Biology subjects

Tan, A. Y.

Publications and source records attributed to Tan, A. Y..

6 recordsLinked to original sources

bioRxiv2026

The bromodomain protein Bdf3 is sufficient to activate expression of a procyclin gene in bloodstream stage African trypanosomes

The early branching eukaryotic parasite, Trypanosoma brucei, lives extracellularly in the mammalian host, where it expresses variant surface glycoprotein (VSG). Antigenic variation of VSGs allows the parasite to evade the host immune response while in the bloodstream. Upon transition to the tsetse fly vector, the parasite remodels its surface to express procyclin protein from a limited set of EP and GPEET genes. While the environmental signals that trigger the switch from expressing VSG genes to expressing EP and GPEET genes are known, the molecular mechanism that initiates transcription of the EP and GPEET genes during parasite differentiation to the procyclic stage within the tsetse is not well understood. Previous work has shown that the chromatin interacting bromodomain protein Bdf3 is absent from the pol I promoter of the EP locus in bloodstream parasites, but appears there shortly after initiation of differentiation from the bloodstream to the procyclic stage. Here, we show that tethering of Bdf3 to the EP promoter using a dCas9-Bdf3 fusion protein and a guide RNA is sufficient to increase transcript levels of EP1 in bloodstream parasites, where the gene is normally silenced. This result supports the model that Bdf3 appears at the EP locus during differentiation to facilitate initiation of transcription, which is consistent with the role for Bdf3 as a transcriptional activator in other systems. Understanding gene regulatory mechanisms in this early branching eukaryote may help build a more complete picture for the conserved and unique features of gene regulatory proteins across diverse biological systems. ImportanceThe Trypanosoma brucei parasite is transmitted to a mammalian host via the tsetse fly vector, where it causes African trypanosomiasis, a fatal disease that causes a severe human and economic burden for people living in in areas of sub-Saharan African. While drug treatments have improved for some strains, some infections still require treatment with drugs that have serious side effects. One avenue for drug development is to try and manipulate the lifecycle of the parasite to make it poorly adapted to the mammalian host. However, this requires detailed knowledge of the mechanisms by which parasites regulate their genes as they progress through the lifecycle. Here, we show that the DNA interacting bromodomain protein Bdf3 may be a key driver for turning on insect-specific genes that code for insect-stage surface proteins. This finding could aid in the development of lifecycle manipulating drugs, and shed light on how gene regulatory mechanisms evolved.

molecular biology↗

bioRxiv2025

High burden of premature ventricular contractions upregulates transcriptional markers of inflammation and promotes adverse cardiac remodeling linked to cardiomyopathy

Premature ventricular contractions (PVCs) are the most prevalent ventricular arrhythmia in adults. High PVC burden can lead to left ventricular (LV) systolic dysfunction, eccentric hypertrophy, and an increased risk of heart failure (HF) and sudden cardiac death (SCD). Inadequate angiogenesis is a key determinant in the transition from adaptive to maladaptive cardiac hypertrophy and fibrosis is a risk factor for arrhythmia and SCD. To quantitatively assess structural remodeling and transcriptional alterations in PVC-induced cardiomyopathy (PVC-CM), animals were implanted with modified pacemakers to deliver bigeminal PVCs (200-220 ms coupling interval) for 12 weeks. Collagen deposition and interstitial ultrastructure of LV samples were analyzed using light and transmission electron microscopy, respectively. Pericytes, fibroblasts, myocytes, smooth muscle, and endothelial cells were imaged using confocal microscopy, quantified with an artificial intelligence-based segmentation analysis, and compared using hierarchical statistics. Transcriptional changes were assessed via RNAseq. Although cardiomyocytes hypertrophied in PVC-CM, capillary rarefaction was overcome by an increase in capillary- to-myocyte ratio. Additionally, thicker blood vessels were more abundant in PVC-CM. Fibroblast-to-myocyte ratio more than doubled, interstitial collagen fibers increased, and interstitial space thickened in PVC-CM. Transcripts involved in interstitial remodeling, inflammatory response, and alarmins were strongly elevated in PVC-CM. Overall, while the angiogenic response meets the metabolic demands of cardiac hypertrophy, upregulated markers of inflammation and cardiomyopathy linked to reactive fibrosis collectively represent an adverse LV remodeling that heightens the risk of HF and SCD in PVC-CM.

physiology↗

bioRxiv2023

Bcl-xL is translocated to the nucleus via CtBP2 to epigenetically promote metastasis

Besides its mitochondria-based anti-apoptotic role, Bcl-xL also travels to the nucleus to promote cancer metastasis by upregulating global histone H3 trimethyl Lys4 (H3K4me3) and TGF{beta} transcription. How Bcl-xL is translocated into the nucleus and how nuclear Bcl-xL regulates H3K4me3 modification are not understood. Here, we report that C-terminal Binding Protein 2 (CtBP2) binds Bcl-xL via its N-terminus and translocates Bcl-xL into the nucleus. Knockdown of CtBP2 by shRNA decreases the nuclear portion of Bcl-xL and reverses Bcl-xL-induced cell migration and metastasis in mouse models. Furthermore, knockout of CtBP2 suppresses Bcl-xL transcription. The binding between Bcl-xL and CtBP2 is required for their interaction with MLL1, a histone H3K4 methyltransferase. Pharmacologic inhibition of MLL1 enzymatic activity reverses Bcl-xL-induced H3K4me3 and TGF{beta} mRNA upregulation as well as cell invasion. Moreover, cleavage under targets and release using nuclease (CUT&RUN) coupled with next generation sequencing reveals that H3K4me3 modifications are particularly enriched in the promotor region of genes encoding TGF{beta} and its signaling pathway in the cancer cells overexpressing Bcl-xL. Altogether, the metastatic function of Bcl-xL is mediated by its interaction with CtBP2 and MLL1.

cancer biology↗

bioRxiv2023

Vascular oxidative stress causes neutrophil arrest in brain capillaries, leading to decreased cerebral blood flow and contributing to memory impairment in a mouse model of Alzheimer's disease

INTRODUCTIONIn this study, we explore the role of oxidative stress produced by NOX2-containing NADPH oxidase as a molecular mechanism causing capillary stalling and cerebral blood flow deficits in the APP/PS1 mouse model of AD. METHODSWe inhibited NOX2 in APP/PS1 mice by administering a 10 mg/kg dose of the peptide inhibitor gp91-ds-tat i.p., for two weeks. We used in vivo two-photon imaging to measure capillary stalling, penetrating arteriole flow, and vascular inflammation. We also characterized short-term memory function and gene expression changes in cerebral microvessels. RESULTSWe found that after NOX2 inhibition capillary stalling, as well as parenchymal and vascular inflammation, were significantly reduced. In addition, we found a significant increase in penetrating arteriole flow, followed by an improvement in short-term memory, and downregulation of inflammatory gene expression pathways. DISCUSSIONOxidative stress is a major mechanism leading to microvascular dysfunction in AD, and represents an important therapeutic target.

neuroscience↗

bioRxiv2021

Intratumoral delivery of engineered recombinant modified vaccinia virus Ankara express-ing Flt3L and OX40L generates potent antitumor immunity through activating the cGAS/STING pathway and depleting tumor-infiltrating regulatory T cells

Intratumoral (IT) delivery of immune-activating viruses can serve as an important strategy to turn "cold" tumors into "hot" tumors, resulting in overcoming resistance to immune checkpoint blockade (ICB). Modified vaccinia virus Ankara (MVA) is a highly attenuated, non-replicative vaccinia virus that has a long history of human use. Here we report that IT recombinant MVA (rMVA), lacking E5R encoding an inhibitor of the DNA sensor cyclic GMP-AMP synthase (cGAS), expressing a dendritic cell growth factor, Fms-like tyrosine kinase 3 ligand (Flt3L), and a T cell co-stimulator, OX40L, generates strong antitumor immunity, which is dependent on CD8+ T cells, the cGAS/STING-mediated cytosolic DNA-sensing pathway, and STAT1/STAT2-mediated type I IFN signaling. Remarkably, IT rMVA depletes OX40hi regulatory T cells via OX40L/OX40 interaction and IFNAR signaling. Taken together, our study provides a proof-of-concept for improving MVA-based cancer immunotherapy, through modulation of both innate and adaptive immunity. One Sentence SummaryIntratumoral delivery of recombinant MVA for cancer immunotherapy

immunology↗

bioRxiv2017

Discovery and reporting of clinically-relevant germline variants in advanced cancer patients assessed using whole-exome sequencing

PurposeIn precision cancer care, WES-based analysis of tumor-normal samples helps reveal somatic alterations but can also identify cancer-associated germline variants important for disease surveillance, treatment choice and cancer prevention. WES can also identify germline secondary findings impacting risk of cardiac, neurodegenerative or metabolic diseases. In patients with advanced cancer, the frequency of reportable secondary findings encountered with WES is not well defined.\n\nMethodsTo address this question, we analyzed a cohort of 343 patients with advanced, metastatic cancer for whom we have performed tumor and germline WES interrogating more than 21,000 genes using a CLIA/CLEP approved assay.\n\nResults17% of patients in our cohort have one or more reportable germline variants, including patients with pathogenic variants in the BRCA1 and BRCA2 genes. The frequency of non-cancer clinically relevant germline variants (8.8%) was within the range of two control non-cancer cohorts (11.0% and 6.5%). The frequency of variants in cancer-associated genes was significantly higher (p<0.0005) in our advanced cancer cohort (8.2%) compared to control cohorts (2.7% and 3.8%). More than 50% of patients with reportable germline cancer variants had a family history of cancer.\n\nConclusionthese results stress the importance of returning germline results found during somatic genomic tumor testing.

genomics↗