Publications by authors named "Eriskay Liston"

10 Publications

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Genes and Pathways Implicated in Tetralogy of Fallot Revealed by Ultra-Rare Variant Burden Analysis in 231 Genome Sequences.

Front Genet 2020 15;11:957. Epub 2020 Sep 15.

Clinical Genetics Research Program, Centre for Addiction and Mental Health, Toronto, ON, Canada.

Recent genome-wide studies of rare genetic variants have begun to implicate novel mechanisms for tetralogy of Fallot (TOF), a severe congenital heart defect (CHD). To provide statistical support for case-only data without parental genomes, we re-analyzed genome sequences of 231 individuals with TOF ( = 175) or related CHD. We adapted a burden test originally developed for variants to assess ultra-rare variant burden in individual genes, and in gene-sets corresponding to functional pathways and mouse phenotypes, accounting for highly correlated gene-sets and for multiple testing. For truncating variants, the gene burden test confirmed significant burden in (Bonferroni corrected -value < 0.01). For missense variants, burden in achieved genome-wide significance only when restricted to constrained genes (i.e., under negative selection, Bonferroni corrected -value = 0.004), and showed enrichment for variants affecting the extracellular domain, especially those disrupting cysteine residues forming disulfide bonds (OR = 39.8 vs. gnomAD). Individuals with ultra-rare missense variants, all with TOF, were enriched for positive family history of CHD. Other genes not previously implicated in CHD had more modest statistical support in gene burden tests. Gene-set burden tests for truncating variants identified a cluster of pathways corresponding to VEGF signaling ( = 0%), and of mouse phenotypes corresponding to abnormal vasculature ( = 0.8%); these suggested additional candidate genes not previously identified (e.g., and ). Results for the most promising genes were driven by the TOF subset of the cohort. The findings support the importance of ultra-rare variants disrupting genes involved in VEGF and NOTCH signaling in the genetic architecture of TOF, accounting for 11-14% of individuals in the TOF cohort. These proof-of-principle data indicate that this statistical methodology could assist in analyzing case-only sequencing data in which ultra-rare variants, whether or inherited, contribute to the genetic etiopathogenesis of a complex disorder.
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http://dx.doi.org/10.3389/fgene.2020.00957DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7522597PMC
September 2020

Endocrine and Growth Abnormalities in 4H Leukodystrophy Caused by Variants in POLR3A, POLR3B, and POLR1C.

J Clin Endocrinol Metab 2021 Jan;106(2):e660-e674

Department of Child Neurology, University Children's Hospital Tübingen, Tübingen, Germany.

Context: 4H or POLR3-related leukodystrophy is an autosomal recessive disorder typically characterized by hypomyelination, hypodontia, and hypogonadotropic hypogonadism, caused by biallelic pathogenic variants in POLR3A, POLR3B, POLR1C, and POLR3K. The endocrine and growth abnormalities associated with this disorder have not been thoroughly investigated to date.

Objective: To systematically characterize endocrine abnormalities of patients with 4H leukodystrophy.

Design: An international cross-sectional study was performed on 150 patients with genetically confirmed 4H leukodystrophy between 2015 and 2016. Endocrine and growth abnormalities were evaluated, and neurological and other non-neurological features were reviewed. Potential genotype/phenotype associations were also investigated.

Setting: This was a multicenter retrospective study using information collected from 3 predominant centers.

Patients: A total of 150 patients with 4H leukodystrophy and pathogenic variants in POLR3A, POLR3B, or POLR1C were included.

Main Outcome Measures: Variables used to evaluate endocrine and growth abnormalities included pubertal history, hormone levels (estradiol, testosterone, stimulated LH and FSH, stimulated GH, IGF-I, prolactin, ACTH, cortisol, TSH, and T4), and height and head circumference charts.

Results: The most common endocrine abnormalities were delayed puberty (57/74; 77% overall, 64% in males, 89% in females) and short stature (57/93; 61%), when evaluated according to physician assessment. Abnormal thyroid function was reported in 22% (13/59) of patients.

Conclusions: Our results confirm pubertal abnormalities and short stature are the most common endocrine features seen in 4H leukodystrophy. However, we noted that endocrine abnormalities are typically underinvestigated in this patient population. A prospective study is required to formulate evidence-based recommendations for management of the endocrine manifestations of this disorder.
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http://dx.doi.org/10.1210/clinem/dgaa700DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823228PMC
January 2021

A novel intronic variant in UBE3A identified by genome sequencing in a patient with an atypical presentation of Angelman syndrome.

Am J Med Genet A 2020 09 11;182(9):2145-2151. Epub 2020 Jul 11.

Centre for Genetic Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada.

Angelman syndrome (AS) is a genetic neurodevelopmental disorder caused by loss or deficient expression of UBE3A on the maternally inherited allele. In 10-15% of individuals with a clinical diagnosis of AS, a molecular diagnosis cannot be established with conventional testing. We describe a 13-year-old male with an atypical presentation of AS, who was found to have a novel, maternally inherited, intronic variant in UBE3A (c.3-12T>A) using genome sequencing (GS). Targeted sequencing of RNA isolated from blood confirmed the creation of a new acceptor splice site. These GS results ended a six-year diagnostic odyssey and revealed a 50% recurrence risk for the unaffected parents. This case illustrates a previously unreported splicing variant causing AS. Intronic variants identifiable by GS may account for a proportion of individuals who are suspected of having well-known genetic disorders despite negative prior genetic testing.
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http://dx.doi.org/10.1002/ajmg.a.61740DOI Listing
September 2020

The Cardiac Genome Clinic: implementing genome sequencing in pediatric heart disease.

Genet Med 2020 06 10;22(6):1015-1024. Epub 2020 Feb 10.

Ted Rogers Centre for Heart Research, Cardiac Genome Clinic, The Hospital for Sick Children, Toronto, ON, Canada.

Purpose: This study investigated the diagnostic utility of nontargeted genomic testing in patients with pediatric heart disease.

Methods: We analyzed genome sequencing data of 111 families with cardiac lesions for rare, disease-associated variation.

Results: In 14 families (12.6%), we identified causative variants: seven were de novo (ANKRD11, KMT2D, NR2F2, POGZ, PTPN11, PURA, SALL1) and six were inherited from parents with no or subclinical heart phenotypes (FLT4, DNAH9, MYH11, NEXMIF, NIPBL, PTPN11). Outcome of the testing was associated with the presence of extracardiac features (p = 0.02), but not a positive family history for cardiac lesions (p = 0.67). We also report novel plausible gene-disease associations for tetralogy of Fallot/pulmonary stenosis (CDC42BPA, FGD5), hypoplastic left or right heart (SMARCC1, TLN2, TRPM4, VASP), congenitally corrected transposition of the great arteries (UBXN10), and early-onset cardiomyopathy (TPCN1). The identified candidate genes have critical functions in heart development, such as angiogenesis, mechanotransduction, regulation of heart size, chromatin remodeling, or ciliogenesis.

Conclusion: This data set demonstrates the diagnostic and scientific value of genome sequencing in pediatric heart disease, anticipating its role as a first-tier diagnostic test. The genetic heterogeneity will necessitate large-scale genomic initiatives for delineating novel gene-disease associations.
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http://dx.doi.org/10.1038/s41436-020-0757-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7272322PMC
June 2020

Return of genetic and genomic research findings: experience of a pediatric biorepository.

BMC Med Genomics 2019 11 27;12(1):173. Epub 2019 Nov 27.

Division of Cardiology, Labatt Family Heart Centre, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada.

Background: Assess process, uptake, validity and resource needs for return of actionable research findings to biobank participants.

Methods: Participants were prospectively enrolled in a multicenter biorepository of childhood onset heart disease. Clinically actionable research findings were reviewed by a Return of Research Results Committee (RRR) and returned to the physician or disclosed directly to the participant through a research genetic counselor. Action taken following receipt of this information was reviewed.

Results: Genetic data was generated in 1963 of 7408 participants. Fifty-nine new findings were presented to the RRR committee; 20 (34%) were deemed reportable. Twelve were returned to the physician, of which 7 were disclosed to participants (median time to disclosure, 192 days). Seven findings were returned to the research genetic counselor; all have been disclosed (median time to disclosure, 19 days). Twelve families (86%) opted for referral to clinical genetics after disclosure of findings; 7 results have been validated, 5 results are pending. Average cost of return and disclosure per reportable finding incurred by the research program was $750 when utilizing a research genetic counselor; clinical costs associated with return were not included.

Conclusions: Return of actionable research findings was faster if disclosed directly to the participant by a research genetic counselor. There was a high acceptability amongst participants for receiving the findings, for referral to clinical genetics, and for clinical validation of research findings, with all referred cases being clinically confirmed.
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http://dx.doi.org/10.1186/s12920-019-0618-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6882371PMC
November 2019

Haploinsufficiency of vascular endothelial growth factor related signaling genes is associated with tetralogy of Fallot.

Genet Med 2019 04 20;21(4):1001-1007. Epub 2018 Sep 20.

Clinical Genetics Research Program, Centre for Addiction and Mental Health, Toronto, Ontario, Canada.

Purpose: To determine disease-associated single-gene variants in conotruncal defects, particularly tetralogy of Fallot (TOF).

Methods: We analyzed for rare loss-of-function and deleterious variants in FLT4 (VEGFR3) and other genes in the vascular endothelial growth factor (VEGF) pathway, as part of a genome sequencing study involving 175 adults with TOF from a single site.

Results: We identified nine (5.1%) probands with novel FLT4 variants: seven loss-of-function, including an 8-kb deletion, and two predicted damaging. In ten other probands we found likely disruptive variants in VEGF-related genes: KDR (VEGFR2; two stopgain and two nonsynonymous variants), VEGFA, FGD5, BCAR1, IQGAP1, FOXO1, and PRDM1. Detection of VEGF-related variants (19/175, 10.9%) was associated with an increased prevalence of absent pulmonary valve (26.3% vs. 3.4%, p < 0.0001) and right aortic arch (52.6% vs. 29.1%, p = 0.029). Extracardiac anomalies were rare. In an attempt to replicate findings, we identified three loss-of-function or damaging variants in FLT4, KDR, and IQGAP1 in ten independent families with TOF.

Conclusion: Loss-of-function variants in FLT4 and KDR contribute substantially to the genetic basis of TOF. The findings support dysregulated VEGF signaling as a novel mechanism contributing to the pathogenesis of TOF.
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http://dx.doi.org/10.1038/s41436-018-0260-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752294PMC
April 2019

Reappraisal of Reported Genes for Sudden Arrhythmic Death: Evidence-Based Evaluation of Gene Validity for Brugada Syndrome.

Circulation 2018 09;138(12):1195-1205

Toronto General Hospital Research Institute, University of Toronto, Ontario, Canada (S.U., M.H.G.).

Background: Implicit in the genetic evaluation of patients with suspected genetic diseases is the assumption that the genes evaluated are causative for the disease based on robust scientific and statistical evidence. However, in the past 20 years, considerable variability has existed in the study design and quality of evidence supporting reported gene-disease associations, raising concerns of the validity of many published disease-causing genes. Brugada syndrome (BrS) is an arrhythmia syndrome with a risk of sudden death. More than 20 genes have been reported to cause BrS and are assessed routinely on genetic testing panels in the absence of a systematic, evidence-based evaluation of the evidence supporting the causality of these genes.

Methods: We evaluated the clinical validity of genes tested by diagnostic laboratories for BrS by assembling 3 gene curation teams. Using an evidence-based semiquantitative scoring system of genetic and experimental evidence for gene-disease associations, curation teams independently classified genes as demonstrating limited, moderate, strong, or definitive evidence for disease causation in BrS. The classification of curator teams was reviewed by a clinical domain expert panel that could modify the classifications based on their independent review and consensus.

Results: Of 21 genes curated for clinical validity, biocurators classified only 1 gene ( SCN5A) as definitive evidence, whereas all other genes were classified as limited evidence. After comprehensive review by the clinical domain Expert panel, all 20 genes classified as limited evidence were reclassified as disputed with regard to any assertions of disease causality for BrS.

Conclusions: Our results contest the clinical validity of all but 1 gene clinically tested and reported to be associated with BrS. These findings warrant a systematic, evidence-based evaluation for reported gene-disease associations before use in patient care.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.118.035070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6147087PMC
September 2018

A Recurrent De Novo Variant in NACC1 Causes a Syndrome Characterized by Infantile Epilepsy, Cataracts, and Profound Developmental Delay.

Am J Hum Genet 2017 Feb 26;100(2):343-351. Epub 2017 Jan 26.

Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.

Whole-exome sequencing (WES) has increasingly enabled new pathogenic gene variant identification for undiagnosed neurodevelopmental disorders and provided insights into both gene function and disease biology. Here, we describe seven children with a neurodevelopmental disorder characterized by microcephaly, profound developmental delays and/or intellectual disability, cataracts, severe epilepsy including infantile spasms, irritability, failure to thrive, and stereotypic hand movements. Brain imaging in these individuals reveals delay in myelination and cerebral atrophy. We observe an identical recurrent de novo heterozygous c.892C>T (p.Arg298Trp) variant in the nucleus accumbens associated 1 (NACC1) gene in seven affected individuals. One of the seven individuals is mosaic for this variant. NACC1 encodes a transcriptional repressor implicated in gene expression and has not previously been associated with germline disorders. The probability of finding the same missense NACC1 variant by chance in 7 out of 17,228 individuals who underwent WES for diagnoses of neurodevelopmental phenotypes is extremely small and achieves genome-wide significance (p = 1.25 × 10). Selective constraint against missense variants in NACC1 makes this excess of an identical missense variant in all seven individuals more remarkable. Our findings are consistent with a germline recurrent mutational hotspot associated with an allele-specific neurodevelopmental phenotype in NACC1.
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http://dx.doi.org/10.1016/j.ajhg.2016.12.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5294886PMC
February 2017

Recommendations for the integration of genomics into clinical practice.

Genet Med 2016 11 12;18(11):1075-1084. Epub 2016 May 12.

Division of Clinical and Metabolic Genetics, Department of Pediatrics, Hospital for Sick Children, University of Toronto, Ontario, Canada.

The introduction of diagnostic clinical genome and exome sequencing (CGES) is changing the scope of practice for clinical geneticists. Many large institutions are making a significant investment in infrastructure and technology, allowing clinicians to access CGES, especially as health-care coverage begins to extend to clinically indicated genomic sequencing-based tests. Translating and realizing the comprehensive clinical benefits of genomic medicine remain a key challenge for the current and future care of patients. With the increasing application of CGES, it is necessary for geneticists and other health-care providers to understand its benefits and limitations in order to interpret the clinical relevance of genomic variants identified in the context of health and disease. New, collaborative working relationships with specialists across diverse disciplines (e.g., clinicians, laboratorians, bioinformaticians) will undoubtedly be key attributes of the future practice of clinical genetics and may serve as an example for other specialties in medicine. These new skills and relationships will also inform the development of the future model of clinical genetics training curricula. To address the evolving role of the clinical geneticist in the rapidly changing climate of genomic medicine, two Clinical Genetics Think Tank meetings were held that brought together physicians, laboratorians, scientists, genetic counselors, trainees, and patients with experience in clinical genetics, genetic diagnostics, and genetics education. This article provides recommendations that will guide the integration of genomics into clinical practice.Genet Med 18 11, 1075-1084.
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http://dx.doi.org/10.1038/gim.2016.17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5557020PMC
November 2016

Whole Genome Sequencing Expands Diagnostic Utility and Improves Clinical Management in Pediatric Medicine.

NPJ Genom Med 2016 Jan;1

Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada.

The standard of care for first-tier clinical investigation of the etiology of congenital malformations and neurodevelopmental disorders is chromosome microarray analysis (CMA) for copy number variations (CNVs), often followed by gene(s)-specific sequencing searching for smaller insertion-deletions (indels) and single nucleotide variant (SNV) mutations. Whole genome sequencing (WGS) has the potential to capture all classes of genetic variation in one experiment; however, the diagnostic yield for mutation detection of WGS compared to CMA, and other tests, needs to be established. In a prospective study we utilized WGS and comprehensive medical annotation to assess 100 patients referred to a paediatric genetics service and compared the diagnostic yield versus standard genetic testing. WGS identified genetic variants meeting clinical diagnostic criteria in 34% of cases, representing a 4-fold increase in diagnostic rate over CMA (8%) (p-value = 1.42e-05) alone and >2-fold increase in CMA plus targeted gene sequencing (13%) (p-value = 0.0009). WGS identified all rare clinically significant CNVs that were detected by CMA. In 26 patients, WGS revealed indel and missense mutations presenting in a dominant (63%) or a recessive (37%) manner. We found four subjects with mutations in at least two genes associated with distinct genetic disorders, including two cases harboring a pathogenic CNV and SNV. When considering medically actionable secondary findings in addition to primary WGS findings, 38% of patients would benefit from genetic counseling. Clinical implementation of WGS as a primary test will provide a higher diagnostic yield than conventional genetic testing and potentially reduce the time required to reach a genetic diagnosis.
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http://dx.doi.org/10.1038/npjgenmed.2015.12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5447450PMC
January 2016