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1.
Genet Med ; 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31578471

RESUMO

PURPOSE: Lamb-Shaffer syndrome (LAMSHF) is a neurodevelopmental disorder described in just over two dozen patients with heterozygous genetic alterations involving SOX5, a gene encoding a transcription factor regulating cell fate and differentiation in neurogenesis and other discrete developmental processes. The genetic alterations described so far are mainly microdeletions. The present study was aimed at increasing our understanding of LAMSHF, its clinical and genetic spectrum, and the pathophysiological mechanisms involved. METHODS: Clinical and genetic data were collected through GeneMatcher and clinical or genetic networks for 41 novel patients harboring various types ofSOX5 alterations. Functional consequences of selected substitutions were investigated. RESULTS: Microdeletions and truncating variants occurred throughout SOX5. In contrast, most missense variants clustered in the pivotal SOX-specific high-mobility-group domain. The latter variants prevented SOX5 from binding DNA and promoting transactivation in vitro, whereas missense variants located outside the high-mobility-group domain did not. Clinical manifestations and severity varied among patients. No clear genotype-phenotype correlations were found, except that missense variants outside the high-mobility-group domain were generally better tolerated. CONCLUSIONS: This study extends the clinical and genetic spectrum associated with LAMSHF and consolidates evidence that SOX5 haploinsufficiency leads to variable degrees of intellectual disability, language delay, and other clinical features.

2.
Am J Med Genet A ; 179(9): 1756-1763, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31241255

RESUMO

Alpha-mannosidosis (AM) is a very rare (prevalence: 1/500000 births) autosomal recessive lysosomal storage disorder. It is characterized by multi-systemic involvement associated with progressive intellectual disability, hearing loss, skeletal anomalies, and coarse facial features. The spectrum is wide, from very severe and lethal to a milder phenotype that usually progresses slowly. AM is caused by a deficiency of lysosomal alpha-mannosidase. A diagnosis can be established by measuring the activity of lysosomal alpha-mannosidase in leucocytes and screening for abnormal urinary excretion of mannose-rich oligosaccharides. Genetic confirmation is obtained with the identification of MAN2B1 mutations. Enzyme replacement therapy (LAMZEDER ) was approved for use in Europe in August 2018. Here, we describe seven individuals from four families, diagnosed at 3-23 years of age, and who were referred to a clinical geneticist for etiologic exploration of syndromic hearing loss, associated with moderate learning disabilities. Exome sequencing had been used to establish the molecular diagnosis in five cases, including a two-sibling pair. In the remaining two patients, the diagnosis was obtained with screening of urinary oligosaccharides excretion and the association of deafness and hypotonia. These observations emphasize that the clinical diagnosis of AM can be challenging, and that it is likely an underdiagnosed rare cause of syndromic hearing loss. Exome sequencing can contribute significantly to the early diagnosis of these nonspecific mild phenotypes, with advantages for treatment and management.

3.
Eur J Hum Genet ; 27(10): 1519-1531, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31231135

RESUMO

In clinical exome sequencing (cES), the American College of Medical Genetics and Genomics recommends limiting variant interpretation to established human-disease genes. The diagnostic yield of cES in intellectual disability and/or multiple congenital anomalies (ID/MCA) is currently about 30%. Though the results may seem acceptable for rare diseases, they mean that 70% of affected individuals remain genetically undiagnosed. Further analysis extended to all mutated genes in a research environment is a valuable strategy for improving diagnostic yields. This study presents the results of systematic research reanalysis of negative cES in a cohort of 313 individuals with ID/MCA. We identified 17 new genes not related to human disease, implicated 22 non-OMIM disease-causing genes recently or previously rarely related to disease, and described 1 new phenotype associated with a known gene. Twenty-six candidate genes were identified and are waiting for future recurrence. Overall, we diagnose 15% of the individuals with initial negative cES, increasing the diagnostic yield from 30% to more than 40% (or 46% if strong candidate genes are considered). This study demonstrates the power of such extended research reanalysis to increase scientific knowledge of rare diseases. These novel findings can then be applied in the field of diagnostics.

4.
Hum Mol Genet ; 28(17): 2937-2951, 2019 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-31152168

RESUMO

KCNMA1 encodes the large-conductance Ca2+- and voltage-activated K+ (BK) potassium channel α-subunit, and pathogenic gain-of-function variants in this gene have been associated with a dominant form of generalized epilepsy and paroxysmal dyskinesia. Here, we genetically and functionally characterize eight novel loss-of-function (LoF) variants of KCNMA1. Genome or exome sequencing and the participation in the international Matchmaker Exchange effort allowed for the identification of novel KCNMA1 variants. Patch clamping was used to assess functionality of mutant BK channels. The KCNMA1 variants p.(Ser351Tyr), p.(Gly356Arg), p.(Gly375Arg), p.(Asn449fs) and p.(Ile663Val) abolished the BK current, whereas p.(Cys413Tyr) and p.(Pro805Leu) reduced the BK current amplitude and shifted the activation curves toward positive potentials. The p.(Asp984Asn) variant reduced the current amplitude without affecting kinetics. A phenotypic analysis of the patients carrying the recurrent p.(Gly375Arg) de novo missense LoF variant revealed a novel syndromic neurodevelopmental disorder associated with severe developmental delay, visceral and cardiac malformations, connective tissue presentations with arterial involvement, bone dysplasia and characteristic dysmorphic features. Patients with other LoF variants presented with neurological and developmental symptoms including developmental delay, intellectual disability, ataxia, axial hypotonia, cerebral atrophy and speech delay/apraxia/dysarthria. Therefore, LoF KCNMA1 variants are associated with a new syndrome characterized by a broad spectrum of neurological phenotypes and developmental disorders. LoF variants of KCNMA1 cause a new syndrome distinctly different from gain-of-function variants in the same gene.

5.
Genet Med ; 21(11): 2504-2511, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31036916

RESUMO

PURPOSE: Next-generation sequencing has revealed the major impact of de novo variants (DNVs) in developmental disorders (DD) such as intellectual disability, autism, and epilepsy. However, a substantial fraction of these predicted pathogenic DNVs remains challenging to distinguish from background DNVs, notably the missense variants acting via nonhaploinsufficient mechanisms on specific amino acid residues. We hypothesized that the detection of the same missense variation in at least two unrelated individuals presenting with a similar phenotype could be a powerful approach to reveal novel pathogenic variants. METHODS: We looked for variations independently present in both our database of >1200 solo exomes and in denovo-db, a large, publicly available collection of de novo variants identified in patients with DD. RESULTS: This approach identified 30 variants with strong evidence of pathogenicity, including variants already classified as pathogenic or probably pathogenic by our team, and also several new variants of interest in known OMIM genes or in novel genes. We identified FEM1B and GNAI2 as good candidate genes for syndromic intellectual disability and confirmed the implication of ACTL6B in a neurodevelopmental disorder. CONCLUSION: Annotation of local variants with denovo-db can highlight missense variants with high potential for pathogenicity, both facilitating the time-consuming reanalysis process and allowing novel DD gene discoveries.

6.
Eur J Hum Genet ; 27(8): 1197-1214, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31019283

RESUMO

With exome/genome sequencing (ES/GS) integrated into the practice of medicine, there is some potential for reporting incidental/secondary findings (IFs/SFs). The issue of IFs/SFs has been studied extensively over the last 4 years. In order to evaluate their implications in care organisation, we retrospectively evaluated, in a cohort of 700 consecutive probands, the frequency and burden of introducing the search for variants in a maximum list of 244 medically actionable genes (genes that predispose carriers to a preventable or treatable disease in childhood/adulthood and genes for genetic counselling issues). We also focused on the 59 PharmGKB class IA/IB pharmacogenetic variants. We also compared the results in different gene lists. We identified variants (likely) affecting protein function in genes for care in 26 cases (3.7%) and heterozygous variants in genes for genetic counselling in 29 cases (3.8%). Mean time for the 700 patients was about 6.3 min/patient for medically actionable genes and 1.3 min/patient for genes for genetic counselling, and a mean time of 37 min/patients for the reinterpreted variants. These results would lead to all 700 pre-test counselling sessions being longer, to 55 post-test genetic consultations and to 27 secondary specialised medical evaluations. ES also detected 42/59 pharmacogenetic variants or combinations of variants in the majority of cases. An extremely low metabolizer status in genes relevant for neurodevelopmental disorders (CYP2C9 and CYP2C19) was found in 57/700 cases. This study provides information regarding the need to anticipate the implementation of genomic medicine, notably the work overload at various steps of the process.

7.
Genet Med ; 21(7): 1657-1661, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30563986

RESUMO

PURPOSE: Exome sequencing (ES) powerfully identifies the molecular bases of heterogeneous conditions such as intellectual disability and/or multiple congenital anomalies (ID/MCA). Current ES analysis, combining diagnosis analysis restricted to disease-causing genes reported in OMIM database and subsequent research investigation extended to other genes, indicated causal and candidate genes around 40% and 10%. Nonconclusive results are frequent in such ultrarare conditions that recurrence and genotype-phenotype correlations are limited. International data-sharing permits the gathering of additional patients carrying variants in the same gene to draw definitive conclusions on their implication as disease causing. Several web-based tools have been developed and grouped in Matchmaker Exchange. In this study, we report our current experience as a regional center that has implemented ES as a first-line diagnostic test since 2013, working with a research laboratory devoted to disease gene identification. METHODS: We used GeneMatcher over 2.5 years to share 71 novel candidate genes identified by ES. RESULTS: Matches occurred in 60/71 candidate genes allowing to confirm the implication of 39% of matched genes as causal and to rule out 6% of them. CONCLUSION: The introduction of user-friendly gene-matching tools, such as GeneMatcher, appeared to be an essential step for the rapid identification of novel disease genes responsible for ID/MCA.

8.
Genet Med ; 20(6): 645-654, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29095811

RESUMO

PurposeCongenital anomalies and intellectual disability (CA/ID) are a major diagnostic challenge in medical genetics-50% of patients still have no molecular diagnosis after a long and stressful diagnostic "odyssey." Solo clinical whole-exome sequencing (WES) was applied in our genetics center to improve diagnosis in patients with CA/ID.MethodsThis retrospective study examined 416 consecutive tests performed over 3 years to demonstrate the effectiveness of periodically reanalyzing WES data. The raw data from each nonpositive test was reanalyzed at 12 months with the most recent pipeline and in the light of new data in the literature. The results of the reanalysis for patients enrolled in the third year are not yet available.ResultsOf the 416 patients included, data for 156 without a diagnosis were reanalyzed. We obtained 24 (15.4%) additional diagnoses: 12 through the usual diagnostic process (7 new publications, 4 initially misclassified, and 1 copy-number variant), and 12 through translational research by international data sharing. The final yield of positive results was 27.9% through a strict diagnostic approach, and 2.9% through an additional research strategy.ConclusionThis article highlights the effectiveness of periodically combining diagnostic reinterpretation of clinical WES data with translational research involving data sharing for candidate genes.


Assuntos
Anormalidades Congênitas/genética , Deficiência Intelectual/genética , Sequenciamento Completo do Exoma/métodos , Bases de Dados Genéticas , Exoma , Testes Genéticos/métodos , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Humanos , Doenças Raras/genética , Estudos Retrospectivos , Análise de Sequência de DNA/métodos
9.
Eur J Med Genet ; 60(11): 595-604, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28807864

RESUMO

BACKGROUND AND OBJECTIVE: Whole-exome sequencing (WES) has now entered medical practice with powerful applications in the diagnosis of rare Mendelian disorders. Although the usefulness and cost-effectiveness of WES have been widely demonstrated, it is essential to reduce the diagnostic turnaround time to make WES a first-line procedure. Since 2011, the automation of laboratory procedures and advances in sequencing chemistry have made it possible to carry out diagnostic whole genome sequencing from the blood sample to molecular diagnosis of suspected genetic disorders within 50 h. Taking advantage of these advances, the main objective of the study was to improve turnaround times for sequencing results. METHODS: WES was proposed to 29 patients with severe undiagnosed disorders with developmental abnormalities and faced with medical situations requiring rapid diagnosis. Each family gave consent. The extracted DNA was sequenced on a NextSeq500 (Illumina) instrument. Data were analyzed following standard procedures. Variants were interpreted using in-house software. Each rare variant affecting protein sequences with clinical relevance was tested for familial segregation. RESULTS: The diagnostic rate was 45% (13/29), with a mean turnaround time of 40 days from reception of the specimen to delivery of results to the referring physician. Besides permitting genetic counseling, the rapid diagnosis for positive families led to two pre-natal diagnoses and two inclusions in clinical trials. CONCLUSIONS: This pilot study demonstrated the feasibility of rapid diagnostic WES in our primary genetics center. It reduced the diagnostic odyssey and helped provide support to families.


Assuntos
Exoma , Testes Genéticos/normas , Análise de Sequência de DNA/normas , Adolescente , Adulto , Criança , Pré-Escolar , Diagnóstico Precoce , Feminino , Testes Genéticos/métodos , Humanos , Lactente , Recém-Nascido , Masculino , Sensibilidade e Especificidade , Análise de Sequência de DNA/métodos , Fatores de Tempo
10.
Eur J Hum Genet ; 24(6): 830-7, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-26395556

RESUMO

The increasing use of array-CGH in malformation syndromes with intellectual disability could lead to the description of new contiguous gene syndrome by the analysis of the gene content of the microdeletion and reverse phenotyping. Thanks to a national and international call for collaboration by Achropuce and Decipher, we recruited four patients carrying de novo overlapping deletions of chromosome 9q33.3q34.11, including the STXBP1, the LMX1B and the ENG genes. We restrained the selection to these three genes because the effects of their haploinsufficency are well described in the literature and easily recognizable clinically. All deletions were detected by array-CGH and confirmed by FISH. The patients display common clinical features, including intellectual disability with epilepsy, owing to the presence of STXBP1 within the deletion, nail dysplasia and bone malformations, in particular patellar abnormalities attributed to LMX1B deletion, epistaxis and cutaneous-mucous telangiectasias explained by ENG haploinsufficiency and common facial dysmorphism. This systematic analysis of the genes comprised in the deletion allowed us to identify genes whose haploinsufficiency is expected to lead to disease manifestations and complications that require personalized follow-up, in particular for renal, eye, ear, vascular and neurological manifestations.


Assuntos
Deleção Cromossômica , Anormalidades Craniofaciais/genética , Endoglina/genética , Epilepsia/genética , Deficiência Intelectual/genética , Proteínas com Homeodomínio LIM/genética , Proteínas Munc18/genética , Fatores de Transcrição/genética , Adolescente , Criança , Cromossomos Humanos Par 9/genética , Anormalidades Craniofaciais/diagnóstico , Epilepsia/diagnóstico , Feminino , Haploinsuficiência , Humanos , Deficiência Intelectual/diagnóstico , Masculino , Fenótipo , Síndrome
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