Biology subjects

Bardel, C.

Publications and source records attributed to Bardel, C..

5 recordsLinked to original sources

bioRxiv2025

Detecting aberrant splicing events in short-read RNA-seq with SAMI, an UMI-aware Nextflow pipeline

SummaryDespite RNA-sequencing solutions have existed for 15 years, successfully replacing micro-arrays for gene expression profiling, their potential to analyse splicing is still to be achieved in clinical settings. Powerful tools were developed to quantify known iso-forms, to compare sample groups or to identify outliers in large datasets, but most fail to address the most common situation in routine diagnostics: identifying non-recurring events in low-dimension data. To fill this gap, we developed SAMI (Splicing Analysis with Molecular Indexes), an UMI-aware pipeline focusing on splicing events which differ from provided annotation. The ability of SAMI and concurrent software to detect intragenic splicing aberrations and gene fusions was assessed, both on real data from a commercial control sample and simulated data generated with ASimulatoR. Availability and ImplementationNextflow pipeline and Singularity container recipe freely available under GPL 3 licence at https://github.com/HCL-HUBL/SAMI Contactsylvain.mareschal@chu-lyon.fr

bioinformatics↗

bioRxiv2025

KILDA: identifying KIV-2 repeats from kmers

MotivationHigh concentration of lipoprotein(a), a lipoprotein with proatherogenic properties, is an important risk factor for cardiovascular disease. This concentration is mostly genetically determined by a complex interplay between the number of Kringle-IV type 2 repeats and Lipoprotein(a)-affecting variants. Besides lipoprotein(a) plasma concentration, there is an unmet need to identify individuals most at risk based on their LPA genotype. ResultsWe developed KILDA, a Nextflow pipeline, to identify the number of Kringle-IV type 2 repeats and Lp(a)-affecting variants directly from kmers generated from FASTQ files. The pipeline was tested on the 1000 Genomes Project (n=2459) and results were equivalent to DRAGEN-LPA (R2=0.93). In-silico datasets proved the robustness of KILDAs predictions under different scenarios of sequencing coverage and quality. ConclusionKILDA is an open-source and free-to-use pipeline to identify the number of Kringle-IV type 2 repeats and lipoprotein(a)-associated variants. Its results are equivalent to DRAGEN-LPA, offering a free and robust tool for determining the LPA kringle number even when inputting low coverage libraries. AvailabilityKILDA is publicly available at https://github.com/HCL-HUBL/KILDA along with a recipe to build an Apptainer image containing all the required dependencies. Contact: corentin.molitor@chu-lyon.fr Supplementary informationSupplementary data are available at Bioinformatics online.

bioinformatics↗

bioRxiv2023

Transposable element expression with variation in gonosome number supports a toxic Y effect on human longevity

AO_SCPLOWBSTRACTC_SCPLOWWhy women live longer than men is still an open question in human biology. Sex chromosomes have been proposed to play a role in the observed sex gap in longevity, and the Y male chromosome has been suspected of having a potential toxic genomic impact on male longevity. It has been hypothesized that in aging individuals, TE repression is diminished, which could lead to detrimental effects (e.g. somatic mutations, perturbed gene expression) and to an acceleration of the aging process. As the Y chromosome is typically enriched in transposable elements (TE), this could explain why the presence of a Y chromosome is associated with shorter longevity. Using transcriptomic data from humans with atypical karyotypes, we found an association between TE expression and the presence and number of Y chromosomes. These findings are consistent with the existence of a toxic Y effect on men's longevity.

molecular biology↗

bioRxiv2020

Performances of targeted RNA-sequencing for the analysis of fusion transcripts, gene mutation and expression in haematological malignancies.

RNA sequencing holds great promise to improve the diagnostic of haematological malignancies, because this technique enables to detect fusion transcripts, to look for somatic mutations in oncogenes, and to capture transcriptomic signatures nosological entities. However, the analytical performances of targeted RNA sequencing have not been extensively described in diagnostic samples. Using a targeted panel of 1385 cancer-related genes in a series of 100 diagnosis samples and 8 controls, we detected all the already known fusion transcripts, and also discovered unknown and/or unsuspected fusion transcripts in 12 samples. Regarding the analysis of transcriptomic profiles, we show that targeted RNA sequencing is performant to discriminate acute lymphoblastic leukemia entities driven by different oncogenic translocations. Additionally, we show that 86% of the mutations identified at the DNA level are also detectable at the mRNA level, except for nonsense mutations which are subjected to mRNA decay. We conclude that targeted RNA sequencing might improve the diagnosis of haematological malignancies. Standardization of the preanalytical steps and further refinements of the panel design and of the bioinformatical pipelines will be an important step towards its use in standard diagnostic procedures.

genomics↗

bioRxiv2020

The enrichment of breakpoints in late-replicating chromatin provides novel insights into chromoanagenesis mechanisms

The rise of pangenomic molecular assays allowed uncovering complex rearrangements named chromoanagenesis that were hypothesized to result from catastrophic shattering events. Constitutional cases have typically been reported individually preventing identification of common features and uncovering the mechanisms at play. We characterized 20 new chromoanagenesis and discovered yet undescribed features. While literature differentiates chromothripsis and its shattering event repaired through non-homologous end joining from chromoanasynthesis born to aberrant replicative processes, we identified shattered chromosomes repaired through a combination of mechanisms. In particular, three samples present with "rearrangement hubs" comprising a fragmented kilobase-long sequence threaded throughout the rearrangement. To assess the mechanisms at play, we merged our data with those of 20 published constitutional complex chromosomal rearrangement cases. We evaluated if the distribution of their 1032 combined breakpoints was distinctive using bootstrap simulations and found that breakpoints tend to keep away from haplosensitive genes suggesting selective pressure. We then compared their distribution with that of 13,310 and 468 breakpoints of cancer complex chromosomal rearrangements and constitutional simple rearrangement samples, respectively. Both complex rearrangement groups showed breakpoint enrichment in late replicating regions suggesting similar origins for constitutional and cancer cases. Simple rearrangement breakpoints but not complex ones were depleted from lamina-associated domains (LADs), possibly as a consequence of reduced mobility of DNA ends bound to lamina. The enrichment of breakpoints in late-replicating chromatin for both constitutional and cancer chromoanagenesis provides an orthogonal support to the premature chromosome condensation hypothesis that was put forward to explain chromoanagenesis.

genomics↗