Biology subjects

Tourancheau, A.

Publications and source records attributed to Tourancheau, A..

4 recordsLinked to original sources

bioRxiv2024

Ultra-long sequencing for contiguous haplotype resolution of the human immunoglobulin heavy chain locus

Genetic diversity within the human immunoglobulin heavy chain (IGH) locus influences the expressed antibody repertoire and susceptibility to infectious and autoimmune diseases. However, repetitive sequences and complex structural variation pose significant challenges for large-scale characterization. Here, we introduce a method using Oxford Nanopore ultra-long sequencing and adaptive sampling, coupled with a bioinformatic pipeline, to generate haplotype-resolved single-contig IGH assemblies. We compared our method to a well-established IGH characterization framework using Pacific Biosciences HiFi sequencing in four donors and observed almost complete sequence congruence between our haplotype-resolved assemblies and the HiFi reads. Applying our approach to the HG002 reference material revealed no base differences to the Telomere-to-Telomere genome benchmark over the IGH locus. Importantly, among the four donors, our approach uncovered 30 novel alleles and previously uncharacterized large structural variants, including a 120 kb segmental duplication spanning IGHE to IGHA1 and an expanded seven-copy IGHV3-23 gene haplotype.

immunology↗

bioRxiv2024

Nanotiming: telomere-to-telomere DNA replication timing profiling by nanopore sequencing

Current temporal studies of DNA replication are either low-resolution or require complex cell synchronisation and/or sorting procedures. Here we introduce Nanotiming, a nanopore sequencing-based method producing high-resolution, telomere-to-telomere replication timing (RT) profiles of eukaryotic genomes by interrogating changes in intracellular dTTP concentration during S phase through competition with its analogue bromodeoxyuridine triphosphate (BrdUTP) for incorporation into replicating DNA. Nanotiming solely demands the labelling of asynchronously growing cells with an innocuous dose of BrdU during one doubling time followed by BrdU quantification along nanopore reads. We demonstrate in yeast S. cerevisiae that Nanotiming precisely reproduces RT profiles generated by reference methods in wild-type and mutant cells inactivated for known RT determinants, for one-tenth of the cost. Nanotiming is simple, accurate, inexpensive, amenable to large-scale analyses, and is capable of unveiling RT at individual telomeres, revealing that Rif1 iconic telomere regulator directly delays the replication only of telomeres with specific subtelomeric elements.

genomics↗

bioRxiv2022

mEnrich-seq: Methylation-guided enrichment sequencing of bacterial taxa of interest from microbiome

Metagenomics has enabled the comprehensive study of microbiomes. However, many applications would benefit from a method that can sequence specific bacterial taxa of interest (pathogens, beneficial microbes, or low-abundance taxa), but not the vast background of other taxa in a microbiome sample. To address this need, we developed mEnrich-seq, a method that can enrich taxa of interest from metagenomic DNA before sequencing. The core idea is to exploit the self vs. non-self genome differentiation provided by natural bacterial DNA methylation and rationally choose methylation-sensitive restriction enzymes (REs), individually or in combination, to deplete host DNA and most background microbial DNA while enriching bacterial taxa of interest. This core idea is integrated with library preparation procedures in a way that only non-digested DNA libraries are sequenced. We performed in-depth evaluations of mEnrich-seq and demonstrated its use in several applications to enrich (up to 117-fold) genomic DNA of pathogenic or beneficial bacteria from human urine and fecal samples, including several species that are hard to culture or of low abundance. We also assessed the broad applicability of mEnrich-seq and found that 3130 (68.03%) of the 4601 strains with mapped methylomes to date can be targeted by at least one commercially available RE, representing 54.78% of the species examined in this analysis. mEnrich-seq provides microbiome researchers with a versatile and cost-effective approach for selective sequencing of diverse taxa of interest directly from the microbiome.

genomics↗

bioRxiv2020

Discovering and exploiting multiple types of DNA methylation from individual bacteria and microbiome using nanopore sequencing

Nanopore sequencing provides a great opportunity for direct detection of chemical DNA modification. However, existing computational methods were either trained for detecting a specific form of DNA modification from one, or a few, specific sequence contexts (e.g. 5-methylcytosine from CpG dinucleotides) or for allowing de novo detection without effectively differentiating between different forms of DNA modifications. As a result, none of these methods supports de novo, systematic study of unknown bacterial methylomes. In this work, by examining three types of DNA methylation in a large diversity of sequence contexts, we observed that nanopore sequencing signal displays complex heterogeneity across methylation events of the same type. To capture this complexity and enable nanopore sequencing for broadly applicable methylation discovery, we generated a training dataset from an assortment of bacterial species and developed a novel method that couples the identification and fine mapping of the three forms of DNA methylation into a multi-label classification design. We evaluated the method and then applied it to individual bacteria and mouse gut microbiome for reliable methylation discovery. In addition, we demonstrated in the microbiome analysis the use of DNA methylation for binning metagenomic contigs, associating mobile genetic elements with their host genomes, and for the first time, identifying misassembled metagenomic contigs. This novel method has broad utility for discovering different forms of DNA methylation from bacteria, assisting functional studies of epigenetic regulation in bacteria, and exploiting bacterial epigenomes for more effective metagenomic analyses.

microbiology↗