Biology subjects

Sarthy, J. F.

Publications and source records attributed to Sarthy, J. F..

12 recordsLinked to original sources

bioRxiv2025

A protocol for high-throughput microplate-based CUT&Tag

Cleavage Under Targets & Tagmentation (CUT&Tag) is a versatile method for measuring genomic occupancy of chromatin-associated proteins with high sensitivity and specificity. CUT&Tag has low sequencing requirements and is therefore suitable for highly multiplexed experiments, but methods to process samples at throughput without specialized equipment are lacking. Here we present a method for simultaneous parallel processing of 96 CUT&Tag samples in a standard microplate. Plate-CUT&Tag can be carried out in a similar time frame to benchtop CUT&Tag and yields data of comparable quality. We present data from cell culture and patient leukemia samples processed with Plate-CUT&Tag to illustrate its utility in large-scale preclinical and translational studies.

genomics↗

bioRxiv2025

Multimodal single-cell analyses reveal distinct fusion-regulated transcriptional programs in Ewing sarcoma.

Ewing sarcoma (EwS) is a fusion-driven malignancy, peaking in adolescence. Although EwS tumors are driven uniquely by EWS::FLI1 and related fusions, patient outcomes vary greatly. If and how tumor plasticity of EWS::FLI1-regulated transcriptional signatures contribute to disease progression is not known. To address this, we utilized a single-cell co-assay of RNA and chromatin accessibility (ATAC) sequencing to identify gene regulatory networks in EwS. By comprehensively characterizing regulatory elements across cell lines, we identified multiple unique modules of gene regulation. Differential usage and prevalence of these modules was evident across cell lines, associated with distinct epigenetic and transcriptomic signatures, and in specific cases, modifiable by exogenous TGF-{beta}. When we examined primary EwS patient tumors, we observed these same regulatory modules were variably enriched both across and within tumors, highlighting the existence of intratumoral heterogeneity in gene regulatory networks. Our findings demonstrate that multiple, co-existing transcriptional programs shape the phenotypic diversity of EwS and suggest that the balance between these networks may have important implications for clinical outcomes and targeted therapy development. SummaryMultimodal transcriptional analysis reveal how Ewing sarcoma tumors use distinct gene programs, including one linked to TGF-{beta}, to drive cancer behavior and progression.

genomics↗

bioRxiv2025

Determining preclinical safety of Aclarubicin in pediatric malignancies

BackgroundAnthracyclines are among the most effective chemotherapeutic agents used to treat pediatric malignancies. However, their clinical use is limited by dose-dependent toxicities, particularly cardiotoxicity and secondary malignancies. Aclarubicin (Acla) is an anthracycline derivative that induces chromatin damage while sparing DNA, offering potential therapeutic benefit with reduced longterm toxicity. MethodsWe evaluated the anti-tumor efficacy and safety profile of Acla in multiple in vitro pediatric cancer models and in vivo mouse models designed to mimic anthracycline re-treatment following prior doxorubicin (Doxo) exposure. Tumor growth, genotoxic stress, survival, and organ toxicity were assessed. ResultsAcla demonstrated robust anti-tumor activity comparable to Doxo across diverse pediatric in vitro models. Unlike Doxo, Acla treatment did not induce significant genotoxic stress. In vivo, mice receiving Acla after Doxo exposure showed no evidence of cumulative cardiotoxicity or end-organ damage. In contrast, a second course of Doxo led to significant toxic mortality, but was surprisingly not attributable to classic cardiac injury. ConclusionOur study highlights Acla as a promising anthracycline derivative for pediatric cancers, with potent anti-tumor efficacy and a superior safety profile, even following prior anthracycline exposure. These results support continued investigation of chromatin-damaging anthracyclines that can kill pediatric cancer cells without inducing genotoxic stress. In addition, our studies underscore the need to refine preclinical models to better understand both acute and chronic anthracycline toxicities in pediatric and adolescent populations.

cancer biology↗

bioRxiv2023

KMT2A oncoproteins induce epigenetic resistance to targeted therapies

Chromosomal translocations involving the Lysine-Methyl-Transferase-2A (KMT2A) locus generate potent oncogenic fusion proteins (oncoproteins) that disrupt regulation of developmental gene expression. By profiling the oncoprotein-target sites of 36 broadly representative KMT2A-rearranged leukemia samples, including three samples that underwent a lymphoid-to-myeloid lineage-switching event in response to therapy, we find the genomic enrichment of the oncoprotein is highly variable between samples and subject to dynamic regulation. At high levels of expression, the oncoproteins preferentially activate either an acute lymphoblastic leukemia (ALL) program, enriched for pro-B-cell genes, or an acute myeloid leukemia (AML) program, enriched for hematopoietic-stem-cell genes. The fusion-partner-specific-binding patterns over these gene sets are highly correlated with the prevalence of each mutation in ALL versus AML. In lineage-switching samples the oncoprotein levels are reduced and the oncoproteins preferentially activate granulocyte-monocyte progenitor (GMP) genes. In a sample that lineage switched during treatment with the menin inhibitor revumenib, the oncoprotein and menin are reduced to undetectable levels, but ENL, a transcriptional cofactor of the oncoprotein, persists on numerous oncoprotein-target loci, including genes in the GMP-like lineage-switching program. We propose KMT2A oncoproteins promote lineage-switching events through dynamic chromatin binding and can induce epigenetic lesions, marked by ENL, that support resistance to targeted therapies.

cancer biology↗

bioRxiv2023

G1 length dictates heterochromatin landscape

Stem cells have lower facultative heterochromatin as defined by trimethylation of histone H3 lysine 27 (H3K27me3) compared to differentiated cells. However, the mechanisms underlying these differential H3K27me3 levels remain elusive. Because H3K27me3 levels are diluted two-fold in every round of replication and then restored through the rest of the cell cycle, we reasoned that the cell cycle length could be a key regulator of total H3K27me3 levels. Here, we propose that a fast cell cycle restricts H3K27me3 levels in stem cells. To test this model, we determined changes to H3K27me3 levels in mESCs globally and at specific loci upon G1 phase lengthening - accomplished by thymidine block or growth in the absence of serum (with the "2i medium"). H3K27me3 levels in mESC increase with G1 arrest when grown in serum and in 2i medium. Additionally, we observed via CUT&RUN and ChIP-seq that regions that gain H3K27me3 in G1 arrest and 2i media overlap, supporting our model of cell cycle length as a critical regulator of the stem cell epigenome and cellular identity. Furthermore, we demonstrate the inverse effect - that G1 shortening in differentiated cells results in a loss of H3K27me3 levels. Finally, in tumor cells with extreme H3K27me3 loss, lengthening of the G1 phase leads to H3K27me3 recovery despite the presence of the dominant negative, sub-stoichiometric H3.1K27M mutation. Our results indicate that G1 length is an essential determinant of H3K27me3 landscapes across diverse cell types.

molecular biology↗

bioRxiv2023

Chromatin Profiling of CBFA2T3-GLIS2 AMLs Identifies Key Transcription Factor Dependencies and BRG1 Inhibition as a Novel Therapeutic Strategy

Oncogenic fusions involving transcription factors are present in the majority of pediatric leukemias; however, the context-specific mechanisms they employ to drive cancer remain poorly understood. CBFA2T3-GLIS2 (C/G) fusions occur in treatment-refractory acute myeloid leukemias and are restricted to young children. To understand how the C/G fusion drives oncogenesis we applied CUT&RUN chromatin profiling to an umbilical cord blood/endothelial cell (EC) co-culture model of C/G AML that recapitulates the biology of this malignancy. We find C/G fusion binding is mediated by its zinc finger domains. Integration of fusion binding sites in C/G- transduced cells with Polycomb Repressive Complex 2 (PRC2) sites in control cord blood cells identifies MYCN, ZFPM1, ZBTB16 and LMO2 as direct C/G targets. Transcriptomic analysis of a large pediatric AML cohort shows that these genes are upregulated in C/G patient samples. Single cell RNA-sequencing of umbilical cord blood identifies a population of megakaryocyte precursors that already express many of these genes despite lacking the fusion. By integrating CUT&RUN data with CRISPR dependency screens we identify BRG1/SMARCA4 as a vulnerability in C/G AML. BRG1 profiling in C/G patient-derived cell lines shows that the CBFA2T3 locus is a binding site, and treatment with clinically-available BRG1 inhibitors reduces fusion levels and downstream C/G targets including N-MYC, resulting in C/G leukemia cell death and extending survival in a murine xenograft model.

cancer biology↗

bioRxiv2022

Nucleosome patterns in circulating tumor DNA reveal transcriptional regulation of advanced prostate cancer phenotypes

Advanced prostate cancers comprise distinct phenotypes, but tumor classification remains clinically challenging. Here, we harnessed circulating tumor DNA (ctDNA) to study tumor phenotypes by ascertaining nucleosome positioning patterns associated with transcription regulation. We sequenced plasma ctDNA whole genomes from patient-derived xenografts representing a spectrum of androgen receptor active (ARPC) and neuroendocrine (NEPC) prostate cancers. Nucleosome patterns associated with transcriptional activity were reflected in ctDNA at regions of genes, promoters, histone modifications, transcription factor binding, and accessible chromatin. We identified the activity of key phenotype-defining transcriptional regulators from ctDNA, including AR, ASCL1, HOXB13, HNF4G, and NR3C1. Using these features, we designed a prediction model which distinguished NEPC from ARPC in patient plasma samples across three clinical cohorts with 97-100% sensitivity and 85-100% specificity. While phenotype classification is typically assessed by immunohistochemistry or transcriptome profiling, we demonstrate that ctDNA provides comparable results with numerous diagnostic advantages for precision oncology. STATEMENT OF SIGNIFICANCEThis study provides key insights into the dynamics of nucleosome positioning and gene regulation associated with cancer phenotypes that can be ascertained from ctDNA. The new methods established for phenotype classification extend the utility of ctDNA beyond assessments of DNA alterations with important implications for molecular diagnostics and precision oncology.

cancer biology↗

bioRxiv2022

HOXD13 is a direct EWS-FLI1 target and moderates fusion-dependent transcriptional states

Oncogenic fusion proteins display exquisite tissue specificity, revealing that malignant transformation requires cooperation with cell-autonomous factors. Recent studies have also demonstrated that tumorigenicity of Ewing sarcoma requires precise regulation of the transcriptional activity of the EWS-FLI1 oncogenic driver. Here we show that the developmentally and anatomically restricted transcription factor HOXD13 is a direct target of EWS-FLI1. Transcriptomic and CUT&RUN studies revealed that HOXD13 binds active, fusion-bound enhancers, resulting in altered expression of EWS-FLI1-induced targets. More strikingly, HOXD13 was found to bind and activate cis-regulatory regions of genes that are normally repressed by EWS-FLI1. Single-cell sequencing demonstrated marked intra-tumoral heterogeneity of HOXD13 transcriptional activity and revealed that antagonism between HOXD13-mediated gene activation and EWS-FLI1-dependent gene repression confers a spectrum of transcriptional cell states along a mesenchymal axis. Thus, HOXD13 serves as an internal rheostat for EWS-FLI1 activity, providing a paradigm for tissue-specific transcription factors as critical partners in fusion-driven cancers.

cancer biology↗

bioRxiv2020

Automated CUT&Tag profiling of chromatin heterogeneity in mixed-lineage leukemia

Acute myeloid and lymphoid leukemias often harbor chromosomal translocations involving the Mixed Lineage Leukemia-1 gene, encoding the KMT2A lysine methyltransferase. The most common translocations produce in-frame fusions of KMT2A to other chromatin regulatory proteins. Here we develop a strategy to map the genome-wide occupancy of oncogenic KMT2A fusion proteins in primary patient samples regardless of fusion partner. By modifying the versatile CUT&Tag method for full automation we identify common and tumor-specific patterns of aberrant chromatin regulation induced by different KMT2A fusion proteins. Integration of automated and single-cell CUT&Tag uncovers epigenomic heterogeneity within patient samples and predicts sensitivity to therapeutic agents.

genomics↗

bioRxiv2020

Single-cell analysis of chromatin silencing programs in developmental and tumor progression

Single-cell analysis has become a powerful approach for the molecular characterization of complex tissues. Methods for quantifying gene expression1 and chromatin accessibility2 of single cells are now well-established, but analysis of chromatin regions with specific histone modifications has been technically challenging. Here, we adapt the recently published CUT&Tag method3 to scalable single-cell platforms to profile chromatin landscapes in single cells (scCUT&Tag) from complex tissues. We focus on profiling Polycomb Group (PcG) silenced regions marked by H3K27 trimethylation (H3K27me3) in single cells as an orthogonal approach to chromatin accessibility for identifying cell states. We show that scCUT&Tag profiling of H3K27me3 distinguishes cell types in human blood and allows the generation of cell-type-specific PcG landscapes from heterogeneous tissues. Furthermore, we use scCUT&Tag to profile H3K27me3 in a brain tumor patient before and after treatment, identifying cell types in the tumor microenvironment and heterogeneity in PcG activity in the primary sample and after treatment.

genomics↗

bioRxiv2020

Histone deposition pathways determine the chromatin landscapes of H3.1 and H3.3 K27M oncohistones

Lysine 27-to-methionine (K27M) mutations in the H3.1 or H3.3 histone genes are characteristic of pediatric diffuse midline gliomas (DMGs). These oncohistone mutations dominantly inhibit histone H3K27 trimethylation and silencing, but it is unknown how oncohistone type affects gliomagenesis. We show that the genomic distributions of H3.1 and H3.3 oncohistones in human patient-derived DMG cells are consistent with the DNA replication-coupled deposition of histone H3.1 and the predominant replication-independent deposition of histone H3.3. Although H3K27 trimethylation is reduced for both oncohistone types, H3.3K27M-bearing cells retain some domains, and only H3.1K27M-bearing cells lack H3K27 trimethylation. Neither oncohistone interferes with PRC2 binding. Using Drosophila as a model, we demonstrate that inhibition of H3K27 trimethylation occurs only when H3K27M oncohistones are deposited into chromatin and only when expressed in cycling cells. We propose that oncohistones inhibit the H3K27 methyltransferase as chromatin patterns are being duplicated in proliferating cells, predisposing them to tumorigenesis.

molecular biology↗

bioRxiv2018

Automated in situ profiling of chromatin modifications resolves cell types and gene regulatory programs

Our understanding of eukaryotic gene regulation is limited by the complexity of protein-DNA interactions that comprise the chromatin landscape and by inefficient methods for characterizing these interactions. We recently introduced CUT&RUN, an antibody-targeted nuclease-cleavage method that profiles DNA-binding proteins, histones and chromatin modifying proteins in situ with exceptional sensitivity and resolution. Here we describe an automated CUT&RUN platform and apply it to characterize the chromatin landscapes of human cell lines. We find that CUT&RUN profiles of histone modifications crisply demarcate active and repressed chromatin regions, and we develop a continuous metric to identify cell-type specific promoter and enhancer activities. We test the ability of automated CUT&RUN to profile frozen tumor samples, and find that our method readily distinguishes two diffuse midline gliomas by their subtype-specific gene expression programs. The easy, cost-effective workflow makes automated CUT&RUN an attractive tool for high-throughput characterization of cell types and patient samples.

genomics↗