Genotype-first in a cohort of 95 fetuses with multiple congenital abnormalities: when exome sequencing reveals unexpected fetal phenotype-genotype correlations

2020 ◽  
pp. jmedgenet-2020-106867
Author(s):  
Mathilde Lefebvre ◽  
Ange-Line Bruel ◽  
Emilie Tisserant ◽  
Nicolas Bourgon ◽  
Yannis Duffourd ◽  
...  
Keyword(s):  
Exome Sequencing ◽  
Congenital Abnormalities ◽  
Diagnostic Yield ◽  
Causal Variant ◽  
Developmental Abnormalities ◽  
Variants Of Unknown Significance ◽  
Unknown Significance ◽  
Bibliographic Search ◽  
The Impact ◽  
Multiple Congenital Abnormalities

PurposeMolecular diagnosis based on singleton exome sequencing (sES) is particularly challenging in fetuses with multiple congenital abnormalities (MCA). Indeed, some studies reveal a diagnostic yield of about 20%, far lower than in live birth individuals showing developmental abnormalities (30%), suggesting that standard analyses, based on the correlation between clinical hallmarks described in postnatal syndromic presentations and genotype, may underestimate the impact of the genetic variants identified in fetal analyses.MethodsWe performed sES in 95 fetuses with MCA. Blind to phenotype, we applied a genotype-first approach consisting of combined analyses based on variants annotation and bioinformatics predictions followed by reverse phenotyping. Initially applied to OMIM-morbid genes, analyses were then extended to all genes. We complemented our approach by using reverse phenotyping, variant segregation analysis, bibliographic search and data sharing in order to establish the clinical significance of the prioritised variants.ResultssES rapidly identified causal variant in 24/95 fetuses (25%), variants of unknown significance in OMIM genes in 8/95 fetuses (8%) and six novel candidate genes in 6/95 fetuses (6%).ConclusionsThis method, based on a genotype-first approach followed by reverse phenotyping, shed light on unexpected fetal phenotype-genotype correlations, emphasising the relevance of prenatal studies to reveal extreme clinical presentations associated with well-known Mendelian disorders.

scholarly journals Novel frameshift variant in MYL2 reveals molecular differences between dominant and recessive forms of hypertrophic cardiomyopathy

2019 ◽  
Author(s):  
Sathiya N. Manivannan ◽  
Sihem Darouich ◽  
Aida Masmoudi ◽  
David Gordon ◽  
Gloria Zender ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Exome Sequencing ◽  
Rapid Screening ◽  
Functional Study ◽  
Ventricular Muscle ◽  
Loss Of Function ◽  
Variants Of Unknown Significance ◽  
Unknown Significance ◽  
The Impact

AbstractHypertrophic cardiomyopathy (HCM) is characterized by enlargement of the ventricular muscle without dilation and is often associated with dominant pathogenic variants in cardiac sarcomeric protein genes. Here, we report a family with two infants diagnosed with infantile-onset HCM and mitral valve dysplasia that led to death before one year of age. Using exome sequencing, we discovered that one of the affected children had a homozygous frameshift variant in Myosin light chain 2 (MYL2:NM_000432.3:c.431_432delCT: p.Pro144Argfs*57;MYL2-fs), which alters the last 20 amino acids of the protein and is predicted to impact the C-terminal EF-hand (CEF) domain. The parents are unaffected heterozygous carriers of the variant and the variant is absent in control cohorts from gnomAD. The absence of the phenotype in carriers and infantile presentation of severe HCM is in contrast to HCM associated with dominant MYL2 variants. Immunohistochemical analysis of the ventricular muscle of the deceased patient with the MYL2-fs variant showed marked reduction of MYL2 expression compared to an unaffected control. In vitro overexpression studies further indicate that the MYL2-fs variant is actively degraded. In contrast, an HCM-associated missense variant (MYL2:p.Gly162Arg) and three other MYL2 stopgain variants that lead to loss of the CEF domain are stably expressed. However, stopgain variants show impaired localization suggesting a functional role for the CEF domain. The degradation of the MYL2-fs can be rescued by inhibiting the cell’s proteasome function supporting a post-translational effect of the variant. In vivo rescue experiments with a Drosophila MYL2-homolog (Mlc2) knockdown model indicate that neither MYL2-fs nor MYL2:p.Gly162Arg supports regular cardiac function. The tools that we have generated provide a rapid screening platform for functional assessment of variants of unknown significance in MYL2. Our study supports an autosomal recessive model of inheritance for MYL2 loss-of-function variants and highlights the variant-specific molecular differences found in MYL2-associated cardiomyopathies.Author SummaryWe report a novel frameshift variant in MYL2 that is associated with a severe form of infantile-onset hypertrophic cardiomyopathy. The impact of the variant is only observed in the recessive form of the disease in the proband and not in the parents who are carriers of the variant. This is in contrast to other dominant variants in MYL2 that are associated with cardiomyopathies. We compared the stability of this variant to that of other cardiomyopathy associated MYL2 variants and found molecular differences in the disease pathology. We also show different protein domain requirement for stability and localization of MYL2 in cardiomyocytes. Further, we used a fly model to demonstrate functional deficits due to the variant in the developing heart. Overall, our study shows a molecular mechanism by which loss-of-function variants in MYL2 are recessive while missense variants are dominant. We highlight the use of exome sequencing and functional testing to assist in the diagnosis of rare forms of diseases where pathogenicity of the variant is not obvious. The new tools we developed for in vitro functional study and the fly fluorescent reporter analysis will permit rapid analysis of MYL2 variants of unknown significance.

scholarly journals Genetic Testing in Various Neurodevelopmental Disorders Which Manifest as Cerebral Palsy: A Case Study From Iran

2021 ◽  
Vol 9 ◽  
Author(s):  
Marzieh Nejabat ◽  
Soroor Inaloo ◽  
Afsaneh Taghipour Sheshdeh ◽  
Shima Bahramjahan ◽  
Fatima Masoomi Sarvestani ◽  
...  
Keyword(s):  
Cerebral Palsy ◽  
Exome Sequencing ◽  
Diagnostic Yield ◽  
Positive Family History ◽  
Eligibility Criteria ◽  
Variants Of Unknown Significance ◽  
Severe Intellectual Disability ◽  
Unknown Significance ◽  
Pediatric Neurologist ◽  
First Year Of Life

Purpose: Cerebral palsy (CP) is a heterogeneous permanent disorder impacting movement and posture. Investigations aimed at diagnosing this disorder are expensive and time-consuming and can eventually inconclusive. This study aimed to determine the diagnostic yield of next generation sequencing in patients with atypical CP (ACP).Methods: Patient eligibility criteria included impaired motor function with onset at birth or within the first year of life, and one or more of the following conditions: severe intellectual disability, positive family history, brain imaging findings not typical for cerebral palsy, abnormal neurometabolic profile, intractable seizure, normal neuroimaging despite severe psychomotor disability, after pediatric neurologist assessment including neuroimaging and biochemical-metabolic study offered for genetic study.Results: Exome sequencing was done for 66 patients which revealed pathogenic, likely pathogenic, and variants of unknown significance in 36.2, 9, and 43.9%, respectively. We also found 10 new mutations and were able to suggest specific and personalized treatments for nine patients. We also found three different mutations with different phenotypical spectrum in one gene that have not been reported for cerebral palsy.Conclusion: An accurate history and physical examination and determination of patients with atypical cerebral palsy for doing exome sequencing result in improved genetic counseling and personalized management.

Whole‐Exome Sequencing of a Saudi Epilepsy Cohort Reveals Association Signals in Known and Potentially Novel Loci

2021 ◽  
Author(s):  
Amein Kadhem AlAli ◽  
Abdulrahman Al-Enazi ◽  
Ahmed Ammar ◽  
Mahmoud Hajj ◽  
Cyril Cyrus ◽  
...  
Keyword(s):  
Exome Sequencing ◽  
Whole Exome Sequencing ◽  
Rare Variants ◽  
High Rate ◽  
Variants Of Unknown Significance ◽  
Pathogenic Variants ◽  
Whole Exome ◽  
Novel Variants ◽  
Unknown Significance ◽  
Rare Genetic Variants

Abstract Background Epilepsy, a serious chronic neurological condition effecting up to 100 million people globally, has clear genetic underpinnings including common and rare variants. In Saudi Arabia the prevalence of epilepsy is high and caused mainly by perinatal and genetic factors. No whole-exome sequencing (WES) studies have been performed to date in Saudi Arabian Epilepsy cohorts. This offers a unique opportunity for the discovery of rare genetic variants impacting this disease as there is a high rate of consanguinity amongst large tribal pedigrees. Results We performed WES on 144 individuals diagnosed with epilepsy, to interrogate known Epilepsy related genes for known and functional novel variants. We also used an American College of Medical Genetics (ACMG) guideline based variant prioritization approach in an attempt to discover putative causative variants. We identified a 32 potentially causative pathogenic variants across 30 different genes in 44/144 (30%) of these Saudi Epilepsy individuals. We also identified 232 variants of unknown significance (VUS) across 101 different genes in 133/144 (92%) subjects. Strong enrichment of variants of likely pathogenicity were observed in previously described epilepsy-associated loci, and a number of putative pathogenic variants in novel loci are also observed. Conclusion Several putative pathogenic variants known to be epilepsy-related loci were identified for the first time in our population, in addition to several potential new loci have been identified which may be prioritized for further investigation.

scholarly journals Targeted next generation sequencing identifies a genetic spectrum of DNA variants in patients with hemiplegic migraine

2019 ◽  
Vol 2 ◽  
pp. 251581631988163 ◽  
Author(s):  
Neven Maksemous ◽  
Robert A Smith ◽  
Heidi G Sutherland ◽  
Bridget H Maher ◽  
Omar Ibrahim ◽  
...  
Keyword(s):  
Next Generation Sequencing ◽  
Diagnostic Yield ◽  
Next Generation ◽  
Hemiplegic Migraine ◽  
Targeted Next Generation Sequencing ◽  
Variants Of Unknown Significance ◽  
High Mutation Frequency ◽  
Unknown Significance ◽  
Atp1a2 Gene ◽  
Generation Sequencing

Objective: Hemiplegic migraine in both familial (FHM) and sporadic (SHM) forms is a rare subtype of migraine with aura that can be traced to mutations in the CACNA1A, ATP1A2 and SCN1A genes. It is characterised by severe attacks of typical migraine accompanied by hemiparesis, as well as episodes of complex aura that vary significantly between individuals. Methods: Using a targeted next generation sequencing (NGS) multigene panel, we have sequenced the genomic DNA of 172 suspected hemiplegic migraine cases, in whom no mutation had previously been found by Sanger sequencing (SS) of a limited number of exons with high mutation frequency in FHM genes. Results: Genetic screening identified 29 variants, 10 of which were novel, in 35 cases in the three FHM genes ( CACNA1A, ATP1A2 and SCN1A). Interestingly, in this suspected HM cohort, the ATP1A2 gene harboured the highest number of variants with 24/35 cases (68.6%), while CACNA1A ranked the second gene, with 5 variants identified in 7/35 cases (20%). All detected variants were confirmed by SS and were absent in 100 non-migraine healthy control individuals. Assessment of variants with the American College of Medical Genetics and Genomics guidelines classified 8 variants as pathogenic, 3 as likely pathogenic and 18 as variants of unknown significance. Targeted NGS gene panel increased the diagnostic yield by fourfold over iterative SS in our diagnostics facility. Conclusion: We have identified 29 potentially causative variants in an Australian and New Zealand cohort of suspected HM cases and found that the ATP1A2 gene was the most commonly mutated gene. Our results suggest that screening using NGS multigene panels to investigate ATP1A2 alongside CACNA1A and SCN1A is a clinically useful and efficient method.

scholarly journals Poor Yield of Routine Transthyretin Screening in Patients with Idiopathic Neuropathy

2020 ◽  
Vol 47 (6) ◽  
pp. 816-819
Author(s):  
Dina Namiranian ◽  
Colin Chalk ◽  
Rami Massie
Keyword(s):  
Genetic Screening ◽  
Diagnostic Yield ◽  
Familial Amyloid Polyneuropathy ◽  
North American Population ◽  
Rare Entity ◽  
Variants Of Unknown Significance ◽  
Unknown Significance ◽  
Life Threatening ◽  
Amyloid Polyneuropathy ◽  
Transthyretin Familial Amyloid Polyneuropathy

ABSTRACT:Background and objectives:Transthyretin familial amyloid polyneuropathy (TTR-FAP) is caused by a mutation in the transthyretin (TTR) gene. Although classically described as rapidly progressive and life-threatening, recent studies on TTR-FAP show significant genetic and phenotypic heterogeneity depending on geographic localization. In light of new therapeutic advances and their implication for patient management, the aim of our study was to determine the prevalence of TTR-FAP within patients with idiopathic neuropathy in a North American population.Methods:We sequenced the TTR gene in a cohort of patients with idiopathic neuropathy. Genetic screening was performed in 110 patients from two neuromuscular clinics in Montreal, Canada.Results:No variants of unknown significance or pathogenic mutations were detected in the TTR gene.Conclusion:Our study confirms that TTR-FAP is a rare entity in our patient population, and that diagnostic yield of screening all patients with idiopathic neuropathy is very low.

scholarly journals Case Report: Infantile Urticaria as a Herald of Neonatal Onset Multisystem Inflammatory Disease With a Novel Mutation in NLRP3

2021 ◽  
Vol 12 ◽  
Author(s):  
Anna E. Patrick ◽  
Eden M. Lyons ◽  
Lisa Ishii ◽  
Alan S. Boyd ◽  
Joseph M. Choi ◽  
...  
Keyword(s):  
Clinical Symptoms ◽  
Early Recognition ◽  
Novel Mutation ◽  
Genetic Diagnosis ◽  
Inflammatory Disorder ◽  
Laboratory Findings ◽  
Genetic Sequencing ◽  
Variants Of Unknown Significance ◽  
Unknown Significance ◽  
The Impact

Neonatal multisystem onset inflammatory disorder (NOMID) is a severe autoinflammatory syndrome that can have an initial presentation as infantile urticaria. Thus, an immediate recognition of the clinical symptoms is essential for obtaining a genetic diagnosis and initiation of early therapies to prevent morbidity and mortality. Herein, we describe a neonate presenting with urticaria and systemic inflammation within hours after birth who developed arthropathy and neurologic findings. Pathologic evaluation of the skin revealed an infiltration of lymphocytes, eosinophils, and scattered neutrophils. Genetic analysis identified a novel heterozygous germline variant of unknown significance in the NLRP3 gene, causing the missense mutation M408T. Variants of unknown significance are common in genetic sequencing studies and are diagnostically challenging. Functional studies of the M408T variant demonstrated enhanced formation and activity of the NLRP3 inflammasome, with increased cleavage of the inflammatory cytokine IL-1β. Upon initiation of IL-1 pathway blockade, the infant had a robust response and improvement in clinical and laboratory findings. Our experimental data support that this novel variant in NLRP3 is causal for this infant’s diagnosis of NOMID. Rapid assessment of infantile urticaria with biopsy and genetic diagnosis led to early recognition and targeted anti-cytokine therapy. This observation expands the NOMID-causing variants in NLRP3 and underscores the role of genetic sequencing in rapidly identifying and treating autoinflammatory disease in infants. In addition, these findings highlight the importance of establishing the functional impact of variants of unknown significance, and the impact this knowledge may have on therapeutic decision making.

scholarly journals Designing Myeloid Gene Panels

2021 ◽  
Author(s):  
Fang Zhao ◽  
David S. Bosler ◽  
James R. Cook
Keyword(s):  
Next Generation Sequencing ◽  
Molecular Pathology ◽  
Diagnostic Yield ◽  
Gene Panel ◽  
Next Generation ◽  
Gene Set ◽  
Variants Of Unknown Significance ◽  
The Core ◽  
Unknown Significance ◽  
Generation Sequencing

Context.— Next-generation sequencing studies are increasingly used in the evaluation of suspected chronic myeloid neoplasms (CMNs), but there is wide variability among laboratories in the genes analyzed for this purpose. Recently, the Association for Molecular Pathology CMN working group recommended a core 34-gene set as a minimum target list for evaluation of CMNs. This list was recommended based on literature review, and its diagnostic yield in clinical practice is unknown. Objective.— To determine the diagnostic yield of the core 34 genes and assess the potential impact of including selected additional genes. Design.— We retrospectively reviewed 185 patients with known or suspected CMNs tested using a 62-gene next-generation sequencing panel that included all 34 core genes. Results.— The Association for Molecular Pathology's core 34 genes had a diagnostic yield of 158 of 185 (85.4%) to detect at least 1 variant with strong/potential clinical significance and 107 of 185 (57.8%) to detect at least 2 such variants. The 62-gene panel had a diagnostic yield of 160 of 185 (86.5%) and 112 of 185 (60.5%), respectively. Variants of unknown significance were identified in 49 of 185 (26.5%) using the core 34 genes versus 76 of 185 (41.1%) using the 62-gene panel. Conclusions.— This study demonstrates that the Association for Molecular Pathology–recommended core 34-gene set has a high diagnostic yield in CMNs. Inclusion of selected additional genes slightly increases the rate of abnormal results, while also increasing the detection of variants of unknown significance. We recommend inclusion of CUX1, DDX41, ETNK1, RIT1, and SUZ12 in addition to the Association for Molecular Pathology's 34-gene core set for routine evaluation of CMNs.

The impact of exome sequencing on the diagnostic yield of muscular dystrophies in consanguineous families

2020 ◽  
Vol 63 (4) ◽  
pp. 103845 ◽  
Author(s):  
Zain Dardas ◽  
Samer Swedan ◽  
Ahmad Al-Sheikh Qassem ◽  
Belal Azab
Keyword(s):  
Exome Sequencing ◽  
Diagnostic Yield ◽  
Muscular Dystrophies ◽  
The Impact

scholarly journals Next-generation sequencing approach to hyperCKemia

2019 ◽  
Vol 5 (5) ◽  
pp. e352 ◽  
Author(s):  
Anna Rubegni ◽  
Alessandro Malandrini ◽  
Claudia Dosi ◽  
Guja Astrea ◽  
Jacopo Baldacci ◽  
...  
Keyword(s):  
Next Generation Sequencing ◽  
Molecular Diagnosis ◽  
Diagnostic Yield ◽  
Clinical Neurology ◽  
Next Generation ◽  
Variants Of Unknown Significance ◽  
Unknown Significance ◽  
Next Generation Sequencing Ngs ◽  
Generation Sequencing

ObjectiveNext-generation sequencing (NGS) was applied in molecularly undiagnosed asymptomatic or paucisymptomatic hyperCKemia to investigate whether this technique might allow detection of the genetic basis of the condition.MethodsSixty-six patients with undiagnosed asymptomatic or paucisymptomatic hyperCKemia, referred to tertiary neuromuscular centers over an approximately 2-year period, were analyzed using a customized, targeted sequencing panel able to investigate the coding exons and flanking intronic regions of 78 genes associated with limb-girdle muscular dystrophies, rhabdomyolysis, and metabolic and distal myopathies.ResultsA molecular diagnosis was reached in 33 cases, corresponding to a positive diagnostic yield of 50%. Variants of unknown significance were found in 17 patients (26%), whereas 16 cases (24%) remained molecularly undefined. The major features of the diagnosed cases were mild proximal muscle weakness (found in 27%) and myalgia (in 24%). Fourteen patients with a molecular diagnosis and mild myopathic features on muscle biopsy remained asymptomatic at a 24-month follow-up.ConclusionsThis study of patients with undiagnosed hyperCKemia, highlighting the advantages of NGS used as a first-tier diagnostic approach in genetically heterogeneous conditions, illustrates the ongoing evolution of molecular diagnosis in the field of clinical neurology. Isolated hyperCKemia can be the sole feature alerting to a progressive muscular disorder requiring careful surveillance.

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