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

Long-Read Structural and Epigenetic Profiling of a Kidney Tumor-Matched Sample with Nanopore Sequencing and Optical Genome Mapping

Carcinogenesis often involves significant alterations in the cancer genome architecture, marked by large structural and copy number variations (SVs and CNVs) that are difficult to capture with short-read sequencing. Traditionally, cytogenetic techniques are applied to detect such aberrations, but they are limited in resolution and do not cover features smaller than several hundred kilobases. Optical genome mapping and nanopore sequencing are attractive technologies that bridge this resolution gap and offer enhanced performance for cytogenetic applications. These methods profile native, individual DNA molecules, thus capturing epigenetic information. We applied both techniques to characterize a clear cell renal cell carcinoma (ccRCC) tumor's structural and copy number landscape, highlighting the relative strengths of each method in the context of variant size and average read length. Additionally, we assessed their utility for methylome and hydroxymethylome profiling, emphasizing differences in epigenetic analysis applicability.

OM2Seq: learning retrieval embeddings for optical genome mapping

Motivation

Genomics-based diagnostic methods that are quick, precise, and economical are essential for the advancement of precision medicine, with applications spanning the diagnosis of infectious diseases, cancer, and rare diseases. One technology that holds potential in this field is optical genome mapping (OGM), which is capable of detecting structural variations, epigenomic profiling, and microbial species identification. It is based on imaging of linearized DNA molecules that are stained with fluorescent labels, that are then aligned to a reference genome. However, the computational methods currently available for OGM fall short in terms of accuracy and computational speed.

Results

This work introduces OM2Seq, a new approach for the rapid and accurate mapping of DNA fragment images to a reference genome. Based on a Transformer-encoder architecture, OM2Seq is trained on acquired OGM data to efficiently encode DNA fragment images and reference genome segments to a common embedding space, which can be indexed and efficiently queried using a vector database. We show that OM2Seq significantly outperforms the baseline methods in both computational speed (by 2 orders of magnitude) and accuracy.

Availability and implementation

https://github.com/yevgenin/om2seq.

The role of imprinting genes' loss of imprints in cancers and their clinical implications

Genomic imprinting plays an important role in the growth and development of mammals. When the original imprint status of these genes is lost, known as loss of imprinting (LOI), it may affect growth, neurocognitive development, metabolism, and even tumor susceptibility. The LOI of imprint genes has gradually been found not only as an early event in tumorigenesis, but also to be involved in progression. More than 120 imprinted genes had been identified in humans. In this review, we summarized the most studied LOI of two gene clusters and 13 single genes in cancers. We focused on the roles they played, that is, as growth suppressors and anti-apoptosis agents, sustaining proliferative signaling or inducing angiogenesis; the molecular pathways they regulated; and especially their clinical significance. It is notable that 12 combined forms of multi-genes' LOI, 3 of which have already been used as diagnostic models, achieved good sensitivity, specificity, and accuracy. In addition, the methods used for LOI detection in existing research are classified into detection of biallelic expression (BAE), differentially methylated regions (DMRs), methylation, and single-nucleotide polymorphisms (SNPs). These all indicated that the detection of imprinting genes' LOI has potential clinical significance in cancer diagnosis, treatment, and prognosis.

Chemo-Enzymatic Fluorescence Labeling Of Genomic DNA For Simultaneous Detection Of Global 5-Methylcytosine And 5-Hydroxymethylcytosine

5-Methylcytosine and 5-hydroxymethylcytosine are epigenetic modifications involved in gene regulation and cancer. We present a new, simple, and high-throughput platform for multi-color 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 labeling 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 3.5-fold reduction in 5hmC levels but no change in DNA methylation levels between sick and healthy individuals. We also measured epigenetic modifications in chronic lymphocytic leukemia and observed a decrease in both modification levels (5-hydroxymethylcytosine: whole blood 30 %; peripheral blood mononuclear cells (PBMCs) 40 %. 5-methylcytosine: whole blood 53 %; PBMCs 48 %). Our findings propose using a simple blood test as a viable method for analysis, simplifying sample handling in diagnostics. Importantly, our results highlight the assay's potential for epigenetic evaluation of clinical samples, benefiting research and patient management.

Design of optimal labeling patterns for optical genome mapping via information theory

MOTIVATION

Optical genome mapping (OGM) is a technique that extracts partial genomic information from optically imaged and linearized DNA fragments containing fluorescently labeled short sequence patterns. This information can be used for various genomic analyses and applications, such as the detection of structural variations and copy-number variations, epigenomic profiling, and microbial species identification. Currently, the choice of labeled patterns is based on the available biochemical methods and is not necessarily optimized for the application.

RESULTS

In this work, we develop a model of OGM based on information theory, which enables the design of optimal labeling patterns for specific applications and target organism genomes. We validated the model through experimental OGM on human DNA and simulations on bacterial DNA. Our model predicts up to 10-fold improved accuracy by optimal choice of labeling patterns, which may guide future development of OGM biochemical labeling methods and significantly improve its accuracy and yield for applications such as epigenomic profiling and cultivation-free pathogen identification in clinical samples.

AVAILABILITY AND IMPLEMENTATION

https://github.com/yevgenin/PatternCode.

Hypomethylation of CD3D promoter induces immune cell infiltration and supports malignant phenotypes in uveal melanoma

Alterations in DNA methylation in malignant diseases have been heralded as promising targets for diagnostic, prognostic, and predictive values. This study was based on epigenetic alterations and immune cell infiltration analysis to investigate the mechanism of CD3D methylation in uveal melanoma (UM). Bioinformatics analysis was performed on transcriptome data, 450 K methylation data, and clinical information of UM patients from the TCGA database. Stromal and immune cell infiltration was evaluated by calculating the StromalScore and ImmuneScore of UM samples. UM samples were divided into high and low StromalScore and ImmuneScore groups, followed by differential and enrichment analyses. PPI network construction and correlation analysis was used to identify the core prognosis-related genes. The bioinformatics analysis results were confirmed in UM cell experiments. StromalScore and ImmuneScore were significantly associated with the prognosis of UM patients. CD3D, IRF1, CCL3, and FN1 were identified as core genes driven by methylation that affected the prognosis of UM patients. CD3D expression showed the highest correlation with its methylation and was closely related to the four key immune cells in UM development. CD3D was hypomethylated and abundantly expressed in UM cells, while silencing of CD3D inhibited the proliferation, migration, and invasion of UM cells in vitro. In summary, this study identifies hypomethylation of CD3D promoter in UM, which was associated with immune cell infiltration of UM.

Single-molecule approaches for DNA damage detection and repair: A focus on Repair Assisted Damage Detection (RADD)

The human genome is continually exposed to various stressors, which can result in DNA damage, mutations, and diseases. Among the different types of DNA damage, single-strand lesions are commonly induced by external stressors and metabolic processes. Accurate detection and quantification of DNA damage are crucial for understanding repair mechanisms, assessing environmental impacts, and evaluating response to therapy. However, traditional techniques have limitations in sensitivity and the ability to detect multiple types of damage. In recent years, single-molecule fluorescence approaches have emerged as powerful tools for precisely localizing and quantifying DNA damage. Repair Assisted Damage Detection (RADD) is a single-molecule technique that employs specific repair enzymes to excise damaged bases and incorporates fluorescently labeled nucleotides to visualize the damage. This technique provides valuable insights into repair efficiency and sequence-specific damage. In this review, we discuss the principles and applications of RADD assays, highlighting their potential for enhancing our understanding of DNA damage and repair processes.

Epigenetic reprogramming during the maternal-to-zygotic transition

After fertilization, sperm and oocyte fused and gave rise to a zygote which is the beginning of a new life. Then the embryonic development is monitored and regulated precisely from the transition of oocyte to the embryo at the early stage of embryogenesis, and this process is termed maternal-to-zygotic transition (MZT). MZT involves two major events that are maternal components degradation and zygotic genome activation. The epigenetic reprogramming plays crucial roles in regulating the process of MZT and supervising the normal development of early development of embryos. In recent years, benefited from the rapid development of low-input epigenome profiling technologies, new epigenetic modifications are found to be reprogrammed dramatically and may play different roles during MZT whose dysregulation will cause an abnormal development of embryos even abortion at various stages. In this review, we summarized and discussed the important novel findings on epigenetic reprogramming and the underlying molecular mechanisms regulating MZT in mammalian embryos. Our work provided comprehensive and detailed references for the in deep understanding of epigenetic regulatory network in this key biological process and also shed light on the critical roles for epigenetic reprogramming on embryonic failure during artificial reproductive technology and nature fertilization.

Dam Assisted Fluorescent Tagging of Chromatin Accessibility (DAFCA) for Optical Genome Mapping in Nanochannel Arrays

Proteins and enzymes in the cell nucleus require physical access to their DNA target sites in order to perform genomic tasks such as gene activation and transcription. Hence, chromatin accessibility is a central regulator of gene expression, and its genomic profile holds essential information on the cell type and state. We utilized the E. coli Dam methyltransferase in combination with a fluorescent cofactor analogue to generate fluorescent tags in accessible DNA regions within the cell nucleus. The accessible portions of the genome are then detected by single-molecule optical genome mapping in nanochannel arrays. This method allowed us to characterize long-range structural variations and their associated chromatin structure. We show the ability to create whole-genome, allele-specific chromatin accessibility maps composed of long DNA molecules extended in silicon nanochannels.

RNA binding protein YTHDF1 mediates bisphenol S-induced Leydig cell damage by regulating the mitochondrial pathway of BCL2 and the expression of CDK2-CyclinE1

Bisphenol S (BPS) causes reproductive adverse effects on humans and animals. However, the detailed mechanism is still unclear. This research aimed to clarify the role of RNA binding protein YTHDF1 in Leydig cell damage induced by BPS. The mouse TM3 Leydig cells were exposed to BPS of 0, 20, 40, and 80 μmol/L for 72 h. Results showed that TM3 Leydig cells apoptosis rate markedly increased in BPS exposure group. Meanwhile, the apoptosis-related molecule BCL2 protein level decreased significantly, and Caspase9, Caspase3, and BAX increased significantly. Moreover, the cell cycle was blocked in the G1/S phase, CDK2 and CyclinE1 were considerably down-regulated in BPS exposure groups, and the protein level of RNA binding protein YTHDF1 decreased sharply. Furthermore, after overexpression of YTHDF1, the cell viability significantly increased, and the apoptosis rate significantly decreased in TM3 Leydig cells. In the meantime, BCL2, CDK2, and CyclinE1 were significantly up-regulated, and BAX, Caspase9, and Caspase3 were significantly down-regulated. Conversely, interference with YTHDF1 decreased cell proliferation and promoted apoptosis. Importantly, overexpression of YTHDF1 alleviated the cell viability decrease induced by BPS, and interference with YTHDF1 exacerbated the situation. RIP assays showed that the binding of YTHDF1 to CDK2, CyclinE1, and BCL2 significantly increased after overexpressing YTHDF1. Collectively, our study suggested that YTHDF1 plays an essential role in BPS-induced TM3 Leydig cell damage by regulating CDK2-CyclinE1 and BCL2 mitochondrial pathway at the translational level.

21 Fluorescent Protein-Based DNA Staining Dyes

Fluorescent protein-DNA-binding peptides or proteins (FP-DBP) are a powerful means to stain and visualize large DNA molecules on a fluorescence microscope. Here, we constructed 21 kinds of FP-DBPs using various colors of fluorescent proteins and two DNA-binding motifs. From the database of fluorescent proteins (FPbase.org), we chose bright FPs, such as RRvT, tdTomato, mNeonGreen, mClover3, YPet, and mScarlet, which are four to eight times brighter than original wild-type GFP. Additionally, we chose other FPs, such as mOrange2, Emerald, mTurquoise2, mStrawberry, and mCherry, for variations in emitting wavelengths. For DNA-binding motifs, we used HMG (high mobility group) as an 11-mer peptide or a 36 kDa tTALE (truncated transcription activator-like effector). Using 21 FP-DBPs, we attempted to stain DNA molecules and then analyzed fluorescence intensities. Most FP-DBPs successfully visualized DNA molecules. Even with the same DNA-binding motif, the order of FP and DBP affected DNA staining in terms of brightness and DNA stretching. The DNA staining pattern by FP-DBPs was also affected by the FP types. The data from 21 FP-DBPs provided a guideline to develop novel DNA-binding fluorescent proteins.