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- Lindstrand, Anna, et al.
(författare)
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From cytogenetics to cytogenomics : whole-genome sequencing as a first-line test comprehensively captures the diverse spectrum of disease-causing genetic variation underlying intellectual disability
- 2019
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Ingår i: Genome Medicine. - : BMC. - 1756-994X .- 1756-994X. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundSince different types of genetic variants, from single nucleotide variants (SNVs) to large chromosomal rearrangements, underlie intellectual disability, we evaluated the use of whole-genome sequencing (WGS) rather than chromosomal microarray analysis (CMA) as a first-line genetic diagnostic test.MethodsWe analyzed three cohorts with short-read WGS: (i) a retrospective cohort with validated copy number variants (CNVs) (cohort 1, n=68), (ii) individuals referred for monogenic multi-gene panels (cohort 2, n=156), and (iii) 100 prospective, consecutive cases referred to our center for CMA (cohort 3). Bioinformatic tools developed include FindSV, SVDB, Rhocall, Rhoviz, and vcf2cytosure.ResultsFirst, we validated our structural variant (SV)-calling pipeline on cohort 1, consisting of three trisomies and 79 deletions and duplications with a median size of 850kb (min 500bp, max 155Mb). All variants were detected. Second, we utilized the same pipeline in cohort 2 and analyzed with monogenic WGS panels, increasing the diagnostic yield to 8%. Next, cohort 3 was analyzed by both CMA and WGS. The WGS data was processed for large (>10kb) SVs genome-wide and for exonic SVs and SNVs in a panel of 887 genes linked to intellectual disability as well as genes matched to patient-specific Human Phenotype Ontology (HPO) phenotypes. This yielded a total of 25 pathogenic variants (SNVs or SVs), of which 12 were detected by CMA as well. We also applied short tandem repeat (STR) expansion detection and discovered one pathologic expansion in ATXN7. Finally, a case of Prader-Willi syndrome with uniparental disomy (UPD) was validated in the WGS data.Important positional information was obtained in all cohorts. Remarkably, 7% of the analyzed cases harbored complex structural variants, as exemplified by a ring chromosome and two duplications found to be an insertional translocation and part of a cryptic unbalanced translocation, respectively.ConclusionThe overall diagnostic rate of 27% was more than doubled compared to clinical microarray (12%). Using WGS, we detected a wide range of SVs with high accuracy. Since the WGS data also allowed for analysis of SNVs, UPD, and STRs, it represents a powerful comprehensive genetic test in a clinical diagnostic laboratory setting.
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| 2. |
- Lindstrand, Anna, et al.
(författare)
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Genome sequencing is a sensitive first-line test to diagnose individuals with intellectual disability
- 2022
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Ingår i: Genetics in Medicine. - : ELSEVIER SCIENCE INC. - 1098-3600 .- 1530-0366. ; 24:11, s. 2296-2307
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Individuals with intellectual disability (ID) and/or neurodevelopment disorders (NDDs) are currently investigated with several different approaches in clinical genetic diagnostics. Methods: We compared the results from 3 diagnostic pipelines in patients with ID/NDD: genome sequencing (GS) first (N = 100), GS as a secondary test (N = 129), or chromosomal microarray (CMA) with or without FMR1 analysis (N = 421). Results: The diagnostic yield was 35% (GS -first), 26% (GS as a secondary test), and 11% (CMA/FMR1). Notably, the age of diagnosis was delayed by 1 year when GS was performed as a secondary test and the cost per diagnosed individual was 36% lower with GS first than with CMA/FMR1. Furthermore, 91% of those with a negative result after CMA/FMR1 analysis (338 individuals) have not yet been referred for additional genetic testing and remain undiagnosed. Conclusion: Our findings strongly suggest that genome analysis outperforms other testing strategies and should replace traditional CMA and FMR1 analysis as a first-line genetic test in individuals with ID/NDD. GS is a sensitive, time-and cost-effective method that results in a confirmed molecular diagnosis in 35% of all referred patients. (c) 2022 The Authors. Published by Elsevier Inc. on behalf of American College of Medical Genetics and Genomics. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 3. |
- Saether, Kristine Bilgrav, et al.
(författare)
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Transposable element insertions in 1000 Swedish individuals
- 2023
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 18:7
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Tidskriftsartikel (refereegranskat)abstract
- The majority of rare diseases are genetic, and regardless of advanced high-throughput genomics-based investigations, 60% of patients remain undiagnosed. A major factor limiting our ability to identify disease-causing alterations is a poor understanding of the morbid and normal human genome. A major genomic contributor of which function and distribution remain largely unstudied are the transposable elements (TE), which constitute 50% of our genome. Here we aim to resolve this knowledge gap and increase the diagnostic yield of rare disease patients investigated with clinical genome sequencing. To this end we characterized TE insertions in 1000 Swedish individuals from the SweGen dataset and 2504 individuals from the 1000 Genomes Project (1KGP), creating seven population-specific TE insertion databases. Of note, 66% of TE insertions in SweGen were present at > 1% in the 1KGP databases, proving that most insertions are common across populations. Focusing on the rare TE insertions, we show that even though similar to 0.7% of those insertions affect protein coding genes, they rarely affect known disease casing genes (< 0.1%). Finally, we applied a TE insertion identification workflow on two clinical cases where disease causing TE insertions were suspected and could verify the presence of pathogenic TE insertions in both. Altogether we demonstrate the importance of TE insertion detection and highlight possible clinical implications in rare disease diagnostics.
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| 4. |
- Tham, Emma, et al.
(författare)
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A novel phenotype in N-glycosylation disorders: Gillessen-Kaesbach-Nishimura skeletal dysplasia due to pathogenic variants in ALG9.
- 2015
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Ingår i: European Journal of Human Genetics. - : Springer Science and Business Media LLC. - 1476-5438 .- 1018-4813.
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Tidskriftsartikel (refereegranskat)abstract
- A rare lethal autosomal recessive syndrome with skeletal dysplasia, polycystic kidneys and multiple malformations was first described by Gillessen-Kaesbach et al and subsequently by Nishimura et al. The skeletal features uniformly comprise a round pelvis, mesomelic shortening of the upper limbs and defective ossification of the cervical spine. We studied two unrelated families including three affected fetuses with Gillessen-Kaesbach-Nishimura syndrome using whole-exome and Sanger sequencing, comparative genome hybridization and homozygosity mapping. All affected patients were shown to have a novel homozygous splice variant NM_024740.2: c.1173+2T>A in the ALG9 gene, encoding alpha-1,2-mannosyltransferase, involved in the formation of the lipid-linked oligosaccharide precursor of N-glycosylation. RNA analysis demonstrated skipping of exon 10, leading to shorter RNA. Mass spectrometric analysis showed an increase in monoglycosylated transferrin as compared with control tissues, confirming that this is a congenital disorder of glycosylation (CDG). Only three liveborn children with ALG9-CDG have been previously reported, all with missense variants. All three suffered from intellectual disability, muscular hypotonia, microcephaly and renal cysts, but none had skeletal dysplasia. Our study shows that some pathogenic variants in ALG9 can present as a lethal skeletal dysplasia with visceral malformations as the most severe phenotype. The skeletal features overlap with that previously reported for ALG3- and ALG12-CDG, suggesting that this subset of glycosylation disorders constitutes a new diagnostic group of skeletal dysplasias.European Journal of Human Genetics advance online publication, 13 May 2015; doi:10.1038/ejhg.2015.91.
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