scholarly journals Genetic heterogeneity of polymicrogyria: study of 123 patients using deep sequencing

2020 ◽  
Author(s):  
Chloe A Stutterd ◽  
Stefanie Brock ◽  
Katrien Stouffs ◽  
Miriam Fanjul-Fernandez ◽  
Paul J Lockhart ◽  
...  
Keyword(s):  
Deep Sequencing ◽  
De Novo ◽  
Diagnostic Yield ◽  
Cortical Development ◽  
Copy Number Variants ◽  
Additional Patient ◽  
Cognitive Disability ◽  
Pathogenic Variants ◽  
Brain Malformations ◽  
Gene Panels

Abstract Polymicrogyria is a malformation of cortical development characterized by overfolding and abnormal lamination of the cerebral cortex. Manifestations include epilepsy, speech disturbance and motor and cognitive disability. Causes include acquired prenatal insults and inherited and de novo genetic variants. The proportion of patients with polymicrogyria and a causative germline or mosaic variant is not known. The aim of this study was to identify the monogenic causes of polymicrogyria in a heterogeneous cohort of patients reflective of specialized referral services. Patients with polymicrogyria were recruited from two clinical centres in Australia and Belgium. Patients with evidence of congenital cytomegalovirus infection or causative chromosomal copy number variants were excluded. One hundred and twenty-three patients were tested using deep sequencing gene panels including known and candidate genes for malformations of cortical development. Causative and potentially causative variants were identified and correlated with phenotypic features. Pathogenic or likely pathogenic variants were identified in 25/123 (20.3%) patients. A candidate variant was identified for an additional patient but could not be confirmed as de novo, and therefore it was classified as being of uncertain significance with high clinical relevance. Of the 22 dominant variants identified, 5 were mosaic with allele fractions less than 0.33 and the lowest allele fraction 0.09. The most common causative genes were TUBA1A and PIK3R2. The other eleven causative genes were PIK3CA, NEDD4L, COL4A1, COL4A2, GPSM2, GRIN2B, WDR62, TUBB3, TUBB2B, ACTG1 and FH. A genetic cause was more likely to be identified in the presence of an abnormal head size or additional brain malformations suggestive of a tubulinopathy, such as dysmorphic basal ganglia. A gene panel test provides greater sequencing depth and sensitivity for mosaic variants than whole exome or genome sequencing but is limited to the genes included, potentially missing variants in newly discovered genes. The diagnostic yield of 20.3% indicates that polymicrogyria may be associated with genes not yet known to be associated with brain malformations, brain-specific somatic mutations or non-genetic causes.

scholarly journals One in seven pathogenic variants can be challenging to detect by NGS: an analysis of 450,000 patients with implications for clinical sensitivity and genetic test implementation

2021 ◽  
Author(s):  
Stephen E. Lincoln ◽  
Tina Hambuch ◽  
Justin M. Zook ◽  
Sara L. Bristow ◽  
Kathryn Hatchell ◽  
...  
Keyword(s):  
Diagnostic Yield ◽  
Copy Number Variants ◽  
Low Complexity ◽  
Clinical Genetic ◽  
Clinical Sensitivity ◽  
Pathogenic Variants ◽  
Wide Range ◽  
Large Indels ◽  
Next Generation Sequencing Ngs ◽  
The Impact

Abstract Purpose To evaluate the impact of technically challenging variants on the implementation, validation, and diagnostic yield of commonly used clinical genetic tests. Such variants include large indels, small copy-number variants (CNVs), complex alterations, and variants in low-complexity or segmentally duplicated regions. Methods An interlaboratory pilot study used synthetic specimens to assess detection of challenging variant types by various next-generation sequencing (NGS)–based workflows. One well-performing workflow was further validated and used in clinician-ordered testing of more than 450,000 patients. Results In the interlaboratory study, only 2 of 13 challenging variants were detected by all 10 workflows, and just 3 workflows detected all 13. Limitations were also observed among 11 less-challenging indels. In clinical testing, 21.6% of patients carried one or more pathogenic variants, of which 13.8% (17,561) were classified as technically challenging. These variants were of diverse types, affecting 556 of 1,217 genes across hereditary cancer, cardiovascular, neurological, pediatric, reproductive carrier screening, and other indicated tests. Conclusion The analytic and clinical sensitivity of NGS workflows can vary considerably, particularly for prevalent, technically challenging variants. This can have important implications for the design and validation of tests (by laboratories) and the selection of tests (by clinicians) for a wide range of clinical indications.

scholarly journals Gene discoveries in autism are biased towards comorbidity with intellectual disability

2020 ◽  
Vol 57 (9) ◽  
pp. 647-652
Author(s):  
Matthew Jensen ◽  
Corrine Smolen ◽  
Santhosh Girirajan
Keyword(s):  
Intellectual Disability ◽  
Genetic Factors ◽  
De Novo ◽  
High Functioning Autism ◽  
Copy Number Variants ◽  
Social Responsiveness ◽  
High Functioning ◽  
Pathogenic Variants ◽  
Increased Risk ◽  
Normal Cognitive Function

BackgroundAutism typically presents with highly heterogeneous features, including frequent comorbidity with intellectual disability (ID). The overlap between these phenotypes has confounded the diagnosis and discovery of genetic factors associated with autism. We analysed pathogenic de novo genetic variants in individuals with autism who had either ID or normal cognitive function to determine whether genes associated with autism also contribute towards ID comorbidity.MethodsWe analysed 2290 individuals from the Simons Simplex Collection for de novo likely gene-disruptive (LGD) variants and copy-number variants (CNVs), and determined their relevance towards IQ and Social Responsiveness Scale (SRS) measures.ResultsIndividuals who carried de novo variants in a set of 173 autism-associated genes showed an average 12.8-point decrease in IQ scores (p=5.49×10−6) and 2.8-point increase in SRS scores (p=0.013) compared with individuals without such variants. Furthermore, individuals with high-functioning autism (IQ >100) had lower frequencies of de novo LGD variants (42 of 397 vs 86 of 562, p=0.021) and CNVs (9 of 397 vs 24 of 562, p=0.065) compared with individuals who manifested both autism and ID (IQ <70). Pathogenic variants disrupting autism-associated genes conferred a 4.85-fold increased risk (p=0.011) for comorbid ID, while de novo variants observed in individuals with high-functioning autism disrupted genes with little functional relevance towards neurodevelopment.ConclusionsPathogenic de novo variants disrupting autism-associated genes contribute towards autism and ID comorbidity, while other genetic factors are likely to be causal for high-functioning autism.

scholarly journals Somatic mutation involving diverse genes leads to a spectrum of focal cortical malformations

2021 ◽  
Author(s):  
Dulcie Lai ◽  
Meethila Gade ◽  
Edward Yang ◽  
Hyun Yong Koh ◽  
Nicole M. Walley ◽  
...  
Keyword(s):  
Focal Cortical Dysplasia ◽  
Hippocampal Sclerosis ◽  
Cortical Development ◽  
Copy Number Variants ◽  
Cortical Dysplasia ◽  
Disease Genes ◽  
Type I ◽  
Type Ii ◽  
Loss Of Function ◽  
Brain Malformations

Post-zygotically acquired genetic variants, or somatic variants, that arise during cortical development have emerged as important causes of focal epilepsies, particularly those due to malformations of cortical development. Pathogenic somatic variants have been identified in many genes within the PI3K-AKT3-mTOR-signaling pathway in individuals with hemimegalencephaly and focal cortical dysplasia (type II), and more recently in SLC35A2 in individuals with focal cortical dysplasia (type I) or non-dysplastic epileptic cortex. Given the expanding role of somatic variants across different brain malformations, we sought to delineate the landscape of somatic variants in a large cohort of patients who underwent epilepsy surgery with hemimegalencephaly or focal cortical dysplasia. We evaluated samples from 123 children with hemimegalencephaly (n=16), focal cortical dysplasia type I and related phenotypes (n=48), focal cortical dysplasia type II (n=44), or focal cortical dysplasia type III (n=15) classified using imaging and pathological findings. We performed high-depth exome sequencing in brain tissue-derived DNA from each case and identified somatic single nucleotide, indel, and large copy number variants. In 75% of individuals with hemimegalencephaly and 29% with focal cortical dysplasia type II, we identified pathogenic variants in PI3K-AKT-mTOR pathway genes. Four of 48 cases with focal cortical dysplasia type I (8%) had a likely pathogenic variant in SLC35A2. While no other gene had multiple disease-causing somatic variants across the focal cortical dysplasia type I cohort, four individuals in this group had a single pathogenic or likely pathogenic somatic variant in CASK, KRAS, NF1, and NIPBL, genes associated with neurodevelopmental disorders. No rare pathogenic or likely pathogenic somatic variants in any neurological disease genes like those identified in the focal cortical dysplasia type I cohort were found in 63 neurologically normal controls (P = 0.017), suggesting a role for these novel variants. We also identified a somatic loss-of-function variant in the known epilepsy gene, PCDH19, present in a very small number of alleles in the dysplastic tissue from a female patient with focal cortical dysplasia IIIa with hippocampal sclerosis. In contrast to focal cortical dysplasia type II, neither focal cortical dysplasia type I nor III had somatic variants in genes that converge on a unifying biological pathway, suggesting greater genetic heterogeneity compared to type II. Importantly, we demonstrate that FCD types I, II, and III, are associated with somatic gene variants across a broad range of genes, many associated with epilepsy in clinical syndromes caused by germline variants, as well as including some not previously associated with radiographically evident cortical brain malformations.

scholarly journals Next-Generation Sequencing Improves Diagnosis, Prognosis and Clinical Management of Myeloid Neoplasms

Cancers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1364 ◽  
Author(s):  
Diego Carbonell ◽  
Julia Suárez-González ◽  
María Chicano ◽  
Cristina Andrés-Zayas ◽  
Juan Carlos Triviño ◽  
...  
Keyword(s):  
Next Generation Sequencing ◽  
Copy Number Variants ◽  
Genetic Alterations ◽  
Next Generation ◽  
Pathogenic Variants ◽  
Myeloid Neoplasms ◽  
Diagnostic Samples ◽  
Gene Panels ◽  
Next Generation Sequencing Ngs ◽  
Generation Sequencing

Molecular diagnosis of myeloid neoplasms (MN) is based on the detection of multiple genetic alterations using various techniques. Next-generation sequencing (NGS) has been proved as a useful method for analyzing many genes simultaneously. In this context, we analyzed diagnostic samples from 121 patients affected by MN and ten relapse samples from a subset of acute myeloid leukemia patients using two enrichment-capture NGS gene panels. Pathogenicity classification of variants was enhanced by the development and application of a custom onco-hematology score. A total of 278 pathogenic variants were detected in 84% of patients. For structural alterations, 82% of those identified by cytogenetics were detected by NGS, 25 of 31 copy number variants and three out of three translocations. The detection of variants using NGS changed the diagnosis of seven patients and the prognosis of 15 patients and enabled us to identify 44 suitable candidates for clinical trials. Regarding AML, six of the ten relapsed patients lost or gained variants, comparing with diagnostic samples. In conclusion, the use of NGS panels in MN improves genetic characterization of the disease compared with conventional methods, thus demonstrating its potential clinical utility in routine clinical testing. This approach leads to better-adjusted treatments for each patient.

scholarly journals The Genomic Landscape of Pediatric Rheumatology Disorders in the Middle East

2020 ◽  
Author(s):  
Basil M Fathalla ◽  
Ali Alsarhan ◽  
Samina Afzal ◽  
Maha EL Naofal ◽  
Ahmad Abou Tayoun
Keyword(s):  
Middle East ◽  
United Arab Emirates ◽  
Diagnostic Yield ◽  
Periodic Fever ◽  
Copy Number Variants ◽  
Loss Of Function ◽  
Management Plans ◽  
Dual Diagnoses ◽  
Positive Rate ◽  
Gene Panels

AbstractGenetic investigations for patients with pediatric rheumatological disorders have been limited to classic genotyping testing, mainly MEFV hotspot mutation analysis, for periodic fever. Therefore, the landscape and clinical utility of comprehensive genomic investigations for a wider range of pediatric rheumatological disorders have not been fully characterized in the Middle East. Here seventy-one pediatric patients, of diverse Arab origins, were clinically and genetically assessed for a spectrum of rheumatology-related disease at the only dedicated tertiary children’s hospital in the United Arab Emirates. Clinical genomic investigations included mainly (76%) next generation sequencing-based gene panels and whole exome sequencing, along with rapid sequencing in the intensive care unit (ICU) and urgent setting. The overall positive yield was 46.5% (16.7%-66.7% for specific indications), while dual diagnoses were made in 2 cases (3%). Although the majority (21/33, 64%) of positive findings involved the MEFV gene, the remaining (12/33, 36%) alterations were attributed to eleven other genes/loci. Copy number variants contributed substantially (5/33, 15.2%) to the overall diagnostic yield. Sequencing-based testing, specifically rapid sequencing, had high positive rate and delivered timely results. Genetic findings guided clinical management plans and interventions in most cases (27/33, 81.8%). We highlight unique findings and provide additional evidence that heterozygous loss of function of the IFIH1 gene increases susceptibility to recurrent fevers. Our study highlights the importance of comprehensive genomic investigations in patients with pediatric rheumatological disorders, and provides new insights into the pathogenic variation landscape in this group of disorders.

scholarly journals Next Generation Sequencing in Pediatric Epilepsy Using Customized Panels: Size Matters

2020 ◽  
Author(s):  
Eva-Katharina Willimsky ◽  
Anna Munzig ◽  
Karin Mayer ◽  
Saskia Biskup ◽  
Angela Abicht ◽  
...  
Keyword(s):  
Next Generation Sequencing ◽  
Diagnostic Yield ◽  
Unknown Etiology ◽  
Pediatric Epilepsy ◽  
Next Generation ◽  
Large Panels ◽  
Pathogenic Variants ◽  
Gene Panels ◽  
Patients With Epilepsy ◽  
Generation Sequencing

Abstract Introduction Next generation sequencing (NGS) with customized gene panels is a helpful tool to identify monogenic epilepsy syndromes. The number of genes tested within a customized panel may vary greatly. The aim of the present study was to compare the diagnostic yield of small (<25 kb) and large (>25 kb) customized epilepsy panels. Methods This retrospective cohort study investigated data of 190 patients of 18 years or younger, with the diagnosis of an epilepsy of unknown etiology who underwent NGS using customized gene panels. Small (<25 kb) and large (>25 kb) panels were compared regarding the distribution of benign/likely benign and pathogenic/likely pathogenic variants and variants of unclear significance. In addition, differences of the diagnostic yield with respect to epilepsy severity, i.e., developmental and epileptic encephalopathy [DEE] vs. non-DEE, were analyzed. Results The diagnostic yield defined as pathogenic or likely pathogenic variants in large panels was significantly increased (29% [n = 14/48] vs. 13% [n = 18/142], p = 0.0198) compared with smaller panels. In non-DEE patients the increase of the diagnostic yield in large panels was significant(35% n = 6/17 vs. 13% n = 12/94, p = 0.0378), which was not true for DEE patients. Discussion This study indicates that large panels are superior for pediatric patients with epilepsy forms without encephalopathy (non-DEE). For patients suffering from DEE small panels of a maximum of 10 genes seem to be sufficient. The proportion of unclear findings increases with rising panel sizes. Conclusion Customized epilepsy panels of >25 kb compared with smaller panels show a significant higher diagnostic yield in patients with epilepsy especially in non-DEE patients.

scholarly journals InDelible: Detection and Evaluation of Clinically-relevant Structural Variation from Exome Sequencing

2020 ◽  
Author(s):  
Eugene J. Gardner ◽  
Alejandro Sifrim ◽  
Sarah J. Lindsay ◽  
Elena Prigmore ◽  
Diana Rajan ◽  
...  
Keyword(s):  
Exome Sequencing ◽  
Developmental Disorders ◽  
Structural Variation ◽  
Developmental Disorder ◽  
De Novo ◽  
Size Range ◽  
Diagnostic Yield ◽  
Structural Variations ◽  
Pathogenic Variants ◽  
Split Read

AbstractPurposeIdentifying structural variations (SVs) associated with developmental disorder (DD) patient phenotype missed by conventional approaches.MethodsWe have developed a novel SV discovery approach that mines split-read information, ‘InDelible’, and applied it to exome sequencing (ES) of 13,438 probands with severe DD recruited as part of the Deciphering Developmental Disorders (DDD) study.ResultsUsing InDelible we were able to find 59 previously undetected variants in genes previously associated with DD, of which 49.2% (29) had phenotypic features that accord with those of the patient in which they were found, and were deemed plausibly pathogenic. InDelible was particularly effective at ascertaining variants between 21-500 bps in size, and increased the total number of potentially pathogenic variants identified by DDD in this size range by 42.0% (n = 29 variants). Of particular interest were seven confirmed de novo SVs in the gene MECP2; these variants represent 31.8% of all de novo protein truncating variants in MECP2 among DDD patients.ConclusionInDelible provides a rapid framework for the discovery of likely pathogenic SVs that are likely to be missed by standard analytical workflows and has the potential to improve the diagnostic yield of ES.

Clinical exome sequencing data reveal high diagnostic yields for congenital diaphragmatic hernia plus (CDH+) and new phenotypic expansions involving CDH

2021 ◽  
pp. jmedgenet-2020-107317
Author(s):  
Tiana M Scott ◽  
Ian M Campbell ◽  
Andres Hernandez-Garcia ◽  
Seema R Lalani ◽  
Pengfei Liu ◽  
...  
Keyword(s):  
Congenital Diaphragmatic Hernia ◽  
Exome Sequencing ◽  
Diaphragmatic Hernia ◽  
De Novo ◽  
Diagnostic Yield ◽  
Fanconi Anaemia ◽  
Compound Heterozygous ◽  
Pathogenic Variants ◽  
Clinical Exome Sequencing ◽  
Made In

BackgroundCongenital diaphragmatic hernia (CDH) is a life-threatening birth defect that often co-occurs with non-hernia-related anomalies (CDH+). While copy number variant (CNV) analysis is often employed as a diagnostic test for CDH+, clinical exome sequencing (ES) has not been universally adopted.MethodsWe analysed a clinical database of ~12 000 test results to determine the diagnostic yields of ES in CDH+ and to identify new phenotypic expansions.ResultsAmong the 76 cases with an indication of CDH+, a molecular diagnosis was made in 28 cases for a diagnostic yield of 37% (28/76). A provisional diagnosis was made in seven other cases (9%; 7/76). Four individuals had a diagnosis of Kabuki syndrome caused by frameshift variants in KMT2D. Putatively deleterious variants in ALG12 and EP300 were each found in two individuals, supporting their role in CDH development. We also identified individuals with de novo pathogenic variants in FOXP1 and SMARCA4, and compound heterozygous pathogenic variants in BRCA2. The role of these genes in CDH development is supported by the expression of their mouse homologs in the developing diaphragm, their high CDH-specific pathogenicity scores generated using a previously validated algorithm for genome-scale knowledge synthesis and previously published case reports.ConclusionWe conclude that ES should be ordered in cases of CDH+ when a specific diagnosis is not suspected and CNV analyses are negative. Our results also provide evidence in favour of phenotypic expansions involving CDH for genes associated with ALG12-congenital disorder of glycosylation, Rubinstein-Taybi syndrome, Fanconi anaemia, Coffin-Siris syndrome and FOXP1-related disorders.

scholarly journals Array-Comparative Genomic Hybridization Analysis in Fetuses with Major Congenital Malformations Reveals that 24% of Cases Have Pathogenic Deletions/Duplications

2015 ◽  
Vol 147 (1) ◽  
pp. 10-16 ◽  
Author(s):  
Eleonora Di Gregorio ◽  
Giorgia Gai ◽  
Giovanni Botta ◽  
Alessandro Calcia ◽  
Patrizia Pappi ◽  
...  
Keyword(s):  
Congenital Malformations ◽  
De Novo ◽  
Copy Number Variants ◽  
Comparative Genomic ◽  
Genetic Determinants ◽  
Pathogenic Variants ◽  
Microdeletion Syndromes ◽  
Organ Systems ◽  
Major Congenital Malformations ◽  
Large Rearrangements

Karyotyping and aCGH are routinely used to identify genetic determinants of major congenital malformations (MCMs) in fetal deaths or terminations of pregnancy after prenatal diagnosis. Pathogenic rearrangements are found with a variable rate of 9-39% for aCGH. We collected 33 fetuses, 9 with a single MCM and 24 with MCMs involving 2-4 organ systems. aCGH revealed copy number variants in 14 out of 33 cases (42%). Eight were classified as pathogenic which account for a detection rate of 24% (8/33) considering fetuses with 1 or more MCMs and 33% (8/24) taking into account fetuses with multiple malformations only. Three of the pathogenic variants were known microdeletion syndromes (22q11.21 deletion, central chromosome 22q11.21 deletion, and TAR syndrome) and 5 were large rearrangements, adding up to >11 Mb per subject and comprising strong phenotype-related genes. One of those was a de novo complex rearrangement, and the remaining 4 duplications and 2 deletions were 130-900 kb in size, containing 1-7 genes, and were classified as variants of unknown clinical significance. Our study confirms aCGH as a powerful technique to ascertain the genetic etiology of fetal major congenital malformations.

scholarly journals Families with BAP1-Tumor Predisposition Syndrome in The Netherlands: Path to Identification and a Proposal for Genetic Screening Guidelines

Cancers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1114 ◽  
Author(s):  
Cindy Chau ◽  
Remco van Doorn ◽  
Natasha M. van Poppelen ◽  
Nienke van der Stoep ◽  
Arjen R. Mensenkamp ◽  
...  
Keyword(s):  
Family History ◽  
The Netherlands ◽  
Genetic Analysis ◽  
De Novo ◽  
Screening Guidelines ◽  
Pathogenic Variants ◽  
Increased Risk ◽  
Gene Panels ◽  
Medical Disciplines ◽  
Associated Tumors

Germline pathogenic variants in the BRCA1-associated protein-1 (BAP1) gene cause the BAP1-tumor predisposition syndrome (BAP1-TPDS, OMIM 614327). BAP1-TPDS is associated with an increased risk of developing uveal melanoma (UM), cutaneous melanoma (CM), malignant mesothelioma (MMe), renal cell carcinoma (RCC), meningioma, cholangiocarcinoma, multiple non-melanoma skin cancers, and BAP1-inactivated nevi. Because of this increased risk, it is important to identify patients with BAP1-TPDS. The associated tumors are treated by different medical disciplines, emphasizing the need for generally applicable guidelines for initiating genetic analysis. In this study, we describe the path to identification of BAP1-TPDS in 21 probands found in the Netherlands and the family history at the time of presentation. We report two cases of de novo BAP1 germline mutations (2/21, 9.5%). Findings of this study combined with previously published literature, led to a proposal of guidelines for genetic referral. We recommend genetic analysis in patients with ≥2 BAP1-TPDS-associated tumors in their medical history and/or family history. We also propose to test germline BAP1 in patients diagnosed with UM <40 years, CM <18 years, MMe <50 years, or RCC <46 years. Furthermore, other candidate susceptibility genes for tumor types associated with BAP1-TPDS are discussed, which can be included in gene panels when testing patients.

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