Biology subjects

Zimmerman, S. M.

Publications and source records attributed to Zimmerman, S. M..

5 recordsLinked to original sources

bioRxiv2025

Arid2 promotes Follicular B-cell differentiation and antibody responses in vivo

SWI/SNF chromatin remodeling complexes regulate gene expression during development and differentiation. These complexes exist in distinct forms, including the polybromo-associated BAF (PBAF) complex, defined by the ARID2 subunit. ARID2 is frequently mutated in B cell leukemias, but its role in normal B cell development remains unknown. Using conditional knockout mice, we show that Arid2 deletion impairs B cell differentiation in vivo. Mb1-Cre-mediated deletion, active in early progenitors, caused a marked reduction of splenic and circulating Follicular B cells, whereas CD19-Cre deletion produced a milder phenotype. These defects were not due to altered proliferation or survival but reflected impaired differentiation potential. Transcriptomic profiling of isolated pro-B, pre-B, and Follicular B cells revealed that Arid2 loss disrupts stage-specific gene expression programs, with cumulative downregulation of B cell receptor signaling and altered lineage-specifying pathways. Functionally, Arid2-deficient mice exhibited impaired germinal center expansion after immunization and reduced IgG antibody production following transplantation. Together, these findings identify Arid2 as a critical regulator of B cell differentiation and maturation by coordinating transcriptional programs during early lymphopoiesis.

immunology↗

bioRxiv2024

Developmental Stage and Cellular Context Determine Oncogenic and Molecular Outcomes of Ezh2Y641F Mutation in Hematopoiesis

Mutations in the histone methyltransferase EZH2, particularly the Y641 hotspot mutation, have been implicated in hematologic malignancies, yet the effect of timing and cellular context on their oncogenic potential has remained unknown. In this study, we utilized a conditional allele with tissue-specific Cre drivers to investigate the effects of Ezh2Y641F mutations at various stages of development, with a focus on the hematopoietic system. We found that ubiquitous heterozygous Ezh2Y641F expression at birth, or conditional expression in hematopoietic or mesenchymal stem cells, led to decreased survival due to hematopoietic defects and bone marrow failure, with no evidence of malignancy. In contrast, Ezh2Y641F expression in committed B cells drives lymphoma formation, highlighting the lineage-specific oncogenic activity of the mutation. Transcriptomic analysis of B cell progenitors revealed key pathway alterations between Cre models such as altered IL2-Stat5 signaling pathway, differential expression of E2F targets, and altered GTPase pathway expression driven by upregulation of Guanylate Binding Proteins (GBPs) in Mx1-Cre Ezh2Y641F pro-B cells. We further found that the GBP locus is regulated by Ezh2-mediated H3K27me3, it is associated with poorer survival in Acute Myeloid Leukemia patients and has variable effects on apoptosis in human lymphoma and leukemia cell lines. These findings suggest that the Ezh2Y641F mutation may alter immune regulatory pathways, cell differentiation and apoptosis, with potential implications for disease progression. Our results highlight the critical role of mutation timing and cellular context in EZH2-driven hematopoietic disease, resulting in distinct downstream changes that shape the oncogenic impact of EZH2.

cancer biology↗

bioRxiv2024

Stat3-mediated Atg7 expression enhances anti-tumor immunity in melanoma

Epigenetic modifications to DNA and chromatin control oncogenic and tumor suppressive mechanisms in melanoma. EZH2, the catalytic component of the Polycomb repressive complex 2 (PRC2), which mediates methylation of lysine 27 on histone 3 (H3K27me3), can regulate both melanoma initiation and progression. We previously found that mutant Ezh2Y641F interacts with the immune regulator Stat3 and together they affect anti-tumor immunity. However, given the numerous downstream targets and pathways affected by EZH2, many mechanisms that determine its oncogenic activity remain largely unexplored. Using genetically engineered mouse models we further investigated the role of pathways downstream of EZH2 in melanoma carcinogenesis and identified significant enrichment in several autophagy signatures, along with increased expression of autophagy regulators, such as Atg7. In this study, we investigated the effect of Atg7 on melanoma growth and tumor immunity within the context of an Ezh2Y641F epigenetic state. We found that expression of Atg7 is largely dependent on Stat3 expression and that deletion of Atg7 slows down melanoma cell growth in vivo, but not in vitro. Atg7 deletion also results in increased CD8+ T cells and reduced myelosuppressive cell infiltration in the tumor microenvironment, suggesting a strong immune system contribution in the role of Atg7 in melanoma progression. These findings highlight the complex interplay between genetic mutations, epigenetic regulators, and autophagy in shaping tumor immunity in melanoma.

cancer biology↗

bioRxiv2022

Proteome-wide identification of amino acid substitutions deleterious for protein function

DNA sequencing has led to the discovery of millions of mutations that change the encoded protein sequences, but the impact of nearly all of these mutations on protein function is unknown. We addressed this scarcity of functional data by developing Miro, a proteomic technology that uses mistranslation to introduce amino acid substitutions and biochemical assays to quantify functional differences of thousands of protein variants by mass spectrometry. We apply this technology to the proteome of yeast to reveal amino acid substitutions that impact protein structure, ligand binding, protein-protein interactions, protein post-translational modifications, and protein thermal stability. Adapting Miro to human cells will provide a means to efficiently accelerate our mechanistic interpretation of genomic mutations to predict disease risk.

genomics↗

bioRxiv2021

Spatially resolved whole transcriptome profiling in human and mouse tissue using Digital Spatial Profiling

Emerging spatial profiling technology has enabled high-plex molecular profiling in biological tissues, preserving the spatial and morphological context of gene expression. Here we describe expanding the chemistry for the Digital Spatial Profiling platform to quantify whole transcriptomes in human and mouse tissues using a wide range of spatial profiling strategies and sample types. We designed multiplexed in situ hybridization probe pools targeting the protein-coding genes in the human and mouse transcriptomes, hereafter referred to as the human or mouse Whole Transcriptome Atlas (WTA). We validated the human and mouse WTA using cell lines to demonstrate concordance with orthogonal gene expression profiling methods in profiled region sizes ranging from ~10-500 cells. By benchmarking against bulk RNAseq and fluorescence in situ hybridization, we demonstrate robust transcript detection possible down to ~100 transcripts per region. To assess the performance of WTA across tissue and sample types, we applied WTA to biological questions in cancer, molecular pathology, and developmental biology. We show that spatial profiling with WTA can detect expected spatial gene expression differences between tumor and tumor microenvironment, identify spatial disease-specific heterogeneity in gene expression in histological structures of the human kidney, and comprehensively map transcriptional programs in anatomical substructures of nine organs in the developing mouse embryo. Digital Spatial Profiling technology with the WTA assays provides a flexible method for spatial whole transcriptome profiling applicable to diverse tissue types and biological contexts.

genomics↗