ROH results from an interhomolog or nonsister chromatid template switch. It has been postulated that these CGRs may lead to genetic abnormalities in carriers due to dosage-sensitive genes mapping within the copy-number variant regions, homozygosity for alleles at a locus causing an autosomal recessive (AR) disease trait within the ROH region, or imprinting-associated diseases. Methods Here, we report a family wherein the affected subject carries a de novo 2.2-Mb TRP followed by 42.2 Mb of ROH and manifests clinical features overlapping with those observed in association with chromosome 14 maternal UPD (UPD(14)mat). UPD(14)mat can cause clinical phenotypic features enabling a diagnosis of Temple syndrome. This CGR was then molecularly characterized by high-density custom aCGH, genome-wide single-nucleotide polymorphism (SNP) and methylation arrays, exome sequencing (ES), and the Oxford Nanopore long-read sequencing technology. Results We confirmed the postulated DUP-TRP/INV-DUP structure by multiple orthogonal genomic technologies in the proband. The methylation status of known differentially methylated regions (DMRs) on chromosome 14 revealed that the subject shows the typical methylation pattern of UPD(14)mat. Consistent with these molecular findings, the clinical features overlap with those observed in Temple syndrome, including speech delay. Conclusions These data provide experimental evidence that, in humans, triplication can lead to segmental UPD and imprinting disease. Importantly, genotype/phenotype analyses further reveal how a post-zygotically generated complex structural variant, resulting from a replication-based mutational mechanism, contributes to expanding the clinical phenotype of known genetic syndromes. Mechanistically, such events can distort transmission genetics resulting in homozygosity at a locus for which only one parent is a carrier as well as cause imprinting diseases. Electronic supplementary material The online version of this article (10.1186/s13073-019-0633-y) contains supplementary material, which is available to authorized users.

Genetic alterations leading to overactivation of mammalian target of rapamycin (mTOR) signaling result in brain overgrowth syndromes such as focal cortical dysplasia (FCD) and megalencephaly. Megalencephaly with cutis tri-color of the Blaschko-linear type pigmentary mosaicism and intellectual disability is a rare neurodevelopmental disorder attributed to the recurrent mosaic c.5930C > T (p.Thr1977Ile) MTOR variant. This variant was previously reported at low to intermediate levels of mosaicism in the peripheral blood of three unrelated individuals with consistent clinical findings. We report a fourth case of a 3-year-old female presenting with megalencephaly, obstructive hydrocephalus due to cerebral aqueductal stenosis, asymmetric polymicrogyria, dysgenesis of the corpus callosum, hypotonia, developmental delay, and cutaneous pigmentary mosaicism. Oligonucleotide and SNP chromosomal microarray (CMA), karyotype, and trio whole exome sequencing (WES) in the peripheral blood, as well as a targeted gene variant panel from fibroblasts derived from hyperpigmented and non-hyperpigmented skin did not detect any abnormalities in MTOR or other genes associated with brain overgrowth syndromes. Unlike the previously reported cases, the de novo c.5930C > T (p.Thr1977Ile) MTOR variant was detected at 32% mosaicism in our patient only after WES was performed on fibroblast-derived DNA from the hyperpigmented skin. This case demonstrates the tissue variability in mosaic expression of the recurrent p.Thr1977Ile MTOR variant, emphasizes the need for skin biopsies in the genetic evaluation of patients with skin pigmentary mosaicism, and expands the clinical phenotype associated with this pathogenic MTOR variant.

Whole-genome sequencing (WGS) is positioned to become one of the most robust strategies for achieving timely diagnosis of rare genomic diseases. Despite its favorable diagnostic performance compared to conventional testing strategies, routine use and reimbursement of WGS are hampered by inconsistencies in the definition and measurement of clinical utility. For example, what constitutes clinical utility for WGS varies by stakeholder’s perspective (physicians, patients, families, insurance companies, health-care organizations, and society), clinical context (prenatal, pediatric, critical care, adult medicine), and test purpose (diagnosis, screening, treatment selection). A rapidly evolving technology landscape and challenges associated with robust comparative study design in the context of rare disease further impede progress in this area of empiric research. To address this challenge, an expert working group of the Medical Genome Initiative was formed. Following a consensus-based process, we align with a broad definition of clinical utility and propose a conceptually-grounded and empirically-guided measurement toolkit focused on four domains of utility: diagnostic thinking efficacy, therapeutic efficacy, patient outcome efficacy, and societal efficacy. For each domain of utility, we offer specific indicators and measurement strategies. While we focus on diagnostic applications of WGS for rare germline diseases, this toolkit offers a flexible framework for best practices around measuring clinical utility for a range of WGS applications. While we expect this toolkit to evolve over time, it provides a resource for laboratories, clinicians, and researchers looking to characterize the value of WGS beyond the laboratory.

Congenital Heart Disease (CHD) affects approximately 7-9 children per 1000 live births. Numerous genetic studies have established a role for rare genomic variants at the copy number variation (CNV) and single nucleotide variant level. In particular, the role of de novo mutations (DNM) has been highlighted in syndromic and non-syndromic CHD. To identify novel haploinsufficient CHD disease genes we performed an integrative analysis of CNVs and DNMs identified in probands with CHD including cases with sporadic thoracic aortic aneurysm (TAA). We assembled CNV data from 7,958 cases and 14,082 controls and performed a gene-wise analysis of the burden of rare genomic deletions in cases versus controls. In addition, we performed mutation rate testing for DNMs identified in 2,489 parent-offspring trios. Our combined analysis revealed 21 genes which were significantly affected by rare genomic deletions and/or constrained non-synonymous de novo mutations in probands. Fourteen of these genes have previously been associated with CHD while the remaining genes (FEZ1, MYO16, ARID1B, NALCN, WAC, KDM5B and WHSC1) have only been associated in singletons and small cases series, or show new associations with CHD. In addition, a systems level analysis revealed shared contribution of CNV deletions and DNMs in CHD probands, affecting protein-protein interaction networks involved in Notch signaling pathway, heart morphogenesis, DNA repair and cilia/centrosome function. Taken together, this approach highlights the importance of re-analyzing existing datasets to strengthen disease association and identify novel disease genes.

BACKGROUND Treatment characteristics such as cranial radiation therapy (CRT) do not fully explain adiposity risk in childhood acute lymphoblastic leukemia (ALL) survivors. This study was aimed at characterizing genetic variation related to adult body mass index (BMI) among survivors of childhood ALL. METHODS Genetic associations of BMI among 1458 adult survivors of childhood ALL (median time from diagnosis, 20 years) were analyzed by multiple approaches. A 2-stage genome-wide association study in the Childhood Cancer Survivor Study (CCSS) and the St. Jude Lifetime Cohort Study (SJLIFE) was performed. BMI was a highly polygenic trait in the general population. Within the known loci, the BMI percent variance explained was estimated, and additive interactions (chi-square test) with CRT in the CCSS were evaluated. The role of DNA methylation in CRT interaction was further evaluated in a subsample of ALL survivors. RESULTS In a meta-analysis of the CCSS and SJLIFE, 2 novel loci associated with adult BMI among survivors of childhood ALL (LINC00856 rs575792008 and EMR1 rs62123082; PMeta < 5E-8) were identified. It was estimated that the more than 700 known loci explained 6.2% of the variation in adult BMI in childhood ALL survivors. Within the known loci, significant main effects for 23 loci and statistical interactions with CRT at 9 loci (P < 7.0E-5) were further identified. At 2 CRT-interacting loci, DNA methylation patterns may have differed by age. CONCLUSIONS Adult survivors of childhood ALL have genetic heritability for BMI similar to that observed in the general population. This study provides evidence that treatment with CRT can modify the effect of genetic variants on adult BMI in childhood ALL survivors.

Whole-genome sequencing (WGS) has shown promise in becoming a first-tier diagnostic test for patients with rare genetic disorders; however, standards addressing the definition and deployment practice of a best-in-class test are lacking. To address these gaps, the Medical Genome Initiative, a consortium of leading healthcare and research organizations in the US and Canada, was formed to expand access to high-quality clinical WGS by publishing best practices. Here, we present consensus recommendations on clinical WGS analytical validation for the diagnosis of individuals with suspected germline disease with a focus on test development, upfront considerations for test design, test validation practices, and metrics to monitor test performance. This work also provides insight into the current state of WGS testing at each member institution, including the utilization of reference and other standards across sites. Importantly, members of this initiative strongly believe that clinical WGS is an appropriate first-tier test for patients with rare genetic disorders, and at minimum is ready to replace chromosomal microarray analysis and whole-exome sequencing. The recommendations presented here should reduce the burden on laboratories introducing WGS into clinical practice, and support safe and effective WGS testing for diagnosis of germline disease.

To estimate the cost-effectiveness of genome sequencing (GS) for diagnosing critically ill infants and noncritically ill pediatric patients (children) with suspected rare genetic diseases from a United States health sector perspective.A decision-analytic model was developed to simulate the diagnostic trajectory of patients. Parameter estimates were derived from a targeted literature review and meta-analysis. The model simulated clinical and economic outcomes associated with 3 diagnostic pathways: (1) standard diagnostic care, (2) GS, and (3) standard diagnostic care followed by GS.For children, costs of GS ($7284) were similar to that of standard care ($7355) and lower than that of standard care followed by GS pathways ($12,030). In critically ill infants, when cost estimates were based on the length of stay in the neonatal intensive care unit, the lowest cost pathway was GS ($209,472). When only diagnostic test costs were included, the cost per diagnosis was $17,940 for standard, $17,019 for GS, and $20,255 for standard care followed by GS.The results of this economic model suggest that GS may be cost neutral or possibly cost saving as a first line diagnostic tool for children and critically ill infants.

De novo variants in DDX3X account for 1-3% of unexplained intellectual disability (ID) cases and are amongst the most common causes of ID especially in females. Forty-seven patients (44 females, 3 males) have been described. We identified 31 additional individuals carrying 29 unique DDX3X variants, including 30 postnatal individuals with complex clinical presentations of developmental delay or ID, and one fetus with abnormal ultrasound findings. Rare or novel phenotypes observed include respiratory problems, congenital heart disease, skeletal muscle mitochondrial DNA depletion, and late-onset neurologic decline. Our findings expand the spectrum of DNA variants and phenotypes associated with DDX3X disorders.

Importance Whole-genome sequencing (WGS) shows promise as a first-line genetic test for acutely ill infants, but widespread adoption and implementation requires evidence of an effect on clinical management. Objective To determine the effect of WGS on clinical management in a racially and ethnically diverse and geographically distributed population of acutely ill infants in the US. Design, setting, and participants This randomized, time-delayed clinical trial enrolled participants from September 11, 2017, to April 30, 2019, with an observation period extending to July 2, 2019. The study was conducted at 5 US academic medical centers and affiliated children's hospitals. Participants included infants aged between 0 and 120 days who were admitted to an intensive care unit with a suspected genetic disease. Data were analyzed from January 14 to August 20, 2020. Interventions Patients were randomized to receive clinical WGS results 15 days (early) or 60 days (delayed) after enrollment, with the observation period extending to 90 days. Usual care was continued throughout the study. Main outcomes and measures The main outcome was the difference in the proportion of infants in the early and delayed groups who received a change of management (COM) 60 days after enrollment. Additional outcome measures included WGS diagnostic efficacy, within-group COM at 90 days, length of hospital stay, and mortality. Results A total of 354 infants were randomized to the early (n = 176) or delayed (n = 178) arms. The mean participant age was 15 days (IQR, 7-32 days); 201 participants (56.8%) were boys; 19 (5.4%) were Asian; 47 (13.3%) were Black; 250 (70.6%) were White; and 38 (10.7%) were of other race. At 60 days, twice as many infants in the early group vs the delayed group received a COM (34 of 161 [21.1%; 95% CI, 15.1%-28.2%] vs 17 of 165 [10.3%; 95% CI, 6.1%-16.0%]; P = .009; odds ratio, 2.3; 95% CI, 1.22-4.32) and a molecular diagnosis (55 of 176 [31.0%; 95% CI, 24.5%-38.7%] vs 27 of 178 [15.0%; 95% CI, 10.2%-21.3%]; P Conclusions and relevance In this randomized clinical trial, for acutely ill infants in an intensive care unit, introduction of WGS was associated with a significant increase in focused clinical management compared with usual care. Access to first-line WGS may reduce health care disparities by enabling diagnostic equity. These data support WGS adoption and implementation in this population. Trail registration ClinicalTrials.gov Identifier: NCT03290469.

To the editor: Langerhans cell histiocytosis (LCH) is a hematologic disorder that presents with a wide spectrum of symptoms, ranging from focal lesions to potentially lethal multiorgan disease, affecting 4 to 8 per million children per year[1][1] and 1 to 2 per million adults per year.[2][2]

Background Left-sided lesions (LSLs) account for an important fraction of severe congenital cardiovascular malformations (CVMs). The genetic contributions to LSLs are complex, and the mutations that cause these malformations span several diverse biological signaling pathways: TGFB, NOTCH, SHH, and more. Here, we use whole exome sequence data generated in 342 LSL cases to identify likely damaging variants in putative candidate CVM genes. Methods Using a series of bioinformatics filters, we focused on genes harboring population-rare, putative loss-of-function (LOF), and predicted damaging variants in 1760 CVM candidate genes constructed a priori from the literature and model organism databases. Gene variants that were not observed in a comparably sequenced control dataset of 5492 samples without severe CVM were then subjected to targeted validation in cases and parents. Whole exome sequencing data from 4593 individuals referred for clinical sequencing were used to bolster evidence for the role of candidate genes in CVMs and LSLs. Results Our analyses revealed 28 candidate variants in 27 genes, including 17 genes not previously associated with a human CVM disorder, and revealed diverse patterns of inheritance among LOF carriers, including 9 confirmed de novo variants in both novel and newly described human CVM candidate genes (ACVR1, JARID2, NR2F2, PLRG1, SMURF1) as well as established syndromic CVM genes (KMT2D, NF1, TBX20, ZEB2). We also identified two genes (DNAH5, OFD1) with evidence of recessive and hemizygous inheritance patterns, respectively. Within our clinical cohort, we also observed heterozygous LOF variants in JARID2 and SMAD1 in individuals with cardiac phenotypes, and collectively, carriers of LOF variants in our candidate genes had a four times higher odds of having CVM (odds ratio = 4.0, 95% confidence interval 2.5–6.5). Conclusions Our analytical strategy highlights the utility of bioinformatic resources, including human disease records and model organism phenotyping, in novel gene discovery for rare human disease. The results underscore the extensive genetic heterogeneity underlying non-syndromic LSLs, and posit potential novel candidate genes and complex modes of inheritance in this important group of birth defects. Electronic supplementary material The online version of this article (doi:10.1186/s13073-017-0482-5) contains supplementary material, which is available to authorized users.

Vascular Ehlers Danlos syndrome (vEDS) is an uncommon genetic disorders characterized by arterial aneurysm, dissection and rupture, bowel rupture, and rupture of the gravid uterus. The frequency is estimated as 1/50,000-1/200,000 and results from pathogenic variants in COL3A1, which encodes the chains of type III procollagen, a major protein in vessel walls and hollow organs. Initial diagnosis depends on the recognitions of clinical features, including family history. Management is complex and requires multiple specialists who can respond to and manage the major complications. A summary of recommendations for management include: Identify causative variants in COL3A1 prior to application of diagnosis, modulate life style to minimize injury, risk of vessel/organ rupture, identify and create care team, provide individual plans for emergency care ("vascular EDS passport") with diagnosis and management plan for use when traveling, centralize management at centers of excellence (experience) when feasible, maintain blood pressure in the normal range and treat hypertension aggressively, surveillance of vascular tree by doppler ultrasound, CTA (low radiation alternatives) or MRA if feasible on an annual basis. These recommendations represent a consensus of an international group of specialists with a broad aggregate experience in the care of individuals with vascular EDS that will need to be assessed on a regular basis as new information develops. © 2017 Wiley Periodicals, Inc.

The introduction of diagnostic clinical genome and exome sequencing (CGES) is changing the scope of practice for clinical geneticists. Many large institutions are making a significant investment in infrastructure and technology, allowing clinicians to access CGES, especially as health-care coverage begins to extend to clinically indicated genomic sequencing-based tests. Translating and realizing the comprehensive clinical benefits of genomic medicine remain a key challenge for the current and future care of patients. With the increasing application of CGES, it is necessary for geneticists and other health-care providers to understand its benefits and limitations in order to interpret the clinical relevance of genomic variants identified in the context of health and disease. New, collaborative working relationships with specialists across diverse disciplines (e.g., clinicians, laboratorians, bioinformaticians) will undoubtedly be key attributes of the future practice of clinical genetics and may serve as an example for other specialties in medicine. These new skills and relationships will also inform the development of the future model of clinical genetics training curricula. To address the evolving role of the clinical geneticist in the rapidly changing climate of genomic medicine, two Clinical Genetics Think Tank meetings were held that brought together physicians, laboratorians, scientists, genetic counselors, trainees, and patients with experience in clinical genetics, genetic diagnostics, and genetics education. This article provides recommendations that will guide the integration of genomics into clinical practice.Genet Med 18 11, 1075-1084.

The introduction of exome sequencing in the clinic has sparked tremendous optimism for the future of rare disease diagnosis, and there is exciting opportunity to further leverage these advances. To provide diagnostic clarity to all of these patients, however, there is a critical need for the field to develop and implement strategies to understand the mechanisms underlying all rare diseases and translate these to clinical care.

Up to 350 million people worldwide suffer from a rare disease, and while the individual diseases are rare, in aggregate they represent a substantial challenge to global health systems. The majority of rare disorders are genetic in origin, with children under the age of five disproportionately affected. As these conditions are difficult to identify clinically, genetic and genomic testing have become the backbone of diagnostic testing in this population. In the last 10 years, next-generation sequencing technologies have enabled testing of multiple disease genes simultaneously, ranging from targeted gene panels to exome sequencing (ES) and genome sequencing (GS). GS is quickly becoming a practical first-tier test, as cost decreases and performance improves. A growing number of studies demonstrate that GS can detect an unparalleled range of pathogenic abnormalities in a single laboratory workflow. GS has the potential to deliver unbiased, rapid and accurate molecular diagnoses to patients across diverse clinical indications and complex presentations. In this paper, we discuss clinical indications for testing and historical testing paradigms. Evidence supporting GS as a diagnostic tool is supported by superior genomic coverage, types of pathogenic variants detected, simpler laboratory workflow enabling shorter turnaround times, diagnostic and reanalysis yield, and impact on healthcare.

Patients with rare, undiagnosed, or genetic disease (RUGD) often undergo years of serial testing, commonly referred to as the “diagnostic odyssey”. Patients in resource-limited areas face even greater challenges—a definitive diagnosis may never be reached due to difficulties in gaining access to clinicians, appropriate specialists, and diagnostic testing. Here, we report on a collaboration of the Illumina iHope Program with the Foundation for the Children of the Californias and Hospital Infantil de Las Californias, to enable deployment of clinical whole genome sequencing (cWGS) as first-tier test in a resource-limited dysmorphology clinic in northern Mexico. A total of 60 probands who were followed for a suspected genetic diagnosis and clinically unresolved after expert examination were tested with cWGS, and the ordering clinicians completed a semi-structured survey to investigate change in clinical management resulting from cWGS findings. Clinically significant genomic findings were identified in 68.3% (n = 41) of probands. No recurrent molecular diagnoses were observed. Copy number variants or gross chromosomal abnormalities accounted for 48.8% (n = 20) of the diagnosed cases, including a mosaic trisomy and suspected derivative chromosomes. A qualitative assessment of clinical management revealed 48.8% (n = 20) of those diagnosed had a change in clinical course based on their cWGS results, despite resource limitations. These data suggest that a cWGS first-tier testing approach can benefit patients with suspected genetic disorders., Pediatrics: Philanthropic clinical whole-genome sequencing program helps children in Mexico Whole-genome sequencing (WGS) provides a valuable first-tier diagnostic test at pediatric clinics in resource-limited parts of the world, according to a study of children with suspected genetic disease treated in northern Mexico. A team led by Marilyn Jones from the Rady Children’s Hospital and Ryan Taft from Illumina Inc., both in San Diego, California, USA, describe a collaboration with a volunteer-led clinic in Tijuana, Mexico, where they offered genome sequencing for children with suspected genetic conditions—philanthropically through the iHope Program. Among the 60 families that participated, the clinical laboratory team identified genomic variants with diagnostic relevance in 41 (68%) cases. The genomic information contributed to changes in clinical management for 20 of these children, demonstrating the impact of WGS in places where patients generally don’t have access to medical specialists or other sophisticated molecular tests.

Because survivors of pediatric acute lymphoblastic leukemia (ALL) are more likely to be obese than unaffected contemporaries, we compared DNA methylation profiles between normal-weight and obese survivors at adiposity-associated CpG sites previously-reported by epigenome-wide association studies (EWAS) of body mass index (BMI) in the general population. We selected 96 ALL survivors from the Childhood Cancer Survivor Study (CCSS): 48 obese (BMI ≥30.0 kg/m(2)) and 48 normal weight (BMI = 18.5–24.9 kg/m(2)). The Illumina HumanMethylation450 BeadChip was used to compare DNA methylation at 211 loci identified in EWAS of BMI in the general population. The false discovery rate (FDR) was used to account for multiple testing. In exploratory analyses, we also tested for interaction between cranial radiotherapy (CRT) status and selected CpG sites to evaluate differences by CRT exposure. Thirty-nine loci were associated (FDR

Purpose: Brain malformations caused by 17p13.3 deletions include lissencephaly with deletions of the larger Miller-Dieker syndrome region or smaller deletions of only PAFAH1B1, white matter changes, and a distinct syndrome due to deletions including YWHAE and CRK but sparing PAFAH1B1. We sought to understand the significance of 17p13.3 deletions between the YWHAE/CRK and PAFAH1B1 loci. Methods: We analyzed the clinical features of six individuals from five families with 17p13.3 deletions between and not including YWHAE/CRK and PAFAH1B1 identified among individuals undergoing clinical chromosomal microarray testing or research genome sequencing. Results: Five individuals from four families have multi-focal white matter lesions while a sixth had a normal MRI. A combination of our individuals and a review of those in the literature with white matter changes and deletions in this chromosomal region narrows the overlapping region for this brain phenotype to ~345 kb, including 11 RefSeq genes, with RTN4RL1 haploinsufficiency as the best candidate for causing this phenotype. Conclusion: While previous literature has hypothesized dysmorphic features and white matter changes related to YWHAE, our cohort contributes evidence to the presence of additional genetic changes within 17p13.3 required for proper brain development.

Each year in the United States, thousands of cases of sudden and unexpected deaths of infants, children, and young adults are assigned an undetermined cause of death after postmortem investigation and autopsy. Heritable genetic variants have been suggested as the cause of up to a third of sudden death (SD) cases. Elucidation of the genetic variants involved in SD cases is important to not only help establish cause and manner of death of these individuals, but to also aid in determining whether familial genetic testing should be considered. Previously, these types of postmortem screenings have not been a feasible option for most county medical examiners’ and coroners’ offices. We sequenced full exons of 64 genes associated with SD in the largest known cohort (351) of infant and young SD decedents using massively parallel sequencing at 1 yr of age), were found to have a reportable genetic variant contributing to SD. These percentages represent an estimate lower than those previously reported. Overall yields and results likely vary between studies due to differences in evaluation techniques and reporting. Additionally, we recommend ongoing assessment of data, including nonreported novel variants, as technology and literature continually advance. This study demonstrates a strategy to implement molecular autopsies in medicolegal investigations of young SD decedents.

We aimed to characterize the lipidomic, metabolomic, and transcriptomic profiles in preterm piglets administered enteral (ENT) formula or three parenteral lipid emulsions [parenteral nutrition (PN)], Intralipid (IL), Omegaven (OV), or SMOFlipid (SL), for 14 days. Piglets in all parenteral lipid groups showed differential organ growth versus ENT piglets; whole body growth rate was lowest in IL piglets, yet there were no differences in either energy expenditure or C-13-palmitate oxidation. Plasma homeostatic model assessment of insulin resistance demonstrated insulin resistance in IL, but not OV or SL, compared with ENT. The fatty acid and acyl-CoA content of the liver, muscle, brain, and plasma fatty acids reflected the composition of the dietary lipids administered. Free carnitine and acylcarnitine (ACT) levels were markedly reduced in the PN groups compared with ENT piglets. Genes associated with oxidative stress and inflammation were increased, whereas those associated with alternative pathways of fatty acid oxidation were decreased in all PN groups. Our results show that new generation lipid emulsions directly enrich tissue fatty acids, especially in the brain, and lead to improved growth and insulin sensitivity compared with a soybean lipid emulsion. In all total PN groups, carnitine levels are limiting to the formation of ACTs and gene expression reflects the stress of excess lipid on liver function.

An experienced physician readily recognizes most common diseases, and the focus of clinical care is management, intervention, or cure. Rare disorders, on the other hand, present a qualitatively dif...

Maternal diabetes is a known teratogen that can cause a wide spectrum of birth defects, collectively referred to as diabetic embryopathy (DE). However, the pathogenic mechanisms underlying DE remain uncertain and there are no definitive tests to establish the diagnosis. Here, we explore the potential of DNA methylation as a diagnostic biomarker for DE and to inform disease pathogenesis.Bisulfite sequencing was used to identify gene regions with differential methylation between DE neonates and healthy infants born with or without prenatal exposure to maternal diabetes, and to investigate the role of allele-specific methylation at implicated sites.We identified a methylation signature consisting of 237 differentially methylated loci that distinguished infants with DE from control infants. These loci were found proximal to genes associated with Mendelian syndromes that overlap the DE phenotype (e.g., CACNA1C, TRIO, ANKRD11) or genes known to influence embryonic development (e.g., BRAX1, RASA3). Further, we identified allele-specific methylation (ASM) at 11 of these loci, within which 61.5% of ASM single-nucleotide variants are known expression quantitative trait loci (eQTLs).Our study suggests a role for aberrant DNA methylation and cis-sequence variation in the pathogenesis of DE and highlights the diagnostic potential of DNA methylation for teratogenic birth defects.

De novo variants in DDX3X account for 1–3% of unexplained intellectual disability (ID) cases and are amongst the most common causes of ID especially in females. Forty‐seven patients (44 females, 3 males) have been described. We identified 31 additional individuals carrying 29 unique DDX3X variants, including 30 postnatal individuals with complex clinical presentations of developmental delay or ID, and one fetus with abnormal ultrasound findings. Rare or novel phenotypes observed include respiratory problems, congenital heart disease, skeletal muscle mitochondrial DNA depletion, and late‐onset neurologic decline. Our findings expand the spectrum of DNA variants and phenotypes associated with DDX3X disorders.

PurposeBrain malformations are caused by 17p13.3 deletions: lissencephaly with deletions of the larger Miller-Dieker syndrome region or smaller deletions of only PAFAH1B1, as well as various abnormalities, including white matter changes, in the distinct syndrome due to deletions including YWHAE and CRK but sparing PAFAH1B1. We sought to understand the significance of 17p13.3 deletions between the YWHAE/CRK and PAFAH1B1 loci.MethodsWe analyzed the clinical features of five individuals from four families with 17p13.3 deletions between and not including YWHAE/CRK and PAFAH1B1 identified among individuals undergoing clinical chromosomal microarray testing.ResultsFour individuals from three families have multi-focal white matter lesions and hypermobile joints, while a fifth had a normal MRI. A combination of our patients and a review of those in the literature with white matter changes and deletions in this chromosomal region narrows the overlapping region for this brain phenotype to ∼345 kb, including 11 RefSeq genes, with RTN4RL1 haploinsufficiency as the best candidate for causing this.ConclusionWhile previous literature has hypothesized dysmorphic features and white matter changes related to YWHAE, our cohort contributes evidence to the presence of additional genes within 17p13.3 required for proper brain development.

De novo variants in DDX3X account for 1-3% of unexplained intellectual disability (ID), one of the most common causes of ID, in females. Forty-seven patients (44 females, 3 males) have been described. We identified 29 additional individuals carrying 27 unique DDX3X variants in the setting of complex clinical presentations including developmental delay or ID. In addition to previously reported manifestations, rare or novel phenotypes were identified including respiratory problems, congenital heart disease, skeletal muscle mitochondrial DNA depletion, and late-onset neurologic decline. Our findings expand the spectrum of DNA variants and phenotypes associated with DDX3X disorders.

Aberrant left-right patterning in the developing human embryo can lead to a broad spectrum of congenital malformations. The causes of most laterality defects are not known, with variants in established genes accounting for

PurposeCurrent diagnostic testing for genetic disorders involves serial use of specialized assays spanning multiple technologies. In principle, whole genome sequencing (WGS) has the potential to detect all genomic mutation types on a single platform and workflow. Here we sought to evaluate copy number variant (CNV) calling as part of a clinically accredited WGS test.MethodsUsing a depth-based copy number caller we performed analytical validation of CNV calling on a reference panel of 17 samples, compared the sensitivity of WGS-based variants to those from a clinical microarray, and set a bound on precision using orthogonal technologies. We developed a protocol for family-based analysis, annotation, filtering, visualization of WGS based CNV calls, and deployed this across a clinical cohort of 79 rare and undiagnosed cases.ResultsWe found that CNV calls from WGS are at least as sensitive as those from microarrays, while only creating a modest increase in the number of variants interpreted (~10 CNVs per case). We identified clinically significant CNVs in 15% of the first 79 cases analyzed. This pipeline also enabled identification of cases of uniparental disomy (UPD) and a 50% mosaic trisomy 14. Directed analysis of some CNVs enabled break-point level resolution of genomic rearrangements and phasing ofde-novoCNVs.ConclusionRobust identification of CNVs by WGS is possible within a clinical testing environment, and further developments will bring improvements in resolution of smaller and more complex CNVs.