Epigenetic Perturbations by Arg882-Mutated DNMT3A Potentiate Aberrant Stem Cell Gene-Expression Program and Acute Leukemia Development

DNA methyltransferase 3A (DNMT3A) is frequently mutated in hematological cancers; however, the underlying oncogenic mechanism remains elusive. Here, we report that DNMT3A mutational hotspot at Arg882 (DNMT3AR882H) cooperates with NRAS mutation to transform hematopoietic stem/progenitor cells and induce acute leukemia development. Mechanistically, DNMT3AR882H directly binds to and potentiates transactivation of stemness genes critical for leukemogenicity including Meis1, Mn1 and Hoxa gene cluster. DNMT3AR882H induces focal epigenetic alterations, including CpG hypomethylation and concurrent gain of active histone modifications, at cis-regulatory elements such as enhancers to facilitate gene transcription. CRISPR/Cas9-mediated ablation of a putative Meis1 enhancer carrying DNMT3AR882H-induced DNA hypomethylation impairs Meis1 expression. Importantly, DNMT3AR882H-induced gene expression programs can be repressed through Dot1l inhibition, providing an attractive therapeutic strategy for DNMT3A-mutated leukemias

MT1-MMP and Type II Collagen Specify Skeletal Stem Cells and Their Bone and Cartilage Progeny

Skeletal formation is dependent on timely recruitment of skeletal stem cells and their ensuing synthesis and remodeling of the major fibrillar collagens, type I collagen and type II collagen, in bone and cartilage tissues during development and postnatal growth. Loss of the major collagenolytic activity associated with the membrane-type 1 matrix metalloproteinase (MT1-MMP) results in disrupted skeletal development and growth in both cartilage and bone, where MT1-MMP is required for pericellular collagen dissolution. We show here that reconstitution of MT1-MMP activity in the type II collagen–expressing cells of the skeleton rescues not only diminished chondrocyte proliferation, but surprisingly, also results in amelioration of the severe skeletal dysplasia associated with MT1-MMP deficiency through enhanced bone formation. Consistent with this increased bone formation, type II collagen was identified in bone cells and skeletal stem/progenitor cells of wildtype mice. Moreover, bone marrow stromal cells isolated from mice expressing MT1-MMP under the control of the type II collagen promoter in an MT1-MMP–deficient background showed enhanced bone formation in vitro and in vivo compared with cells derived from nontransgenic MT1-MMP–deficient littermates. These observations show that type II collagen is not stringently confined to the chondrocyte but is expressed in skeletal stem/progenitor cells (able to regenerate bone, cartilage, myelosupportive stroma, marrow adipocytes) and in the chondrogenic and osteogenic lineage progeny where collagenolytic activity is a requisite for proper cell and tissue function

Membrane-type MMPs enable extracellular matrix permissiveness and mesenchymal cell proliferation during embryogenesis

AbstractPeri-cellular remodeling of mesenchymal extracellular matrices is considered a prerequisite for cell proliferation, motility and development. Here we demonstrate that membrane-type 3 MMP, MT3-MMP, is expressed in mesenchymal tissues of the skeleton and in peri-skeletal soft connective tissue. Consistent with this localization, MT3-MMP-deficient mice display growth inhibition tied to a decreased viability of mesenchymal cells in skeletal tissues. We document that MT3-MMP works as a major collagenolytic enzyme, enabling cartilage and bone cells to cleave high-density fibrillar collagen and modulate their resident matrix to make it permissive for proliferation and migration. Collectively, these data uncover a novel extracellular matrix remodeling mechanism required for proper function of mesenchymal cells. The physiological significance of MT3-MMP is highlighted in mice double deficient for MT1-MMP and MT3-MMP. Double deficiency transcends the combined effects of the individual single deficiencies and leads to severe embryonic defects in palatogenesis and bone formation incompatible with life. These defects are directly tied to loss of indispensable collagenolytic activities required in collagen-rich mesenchymal tissues for extracellular matrix remodeling and cell proliferation during embryogenesis

L'Avenir de Luchon : journal scientifique, littéraire, annonces et réclames : guide général des baigneurs et des touristes aux eaux thermales, bains de mer de la France et de l'étranger

09 mai 19201920/05/09 (N40)-1920/05/09.Appartient à l’ensemble documentaire : MidiPyren

Additional file 2: Figures S1–S8. of An obesity-associated gut microbiome reprograms the intestinal epigenome and leads to altered colonic gene expression

Along with figure legends. (PDF 2613 kb

Additional file 1: Table S1. of An obesity-associated gut microbiome reprograms the intestinal epigenome and leads to altered colonic gene expression

This file contains Table S1 which provides detailed descriptions of the components of the diets used in this study. (XLSX 9 kb

Base-Resolution Analysis of DNA Methylation Patterns Downstream of Dnmt3a in Mouse Naïve B Cells

The DNA methyltransferase, Dnmt3a, is dynamically regulated throughout mammalian B cell development and upon activation by antigenic stimulation. Dnmt3a inactivation in hematopoietic stem cells has been shown to drive B cell-related malignancies, including chronic lymphocytic leukemia, and associates with specific DNA methylation patterns in transformed cells. However, while it is clear that inactivation of Dnmt3a in hematopoietic stem cells has profound functional effects, the consequences of Dnmt3a inactivation in cells of the B lineage are unclear. To assess whether loss of Dnmt3a at the earliest stages of B cell development lead to DNA methylation defects that might impair function, we selectively inactivated Dnmt3a early in mouse B cell development and then utilized whole genome bisulfite sequencing to generate base-resolution profiles of Dnmt3a+/+ and Dnmt3a−/− naïve splenic B cells. Overall, we find that global methylation patterns are largely consistent between Dnmt3a+/+ and Dnmt3a−/− naïve B cells, indicating a minimal functional effect of DNMT3A in mature B cells. However, loss of Dnmt3a induced 449 focal DNA methylation changes, dominated by loss-of-methylation events. Regions found to be hypomethylated in Dnmt3a−/− naïve splenic B cells were enriched in gene bodies of transcripts expressed in B cells, a fraction of which are implicated in B cell-related disease. Overall, the results from this study suggest that factors other than Dnmt3a are the major drivers for methylome maintenance in B cell development

Additional file 1: Table S1. of An obesity-associated gut microbiome reprograms the intestinal epigenome and leads to altered colonic gene expression

This file contains Table S1 which provides detailed descriptions of the components of the diets used in this study. (XLSX 9 kb

Epigenetic Perturbations by Arg882-Mutated DNMT3A Potentiate Aberrant Stem Cell Gene-Expression Program and Acute Leukemia Development

DNA methyltransferase 3A (DNMT3A) is frequently mutated in hematological cancers; however, the underlying oncogenic mechanism remains elusive. Here, we report that DNMT3A mutational hotspot at Arg882 (DNMT3A(R882H)) cooperates with NRAS mutation to transform hematopoietic stem/progenitor cells and induce acute leukemia development. Mechanistically, DNMT3A(R882H) directly binds to and potentiates transactivation of stemness genes critical for leukemogenicity including Meis1, Mn1 and Hoxa gene cluster. DNMT3A(R882H) induces focal epigenetic alterations, including CpG hypomethylation and concurrent gain of active histone modifications, at cis-regulatory elements such as enhancers to facilitate gene transcription. CRISPR/Cas9-mediated ablation of a putative Meis1 enhancer carrying DNMT3A(R882H)-induced DNA hypomethylation impairs Meis1 expression. Importantly, DNMT3A(R882H)-induced gene expression programs can be repressed through Dot1l inhibition, providing an attractive therapeutic strategy for DNMT3A-mutated leukemias