DNA Modification Research Articles

Epigenetic modifications of DNA and RNA in Alzheimer's disease.

Alzheimer's disease (AD) is a complex neurodegenerative disorder and the most common form of dementia. There are two main types of AD: familial and sporadic. Familial AD is linked to mutations in amyloid precursor protein (APP), presenilin-1 (PSEN1), and presenilin-2 (PSEN2). On the other hand, sporadic AD is the more common form of the disease and has genetic, epigenetic, and environmental components that influence disease onset and progression. Investigating the epigenetic mechanisms associated with AD is essential for increasing understanding of pathology and identifying biomarkers for diagnosis and treatment. Chemical covalent modifications on DNA and RNA can epigenetically regulate gene expression at transcriptional and post-transcriptional levels and play protective or pathological roles in AD and other neurodegenerative diseases.

Dependence of nucleosome mechanical stability on DNA mismatches

The organization of nucleosomes into chromatin and their accessibility are shaped by local DNA mechanics. Conversely, nucleosome positions shape genetic variations, which may originate from mismatches during replication and chemical modification of DNA. To investigate how DNA mismatches affect the mechanical stability and the exposure of nucleosomal DNA, we used an optical trap combined with single-molecule FRET and a single-molecule FRET cyclization assay. We found that a single base-pair C-C mismatch enhances DNA bendability and nucleosome mechanical stability for the 601-nucleosome positioning sequence. An increase in force required for DNA unwrapping from the histone core is observed for single base-pair C-C mismatches placed at three tested positions: at the inner turn, at the outer turn, or at the junction of the inner and outer turn of the nucleosome. The results support a model where nucleosomal DNA accessibility is reduced by mismatches, potentially explaining the preferred accumulation of single-nucleotide substitutions in the nucleosome core and serving as the source of genetic variation during evolution and cancer progression. Mechanical stability of an intact nucleosome, that is mismatch-free, is also dependent on the species as we find that yeast nucleosomes are mechanically less stable and more symmetrical in the outer turn unwrapping compared to Xenopus nucleosomes.

Dependence of nucleosome mechanical stability on DNA mismatches.

The organization of nucleosomes into chromatin and their accessibility are shaped by local DNA mechanics. Conversely, nucleosome positions shape genetic variations, which may originate from mismatches during replication and chemical modification of DNA. To investigate how DNA mismatches affect the mechanical stability and the exposure of nucleosomal DNA, we used an optical trap combined with single-molecule FRET and a single-molecule FRET cyclization assay. We found that a single base-pair C-C mismatch enhances DNA bendability and nucleosome mechanical stability for the 601-nucleosome positioning sequence. An increase in force required for DNA unwrapping from the histone core is observed for single base-pair C-C mismatches placed at three tested positions: at the inner turn, at the outer turn, or at the junction of the inner and outer turn of the nucleosome. The results support a model where nucleosomal DNA accessibility is reduced by mismatches, potentially explaining the preferred accumulation of single-nucleotide substitutions in the nucleosome core and serving as the source of genetic variation during evolution and cancer progression. Mechanical stability of an intact nucleosome, that is mismatch-free, is also dependent on the species as we find that yeast nucleosomes are mechanically less stable and more symmetrical in the outer turn unwrapping compared to Xenopus nucleosomes.

Genome-wide characterization of DNA methyltransferase family genes implies GhDMT6 improving tolerance of salt and drought on cotton

BackgroundDNA methylation is an important epigenetic mode of genomic DNA modification and plays a vital role in maintaining epigenetic content and regulating gene expression. Cytosine-5 DNA methyltransferase (C5-MTase) are the key enzymes in the process of DNA methylation. However, there is no systematic analysis of the C5-MTase in cotton so far, and the function of DNMT2 genes has not been studied.MethodsIn this study, the whole genome of cotton C5-MTase coding genes was identified and analyzed using a bioinformatics method based on information from the cotton genome, and the function of GhDMT6 was further validated by VIGS experiments and subcellular localization analysis.Results33 C5-MTases were identified from three cotton genomes, and were divided into four subfamilies by systematic evolutionary analysis. After the protein domain alignment of C5-MTases in cotton, 6 highly conserved motifs were found in the C-terminus of 33 proteins involved in methylation modification, which indicated that C5-MTases had a basic catalytic methylation function. These proteins were divided into four classes based on the N-terminal difference, of which DNMT2 lacks the N-terminal regulatory domain. The expression of C5-MTases in different parts of cotton was different under different stress treatments, which indicated the functional diversity of cotton C5-MTase gene family. Among the C5-MTases, the GhDMT6 had a obvious up-regulated expression. After silencing GhDMT6 with VIGS, the phenotype of cotton seedlings under different stress treatments showed a significant difference. Compared with cotton seedlings that did not silence GhDMT6, cotton seedlings silencing GhDMT6 showed significant stress resistance.ConclusionThe results show that C5-MTases plays an important role in cotton stress response, which is beneficial to further explore the function of DNMT2 subfamily genes.

Characterization of structural, genotoxic, and immunological effects of methyl methanesulfonate (MMS) induced DNA modifications: Implications for inflammation-driven carcinogenesis

Genotoxic DNA damaging agents are the choice of chemicals for studying DNA repair pathways and the associated genome instability. One such preferred laboratory chemical is methyl methanesulfonate (MMS). MMS, an SN2-type alkylating agent known for its ability to alkylate adenine and guanine bases, causes strand breakage. Exploring the outcomes of MMS interaction with DNA and the associated cytotoxicity will pave the way to decipher how the cell confronts methylation-associated stress. This study focuses on an in-depth understanding of the structural instability, induced antigenicity on the DNA molecule, cross-reactive anti-DNA antibodies, and cytotoxic potential of MMS in peripheral lymphocytes and cancer cell lines. The findings are decisive in identifying the hazardous nature of MMS to alter the intricacies of DNA and morphology of the cell. Structural alterations were assessed through UV–Vis, fluorescence, liquid chromatography, and mass spectroscopy (LCMS). The thermal instability of DNA was analyzed using duplex melting temperature profiles. Scanning and transmission electron microscopy revealed gross topographical and morphological changes. MMS-modified DNA exhibited increased antigenicity in animal subjects. MMS was quite toxic for the cancer cell lines (HCT116, A549, and HeLa). This research will offer insights into the potential role of MMS in inflammatory carcinogenesis and its progression.

Characterization of winged helix domain fusion endonucleases as N6-methyladenine-dependent type IV restriction systems.

Winged helix (wH) domains, also termed winged helix-turn-helix (wHTH) domains, are widespread in all kingdoms of life and have diverse roles. In the context of DNA binding and DNA modification sensing, some eukaryotic wH domains are known as sensors of non-methylated CpG. In contrast, the prokaryotic wH domains in DpnI and HhiV4I act as sensors of adenine methylation in the 6mApT (N6-methyladenine, 6mA, or N6mA) context. DNA-binding modes and interactions with the probed dinucleotide are vastly different in the two cases. Here, we show that the role of the wH domain as a sensor of adenine methylation is widespread in prokaryotes. We present previously uncharacterized examples of PD-(D/E)XK-wH (FcyTI, Psp4BI), PUA-wH-HNH (HtuIII), wH-GIY-YIG (Ahi29725I, Apa233I), and PLD-wH (Aba4572I, CbaI) fusion endonucleases that sense adenine methylation in the Dam+ Gm6ATC sequence contexts. Representatives of the wH domain endonuclease fusion families with the exception of the PLD-wH family could be purified, and an in vitro preference for adenine methylation in the Dam context could be demonstrated. Like most other modification-dependent restriction endonucleases (MDREs, also called type IV restriction systems), the new fusion endonucleases except those in the PD-(D/E)XK-wH family cleave close to but outside the recognition sequence. Taken together, our data illustrate the widespread combinatorial use of prokaryotic wH domains as adenine methylation readers. Other potential 6mA sensors in modified DNA are also discussed.

Nanopore Current Events Magnifier (nanoCEM): a novel tool for visualizing current events at modification sites of nanopore sequencing.

Nanopore sequencing technologies have enabled the direct detection of base modifications in DNA or RNA molecules. Despite these advancements, the tools for visualizing electrical current, essential for analyzing base modifications, are often lacking in clarity and compatibility with diverse nanopore pipelines. Here, we present Nanopore Current Events Magnifier (nanoCEM, https://github.com/lrslab/nanoCEM), a Python command-line tool designed to facilitate the identification of DNA/RNA modification sites through enhanced visualization and statistical analysis. Compatible with the four preprocessing methods including 'f5c resquiggle', 'f5c eventalign', 'Tombo' and 'move table', nanoCEM is applicable to RNA and DNA analysis across multiple flow cell types. By utilizing rescaling techniques and calculating various statistical features, nanoCEM provides more accurate and comparable visualization of current events, allowing researchers to effectively observe differences between samples and showcase the modified sites.

Roles of Epigenetics and Glial Cells in Drug-Induced Autism Spectrum Disorder.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by severe deficits in social communication and interaction, repetitive movements, abnormal focusing on objects, or activity that can significantly affect the quality of life of the afflicted. Neuronal and glial cells have been implicated. It has a genetic component but can also be triggered by environmental factors or drugs. For example, prenatal exposure to valproic acid or acetaminophen, or ingestion of propionic acid, can increase the risk of ASD. Recently, epigenetic influences on ASD have come to the forefront of investigations on the etiology, prevention, and treatment of this disorder. Epigenetics refers to DNA modifications that alter gene expression without making any changes to the DNA sequence. Although an increasing number of pharmaceuticals and environmental chemicals are being implicated in the etiology of ASD, here, we specifically focus on the molecular influences of the abovementioned chemicals on epigenetic alterations in neuronal and glial cells and their potential connection to ASD. We conclude that a better understanding of these phenomena can lead to more effective interventions in ASD.

Guardians of Neurons: The Cntf Gene and Ciliary Neurotrophic Factor (CNTF) in the Genetic Landscape of Alzheimer’s Disease Neuroprotection

Background: Type II Diabetes Mellitus (Type II DM) is a complex systemic disorder that affects various organs and has been strongly associated with an increased risk of cognitive impairments, including dementia. The Ciliary Neurotrophic Factor (CNTF) gene is implicated in the pathophysiology of diabetes-induced cognitive decline, suggesting its potential as a biomarker for neurodegenerative diseases. Objective: The primary objective of this study was to investigate the expression of the CNTF gene in diabetic patients with dementia and to evaluate its correlation with cognitive dysfunction. Methods: A cohort of 88 diabetic dementia patients and 12 healthy controls was selected based on inclusion criteria. CNTF serum levels were measured using Chemiluminescent immunoassay (CLIA), and CNTF gene expression was assessed through real-time PCR. DNA was isolated using the QIAgen blood kit, followed by bisulfite DNA modification and Methylation Specific PCR for methylation profiling. Data analysis included comparative studies using GraphPad Prism 9.0 with statistical significance set at a p-value of <0.05. Results: The study found that CNTF serum levels in diabetic dementia patients (n=88) were significantly lower at 4.98 µg/mL compared to 14.21 µg/mL in healthy controls (n=12). MMSE scores were also reduced in the patient cohort, averaging 10.98 versus 25.6 in controls. A notable decrease in CNTF gene expression was observed with a fold change of approximately 4.1 in diabetic dementia patients, indicating underexpression in this group. Conclusion: CNTF gene expression is inversely correlated with cognitive function in diabetic patients, suggesting that CNTF could serve as a useful biomarker for the early detection of dementia in this population. The identification of this gene's role opens new avenues for targeted therapeutic interventions and enhances the understanding of dementia's etiology in diabetic patients.

Recent advances in high-performance liquid chromatography tandem mass spectrometry techniques for analysis of DNA damage and epigenetic modifications

Environmental exposure would cause DNA damage and epigenetic modification changes, potentially resulting in physiological dysfunction, thereby triggering diseases and even cancer. DNA damage and epigenetic modifications are thus promising biomarkers for environmental exposures and disease states. Benefiting from its high sensitivity and accuracy, high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) is considered the “gold standard technique” for investigating epigenetic DNA modifications. This review summarizes the recent advancements of UHPLC-MS/MS-based technologies for DNA damage and epigenetic modifications analysis, mainly focusing on the innovative methods developed for UHPLC-MS/MS-related pretreatment technologies containing efficient genomic DNA digestion and effective removal of the inorganic salt matrix, and the new strategies for improving detection sensitivity of liquid chromatography-mass spectrometry. Moreover, we also summarized the novel hyphenated techniques of the advanced UHPLC-MS/MS coupled with other separation and analysis methods for the measurement of DNA damage and epigenetic modification changes in special regions and fragments of chromosomes.

Maternal Ezh1/2 deficiency impairs the function of mitochondria in mouse oocytes and early embryos.

Maternal histone methyltransferase is critical for epigenetic regulation and development of mammalian embryos by regulating histone and DNA modifications. Here, we reported a novel mechanism by revealing the critical effects of maternal Ezh1/2 deletion on mitochondria in MIIoocytes and early embryos in mice. We found that Ezh1/2 knockout in mouse MIIoocytes impaired the structure of mitochondria and decreased its number, but membrane potential and respiratory function of mitochondrion were increased. The similar effects of Ezh1/2 deletion have been observed in 2-cell and morula embryos, indicating that the effects of maternal Ezh1/2 deficiency on mitochondrion extend to early embryos. However, the loss of maternal Ezh1/2 resulted in a severe defect of morula: the number, membrane potential, respiratory function, and ATP production of mitochondrion dropped significantly. Content of reactive oxygen specieswas raised in both MIIoocytes and early embryos, suggesting maternal Ezh1/2 knockout induced oxidative stress. In addition, maternal Ezh1/2 ablation interfered the autophagy in morula and blastocyst embryos. Finally, maternal Ezh1/2 deletion led to cell apoptosis in blastocyst embryos in mice. By analyzing the gene expression profile, we revealed that maternal Ezh1/2 knockout affected the expression of mitochondrial related genes in MIIoocytes and early embryos. Thechromatin immunoprecipitation-polymerase chain reaction assay demonstrated that Ezh1/2 directly regulated the expression of genes Fxyd6, Adpgk, Aurkb, Zfp521, Ehd3, Sgms2, Pygl, Slc1a1, and Chst12 by H3K27me3 modification. In conclusion, our study revealed the critical effect of maternal Ezh1/2 on the structure and function of mitochondria in oocytes and early embryos, and suggested a novel mechanism underlying maternal epigenetic regulation on early embryonic development through the modulation of mitochondrial status.

AI-driven Protein Engineering for DNA Sequence Modification

The integration of artificial intelligence (AI) with gene editing technologies like CRISPR-Cas9 holds immense promise for advancing biomedical research and personalized medicine. This article highlights the crucial role of AI in predicting and minimizing off-target effects, thereby enhancing the precision and efficiency of gene editing. Researchers have developed algorithms like BE-DICT to accurately predict base editing outcomes, showcasing the potential of AI-driven strategies in optimizing gene editing processes. By combining AI with bioengineering, this interdisciplinary approach aims to automate and refine DNA modifications, paving the way for innovative applications in personalized gene therapy and biofabrication. Ultimately, this research endeavors to revolutionize the life sciences field, leading to significant breakthroughs in healthcare and biotechnology.

Abstract 759: Soy protein diet changes metabolic profile in liver of 7,12-dimethylbenz(α)anthracene (DMBA)-induced mammary tumors in obese zucker rats

Abstract Obesity is associated with the risk of certain types of cancers development including breast cancer. Previously, we reported that obesity increased mammary tumor development using obese Zucker rat model. Several studies have shown the health benefit of soy protein consumption. However, the effects of soy protein diet on liver of mammary tumor for oxidative stress and DNA reaction is less known. We used DMBA induced-mammary tumor model to investigate the effects of soy protein diet on pro-oxidative environment and oxidative DNA modification in liver of obese DMBA mammary tumors rats. Female obese zucker rats (n=45) were either fed casein as control (OC; n=20) or soy protein isolate (OS; n=25), received DMBA (65mg/kg BW) at the age 50 days and sacrificed 20 weeks later. We used HPLC-ECD, HPLC-UV and LC-MS techniques for liver metabolic analysis. Comparing liver of OS vs. OC, soy protein 1) decreased the level of Methionine (P<0.02), increased 2) free reduced Homocysteine (P<0.02), 3) S-Adenosylmethionine (SAM, P<0.03), 4) S-Adenosyhomocysteine (SAH, P<0.001) and 5) 5methyl-Cytosine (5mC, P<0.03). Also, soy protein decreased (P<0.003) level of free oxidized Glutathione (GSSG), increased (P<0.02) GSH/GSSG oxidative stress ratio, without any changes a level of free reduced Glutathione (GSH), followed decrease (P<0.04) in liver DNA level of 8-OH-Guanosine (8-OH-G) and level (P<0.02) of 5hmethyl-Cytosine (5hmC). Our results shows soy protein diet capable change liver metabolism: a. Modify a methylation status by increasing levels of SAM (universal methyl group donor) following global liver DNA hypermethylation (5mC), and SAH (methylases inhibitor); b. Alleviate level of oxidative stress in liver by decreasing level of GSSG (not active glutathione), increasing GSH/GSSG ratio (antioxidative capacities), following lower ROS liver DNA damages by decrease levels of 8-OH-G and 5hmC. In conclusion, using obese DMBA-induced mammary tumor Zucker rat model, soy diet making a complex and significantly modification of metabolic conditions in liver affecting both methionine cycle and transsulfuration metabolic pathways. Citation Format: Reza Hakkak, Stepan Melnyk. Soy protein diet changes metabolic profile in liver of 7,12-dimethylbenz(α)anthracene (DMBA)-induced mammary tumors in obese zucker rats [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 759.

Abstract 6218: Haplotype-resolved analysis of cancer genomes and epigenomes using Oxford Nanopore sequencing

Abstract Cancer is a complex and dynamic disease driven by somatic genomic and epigenomic alterations that accumulate over time. These changes give rise to heterogeneous collections of cells or clones, each with distinct (epi)genomic profiles within a single tumour. Accurate characterisation of these changes is crucial for understanding the mechanisms driving the disease, identifying potential therapeutic targets, and personalising treatment strategies. Due to the technological constraints of short-read and array-based approaches, cancer research has historically had a strong focus on detecting small genomic changes like SNPs and small indels (SNVs) as well as the broad characterisation of large-scale copy number changes (CNVs), mostly ignoring other important variant classes and epigenetic modifications. Here we demonstrate how Oxford Nanopore native long-read sequencing enables the direct detection of not only SNVs, but also break point-resolved simple and complex structural variants (SVs and CNVs), haplotype phasing of all variant types, and identification of DNA modifications like 5-methylcytosine (5mC) and 5-hydroxy-methylcytosine (5hmC) from a single tumour-normal dataset. We illustrate how our end-to-end somatic workflow streamlines analysis for the different variant classes and benchmark somatic SNV and SV calling performance using well characterised cancer cell lines and in-silico benchmarking datasets at different sequencing depths. Finally, we use real-world tumour-normal pairs to showcase a comprehensive sample to answer tumour-normal analysis using Nanopore sequencing. This includes the characterisation of complex patterns of somatic SVs in the different cancer samples, the identification of unique 5mC methylation patterns, exploring characteristic differences in 5hmC levels between tumour and normal samples as well as showing how Nanopore long reads enable haplotype and clone specific CNV calling as well as phasing of genetic and epigenetic variation. Citation Format: Philipp Rescheneder, Phill James, Sean McKenzie, Andrea Talenti, Sergey Aganezov, Dan Turner, Sissel Juul. Haplotype-resolved analysis of cancer genomes and epigenomes using Oxford Nanopore sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6218.

Abstract 2629: N6AMT1-mediated DNA 6mA modification in DNA repetitive elements LINE-1 dynamically regulates the IFN signal pathway in colorectal cancer

Abstract Background: DNA N6-methyldeoxyadenosine (6mA) modification is the most prevalent DNA modification in prokaryotes, like bacteria, which participates in the host defense system. However, the presence and function of DNA 6mA in eukaryotes remains elusive. Many studies have reported that DNA 6mA modification is distributed across the genome and regulates transcription and the activity of transposable elements, in which the DNA 6mA methyltransferases and demethylases are involved, including the methyltransferase N6AMT1. LINE-1 is a genome-wide DNA repetitive element that acts as a diagnostic and prognostic biomarker for colorectal cancer. Therefore, we aimed to map the DNA 6mA in LINE-1 and investigate its role in the colorectal cancer (CRC) development. Methods: The restriction-enzyme-digestion assay followed by quantitative PCR (6mA-RE-qPCR) was used to evaluate the LINE-1 DNA 6mA levels in the tumor and normal tissues. The DNA Nanopore sequencing was utilized to determine DNA 6mA and 5mC modifications. After the knockdown of N6AMT1, the dynamic changes of LINE-1 DNA 6mA methylation and RNA transcription under various stresses were determined by 6mA-RE-qPCR and qPCR, and the subsequent RNA-seq was performed to explore the downstream regulated pathways. Results: The DNA 6mA methylation in LINE-1 is highly variant in the tumor and normal tissues, and it was significantly less prevalent in tumor tissues. The genomic distribution of LINE-1 DNA 6mA is significantly different from that of LINE-1 5mC. The LINE-1 DNA 6mA methylation and RNA transcription levels were dynamically changed in response to various stimuli, including 5-FU and H2O2. Knockdown of N6AMT1 downregulated LINE-1 DNA 6mA methylation and RNA transcription, promoted the proliferation, migration and invasion of CRC cells in vitro, and suppressed the IFN-gamma pathway. The co-culture assay showed N6AMT1 facilitated chemotaxis of macrophages and cytotoxicity of T cells via the IFN-gamma signal pathway. Conclusions: The heterogeneity of DNA 6mA methylation in LINE-1 and its dynamic change in response to stimuli indicate a biological role of LINE-1 6mA methylation in the primary and adaptive tumor heterogeneities, which provides a novel insight into cancer development. The N6AMT1-mediated DNA 6mA modification in LINE-1 regulates CRC development through the IFN-gamma pathway. Keywords: N6AMT1, LINE-1, DNA 6mA methylation, colorectal cancer Citation Format: Ze Yuan, Xiaoxia Liu, Xiaolin Wang, Yanxin Luo, Huichuan Yu. N6AMT1-mediated DNA 6mA modification in DNA repetitive elements LINE-1 dynamically regulates the IFN signal pathway in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2629.

Abstract 544: Reverse engineering strategy for new targets identification

Abstract The issue of drug resistance in cancer is very similar to the field of infectious disease, either existing before treatment (intrinsic) or generated during therapy (acquired), highly affected by cell endogenous factors and/or the surrounding environment. Acquired resistance can be occurred several months after targeted therapy via alternations of drug targets due to the genomic mutations of the targets, epigenetic transcriptional or translational changes, for example the C797S mutation impairs AZ9291 binding to the EGFR kinase domain. To overcome this, novel well-designed chemical compounds targeting new mutations would be urgently needed, as well as the potential new oncogenes/susceptible genes driving the resistance. Considering about the heterogeneity of primary tumor tissues, LIDE has established one functional cost-effective in vitro and in vivo screening method, named reverse engineering strategy for targets identification by using patients-derived conditional reprogramed cancer cell lines (CRs) and IO-FIVE (Immuno-Oncology drugs Five In Vivo Efficacy test). Basically, pro-siRNA library or CRISPR/sgRNA library is carried out in CRs for candidates hunting, alternatively drug-response evaluation among multiple clinical biopsies in mice cancer trials, after filtered with bioinformatic scanning from large groups of patients, and finally it is validated in vivo by CRISPR, shRNA silence or targeted compounds. In addition to these known factors (EGFR C797S, Her2/Met amplification, Ras and MAPK activation), we have discovered that epigenetic factors for DNA modification, protein translation kinases, mitochondrial/peroxisomal transporters and cell membrane lectins may contribute to AZ92921 resistance in vivo. And one previously unknown acyltransferase member has been identified as key driver gene for pan-cancer development by IO-FIVE, and patients with high expression level of this enzyme have had poor survival outcomes, accompany with uncontrolled tumor growth and immunotherapy resistance, which is becoming a promising therapeutic target. Citation Format: Bin Xie, Taimei Zhang, Le Li, Hongkui Chen, Yang Liu, Lintao Bi, Danyi Wen. Reverse engineering strategy for new targets identification [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 544.

Abstract 4415: Utilization of MBD-seq to elucidate differentially methylated regions in cfDNA across healthy and cancer patients

Abstract 5-Methylcytosine (5-mC) is the most abundant epigenetic DNA modification in eukaryotes. The presence of 5-mC alters gene expression and genome metabolism, and its deregulation is associated with many human diseases. Cell-free DNA (cfDNA) released from apoptotic cells has recently gained attention, as mutations or epimutations (e.g. 5-mC variations) detected in cfDNA were shown to have high diagnostic potential to assess the presence, stage and outcome of several cancers. However, 5-mC detection in cfDNA remains a challenge as input material is often very scarce. MBD-Seq is a method that leverages the ability of Methyl-CpG-binding domain protein 2 (MBD2) to capture and detect highly methylated regions of DNA genome-wide. We evaluated MBD-Seq for the detection of aberrant methylation patterns in cfDNA from healthy and diseased patients. We found MBD-seq on cfDNA to be specific (over 100-fold mC:C detection ratio) and sensitive (5 ng of input cfDNA). Applying MBD-seq to samples from healthy vs colorectal and breast cancer patients showed striking differences in methylation of key tumor-associated genes. Hence, MBD-Seq can elucidate aberrant methylation patterns from cfDNA, highlighting its potential as a diagnostics tool for the detection of cancer. Citation Format: Camille Michelon, Brian Egan, Benjamin Delatte. Utilization of MBD-seq to elucidate differentially methylated regions in cfDNA across healthy and cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4415.

NeuroGenetics of Alzheimer’s Disease: Crosslinking SIRT1 Gene in the Genetic Nexus of Type II Diabetes and Dementia

Background: Background: Type II Diabetes Mellitus (DM) is a chronic condition that not only affects organ function but also contributes to the development of dementia. SIRT1, a gene implicated in the pathophysiology of Type II DM, has been associated with neurodegenerative processes and cognitive decline. Objective: This study aimed to evaluate the expression of the SIRT1 gene in patients with Type II DM and dementia, elucidating its potential role as a biomarker for cognitive impairment and neurodegeneration in this population. Methods: A cohort of 88 diabetic patients with dementia and 12 healthy controls were recruited, and EDTA blood samples were collected. SIRT1 serum levels were quantified using chemiluminescent immunoassay (CLIA). Genomic DNA was extracted and assessed for quality before bisulfite DNA modification and Methylation Specific PCR (MSP) to profile SIRT1 gene methylation. Real-time PCR was conducted to determine SIRT1 gene expression levels. Cognitive function was assessed using Mini-Mental State Examination (MMSE) scores. Results: The average SIRT1 serum levels in diabetic dementia patients (4.98 ± 1.38 µg/mL) were significantly lower than those in healthy controls (14.21 ± 3.64 µg/mL). MMSE scores mirrored this trend, with patients scoring 12.26 ± 4.56, indicating more considerable cognitive impairment compared to healthy controls' score of 24.1 ± 3.12. SIRT1 gene expression was found to be underexpressed with a fold decrease of approximately 4.1 in dementia cases. Conclusion: The study's findings highlight the downregulated expression of the SIRT1 gene in diabetic patients with dementia, confirming its potential as a biomarker for cognitive decline. Identifying SIRT1 alterations may provide a non-invasive approach for early diagnosis and management of dementia in the diabetic population.

Methylation‑sensitive restriction enzyme‑droplet digital PCR assay for the one‑step highly sensitive analysis of DNA methylation hotspots.

DNA methylation is an epigenetic modification that plays a key role in several cellular processes mediating the fine regulation of gene expression. Aberrant DNA methylation is observed in a wide range of pathologies, including cancer. Since these DNA modifications are transferred to the cell progenies and are stable over the time, the analysis of DNA methylation status has been proposed for diagnostic and prognostic purposes in cancer. Currently, DNA bisulfite conversion is the gold standard method for the high‑throughput analysis of DNA methylation alterations. However, bisulfite treatment induces DNA fragmentation affecting its quality for the downstream analyses. In this field, it is mandatory to identify novel methods to overcome the limits of conventional approaches. In the present study, the Methylation‑Sensitive Restriction Enzyme‑droplet digital PCR (MSRE‑ddPCR) assay was developed as a novel sensitive method for the analysis of DNA methylation of short genomic regions, combining the MSRE assay with the high‑sensitivity ddPCR and using an exogenous methylation sequence as control. Setup and validation experiments were performed analyzing a methylation hotspot of the Solute Carrier Family 22 Member 17 in DNA samples derived from melanoma cell lines as well as from tissues and serum samples obtained from patients with melanoma and healthy controls. Compared with the standard MSRE approaches, the MSRE‑ddPCR assay is more appropriate for the analysis of DNA methylation (methDNA) in samples with low amounts of DNA (up to 0.651 ng) showing a greater sensitivity. These findings suggested the potential clinical application of MSRE‑ddPCR paving the way to the analysis of other methDNA hotspots in different tumors.

NeuroGenetics of Alzheimer’s Disease: Cross-Linking BDNF Brain-Derived Neurotrophic Factor in the Genetic Nexus of Type II Diabetes and Dementia

Background: Alzheimer’s disease and dementia are commonly associated with aging, particularly in the context of Type II Diabetes Mellitus (Type II DM), which is known to exacerbate micro and macrovascular complications that affect cognitive functions. The Brain-Derived Neurotrophic Factor (BDNF) gene has been implicated in the neurodegenerative processes that underscore these conditions. Objective: This study aimed to investigate the expression of the BDNF gene in diabetic patients with dementia and analyze its correlation with cognitive impairment, to establish BDNF as a potential biomarker for early detection and therapeutic targeting. Methods: A cohort of 102 patients with diabetic dementia and 32 healthy controls was enrolled. EDTA blood samples were collected and processed to measure BDNF serum levels using a Chemiluminescent Immunoassay (CLIA). Genomic DNA was isolated, and its integrity was confirmed via UV spectrophotometry and gel electrophoresis. The bisulfite DNA modification and Methylation-Specific PCR were conducted to analyze BDNF gene expression, followed by quantitative real-time PCR. Cognitive function was assessed using Mini-Mental State Examination (MMSE). Results: The study revealed a significant decrease in BDNF serum levels in diabetic dementia patients (12.6 ng/mL) compared to healthy controls (34.8 ng/mL), with MMSE scores averaging at 13.2 and 24.6, respectively. BDNF gene expression showed a 4.1-fold decrease in the dementia group. Statistical analysis indicated that these differences were significant (p<0.05). Conclusion: The reduced expression of BDNF in patients with diabetic dementia confirms its potential as a biomarker for cognitive impairment. Early detection and intervention strategies that modulate BDNF could ameliorate the impact of dementia in the context of diabetes.