Antibody generation and secretion by B cells provides the basis for humoral immunity. Antibodies bind viral, bacterial and parasitic epitopes facilitatin antigen neutralization and clearance. This immune function results in protective immunity to the host and is exploited to prevent disease by the practice of vaccination. However, very young and old individuals often fail to produce a protective immune response1. Conversely, uncontrolled B cell differentiation can result in hematological malignancy or production of autoreactive antibodies. B cell differentiation is initiated by binding of extracellular stimuli to cellular receptors that trigger a signaling cascade resulting in the induction of transcription factors that reprogram B cells to secrete antibody. Transcription factor function is restricted by the availability of DNA through epigenetic modifications, which are covalent chemical additions to DNA and histones that control the accessibility of chromatin. Epigenetic modifications are heritable through the cell cycle and maintain specific gene expression programs, such as that required to maintain B cell identity. While the epigenetic programming of many hematopoietic processes have been extensively studied2-4, comparatively little work has been conducted to understand the epigenetic mechanisms that govern B cell terminal differentiation into antibody secreting plasma cells. In the following application we propose that epigenetic reprogramming contributes to the humoral immune response. We hypothesize that Lsd1, a histone 3 lysine 4 (H3K4) demethylase, silences the B cell gene expression repertoire by interacting with Blimp1, a key transcription factor in the development of plasma cells. B cell conditional deletion of Lsd1 in mice resulted in diminished plasma cell responses. Genes repressed during B cell differentiation were preferentially enriched for H3K4me1 prior to differentiation and in at least the case of major histocompatibility complex class II (MHCII), were derepressed in Lsd1-deficient plasma cells. These data suggest that Lsd1 epigenetically facilitates reprogramming of B cells into plasma cells. We pose that this is by repression of B cell enhancers, first through demethylation of H3K4me1/2 and subsequently by de novo DNA methylation5,6.
We aim to test these hypotheses using genetic models currently in our laboratory in combination with cellular and molecular analyses. The results of these studies will determine the functional and phenotypic impact of Lsd1 in plasma cell formation, reveal Lsd1-induced epigenetic modifications at key B cell genes during plasma cell differentiation, and determine how these epigenetic changes impact the plasma cell gene expression program. Data from this project will illuminate how the humoral immune system is epigenetically reprogrammed in response to antigenic challenge and provide insight into how it can be modulated to improve vaccine design and for the treatment of disease.
Protective immunity requires the generation and secretion of antibodies by terminally differentiated B cells known as plasma cells. Normal immune responses are coordinated by the correct epigenetic reprogramming of B cells. The aim of this proposal is to identify epigenetic changes imposed by key enzymes during plasma cell formation and the functional consequences to humoral immunity. These data will provide insight into how B cell responses can be modulated in hematological malignancies, autoimmunity and vaccine design.
|Haines, Robert R; Barwick, Benjamin G; Scharer, Christopher D et al. (2018) The Histone Demethylase LSD1 Regulates B Cell Proliferation and Plasmablast Differentiation. J Immunol 201:2799-2811|
|Barwick, Benjamin G; Scharer, Christopher D; Martinez, Ryan J et al. (2018) B cell activation and plasma cell differentiation are inhibited by de novo DNA methylation. Nat Commun 9:1900|
|Kennedy, E M; Powell, D R; Li, Z et al. (2018) Galactic Cosmic Radiation Induces Persistent Epigenome Alterations Relevant to Human Lung Cancer. Sci Rep 8:6709|
|Guo, Muyao; Price, Madeline J; Patterson, Dillon G et al. (2018) EZH2 Represses the B Cell Transcriptional Program and Regulates Antibody-Secreting Cell Metabolism and Antibody Production. J Immunol 200:1039-1052|
|Scharer, Christopher D; Barwick, Benjamin G; Guo, Muyao et al. (2018) Plasma cell differentiation is controlled by multiple cell division-coupled epigenetic programs. Nat Commun 9:1698|
|Christopher, Michael A; Myrick, Dexter A; Barwick, Benjamin G et al. (2017) LSD1 protects against hippocampal and cortical neurodegeneration. Nat Commun 8:805|
|Bell, Joshua S K; Kagey, Jacob D; Barwick, Benjamin G et al. (2016) Factors affecting the persistence of drug-induced reprogramming of the cancer methylome. Epigenetics 11:273-87|
|Scharer, Christopher D; Blalock, Emily L; Barwick, Benjamin G et al. (2016) ATAC-seq on biobanked specimens defines a unique chromatin accessibility structure in naïve SLE B cells. Sci Rep 6:27030|
|Barwick, Benjamin G; Scharer, Christopher D; Bally, Alexander P R et al. (2016) Plasma cell differentiation is coupled to division-dependent DNA hypomethylation and gene regulation. Nat Immunol 17:1216-1225|
|Scharer, Christopher D; Choi, Nancy M; Barwick, Benjamin G et al. (2015) Genome-wide CIITA-binding profile identifies sequence preferences that dictate function versus recruitment. Nucleic Acids Res 43:3128-42|
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