Enhanced utility of family-centered diagnostic exome sequencing with inheritance model–based analysis: results from 500 unselected families with undiagnosed genetic conditions

PurposeDiagnostic exome sequencing was immediately successful in diagnosing patients in whom traditional technologies were uninformative. Herein, we provide the results from the first 500 probands referred to a clinical laboratory for diagnostic exome sequencing.MethodsFamily-based exome sequencing included whole-exome sequencing followed by family inheritance−based model filtering, comprehensive medical review, familial cosegregation analysis, and analysis of novel genes.ResultsA positive or likely positive result in a characterized gene was identified in 30% of patients (152/500). A novel gene finding was identified in 7.5% of patients (31/416). The highest diagnostic rates were observed among patients with ataxia, multiple congenital anomalies, and epilepsy (44, 36, and 35%, respectively). Twenty-three percent of positive findings were within genes characterized within the past 2 years. The diagnostic rate was significantly higher among families undergoing a trio (37%) as compared with a singleton (21%) whole-exome testing strategy.ConclusionOverall, we present results from the largest clinical cohort of diagnostic exome sequencing cases to date. These data demonstrate the utility of family-based exome sequencing and analysis to obtain the highest reported detection rate in an unselected clinical cohort, illustrating the utility of diagnostic exome sequencing as a transformative technology for the molecular diagnosis of genetic disease.Genet Med 17 7, 578–586.     

Improved diagnostics by exome sequencing following raw data reevaluation by clinical geneticists involved in the medical care of the individuals tested

PurposeReanalysis of exome sequencing data when results are negative may yield additional diagnoses. We sought to estimate the contribution of clinical geneticists to the interpretation of sequencing data of their patients.MethodsThe cohort included 84 probands attending a tertiary genetics institute (2015–2018) with a nondiagnostic result on clinical exome sequencing performed in one of five external laboratories. The raw data were uploaded to the Emedgene bioinformatics and interpretation platform for reanalysis by a team of two clinical geneticists, the geneticist directly involved in the patient’s care, and a bioinformatician.ResultsIn ten probands (11.9%), a new definitive diagnosis was reached based on genes that were known to be associated with the phenotype at the time the original report was issued. The main reasons for a negative exome result were incorrect interpretation of the clinical context and absence of OMIM entry. Pathogenic variants in genes with previously unknown gene–disease associations were discovered to be causative in three probands. In total, new diagnoses were established in 13/84 individuals (15.5%).ConclusionDirect access to complete clinical data and shortening of time to including gene–phenotype associations in databases can assist the analytics team and reduce the need for additional unnecessary tests.     

Rapid exome sequencing in critically ill children impacts acute and long-term management of patients and their families: A retrospective regional evaluation

IntroductionGenetic disorders are a significant cause of paediatric morbidity and mortality. Rapid exome sequencing was introduced by the National Health Service (NHS) in England on 1^st October 2019 for acutely unwell children with a likely monogenic disorder, or to inform current pregnancy management where there was a previously affected child or fetus. We present results of a 12-month patient cohort from one large clinical genetics centre in England.MethodsPatients were identified through local genetics laboratory records. We included all cases which underwent rapid exome sequencing between 1^st October 2020 and 30^th September 2021. DNA was extracted, quality checked and exported to the Exeter Genomic laboratory where library preparation, exome sequencing of all known human genes, gene-agnostic bioinformatic analysis, variant interpretation, MDT discussions and reporting were performed.ResultsNinety-five probands were included. Trio analysis was performed in 90% (85), duo in 8% (8), singleton in 2% (2). The median turnaround time for preliminary reports was 11 days. The overall diagnostic yield was 40% (38 patients); 36% (34 patients) made solely on exome with a further 4% on concomitant exome and microarray analysis. Highest diagnostic rates were seen in patients with neuro-regression, skeletal dysplasia, neuromuscular and neurometabolic conditions.Where the diagnosis was made solely through exome sequencing, management was altered for the proband or family in 97% (33/34). For the proband, this was most commonly that the diagnosis was able to inform current management and prognosis (20 patients, 59%), as well as direct specialist referrals (10 patients, 29%). For families, the exome sequencing results provided accurate recurrence risk counselling in 88% (30/34) with cascade testing offered if indicated in some families.ConclusionsIn the majority of cases, the genetic diagnoses influenced acute and long-term management for critically ill children and their families. Paediatric and neonatal clinicians in the NHS now have direct access to exome sequencing for their patients. The rapid turnaround time was particularly helpful to alter the management in acute clinical settings and is a powerful tool for diagnosing monogenic conditions. This study is an example of a highly successful integration of a national rapid exome sequencing service with diagnostic rates comparable to previously reported literature.     

Genetic and clinical landscape of childhood cerebellar hypoplasia and atrophy

PurposeCerebellar hypoplasia and atrophy (CBHA) in children is an extremely heterogeneous group of disorders, but few comprehensive genetic studies have been reported. Comprehensive genetic analysis of CBHA patients may help differentiating atrophy and hypoplasia and potentially improve their prognostic aspects.MethodsPatients with CBHA in 176 families were genetically examined using exome sequencing. Patients with disease-causing variants were clinically evaluated.ResultsDisease-causing variants were identified in 96 of the 176 families (54.5%). After excluding 6 families, 48 patients from 42 families were categorized as having syndromic associations with CBHA, whereas the remaining 51 patients from 48 families had isolated CBHA. In 51 patients, 26 aberrant genes were identified, of which, 20 (76.9%) caused disease in 1 family each. The most prevalent genes were CACNA1A, ITPR1, and KIF1A. Of the 26 aberrant genes, 21 and 1 were functionally annotated to atrophy and hypoplasia, respectively. CBHA+S was more clinically severe than CBHA–S. Notably, ARG1 and FOLR1 variants were identified in 2 families, leading to medical treatments.ConclusionA wide genetic and clinical diversity of CBHA was revealed through exome sequencing in this cohort, which highlights the importance of comprehensive genetic analyses. Furthermore, molecular-based treatment was available for 2 families.     

Cascade testing after exome sequencing: Retrospective analysis of linked family data at 2 US laboratories

PurposeCascade testing, the process of testing a proband’s at-risk relatives, is integral to realizing the full value of genomic sequencing. However, there is little empirical evidence on the uptake of cascade testing after a positive exome sequencing (ES) result in a population of probands with diverse clinical indications.MethodsWe retrospectively reviewed administrative data from 2 US clinical laboratories that perform ES. For each proband with a positive ES result, we used linked family data to describe the frequency of relatives’ cascade testing performed at the same laboratory, variant detection yield of cascade tests, and characteristics of probands and relatives categorized on the basis of cascade testing completion.ResultsAmong the 3723 positive ES results across both laboratories, 426 relatives of 282 probands completed cascade testing (uptake = 7.6%). An average of 1.5 relatives (SD = 0.9) were tested per proband. Of the 426 relatives tested, 200 had a variant of interest detected (variant detection yield = 47.0%).ConclusionIn our real-world data analysis, a small proportion of probands with a positive ES result subsequently had relatives complete cascade testing at the same laboratory. However, approximately half of the tested relatives received a clinically significant result that could have implications for clinical management or reproductive planning. Additional research on ways to increase cascade testing uptake is warranted.     

Patient decisions for disclosure of secondary findings among the first 200 individuals undergoing clinical diagnostic exome sequencing

PurposeExome sequencing of a single individual for a clinical indication may result in the identification of incidental deleterious variants unrelated to the indication for testing (secondary findings). Given the recent availability of clinical exome testing, there is a limited knowledge regarding the disclosure preferences and impact of secondary findings in a clinical diagnostic setting. In this article, we provide preliminary data regarding the preferences for secondary findings results disclosure based on the first 200 families referred to Ambry Genetics for diagnostic exome sequencing.MethodsSecondary findings were categorized into four groups in the diagnostic exome sequencing consent: carrier status of recessive disorders, predisposition to later-onset disease, predisposition to increased cancer risk, and early-onset disease. In this study, we performed a retrospective analysis of patient responses regarding the preferences for secondary findings disclosure.ResultsThe majority of patients (187/200; 93.5%) chose to receive secondary results for one or more available categories. Adult probands were more likely than children to opt for blinding of secondary data (16 vs. 4%, respectively). Among responses for blinding, preferences were evenly scattered among categories.ConclusionThese data represent the unprecedented results of a large reference laboratory providing clinical exome sequencing. We report, for the first time, the preferences of patients and families for the receipt of secondary findings based on clinical genome sequencing. Overwhelmingly, families undergoing exome sequencing opt for the disclosure of secondary findings. The data may have implications regarding the development of guidelines for secondary findings reporting among patients with severe and/or life-threatening disease undergoing clinical genomic sequencing.     

Evaluating CHARGE syndrome in congenital hypogonadotropic hypogonadism patients harboring CHD7 variants

PurposeCongenital hypogonadotropic hypogonadism (CHH), a rare genetic disease caused by gonadotropin-releasing hormone deficiency, can also be part of complex syndromes (e.g., CHARGE syndrome). CHD7 mutations were reported in 60% of patients with CHARGE syndrome, and in 6% of CHH patients. However, the definition of CHD7 mutations was variable, and the associated CHARGE signs in CHH were not systematically examined.MethodsRare sequencing variants (RSVs) in CHD7 were identified through exome sequencing in 116 CHH probands, and were interpreted according to American College of Medical Genetics and Genomics guidelines. Detailed phenotyping was performed in CHH probands who were positive for CHD7 RSVs, and genotype–phenotype correlations were evaluated.ResultsOf the CHH probands, 16% (18/116) were found to harbor heterozygous CHD7 RSVs, and detailed phenotyping was performed in 17 of them. Of CHH patients with pathogenic or likely pathogenic CHD7 variants, 80% (4/5) were found to exhibit multiple CHARGE features, and 3 of these patients were reclassified as having CHARGE syndrome. In contrast, only 8% (1/12) of CHH patients with nonpathogenic CHD7 variants exhibited multiple CHARGE features (P = 0.01).ConclusionPathogenic or likely pathogenic CHD7 variants rarely cause isolated CHH. Therefore a detailed clinical investigation is indicated to clarify the diagnosis (CHH versus CHARGE) and to optimize clinical management.     

Recall by genotype and cascade screening for familial hypercholesterolemia in a population-based biobank from Estonia

PurposeLarge-scale, population-based biobanks integrating health records and genomic profiles may provide a platform to identify individuals with disease-predisposing genetic variants. Here, we recall probands carrying familial hypercholesterolemia (FH)-associated variants, perform cascade screening of family members, and describe health outcomes affected by such a strategy.MethodsThe Estonian Biobank of Estonian Genome Center, University of Tartu, comprises 52,274 individuals. Among 4776 participants with exome or genome sequences, we identified 27 individuals who carried FH-associated variants in the LDLR, APOB, or PCSK9 genes. Cascade screening of 64 family members identified an additional 20 carriers of FH-associated variants.ResultsVia genetic counseling and clinical management of carriers, we were able to reclassify 51% of the study participants from having previously established nonspecific hypercholesterolemia to having FH and identify 32% who were completely unaware of harboring a high-risk disease-associated genetic variant. Imaging-based risk stratification targeted 86% of the variant carriers for statin treatment recommendations.ConclusionGenotype-guided recall of probands and subsequent cascade screening for familial hypercholesterolemia is feasible within a population-based biobank and may facilitate more appropriate clinical management.     

Clinical implications of systematic phenotyping and exome sequencing in patients with primary antibody deficiency

PurposeThe etiology of 80% of patients with primary antibody deficiency (PAD), the second most common type of human immune system disorder after human immunodeficiency virus infection, is yet unknown.MethodsClinical/immunological phenotyping and exome sequencing of a cohort of 126 PAD patients (55.5% male, 95.2% childhood onset) born to predominantly consanguineous parents (82.5%) with unknown genetic defects were performed. The American College of Medical Genetics and Genomics criteria were used for validation of pathogenicity of the variants.ResultsThis genetic approach and subsequent immunological investigations identified potential disease-causing variants in 86 patients (68.2%); however, 27 of these patients (31.4%) carried autosomal dominant (24.4%) and X-linked (7%) gene defects. This genetic approach led to the identification of new phenotypes in 19 known genes (38 patients) and the discovery of a new genetic defect (CD70 pathogenic variants in 2 patients). Medical implications of a definite genetic diagnosis were reported in ~50% of the patients.ConclusionDue to misclassification of the conventional approach for targeted sequencing, employing next-generation sequencing as a preliminary step of molecular diagnostic approach to patients with PAD is crucial for management and treatment of the patients and their family members.     

Rare variants in the genetic background modulate cognitive and developmental phenotypes in individuals carrying disease-associated variants

PurposeTo assess the contribution of rare variants in the genetic background toward variability of neurodevelopmental phenotypes in individuals with rare copy-number variants (CNVs) and gene-disruptive variants.MethodsWe analyzed quantitative clinical information, exome sequencing, and microarray data from 757 probands and 233 parents and siblings who carry disease-associated variants.ResultsThe number of rare likely deleterious variants in functionally intolerant genes (“other hits”) correlated with expression of neurodevelopmental phenotypes in probands with 16p12.1 deletion (n=23, p=0.004) and in autism probands carrying gene-disruptive variants (n=184, p=0.03) compared with their carrier family members. Probands with 16p12.1 deletion and a strong family history presented more severe clinical features (p=0.04) and higher burden of other hits compared with those with mild/no family history (p=0.001). The number of other hits also correlated with severity of cognitive impairment in probands carrying pathogenic CNVs (n=53) or de novo pathogenic variants in disease genes (n=290), and negatively correlated with head size among 80 probands with 16p11.2 deletion. These co-occurring hits involved known disease-associated genes such as SETD5, AUTS2, and NRXN1, and were enriched for cellular and developmental processes.ConclusionAccurate genetic diagnosis of complex disorders will require complete evaluation of the genetic background even after a candidate disease-associated variant is identified.     

The genetic and clinical landscape of nanophthalmos and posterior microphthalmos in an Australian cohort

Nanophthalmos and posterior microphthalmos are ocular abnormalities in which both eyes are abnormally small, and typically associated with extreme hyperopia. We recruited 40 individuals from 13 kindreds with nanophthalmos or posterior microphthalmos, with 12 probands subjected to exome sequencing. Nine probands (69.2%) were assigned a genetic diagnosis, with variants in MYRF, TMEM98, MFRP, and PRSS56. Two of four PRSS56 families harbored the previously described c.1066dupC variant implicated in over half of all reported PRSS56 kindreds, with different surrounding haplotypes in each family suggesting a mutational hotspot. Individuals with a genetic diagnosis had shorter mean axial lengths and higher hyperopia than those without, with recessive forms associated with the most extreme phenotypes. These findings detail the genetic architecture of nanophthalmos and posterior microphthalmos in a cohort of predominantly European ancestry, their relative clinical phenotypes, and highlight the shared genetic architecture of rare and common disorders of refractive error.     

The Geisinger MyCode community health initiative: an electronic health record–linked biobank for precision medicine research

PurposeGeisinger 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.MethodsPatient-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.ResultsMyCode has a consent rate of >85%, with more than 90,000 participants currently and 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.ConclusionThe 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.Genet Med 18 9, 906–913.     

Exome sequencing–based molecular autopsy of formalin-fixed paraffin-embedded tissue after sudden death

PurposeSudden death in the young is a devastating complication of inherited heart disorders. Finding the precise cause of death is important, but it is often unresolved after postmortem investigation. The addition of postmortem genetic testing, i.e., the molecular autopsy, can identify additional causes of death. We evaluated DNA extracted from formalin-fixed paraffin-embedded postmortem tissue for exome sequencing–based molecular autopsy after sudden death in the young.MethodsWe collected clinical and postmortem information from patients with sudden death. Exome sequencing was performed on DNA extracted from fixed postmortem tissue. Variants relevant to the cause of death were sought.ResultsFive patients with genetically unresolved sudden death were recruited. DNA extracted from fixed postmortem tissue was degraded. Exome sequencing achieved 20-fold coverage of at least 82% of coding regions. A threefold excess of singleton variants was found in the exome sequencing data of one patient. We found a de novo SCN1A frameshift variant in a patient with sudden unexpected death in epilepsy and a LMNA nonsense variant in a patient with dilated cardiomyopathy.ConclusionDNA extracted from fixed postmortem tissue is applicable to exome sequencing–based molecular autopsy. Fixed postmortem tissues are an untapped resource for exome-based studies of rare causes of sudden death.Genet Med advance online publication 23 March 2017     

The implications of familial incidental findings from exome sequencing: the NIH Undiagnosed Diseases Program experience

PurposeUsing exome sequence data from 159 families participating in the National Institutes of Health Undiagnosed Diseases Program, we evaluated the number and inheritance mode of reportable incidental sequence variants.MethodsFollowing the American College of Medical Genetics and Genomics recommendations for reporting of incidental findings from next-generation sequencing, we extracted variants in 56 genes from the exome sequence data of 543 subjects and determined the reportable incidental findings for each participant. We also defined variant status as inherited or de novo for those with available parental sequence data.ResultsWe identified 14 independent reportable variants in 159 (8.8%) families. For nine families with parental sequence data in our cohort, a parent transmitted the variant to one or more children (nine minor children and four adult children). The remaining five variants occurred in adults for whom parental sequences were unavailable.ConclusionOur results are consistent with the expectation that a small percentage of exomes will result in identification of an incidental finding under the American College of Medical Genetics and Genomics recommendations. Additionally, our analysis of family sequence data highlights that genome and exome sequencing of families has unavoidable implications for immediate family members and therefore requires appropriate counseling for the family.     

Identification of clinically actionable variants from genome sequencing of families with congenital heart disease

PurposeCongenital heart disease (CHD) affects up to 1% of live births. However, a genetic diagnosis is not made in most cases. The purpose of this study was to assess the outcomes of genome sequencing (GS) of a heterogeneous cohort of CHD patients.MethodsNinety-seven families with probands born with CHD requiring surgical correction were recruited for genome sequencing. At minimum, a proband-parents trio was sequenced per family. GS data were analyzed via a two-tiered method: application of a high-confidence gene screen (hcCHD), and comprehensive analysis. Identified variants were assessed for pathogenicity using the American College of Medical Genetics and Genomics-Association for Molecular Pathology (ACMG-AMP) guidelines.ResultsClinically relevant genetic variants in known and emerging CHD genes were identified. The hcCHD screen identified a clinically actionable variant in 22% of families. Subsequent comprehensive analysis identified a clinically actionable variant in an additional 9% of families in genes with recent disease associations. Overall, this two-tiered approach provided a clinically relevant variant for 31% of families.ConclusionsInterrogating GS data using our two-tiered method allowed identification of variants with high clinical utility in a third of our heterogeneous cohort. However, association of emerging genes with CHD etiology, and development of novel technologies for variant assessment and interpretation, will increase diagnostic yield during future reassessment of our GS data.     

Pathogenic mosaic variants in congenital hypogonadotropic hypogonadism

PurposeCongenital hypogonadotropic hypogonadism (CHH) is a rare disorder resulting in absent puberty and infertility. The genetic architecture is complex with multiple loci involved, variable expressivity, and incomplete penetrance. The majority of cases are sporadic, consistent with a disease affecting fertility. The current study aims to investigate mosaicism as a genetic mechanism for CHH, focusing on de novo rare variants in CHH genes.MethodsWe evaluated 60 trios for de novo rare sequencing variants (RSV) in known CHH genes using exome sequencing. Potential mosaicism was suspected among RSVs with altered allelic ratios and confirmed using customized ultradeep sequencing (UDS) in multiple tissues.ResultsAmong the 60 trios, 10 probands harbored de novo pathogenic variants in CHH genes. Custom UDS demonstrated that three of these de novo variants were in fact postzygotic mosaicism—two in FGFR1 (p.Leu630Pro and p.Gly348Arg), and one in CHD7 (p.Arg2428*). Statistically significant variation across multiple tissues (DNA from blood, buccal, hair follicle, urine) confirmed their mosaic nature.ConclusionsWe identified a significant number of de novo pathogenic variants in CHH of which a notable number (3/10) exhibited mosaicism. This report of postzygotic mosaicism in CHH patients provides valuable information for accurate genetic counseling.     

Patient experiences with gene panels based on exome sequencing in clinical diagnostics: high acceptance and low distress

The Radboud University Medical Center was among the first to implement two‐step exome sequencing in clinical genetic diagnostics. This study is the first to evaluate patient experiences with gene panels based on exome sequencing, using quantified psychological variables: acceptance, psychological distress, expectations of heredity and unsolicited findings. Between August 2011 and July 2012, 177 patients diagnosed with early‐onset colorectal/kidney cancer, deafness, blindness or movement disorder consented to diagnostic exome sequencing offered by clinical geneticists. Baseline questionnaires were sent to 141 adults, returned by 111 with median age of 49 [22–79] years and positive family history in 81%. Follow‐up included 91 responders at median 4 [2–22] weeks after results from known gene panels per diagnosis group; exome‐wide analysis is ongoing. Confirmed or possibly pathogenic mutations were found in 31% with one unsolicited finding (oncogenetic panel). Most patients (92%) were satisfied. There were no significant changes in heredity‐specific distress (18% at baseline, 17% at follow‐up) and expectations of heredity. Fewer patients expected unsolicited findings at follow‐up (29% vs 18%, p = 0.01). Satisfaction and distress were equal in those with vs without mutations. In conclusion, most adults accepted and were satisfied with gene panels based on diagnostic exome sequencing, few reporting distress.     

Comprehensive use of extended exome analysis improves diagnostic yield in rare disease: a retrospective survey in 1,059 cases

PurposeWe sought to determine the analytical sensitivity of several extended exome variation analysis approaches in terms of their contribution to diagnostic yield and their clinical feasibility.MethodsWe retrospectively analyzed the results of genetic testing in 1,059 distinct cases referred for exome sequencing to our institution. In these, we routinely employed extended exome analysis approaches in addition to basic variant analysis, including (i) copy-number variation (CNV) detection, (ii) nonconsensus splice defect detection, (ii) genomic breakpoint detection, (iv) homozygosity mapping, and (v) mitochondrial variant analysis.ResultsExtended exome analysis approaches assisted in identification of causative genetic variant in 44 cases, which represented a 4.2% increase in diagnostic yield. The greatest contribution was associated with CNV analysis (1.8%) and splice variant prediction (1.2%), and the remaining approaches contributed an additional 1.2%. Analysis of workload has shown that on average nine additional variants per case had to be interpreted in the extended analysis.ConclusionWe show that extended exome analysis approaches improve the diagnostic yield of heterogeneous genetic disorders and result in considerable increase of diagnostic yield of exome sequencing with a minor increase of interpretative workload.