scholarly journals Long-Read Sequencing to Unravel Complex Structural Variants of CEP78 Leading to Cone-Rod Dystrophy and Hearing Loss

2021 ◽  
Vol 9 ◽  
Author(s):  
Giulia Ascari ◽  
Nanna D. Rendtorff ◽  
Marieke De Bruyne ◽  
Julie De Zaeytijd ◽  
Michel Van Lint ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Gene Deletion ◽  
Splice Variants ◽  
Quantitative Polymerase Chain Reaction ◽  
Whole Genome ◽  
Loss Of Function ◽  
Expression Domain ◽  
Long Read ◽  
Complex Structural

Inactivating variants as well as a missense variant in the centrosomal CEP78 gene have been identified in autosomal recessive cone-rod dystrophy with hearing loss (CRDHL), a rare syndromic inherited retinal disease distinct from Usher syndrome. Apart from this, a complex structural variant (SV) implicating CEP78 has been reported in CRDHL. Here we aimed to expand the genetic architecture of typical CRDHL by the identification of complex SVs of the CEP78 region and characterization of their underlying mechanisms. Approaches used for the identification of the SVs are shallow whole-genome sequencing (sWGS) combined with quantitative polymerase chain reaction (PCR) and long-range PCR, or ExomeDepth analysis on whole-exome sequencing (WES) data. Targeted or whole-genome nanopore long-read sequencing (LRS) was used to delineate breakpoint junctions at the nucleotide level. For all SVs cases, the effect of the SVs on CEP78 expression was assessed using quantitative PCR on patient-derived RNA. Apart from two novel canonical CEP78 splice variants and a frameshifting single-nucleotide variant (SNV), two SVs affecting CEP78 were identified in three unrelated individuals with CRDHL: a heterozygous total gene deletion of 235 kb and a partial gene deletion of 15 kb in a heterozygous and homozygous state, respectively. Assessment of the molecular consequences of the SVs on patient’s materials displayed a loss-of-function effect. Delineation and characterization of the 15-kb deletion using targeted LRS revealed the previously described complex CEP78 SV, suggestive of a recurrent genomic rearrangement. A founder haplotype was demonstrated for the latter SV in cases of Belgian and British origin, respectively. The novel 235-kb deletion was delineated using whole-genome LRS. Breakpoint analysis showed microhomology and pointed to a replication-based underlying mechanism. Moreover, data mining of bulk and single-cell human and mouse transcriptional datasets, together with CEP78 immunostaining on human retina, linked the CEP78 expression domain with its phenotypic manifestations. Overall, this study supports that the CEP78 locus is prone to distinct SVs and that SV analysis should be considered in a genetic workup of CRDHL. Finally, it demonstrated the power of sWGS and both targeted and whole-genome LRS in identifying and characterizing complex SVs in patients with ocular diseases.

scholarly journals Molecular characterization of pathogenic OTOA gene conversions in hearing loss patients

2021 ◽  
Author(s):  
Sacha Laurent ◽  
Corinne Gehrig ◽  
Thierry Nouspikel ◽  
Sami S Amr ◽  
Andrea Oza ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Stop Codon ◽  
Premature Stop Codon ◽  
Allelic Loss ◽  
Loss Of Function ◽  
Chain Reactions ◽  
Polymerase Chain Reactions ◽  
Long Read ◽  
Gene Conversions

Bi-allelic loss-of-function variants of OTOA are a well-known cause of moderate-to-severe hearing loss. Whereas non-allelic homologous recombination-mediated deletions of the gene are well known, gene conversions to pseudogene OTOAP1 have been reported in the literature but never fully described nor their pathogenicity assessed. Here, we report two unrelated patients with moderate hearing-loss, who were compound heterozygotes for a converted allele and a deletion of OTOA. The conversions were initially detected through sequencing depths anomalies at the OTOA locus after exome sequencing, then confirmed with long range polymerase chain reactions. Both conversions lead to loss-of-function by introducing a premature stop codon in exon 22 (p.Glu787*). Using genomic alignments and long read nanopore sequencing, we found that the two probands carry stretches of converted DNA of widely different lengths (at least 9 kbp and around 900 bp, respectively).

scholarly journals Exploring the Missing Heritability in Subjects With Hearing Loss, Enlarged Vestibular Aqueducts, and A Single or No Pathogenic SLC26A4 Variant

2021 ◽  
Author(s):  
Jeroen Smits ◽  
Suzanne E. de Bruijn ◽  
Cornelis P. Lanting ◽  
Jaap Oostrik ◽  
Luke O’Gorman ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Whole Genome Sequencing ◽  
Genome Sequencing ◽  
Genome Mapping ◽  
Copy Number Variants ◽  
Whole Genome ◽  
Missing Heritability ◽  
Vestibular Aqueduct ◽  
Pathogenic Variants ◽  
Long Read

Abstract Pathogenic variants in SLC26A4 have been associated with autosomal recessive hearing loss (arHL) and a unilateral or bilateral enlarged vestibular aqueduct (EVA). SLC26A4 is the second most frequently mutated gene in arHL. Despite the strong genotype-phenotype correlation, a significant part of SLC26A4 cases remains genetically unresolved. In this study, we investigated a cohort of 28 Dutch index cases diagnosed with HL in combination with an EVA but without (M0) or with a single (M1) pathogenic variant in SLC26A4. To explore the missing heritability, short- and long-read whole genome sequencing and optical genome mapping were performed. We found a previously described EVA-associated haplotype (Caucasian EVA (CEVA)) to be significantly enriched in our M1 patient cohort. The haplotype was also present in two M0 cases. Despite extensive genetic analyses, we were not able to prioritize any of the variants present within the haplotype as the likely pathogenic defect, and therefore additional analyses addressing the defect(s) at the RNA, protein, or epigenetic level are required. Whole genome sequencing also revealed splice-altering SLC26A4 variants in two M1 cases, which are now genetically explained, but no deep-intronic or copy number variants. With these findings, we have provided important insights that will pave the way for elucidating the missing heritability in M0 and M1 SLC26A4 cases.

scholarly journals Characterization of Genetically Modified Microorganisms Using Short- and Long-Read Whole-Genome Sequencing Reveals Contaminations of Related Origin in Multiple Commercial Food Enzyme Products

Foods ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2637
Author(s):  
Jolien D’aes ◽  
Marie-Alice Fraiture ◽  
Bert Bogaerts ◽  
Sigrid C. J. De Keersmaecker ◽  
Nancy H. C. Roosens ◽  
...  
Keyword(s):  
Whole Genome Sequencing ◽  
Genome Sequencing ◽  
Genetically Modified ◽  
Added Value ◽  
Phylogenomic Analysis ◽  
Whole Genome ◽  
Antimicrobial Resistance Genes ◽  
Long Read ◽  
Genomic Characterization

Despite their presence being unauthorized on the European market, contaminations with genetically modified (GM) microorganisms have repeatedly been reported in diverse commercial microbial fermentation produce types. Several of these contaminations are related to a GM Bacillus velezensis used to synthesize a food enzyme protease, for which genomic characterization remains currently incomplete, and it is unknown whether these contaminations have a common origin. In this study, GM B. velezensis isolates from multiple food enzyme products were characterized by short- and long-read whole-genome sequencing (WGS), demonstrating that they harbor a free recombinant pUB110-derived plasmid carrying antimicrobial resistance genes. Additionally, single-nucleotide polymorphism (SNP) and whole-genome based comparative analyses showed that the isolates likely originate from the same parental GM strain. This study highlights the added value of a hybrid WGS approach for accurate genomic characterization of GMM (e.g., genomic location of the transgenic construct), and of SNP-based phylogenomic analysis for source-tracking of GMM.

scholarly journals Exploring the missing heritability in subjects with hearing loss, enlarged vestibular aqueducts, and a single or no pathogenic SLC26A4 variant

2021 ◽  
Author(s):  
Jeroen J. Smits ◽  
Suzanne E. de Bruijn ◽  
Cornelis P. Lanting ◽  
Jaap Oostrik ◽  
Luke O’Gorman ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Whole Genome Sequencing ◽  
Genome Sequencing ◽  
Genome Mapping ◽  
Whole Genome ◽  
Missing Heritability ◽  
Single Nucleotide Variants ◽  
Vestibular Aqueduct ◽  
Pathogenic Variants ◽  
Long Read

AbstractPathogenic variants in SLC26A4 have been associated with autosomal recessive hearing loss (arHL) and a unilateral or bilateral enlarged vestibular aqueduct (EVA). SLC26A4 is the second most frequently mutated gene in arHL. Despite the strong genotype–phenotype correlation, a significant part of cases remains genetically unresolved. In this study, we investigated a cohort of 28 Dutch index cases diagnosed with HL in combination with an EVA but without (M0) or with a single (M1) pathogenic variant in SLC26A4. To explore the missing heritability, we first determined the presence of the previously described EVA-associated haplotype (Caucasian EVA (CEVA)), characterized by 12 single nucleotide variants located upstream of SLC26A4. We found this haplotype and a delimited V1-CEVA haplotype to be significantly enriched in our M1 patient cohort (10/16 cases). The CEVA haplotype was also present in two M0 cases (2/12). Short- and long-read whole genome sequencing and optical genome mapping could not prioritize any of the variants present within the CEVA haplotype as the likely pathogenic defect. Short-read whole-genome sequencing of the six M1 cases without this haplotype and the two M0/CEVA cases only revealed previously overlooked or misinterpreted splice-altering SLC26A4 variants in two cases, who are now genetically explained. No deep-intronic or structural variants were identified in any of the M1 subjects. With this study, we have provided important insights that will pave the way for elucidating the missing heritability in M0 and M1 SLC26A4 cases. For pinpointing the pathogenic effect of the CEVA haplotype, additional analyses are required addressing defect(s) at the RNA, protein, or epigenetic level.

scholarly journals Small Deletion at the 7q21.2 Locus in a CCM Family Detected by Real-Time Quantitative PCR

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Lucia Anna Muscarella ◽  
Vito Guarnieri ◽  
Michelina Coco ◽  
Serena Belli ◽  
Paola Parrella ◽  
...  
Keyword(s):  
Real Time ◽  
Molecular Characterization ◽  
Quantitative Polymerase Chain Reaction ◽  
Genetic Diseases ◽  
Complete Loss ◽  
Loss Of Function ◽  
Autosomal Dominant Disorder ◽  
Cavernous Malformations ◽  
Genomic Deletions

Cerebral cavernous malformations (CCMs) represent a common autosomal dominant disorder that predisposes patients to haemorrhagic strokes and focal neurological signs. About 56% of the hereditary forms of CCMs have been so far associated with mutations in theKRIT1(Krev Interaction Trapped 1) gene, located at 7q21.2 (CCM1 locus). We described the complete loss of 7q21.2 locus encompassing theKRIT1gene and 4 flanking genes in a CCM family by using a dense set of 12 microsatellite markers. The complete loss of the maternal copy ofKRIT1gene region was confirmed by Real-Time Quantitative Polymerase Chain Reaction (RT-QPCR) and the same approach was used for expression analysis. Additional RT-QPCR analysis showed the extension of the deletion, for a total of 700 kb, to the adjacent downstream and upstream-located genes,MTERF, AKAP9, CYP51A1, as well as a partial loss of theANKIB1gene. Here we report the molecular characterization of an interstitial small genomic deletion of the 7q21.2 region in a CCMs affected family, encompassing theKRIT1gene. Our findings confirm the loss of function mechanism for the already known CCM1 locus, without any evident involvement of the other deleted genes. Moreover, our investigations highlight the usefulness of the RT-QPCR to the molecular characterization of the breakpoints genomic deletions and to the identification of internal deleted genes involved in the human genetic diseases.

scholarly journals Global characterization of copy number variants in epilepsy patients from whole genome sequencing

2017 ◽  
Author(s):  
Jean Monlong ◽  
Simon L. Girard ◽  
Caroline Meloche ◽  
Maxime Cadieux-Dion ◽  
Danielle M. Andrade ◽  
...  
Keyword(s):  
Whole Genome Sequencing ◽  
Genome Sequencing ◽  
Copy Number ◽  
Copy Number Variants ◽  
Genetic Variations ◽  
Genome Wide Association Studies ◽  
Whole Genome ◽  
Loss Of Function ◽  
Genome Wide

AbstractEpilepsy will affect nearly 3% of people at some point during their lifetime. Previous copy number variants (CNVs) studies of epilepsy have used array-based technology and were restricted to the detection of large or exonic events. In contrast, whole-genome sequencing (WGS) has the potential to more comprehensively profile CNVs but existing analytic methods suffer from limited accuracy. We show that this is in part due to the non-uniformity of read coverage, even after intra-sample normalization. To improve on this, we developed PopSV, an algorithm that uses multiple samples to control for technical variation and enables the robust detection of CNVs. Using WGS and PopSV, we performed a comprehensive characterization of CNVs in 198 individuals affected with epilepsy and 301 controls. For both large and small variants, we found an enrichment of rare exonic events in epilepsy patients, especially in genes with predicted loss-of-function intolerance. Notably, this genome-wide survey also revealed an enrichment of rare non-coding CNVs near previously known epilepsy genes. This enrichment was strongest for non-coding CNVs located within 100 Kbp of an epilepsy gene and in regions associated with changes in the gene expression, such as expression QTLs or DNase I hypersensitive sites. Finally, we report on 21 potentially damaging events that could be associated with known or new candidate epilepsy genes. Our results suggest that comprehensive sequence-based profiling of CNVs could help explain a larger fraction of epilepsy cases.Author summaryEpilepsy is a common neurological disorder affecting around 3% of the population. In some cases, epilepsy is caused by brain trauma or other brain anomalies but there are often no clear causes. Genetic factors have been associated with epilepsy in the past such as rare genetic variations found by linkage studies as well as common genetic variations found by genome-wide association studies and large copy-number variants. We sequenced the genome of ∼200 epilepsy patients and ∼300 healthy controls and compared the distribution of deletion (loss of a copy) and duplication (additional copy) of genomic regions. Thanks to the sequencing technology and a new method that takes advantage of the large sample size, we could compare the distribution of small copy- number variants between epilepsy patients and controls. Overall, we found that small variants are also associated with epilepsy. Indeed, the genome of epilepsy patients had more exonic copy- number variants, especially when rare or affecting genes with predicted loss-of-function intolerance. Focusing on regions around genes that have been previously associated with epilepsy, we also found more non-coding variants in epilepsy patients, especially deletions or variants in regulatory regions. Finally, we provide a list of 21 regions in which we found likely pathogenic variants.

scholarly journals Complex Structural Variants Resolved by Short-Read and Long-Read Whole Genome Sequencing in Mendelian Disorders

2018 ◽  
Author(s):  
Alba Sanchis-Juan ◽  
Jonathan Stephens ◽  
Courtney E French ◽  
Nicholas Gleadall ◽  
Karyn Mégy ◽  
...  
Keyword(s):  
Whole Genome Sequencing ◽  
Genome Sequencing ◽  
De Novo ◽  
Genomic Variation ◽  
Mendelian Disease ◽  
Whole Genome ◽  
Structural Variants ◽  
Short Read ◽  
Long Read ◽  
Complex Structural

AbstractComplex structural variants (cxSVs) are genomic rearrangements comprising multiple structural variants, typically involving three or more breakpoint junctions. They contribute to human genomic variation and can cause Mendelian disease, however they are not typically considered during genetic testing. Here, we investigate the role of cxSVs in Mendelian disease using short-read whole genome sequencing (WGS) data from 1,324 individuals with neurodevelopmental or retinal disorders from the NIHR BioResource project. We present four cases of individuals with a cxSV affecting Mendelian disease-associated genes. Three of the cxSVs are pathogenic: a de novo duplication-inversion-inversion-deletion affecting ARID1B in an individual with Coffin-Siris syndrome, a deletion-inversion-duplication affecting HNRNPU in an individual with intellectual disability and seizures, and a homozygous deletion-inversion-deletion affecting CEP78 in an individual with cone-rod dystrophy. Additionally, we identified a de novo duplication-inversion-duplication overlapping CDKL5 in an individual with neonatal hypoxic-ischaemic encephalopathy. Long-read sequencing technology used to resolve the breakpoints demonstrated the presence of both a disrupted and an intact copy of CDKL5 on the same allele; therefore, it was classified as a variant of uncertain significance. Analysis of sequence flanking all breakpoint junctions in all the cxSVs revealed both microhomology and longer repetitive sequences, suggesting both replication and homology based processes. Accurate resolution of cxSVs is essential for clinical interpretation, and here we demonstrate that long-read WGS is a powerful technology by which to achieve this. Our results show cxSVs are an important although rare cause of Mendelian disease, and we therefore recommend their consideration during research and clinical investigations.

scholarly journals Accurate characterization of expanded tandem repeat length and sequence through whole genome long-read sequencing on PromethION

2018 ◽  
Author(s):  
Arne De Roeck ◽  
Wouter De Coster ◽  
Liene Bossaerts ◽  
Rita Cacace ◽  
Tim De Pooter ◽  
...  
Keyword(s):  
Southern Blotting ◽  
Flow Cell ◽  
Current Data ◽  
Whole Genome ◽  
Genome Coverage ◽  
Base Calling ◽  
Length Estimation ◽  
Long Read ◽  
Repeat Expansions

AbstractTandem repeats (TRs) can cause disease through their length, sequence motif interruptions, and nucleotide modifications. For many TRs, however, these features are very difficult - if not impossible - to assess, requiring low-throughput and labor-intensive assays. One example is a VNTR in ABCA7 for which we recently discovered that expanded alleles strongly increase risk of Alzheimer’s disease. Here, we investigated the potential of long-read whole genome sequencing to surmount these challenges, using the high-throughput PromethION platform from Oxford Nanopore Technologies. To overcome the limitations of conventional base calling and alignment, we developed an algorithm to study the TR size and sequence directly on raw PromethION current data.We report the long-read sequencing of multiple human genomes (n = 11) using only a single sequencing run and flow cell per individual. With the use of fresh DNA extractions, DNA shearing to approximately 20kb and size selection, we obtained an average output of 70 gigabases (Gb) per flow cell, corresponding to a 21x genome coverage, and a maximum yield of 98 Gb (30x genome coverage). All ABCA7 VNTR alleles, including expansions up to 10,000 bases, were spanned by long sequencing reads, validated by Southern blotting. Classical approaches of TR length estimation suffered from low accuracy, low precision, DNA strand effects and/or inability to call pathogenic repeat expansions. In contrast, our novel NanoSatellite algorithm, which circumvents base calling by using dynamic time warping on raw PromethION current data, achieved more than 90% accuracy and high precision (5.6% relative standard deviation) of TR length estimation, and detected all clinically relevant repeat expansions. In addition, we identified alternative TR sequence motifs with high consistency, allowing determination of TR sequence and distinction of VNTR alleles with homozygous length.In conclusion, we validated the robustness of single-experiment whole genome long-read sequencing on PromethION, a prerequisite for application of long-read sequencing in the clinic. In addition, we outperformed Southern blotting, enabling improved characterization of the role of expanded ABCA7 VNTR alleles in Alzheimer’s disease, and opening new opportunities for TR research.

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