Biology subjects

Torchinsky, D.

Publications and source records attributed to Torchinsky, D..

6 recordsLinked to original sources

bioRxiv2022

Simultaneous global labeling (SiGL) of 5-methylcytosine and 5-hydroxymethylcytosine by DNA alkylation with a synthetic cofactor and engineered methyltransferase

5-methylcytosine and 5-hydroxymethylcytosine are epigenetic modifications involved in gene regulation and cancer. Here, we describe a new, simple, and high-throughput platform for multi-colour epigenetic analysis. The novelty of our approach is the ability to multiplex methylation and de-methylation signals in the same assay. We utilize an engineered methyltransferase enzyme that recognizes and labels all unmodified CpG sites with a fluorescent cofactor. In combination with the already established labelling of the de-methylation mark 5-hydroxymethylcytosine via enzymatic glycosylation, we obtained a robust platform for simultaneous epigenetic analysis of these marks. We assessed the global epigenetic levels in multiple samples of colorectal cancer and observed a reduction in 5-hydroxymethylcytosine levels, but no change in DNA methylation levels between sick and healthy individuals. We also measured epigenetic modifications in chronic lymphocytic leukaemia and observed a decrease in both modification levels. Our results indicate that this assay may be used for the epigenetic characterization of clinical samples for research and patient management.

genetics↗

bioRxiv2021

Chemoenzymatic labeling of DNA methylation patterns for single-molecule epigenetic mapping

DNA methylation, specifically, methylation of cytosine (C) nucleotides at the 5-carbon position (5-mC), is the most studied and among the most significant epigenetic modifications. Here we developed a chemoenzymatic procedure to fluorescently label non-methylated cytosines in the CpG context allowing epigenetic profiling of single DNA molecules spanning hundreds of thousands of base pairs. For this method, a CpG methyltransferase was used to transfer an azide to cytosines from a synthetic S-adenosyl-l-methionine cofactor analog. A fluorophore was then clicked onto the DNA, reporting on the amount and position of non-methylated CpGs. We found that labeling efficiency was increased two-fold by the addition of a nucleosidase that degrades the inactive by-product of the azide-cofactor after labeling, and prevents its inhibitory effect. We first used the method to determine the decline in global DNA methylation in chronic lymphocytic leukemia patients and then performed whole genome methylation mapping of the model plant Arabidopsis thaliana. Our genome maps show high concordance with published methylation maps produced by bisulfite sequencing. Although mapping resolution is limited by optical detection to 500-1000 base pairs, the labeled DNA molecules produced by this approach are hundreds of thousands of base pairs long, allowing access to long repetitive and structurally variable genomic regions.

genomics↗

bioRxiv2020

Multi-Modal Single-Molecule Imaging with Continuously Controlled Spectral-resolution (CoCoS) Microscopy

Color is a fundamental contrast mechanism in fluorescence microscopy, providing the basis for numerous imaging and spectroscopy techniques. The ever-growing need to acquire high-throughput, dynamic data from multicolor species is driving the development of optical schemes that optimize the achievable spectral, temporal, and spatial resolution needed in order to follow biological, chemical and physical processes. Here we introduce Continuously Controlled Spectral-resolution (CoCoS) microscopy, an imaging scheme that encodes color into spatial read-out in the image plane, with continuous control over the spectral resolution. The concept enables single-frame acquisition of multiple color channels, allowing simultaneous, single-molecule colocalization for barcoding and Forster resonance energy transfer (FRET) experiments. The simple control over the spectral dispersion allows switching between imaging modalities at a click of a button. We demonstrate the utility of CoCoS for multicolor localization microscopy of microRNA barcodes in clinical samples, single-molecule FRET measurements, and single-molecule spectroscopy. CoCoS may be integrated as a simple add-on to existing microscopes and will find use in applications that aim to record dynamic, multicolor localization events such as in multiplex FRET and tracking of multi-component, interacting complexes.

biophysics↗

bioRxiv2019

Global Modulation in DNA Epigenetics during Pro-Inflammatory Macrophage Activation

DNA methylation patterns create distinct gene expression profiles. These patterns are maintained after cell division, thus enabling the differentiation and maintenance of multiple cell types from the same genome sequence. The advantage of this mechanism for transcriptional control is that chemical-encoding allows to rapidly establish new epigenetic patterns \"on-demand\" through enzymatic methylation and de-methylation of DNA. Here we show that this feature is associated with the fast response of macrophages during their pro-inflammatory activation. By using a combination of mass spectroscopy and single-molecule imaging to quantify global epigenetic changes in the genomes of primary macrophages, we followed three distinct DNA marks (methylated, hydroxymethylated and unmethylated), involved in establishing new DNA methylation patterns during pro-inflammatory activation. The observed epigenetic modulation together with gene expression data generated for the involved enzymatic machinery, may suggest that de-methylation upon LPS-activation starts with oxidation of methylated CpGs, followed by excision-repair of these oxidized bases and their replacement with unmodified cytosine.

immunology↗

bioRxiv2017

Reduced representation optical methylation mapping (R2OM2).

Reduced representation methylation profiling is a method of analysis in which a subset of CpGs is used to report the overall methylation status of the probed genomic regions. This approach has been widely adopted for genome-scale bisulfite sequencing since it requires fewer sequencing reads and uses significantly less starting material than whole-genome analysis. Consequently, this method is suitable for profiling medical samples and single cells at high throughput and reduced costs. Here, we use this concept in order to create a pattern of fluorescent optical methylation profiles along individual DNA molecules. Reduced representation optical methylation mapping (R2OM2) in combination with Bionano Genomics next generation genome mapping (NGM) technology provides a hybrid genetic/epigenetic genome map of individual chromosome segments spanning hundreds of kilobase pairs (kbp). These long reads, along with the single-molecule resolution, allow for epigenetic variation calling and methylation analysis of large structural aberrations such as pathogenic macrosatellite arrays not accessible to single-cell next generation sequencing (NGS). We apply this method to facioscapulohumeral dystrophy (FSHD) showing both structural variation and hypomethylation status of a disease-associated, highly repetitive locus on chromosome 4q.

genetics↗

bioRxiv2017

Reduced representation optical methylation mapping (R2OM2).

Reduced representation methylation analysis utilizes a subset of CpGs in order to report the overall methylation status of the probed genomic regions. Here, we use this concept in order to create fluorescent optical methylation profiles along chromosomal DNA molecules for epigenetic profiling. Reduced representation optical methylation mapping (R2OM2) in combination with Bionano Genomics next generation genome mapping (NGM) technology provides a hybrid genetic/epigenetic genome map of individual chromosome segments spanning hundreds of kilobase pairs (kbp). These long reads, along with the single-molecule resolution, allow for epigenetic variation calling and methylation analysis of large structural aberrations such as pathogenic macrosatellite arrays not accessible to single-cell next generation sequencing (NGS). We show that in addition to the inherent long-read benefits of R2OM2, it provides genomic methylation patterns comparable to whole genome bisulfite sequencing (WGBS) while retaining single-molecule information. The method is applied here to detect methylation along genes, around regulatory histone marks and to study facioscapulohumeral muscular dystrophy (FSHD), simultaneously recording the haplotype, copy number and methylation status of the disease-associated, highly repetitive locus onchromosome 4q.

genetics↗