Project description:5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) are modified versions of cytosine in DNA with roles in regulating gene expression. Using whole genomic DNA from mouse cerebellum, we have benchmarked 5mC and 5hmC detection by Oxford Nanopore Technologies sequencing against other standard techniques. In addition, we assessed the ability of duplex base-calling to study strand asymmetric modification. Nanopore detection of 5mC and 5hmC is accurate relative to compared techniques and opens new means of studying these modifications. Strand asymmetric modification is widespread across the genome but reduced at imprinting control regions and CTCF binding sites in mouse cerebellum. This study demonstrates the unique ability of nanopore sequencing to improve the resolution and detail of cytosine modification mapping.
Project description:Cytosine base modifications 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) are present in mammalian DNA. Here, reduced bisulfite sequencing is developed for quantitatively sequencing 5fC at single-base resolution. This method is then applied with oxidative bisulfite sequencing to gain a map of 5mC, 5hmC and 5fC in mouse embryonic stem cells. 12 samples, reduced representation bisulphite treatment: 4 replicates each for bisulphite (BS), oxidative BS (oxBS) and reduced BS (redBS) for the detection of 5mC, 5hmC and 5fC. Mouse (strain B6C) embryonic stem cells.
Project description:Cytosine deaminases have important uses in the detection of epigenetic modifications and in genome editing. However, the range of applications of deaminases is limited by their substrate preference. To expand the toolkit of deaminases, we developed an in-vitro approach that bypasses a major hurdle with their severe toxicity in expression hosts. We screened 175 putative cytosine deaminases, primarily from bacteria, and found enzymes with strong activity on double- and single-stranded DNA in various sequence contexts, including some without any sequence constraints. We also found enzymes that do not deaminate modified cytosines. The remarkable diversity of cytosine deaminases opens new avenues for biotechnological and medical applications. As a demonstration, we developed a single-enzyme methylation sequencing (SEM-seq) method for 5-methylcytosine detection using a novel non-specific, modification-sensitive double-stranded DNA deaminase, MsddA. SEM-seq generated accurate base-resolution maps of 5-methylcytosine in human genome samples including cell free DNA and samples of 10 pg DNA, equivalent to single cell input. This simple and efficient protocol has the potential to allow high-throughput epigenome profiling of scarce biological material.
Project description:Tuberous sclerosis complex (TSC) is a relatively common autosomal dominant disorder characterized by multiple dysplastic organ lesions and neuropsychiatric symptoms, caused by loss-of-function mutation of either TSC1 or TSC2. Target-capture full-length double-stranded cDNA sequencing using long-read sequencer Nanopore (Nanopore Long-read Target Sequencing) revealed that the various kinds of the TSC1 and TSC2 full-length transcripts and the novel intron retention transcripts of TSC2 in TSC patient. Our results indicate that the Nanopore Long-read Target Sequencing is useful for the detection of mutations and confers information on the full-length alternative splicing transcripts for the genetic diagnosis.
Project description:Whole-genome bisulfite sequencing (WGBS) is currently the gold standard for DNA methylation (5-methylcytosine, 5mC) profiling, however the destructive nature of sodium bisulfite results in DNA fragmentation and subsequent biases in sequencing data. Such issues have led to the development of bisulfite-free methods for 5mC detection. Nanopore sequencing is a long read non-destructive approach that directly analyzes DNA and RNA fragments in real time. Recently, computational tools have been developed that enable base-resolution detection of 5mC from Oxford Nanopore sequencing data. In this chapter we provide a detailed protocol for preparation, sequencing, read assembly and analysis of genome-wide 5mC using Nanopore sequencing technologies.
Project description:While the role of 5-methylcytosine has been well studied, the biological role of 5-hydroxymethylcytosine still remains unclear due to the limited methods available for single-base detection of 5-hydroxymethylcytosine (5hmC). Here we present Mirror bisulfite sequencing for the detection of 5hmC at a single CpG site by synthesizing a DNA strand to mirror the parental strand. This semi-conservative duplex is sequentially treated with β-glucosyltransferase and M.SssI methylase. A glucosyl-5hmCpG in the parental strand inhibits methylation of the mirroring CpG site, and after bisulfite conversion, a thymine in the mirroring strand indicates a 5hmCpG site in the parental strand whereas a cytosine indicates a non-5hmC site. Using this method, the 5hmC levels of various human tissues and paired tumor liver tissues were mapped genome-wide.
Project description:We report the existence of both methylcytosine and hydroxymethylcytosine in the genomic DNA of the ciliate Oxytricha trifallax during its genome rearrangement process. These modifications are dynamically added, de novo, to sequences targeted for elimination and are not present after the rearrangement process (in vegetative cells). We performed methyl-DNA immunoprecipitation-sequencing (meDIP-seq) with antibodies against methylcytosine and hydroxymethylcytosine. We performed methyl-DNA immunoprecipitation-sequencing (meDIP-seq) with antibodies against methylcytosine and hydroxymethylcytosine, and used an IgG control for nonspecific immunoprecpitation. Immunoprecipitation was performed on both vegetative (negative control) and 46h cells (with methylation). The data were normalized to RPKM, then the number of vegetative reads was subtracted from the number of 46h reads, giving excess reads at 46h, which we denote as the methylation/hydroxymethylation "signal". Those data are reported in the tab-deliminated data files included with this dataset.
Project description:We present scNanoATAC-seq (Single-cell Assay for Transposase Accessible Chromatin by Oxford Nanopore Technologies Sequencing), an effective method for simultaneous detection of chromatin accessibility and genetic variation. Long fragments (about 4-5Kb) of single-cell ATAC-seq library were enriched and sequenced by Oxford Nanopore Technologies platform. Ends of long ATAC-seq fragments are regarded as chromatin accessibility signal in downstream analysis.
Project description:We present scNanoATAC-seq (Single-cell Assay for Transposase Accessible Chromatin by Oxford Nanopore Technologies Sequencing), an effective method for simultaneous detection of chromatin accessibility and genetic variation. Long fragments (about 4-5Kb) of single-cell ATAC-seq library were enriched and sequenced by Oxford Nanopore Technologies platform. Ends of long ATAC-seq fragments are regarded as chromatin accessibility signal in downstream analysis.
Project description:Meiotic DNA double stranded breaks (DSBs) initiate genetic recombination in discrete areas of the genome called recombination hotspots. Although DSBs can be directly mapped using ChIP-Seq and antibody against ssDNA-associated proteins, genome-wide mapping of recombination hotspots in mammals is still a challenge due to the low frequency of recombination, high heterogeneity of the germ cell population and the relatively low efficiency of ChIP. To overcome these limitations we have developed a novel method, single-stranded DNA (ssDNA) sequencing (SSDS), that specifically detects protein-bound single-stranded DNA at DSB ends. SSDS consists of a computational framework for the specific detection of ssDNA-derived reads in a sequencing library and a new library preparation procedure for the enrichment of fragments originating from ssDNA. When applied to mapping meiotic DSBs, the use of SSDS reduces the non-specific dsDNA background more than ten-fold. Our method can be extended to other systems where the identification of ssDNA or DSBs is desired. Development and validation of the method, SSDS, for the specific detection of ssDNA-derived and dsDNA-derived fragments in sequencing libraries and enrichment of ssDNA-derived fragments. SSDS was used to detect meiotic DSBs in 9R/13R mice.