The role of H3K27me3 demethylases in B cell differentiation Öffentlichkeit

Abstract

B cell differentiation into antibody-secreting plasma cells (PC) requires substantial metabolic, transcriptional, and epigenetic reprogramming, including changes in the distribution of the histone modification H3 lysine 27 trimethylation (H3K27me3). This histone modification is associated with repressive chromatin state and gene silencing. While the role of EZH2, the H3K27me3 methyltransferase, in B cells has been well established, little is known about the role of active demethylation of this histone modification by UTX and JMJD3. Here, the role of the two H3K27me3 demethylases in B cell differentiation was investigated using chemical inhibition and genetic deletion of these enzymes. Pharmacological inhibition of these enzymes in ex vivo cultured B cells led to an increase in PC, which was associated with upregulation of cell cycle genes and increased proliferation. The findings were further investigated using mice with conditional deletion of Utx and Jmjd3 in B cells (dKO). Similar to what has been observed with the inhibitor, loss of both enzymes led to an increase in PC following stimulation with TI antigens. This phenotype occurred in a UTX-dependent manner as UTX single knockout mice mimicked the dKO mice. Loss of Utx and Jmjd3 also resulted in an increase in marginal zone B cells; however, increased differentiation was also observed in follicular B cells, suggesting a common mechanism by which H3K27me3 demethylases regulate B cell differentiation. UTX and JMJD3-deficient PC upregulated genes associated with OXPHOS and showed increased spare respiratory capacity. Furthermore, loss of Utx and Jmjd3 led to vast changes in chromatin accessibility and resulted in an increase in H3K27me3 levels at pro-apoptotic genes, which corresponded to reduced apoptosis of dKO PC. Analysis of B cell responses following infection with PR8 influenza virus revealed that UTX and JMJD3 regulated germinal center (GC) response in a cell-intrinsic manner. Loss of Utx and Jmjd3 led to an increase in GC B cells, which downregulated genes associated with signaling and chemotaxis. Taken together, this work identified UTX as a novel epigenetic regulator restraining B cell responses.

Table of Contents

TABLE OF CONTENTS

Chapter 1. Introduction …………...…………………………………………………………….1

     I.        The role of B cells in health and disease…………………………………………….…….2

a.    The good: immunity and vaccines…………………………………………….…...2

b.    The bad: cancer and autoimmunity…………………………………………….…..3

   II.        B cell development and differentiation……………………………………………….……4

a.    B cell development…………………………………………………………….…. 4

b.    B cell differentiation………………………………………………………….……6

 III.        Unique biology of a plasma cell*…………………………………………………….……8

a.    Metabolic adaptations to manufacture and secrete antibodies…………………….8

b.    Antibody-secreting cell survival and homing……………………………….……10

 IV.        Cellular and molecular reprogramming accompanying PC formation…………….……..11

a.    B cell differentiation is associated with extensive cell proliferation………….….12

b.    Transcriptional regulation of B cell differentiation…………………………....…13

c.    Changes in chromatin accessibility accompany B cell differentiation ……….….14

  V.        Epigenetic control of B cell differentiation*………………………………………….….15

a.    DNA methylation……………………………………………………………...…15

b.    Enhancer of zeste homolog 2 (EZH2)………………………………………....…17

c.    Lysine-specific histone demethylase 1A (LSD1)………………………….……..18

d.    Disruptor of telomeric silencing 1- like (DOT1L)……………………….……….19

e.    3D architecture during b cell differentiation………………………….…………..20

 VI.        The role of UTX and JMJD3 in health and disease……………………………….……...23

a.    The biochemical function of UTX and JMJD3…………..………………………23

b.    Role of H3K27me3 demethylase in mammalian development…………….…….24

c.    Role in the adaptive immune system………………………………….…….……26

d.    Role in disease …………………………………………………………….……..31

VII.        Rational and overview……………………………………………....................................32

 

Chapter 2. Inhibition of H3K27me3 demethylase promotes plasmablast formation………33

     I.        Abstract ………………………………………………………………..............................34

   II.        Introduction ……………………………………………………………………………...35

 III.        Results …………………………………………………………………...........................38

 IV.        Discussion ..........................................................................................................................50

  V.        Supporting data ..................................................................................................................55

 VI.        Methods .............................................................................................................................56

 

Chapter 3. H3K27me3 demethylase UTX restrains plasma cell formation…………………60

     I.        Abstract ..............................................................................................................................61

   II.        Introduction .......................................................................................................................62

 III.        Results ...............................................................................................................................65

 IV.        Discussion ..........................................................................................................................82

  V.        Supporting data ..................................................................................................................88

 VI.        Methods ..............................................................................................................................92

 

Chapter 4. Work in progress: The role of UTX and JMJD3 in response to TD antigens……100

 

Chapter 5. Discussion.................................................................................................................113

References ..................................................................................................................................123

About this Dissertation

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School	Laney Graduate School
Department	Biological and Biomedical Sciences
Subfield / Discipline	Genetics and Molecular Biology
Degree	Ph.D.
Submission	Dissertation
Language	English
Research Field	Biology, Genetics Biology, Molecular Health Sciences, Immunology
Stichwort	UTX and JMJD3 H3K27me3 demethylases Plasma cells
Committee Chair / Thesis Advisor	Boss, Jeremy, Emory University

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