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1.
Am J Hum Genet ; 105(5): 921-932, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31607426

RESUMO

Meiotic nondisjunction and resulting aneuploidy can lead to severe health consequences in humans. Aneuploidy rescue can restore euploidy but may result in uniparental disomy (UPD), the inheritance of both homologs of a chromosome from one parent with no representative copy from the other. Current understanding of UPD is limited to ∼3,300 case subjects for which UPD was associated with clinical presentation due to imprinting disorders or recessive diseases. Thus, the prevalence of UPD and its phenotypic consequences in the general population are unknown. We searched for instances of UPD across 4,400,363 consented research participants from the personal genetics company 23andMe, Inc., and 431,094 UK Biobank participants. Using computationally detected DNA segments identical-by-descent (IBD) and runs of homozygosity (ROH), we identified 675 instances of UPD across both databases. We estimate that UPD is twice as common as previously thought, and we present a machine-learning framework to detect UPD using ROH. While we find a nominally significant association between UPD of chromosome 22 and autism risk, we do not find significant associations between UPD and deleterious traits in the 23andMe database.

2.
Am J Hum Genet ; 104(6): 1210-1222, 2019 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-31079897

RESUMO

We delineate a KMT2E-related neurodevelopmental disorder on the basis of 38 individuals in 36 families. This study includes 31 distinct heterozygous variants in KMT2E (28 ascertained from Matchmaker Exchange and three previously reported), and four individuals with chromosome 7q22.2-22.23 microdeletions encompassing KMT2E (one previously reported). Almost all variants occurred de novo, and most were truncating. Most affected individuals with protein-truncating variants presented with mild intellectual disability. One-quarter of individuals met criteria for autism. Additional common features include macrocephaly, hypotonia, functional gastrointestinal abnormalities, and a subtle facial gestalt. Epilepsy was present in about one-fifth of individuals with truncating variants and was responsive to treatment with anti-epileptic medications in almost all. More than 70% of the individuals were male, and expressivity was variable by sex; epilepsy was more common in females and autism more common in males. The four individuals with microdeletions encompassing KMT2E generally presented similarly to those with truncating variants, but the degree of developmental delay was greater. The group of four individuals with missense variants in KMT2E presented with the most severe developmental delays. Epilepsy was present in all individuals with missense variants, often manifesting as treatment-resistant infantile epileptic encephalopathy. Microcephaly was also common in this group. Haploinsufficiency versus gain-of-function or dominant-negative effects specific to these missense variants in KMT2E might explain this divergence in phenotype, but requires independent validation. Disruptive variants in KMT2E are an under-recognized cause of neurodevelopmental abnormalities.

3.
Eur J Hum Genet ; 27(9): 1398-1405, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30979967

RESUMO

Clinical exome sequencing (CES) is increasingly being utilized; however, a large proportion of patients remain undiagnosed, creating a need for a systematic approach to increase the diagnostic yield. We have reanalyzed CES data for a clinically heterogeneous cohort of 102 probands with likely Mendelian conditions, including 74 negative cases and 28 cases with candidate variants, but reanalysis requested by clinicians. Reanalysis was performed by an interdisciplinary team using a validated custom-built pipeline, "Variant Explorer Pipeline" (VExP). This reanalysis approach and results were compared with existing literature. Reanalysis of candidate variants from CES in 28 cases revealed 1 interpretation that needed to be reclassified. A confirmed or potential genetic diagnosis was identified in 24 of 75 CES-negative/reclassified cases (32.0%), including variants in known disease-causing genes (n = 6) or candidate genes (n = 18). This yield was higher compared with similar studies demonstrating the utility of this approach. In summary, reanalysis of negative CES in a research setting enhances diagnostic yield by about a third. This study suggests the need for comprehensive, continued reanalysis of exome data when molecular diagnosis is elusive.

5.
Genet Med ; 21(4): 798-812, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30655598

RESUMO

Identifying genes and variants contributing to rare disease phenotypes and Mendelian conditions informs biology and medicine, yet potential phenotypic consequences for variation of >75% of the ~20,000 annotated genes in the human genome are lacking. Technical advances to assess rare variation genome-wide, particularly exome sequencing (ES), enabled establishment in the United States of the National Institutes of Health (NIH)-supported Centers for Mendelian Genomics (CMGs) and have facilitated collaborative studies resulting in novel "disease gene" discoveries. Pedigree-based genomic studies and rare variant analyses in families with suspected Mendelian conditions have led to the elucidation of hundreds of novel disease genes and highlighted the impact of de novo mutational events, somatic variation underlying nononcologic traits, incompletely penetrant alleles, phenotypes with high locus heterogeneity, and multilocus pathogenic variation. Herein, we highlight CMG collaborative discoveries that have contributed to understanding both rare and common diseases and discuss opportunities for future discovery in single-locus Mendelian disorder genomics. Phenotypic annotation of all human genes; development of bioinformatic tools and analytic methods; exploration of non-Mendelian modes of inheritance including reduced penetrance, multilocus variation, and oligogenic inheritance; construction of allelic series at a locus; enhanced data sharing worldwide; and integration with clinical genomics are explored. Realizing the full contribution of rare disease research to functional annotation of the human genome, and further illuminating human biology and health, will lay the foundation for the Precision Medicine Initiative.


Assuntos
Doenças Genéticas Inatas/genética , Heterogeneidade Genética , Genoma Humano/genética , Genômica/tendências , Bases de Dados Genéticas , Predisposição Genética para Doença , Humanos , National Institutes of Health (U.S.) , Linhagem , Estados Unidos , Sequenciamento Completo do Exoma/métodos
7.
Am J Hum Genet ; 2018 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-30503522

RESUMO

Diamond-Blackfan anemia (DBA) is a rare bone marrow failure disorder that affects 7 out of 1,000,000 live births and has been associated with mutations in components of the ribosome. In order to characterize the genetic landscape of this heterogeneous disorder, we recruited a cohort of 472 individuals with a clinical diagnosis of DBA and performed whole-exome sequencing (WES). We identified relevant rare and predicted damaging mutations for 78% of individuals. The majority of mutations were singletons, absent from population databases, predicted to cause loss of function, and located in 1 of 19 previously reported ribosomal protein (RP)-encoding genes. Using exon coverage estimates, we identified and validated 31 deletions in RP genes. We also observed an enrichment for extended splice site mutations and validated their diverse effects using RNA sequencing in cell lines obtained from individuals with DBA. Leveraging the size of our cohort, we observed robust genotype-phenotype associations with congenital abnormalities and treatment outcomes. We further identified rare mutations in seven previously unreported RP genes that may cause DBA, as well as several distinct disorders that appear to phenocopy DBA, including nine individuals with biallelic CECR1 mutations that result in deficiency of ADA2. However, no new genes were identified at exome-wide significance, suggesting that there are no unidentified genes containing mutations readily identified by WES that explain >5% of DBA-affected case subjects. Overall, this report should inform not only clinical practice for DBA-affected individuals, but also the design and analysis of rare variant studies for heterogeneous Mendelian disorders.

8.
Hum Mutat ; 39(12): 1827-1834, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30240502

RESUMO

Rare disease investigators constantly face challenges in identifying additional cases to build evidence for gene-disease causality. The Matchmaker Exchange (MME) addresses this limitation by providing a mechanism for matching patients across genomic centers via a federated network. The MME has revolutionized searching for additional cases by making it possible to query across institutional boundaries, so that what was once a laborious and manual process of contacting researchers is now automated and computable. However, while the MME network is beginning to scale, the growth of additional nodes is limited by the lack of easy-to-use solutions that can be implemented by any rare disease database owner, even one without significant software engineering resources. Here, we describe matchbox, which is an open-source, platform-independent, portable bridge between any given rare disease genomic center and the MME network, which has already led to novel gene discoveries. We also describe how matchbox greatly reduces the barrier to participation by overcoming challenges for new databases to join the MME.

9.
J Pediatr ; 202: 315-319.e2, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30057141

RESUMO

We describe 2 children with cobalamin G disease, a disorder of vitamin B12 metabolism with normal serum B12 levels. They presented with megaloblastic anemia progressing rapidly to severe thrombotic microangiopathy. In infants presenting with acute thrombotic microangiopathy, cobalamin disorders should be considered early as diagnosis and targeted treatment can be lifesaving.

10.
Wellcome Open Res ; 2: 33, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28630944

RESUMO

This software repository provides a pipeline for converting raw ClinVar data files into analysis-friendly tab-delimited tables, and also provides these tables for the most recent ClinVar release. Separate tables are generated for genome builds GRCh37 and GRCh38 as well as for mono-allelic variants and complex multi-allelic variants. Additionally, the tables are augmented with allele frequencies from the ExAC and gnomAD datasets as these are often consulted when analyzing ClinVar variants. Overall, this work provides ClinVar data in a format that is easier to work with and can be directly loaded into a variety of popular analysis tools such as R, python pandas, and SQL databases.

11.
Genet Med ; 19(10): 1151-1158, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28518168

RESUMO

PurposeWhole-exome and whole-genome sequencing have transformed the discovery of genetic variants that cause human Mendelian disease, but discriminating pathogenic from benign variants remains a daunting challenge. Rarity is recognized as a necessary, although not sufficient, criterion for pathogenicity, but frequency cutoffs used in Mendelian analysis are often arbitrary and overly lenient. Recent very large reference datasets, such as the Exome Aggregation Consortium (ExAC), provide an unprecedented opportunity to obtain robust frequency estimates even for very rare variants.MethodsWe present a statistical framework for the frequency-based filtering of candidate disease-causing variants, accounting for disease prevalence, genetic and allelic heterogeneity, inheritance mode, penetrance, and sampling variance in reference datasets.ResultsUsing the example of cardiomyopathy, we show that our approach reduces by two-thirds the number of candidate variants under consideration in the average exome, without removing true pathogenic variants (false-positive rate<0.001).ConclusionWe outline a statistically robust framework for assessing whether a variant is "too common" to be causative for a Mendelian disorder of interest. We present precomputed allele frequency cutoffs for all variants in the ExAC dataset.


Assuntos
Variação Genética/genética , Análise de Sequência de DNA/métodos , Análise de Sequência de DNA/estatística & dados numéricos , Cardiomiopatias/genética , Bases de Dados Genéticas , Exoma , Frequência do Gene/genética , Humanos , Penetrância , Sequenciamento Completo do Exoma/métodos , Sequenciamento Completo do Genoma/métodos
12.
Mol Genet Metab ; 121(1): 9-15, 2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28408159

RESUMO

Acute idiopathic hyperammonemia in an adult patient is a life-threatening condition often resulting in a rapid progression to irreversible cerebral edema and death. While ammonia-scavenging therapies lower blood ammonia levels, in comparison, clearance of waste nitrogen from the brain may be delayed. Therefore, we used magnetic resonance spectroscopy (MRS) to monitor cerebral glutamine levels, the major reservoir of ammonia, in a gastric bypass patient with hyperammonemic coma undergoing therapy with N-carbamoyl glutamate and the ammonia-scavenging agents, sodium phenylacetate and sodium benzoate. Improvement in mental status mirrored brain glutamine levels, as coma persisted for 48h after plasma ammonia normalized. We hypothesize that the slower clearance for brain glutamine levels accounts for the delay in improvement following initiation of treatment in cases of chronic hyperammonemia. We propose MRS to monitor brain glutamine as a noninvasive approach to be utilized for diagnostic and therapeutic monitoring purposes in adult patients presenting with idiopathic hyperammonemia.


Assuntos
Encéfalo/diagnóstico por imagem , Coma/tratamento farmacológico , Glutamina/metabolismo , Hiperamonemia/tratamento farmacológico , Espectroscopia de Ressonância Magnética/métodos , Encéfalo/metabolismo , Coma/etiologia , Feminino , Derivação Gástrica/efeitos adversos , Glutamatos/uso terapêutico , Humanos , Hiperamonemia/complicações , Hiperamonemia/diagnóstico por imagem , Hiperamonemia/metabolismo , Pessoa de Meia-Idade , Fenilacetatos/uso terapêutico , Benzoato de Sódio/uso terapêutico , Resultado do Tratamento
13.
Sci Transl Med ; 9(386)2017 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-28424332

RESUMO

Exome and whole-genome sequencing are becoming increasingly routine approaches in Mendelian disease diagnosis. Despite their success, the current diagnostic rate for genomic analyses across a variety of rare diseases is approximately 25 to 50%. We explore the utility of transcriptome sequencing [RNA sequencing (RNA-seq)] as a complementary diagnostic tool in a cohort of 50 patients with genetically undiagnosed rare muscle disorders. We describe an integrated approach to analyze patient muscle RNA-seq, leveraging an analysis framework focused on the detection of transcript-level changes that are unique to the patient compared to more than 180 control skeletal muscle samples. We demonstrate the power of RNA-seq to validate candidate splice-disrupting mutations and to identify splice-altering variants in both exonic and deep intronic regions, yielding an overall diagnosis rate of 35%. We also report the discovery of a highly recurrent de novo intronic mutation in COL6A1 that results in a dominantly acting splice-gain event, disrupting the critical glycine repeat motif of the triple helical domain. We identify this pathogenic variant in a total of 27 genetically unsolved patients in an external collagen VI-like dystrophy cohort, thus explaining approximately 25% of patients clinically suggestive of having collagen VI dystrophy in whom prior genetic analysis is negative. Overall, this study represents a large systematic application of transcriptome sequencing to rare disease diagnosis and highlights its utility for the detection and interpretation of variants missed by current standard diagnostic approaches.


Assuntos
Sequenciamento de Nucleotídeos em Larga Escala/métodos , Transcriptoma/genética , Colágeno Tipo VI/genética , Colágeno Tipo VI/metabolismo , Humanos , Doenças Musculares/genética , Doenças Musculares/metabolismo , Mutação
14.
Nature ; 544(7649): 235-239, 2017 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-28406212

RESUMO

A major goal of biomedicine is to understand the function of every gene in the human genome. Loss-of-function mutations can disrupt both copies of a given gene in humans and phenotypic analysis of such 'human knockouts' can provide insight into gene function. Consanguineous unions are more likely to result in offspring carrying homozygous loss-of-function mutations. In Pakistan, consanguinity rates are notably high. Here we sequence the protein-coding regions of 10,503 adult participants in the Pakistan Risk of Myocardial Infarction Study (PROMIS), designed to understand the determinants of cardiometabolic diseases in individuals from South Asia. We identified individuals carrying homozygous predicted loss-of-function (pLoF) mutations, and performed phenotypic analysis involving more than 200 biochemical and disease traits. We enumerated 49,138 rare (<1% minor allele frequency) pLoF mutations. These pLoF mutations are estimated to knock out 1,317 genes, each in at least one participant. Homozygosity for pLoF mutations at PLA2G7 was associated with absent enzymatic activity of soluble lipoprotein-associated phospholipase A2; at CYP2F1, with higher plasma interleukin-8 concentrations; at TREH, with lower concentrations of apoB-containing lipoprotein subfractions; at either A3GALT2 or NRG4, with markedly reduced plasma insulin C-peptide concentrations; and at SLC9A3R1, with mediators of calcium and phosphate signalling. Heterozygous deficiency of APOC3 has been shown to protect against coronary heart disease; we identified APOC3 homozygous pLoF carriers in our cohort. We recruited these human knockouts and challenged them with an oral fat load. Compared with family members lacking the mutation, individuals with APOC3 knocked out displayed marked blunting of the usual post-prandial rise in plasma triglycerides. Overall, these observations provide a roadmap for a 'human knockout project', a systematic effort to understand the phenotypic consequences of complete disruption of genes in humans.


Assuntos
Consanguinidade , Análise Mutacional de DNA , Deleção de Genes , Genes/genética , Estudos de Associação Genética/métodos , Homozigoto , Fenótipo , 1-Alquil-2-acetilglicerofosfocolina Esterase/deficiência , 1-Alquil-2-acetilglicerofosfocolina Esterase/genética , Apolipoproteína C-III/deficiência , Apolipoproteína C-III/genética , Estudos de Coortes , Doença das Coronárias/sangue , Doença das Coronárias/genética , Família 2 do Citocromo P450/genética , Gorduras na Dieta/farmacologia , Exoma/genética , Jejum/sangue , Feminino , Frequência do Gene , Humanos , Interleucina-8/sangue , Masculino , Pessoa de Meia-Idade , Infarto do Miocárdio/sangue , Infarto do Miocárdio/genética , Neurregulinas/genética , Paquistão , Linhagem , Fosfoproteínas/genética , Período Pós-Prandial , Sítios de Splice de RNA/genética , Genética Reversa/métodos , Trocadores de Sódio-Hidrogênio/genética , Triglicerídeos/sangue
15.
Hum Mutat ; 38(5): 517-523, 2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28229513

RESUMO

The clinical interpretation of genetic variants has come to rely heavily on reference population databases such as the Exome Aggregation Consortium (ExAC) database. Pathogenic variants in genes associated with severe, pediatric-onset, highly penetrant, autosomal dominant conditions are assumed to be absent or rare in these databases. Exome sequencing of a 6-year-old female patient with seizures, developmental delay, dysmorphic features, and failure to thrive identified an ASXL1 variant previously reported as causative of Bohring-Opitz syndrome (BOS). Surprisingly, the variant was observed seven times in the ExAC database, presumably in individuals without BOS. Although the BOS phenotype fit, the presence of the variant in reference population databases introduced ambiguity in result interpretation. Review of the literature revealed that acquired somatic mosaicism of ASXL1 variants (including pathogenic variants) during hematopoietic clonal expansion can occur with aging in healthy individuals. We examined all ASXL1 truncating variants in the ExAC database and determined most are likely somatic. Failure to consider somatic mosaicism may lead to the inaccurate assumption that conditions like BOS have reduced penetrance, or the misclassification of potentially pathogenic variants.


Assuntos
Craniossinostoses/diagnóstico , Craniossinostoses/genética , Estudos de Associação Genética , Mutação em Linhagem Germinativa , Deficiência Intelectual/diagnóstico , Deficiência Intelectual/genética , Mutação , Proteínas Repressoras/genética , Idoso , Idoso de 80 Anos ou mais , Alelos , Substituição de Aminoácidos , Pré-Escolar , Bases de Dados Genéticas , Facies , Feminino , Estudos de Associação Genética/métodos , Humanos , Lactente , Masculino , Pessoa de Meia-Idade , Fenótipo
16.
Nature ; 536(7616): 285-91, 2016 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-27535533

RESUMO

Large-scale reference data sets of human genetic variation are critical for the medical and functional interpretation of DNA sequence changes. Here we describe the aggregation and analysis of high-quality exome (protein-coding region) DNA sequence data for 60,706 individuals of diverse ancestries generated as part of the Exome Aggregation Consortium (ExAC). This catalogue of human genetic diversity contains an average of one variant every eight bases of the exome, and provides direct evidence for the presence of widespread mutational recurrence. We have used this catalogue to calculate objective metrics of pathogenicity for sequence variants, and to identify genes subject to strong selection against various classes of mutation; identifying 3,230 genes with near-complete depletion of predicted protein-truncating variants, with 72% of these genes having no currently established human disease phenotype. Finally, we demonstrate that these data can be used for the efficient filtering of candidate disease-causing variants, and for the discovery of human 'knockout' variants in protein-coding genes.


Assuntos
Exoma/genética , Variação Genética/genética , Análise Mutacional de DNA , Conjuntos de Dados como Assunto , Humanos , Fenótipo , Proteoma/genética , Doenças Raras/genética , Tamanho da Amostra
17.
Hum Genet ; 135(6): 643-54, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-27126233

RESUMO

Clinical exome sequencing has clearly improved our ability as clinicians to identify the cause of a wide variety of disorders. Prior to exome sequencing, a majority of patients with apparent syndromes never received a specific molecular genetic diagnosis despite extensive diagnostic odysseys. Even for those receiving an answer to the question of what caused their disorder, the diagnostic odyssey often spanned years to decades. Determining the particular genetic cause in an individual patient can be challenging due to inherent phenotypic and genetic heterogeneity of disease, technical limitations of testing or both. Blended phenotypes, due to multiple monogenic disorders in the same patient, are true dilemmas for traditional genetic evaluations, but are increasingly being diagnosed through clinical exome sequencing. New sequencing technologies have increased the proportion of patients receiving molecular diagnoses, while significantly shortening the time scale, providing multiple benefits for the health-care team, patient and family.


Assuntos
Exoma/genética , Testes Genéticos , Patologia Molecular/tendências , Médicos/tendências , Humanos , Análise de Sequência de DNA
18.
Sci Transl Med ; 8(322): 322ra9, 2016 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-26791950

RESUMO

More than 100,000 genetic variants are reported to cause Mendelian disease in humans, but the penetrance-the probability that a carrier of the purported disease-causing genotype will indeed develop the disease-is generally unknown. We assess the impact of variants in the prion protein gene (PRNP) on the risk of prion disease by analyzing 16,025 prion disease cases, 60,706 population control exomes, and 531,575 individuals genotyped by 23andMe Inc. We show that missense variants in PRNP previously reported to be pathogenic are at least 30 times more common in the population than expected on the basis of genetic prion disease prevalence. Although some of this excess can be attributed to benign variants falsely assigned as pathogenic, other variants have genuine effects on disease susceptibility but confer lifetime risks ranging from <0.1 to ~100%. We also show that truncating variants in PRNP have position-dependent effects, with true loss-of-function alleles found in healthy older individuals, a finding that supports the safety of therapeutic suppression of prion protein expression.


Assuntos
Penetrância , Doenças Priônicas/genética , Estudos de Casos e Controles , Estudos de Coortes , Predisposição Genética para Doença , Humanos , Mutação/genética , Príons/genética , Fatores de Risco
19.
Neurogenetics ; 16(4): 307-14, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26238514

RESUMO

The etiology of intellectual disabilities (ID) remains unknown for the majority of patients. Due to reduced reproductive fitness in many individuals with ID, de novo mutations account for a significant portion of severe ID. The ATP-dependent SWI/SNF chromatin modifier has been linked with neurodevelopmental disorders including ID and autism. ARID2 is an intrinsic component of polybromo-associated BAF (PBAF), the SWI/SNF subcomplex. In this study, we used clinical whole exome sequencing (WES) in proband-parent-trios to identify the etiology of ID. We identified four independent, novel, loss of function variants in ARID2 gene in four patients, three of which were confirmed to be de novo. The patients all have ID and share other clinical characteristics including attention deficit hyperactivity disorder, short stature, dysmorphic facial features, and Wormian bones. All four novel variants are predicted to lead to a premature termination with the loss of the two conservative zinc finger motifs. This is the first report of mutations in ARID2 associated with developmental delay and ID.


Assuntos
Deficiências do Desenvolvimento/genética , Deficiência Intelectual/genética , Mutação , Fatores de Transcrição/genética , Adolescente , Criança , Exoma , Feminino , Humanos , Masculino
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