Project description:The transcription factor PU.1 is a central regulator of hematopoiesis, required for the normal differentiation of the myeloid and lymphoid lineages. Due to its essential role in early development and the importance of PU.1 in regulating several defining markers of lymphoid progenitors, its precise function in early lymphopoiesis has remained unclear. Using conditional mutagenesis and alternative lineage identification strategies, we demonstrate the developmental stage restricted function for PU.1 in early lymphopoiesis. PU.1 was required for efficient generation of “lymphoid primed multipotent progenitors (LMPPs)” from hematopoietic stem cells and was essential for the subsequent formation of “common lymphoid progenitors (CLPs)”. In contrast, further differentiation into the B cell lineage was independent of PU.1. The function of PU.1 was dosage sensitive as loss of one allele decreased all stages of early lymphopoiesis. PU.1 expression mirrored its functional role during lineage differentiation. PU.1 peaked at LMPPs and was maintained in CLPs, before being down regulated in committed pro-B cells. Examination of the transcriptional changes in PU.1 conditionally deficient LSK cells revealed that PU.1 activates lymphoid and dendritic cell associated genes in LMPPs, while repressing genes normally expressed in neutrophils. These data identify PU.1 as a critical regulator of lymphoid priming and the transition between LMPPs and CLPs.
Project description:Despite recent advances in the identification of lymphoid-restricted progenitors, the transcription factors essential for their generation remain to be identified. Here we describe an unexpected role for the myeloid oncogene Mef2c in multipotent progenitors (MPPs), where it is required for pan-lymphoid differentiation. Mef2c deficiency was associated with profound defects in B, T, NK cell and common lymphoid progenitor production and an enhanced myeloid output. Mef2c deficiency in MPPs leads to downregulation of several key lymphoid regulators and the upregulation of the myeloid factor C/EBPa. Our studies also show that Mef2c is a critical transcriptional target of PU.1 during lymphopoiesis. Thus, Mef2c is a crucial component of the transcriptional network that regulates lymphoid specification and cell fate choice in MPPs.
Project description:Collombet2016 - Lymphoid and myeloid cell
specification and transdifferentiation
This model is described in the article:
Logical modeling of lymphoid
and myeloid cell specification and transdifferentiation
Samuel Collombet, Chris van Oevelen,
Jose Luis Sardina Ortega, Wassim Abou-Jaoudé, Bruno Di
Stefano, Morgane Thomas-Chollier, Thomas Graf, and Denis
Thieffry
Proceedings of the National Academy of
Sciences of the United States of America
Abstract:
Blood cells are derived from a common set of hematopoietic
stem cells, which differentiate into more specific progenitors
of the myeloid and lymphoid lineages, ultimately leading to
differentiated cells. This developmental process is controlled
by a complex regulatory network involving cytokines and their
receptors, transcription factors, and chromatin remodelers.
Using public data and data from our own molecular genetic
experiments (quantitative PCR, Western blot, EMSA) or
genome-wide assays (RNA-sequencing, ChIP-sequencing), we have
assembled a comprehensive regulatory network encompassing the
main transcription factors and signaling components involved in
myeloid and lymphoid development. Focusing on B-cell and
macrophage development, we defined a qualitative dynamical
model recapitulating cytokine-induced differentiation of common
progenitors, the effect of various reported gene knockdowns,
and the reprogramming of pre-B cells into macrophages induced
by the ectopic expression of specific transcription factors.
The resulting network model can be used as a template for the
integration of new hematopoietic differentiation and
transdifferentiation data to foster our understanding of
lymphoid/myeloid cell-fate decisions.
This model is hosted on
BioModels Database
and identified by:
MODEL1610240000.
To cite BioModels Database, please use:
BioModels Database:
An enhanced, curated and annotated resource for published
quantitative kinetic models.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
Project description:Cellular binary fate decisions require the progeny to silence genes associated with the alternative fate. The major subsets of alpha:beta T cells have been extensively studied as a model system for fate decisions. While the transcription factor RUNX3 is required for the initiation of Cd4 silencing in CD8 T cell progenitors, it is not required to maintain the silencing of Cd4 and other helper T lineage genes. The other runt domain containing protein, RUNX1, silences Cd4 in an earlier T cell progenitor, but this silencing is reversed whereas the gene silencing after RUNX3 expression is not reverse. Therefore, we hypothesized that RUNX3 and not RUNX1 recruits other factors that maintains the silencing of helper T lineage genes in CD8 T cells. To this end, we performed a proteomics screen of RUNX1 and RUNX3 to determine candidate silencing factors.
Project description:Growth factor independent 1 (Gfi1) is a transcriptional repressor originally identified as a common integration site in Moloney-murine-leukemia-virus-induced T-cell leukemia. Gfi1-/- mice display increased apoptosis of developing thymocytes and T lymphopenia; however, there are contradictory reports of the absolute number of Gfi1-/- early T lineage progenitors. We used floxed alleles of Gfi1 crossed to various T-cell-specific Cre transgenes to map the requirements for Gfi1 during lymphoid priming and development. We show that Gfi1 is necessary for the proper formation and function of both lymphoid-primed multipotent progenitors and early T lineage progenitors. These defects correlate with a global inability of Gfi1-/- progenitors to enforce the activation of lymphoid genes including IL7R, Rag1, Flt3 and Notch1. Forced expression of intracellular Notch1 fails to rescue the Gfi1-/- defective lymphoid gene signature or Gfi1-/- T cell development. Instead, activation of Notch1 in Gfi1-/- cells results in a potent synthetic lethal phenotype that is most dramatic in immature thymocytes, but absent in mature peripheral T cells where developmental transcriptional programs are silent. Moreover, we find that the requirement for Gfi1-transcriptional integration of Notch-driven lymphoid transcriptional programs is cell autonomous. Our data indicate that Gfi1 is required at multiple independent stages of lymphoid development. In hematopoietic progenitors Gfi1 is necessary to integrate Notch1 signaling, mediate lymphoid priming, the formation of early T lineage progenitors and subsequent T lineage commitment. Lineage negative cells were purified by magnetic beads from RosaCreERT2 Gfi1 ex4-5 floxed mice and an activated Notch1 signal was introduced using a GFP+ retroviral vector. GFP+ progenitors were FACS-sorted and cultured in semi-solid media for one week to allow sufficient time to to instruct lymphoid differentiation, then replated in 1uM 4-OHT or EtOH control. After an additional 7 days, CFU were disrupted and RNA was isolated for global gene expression using microarrays.
Project description:Recent studies have documented genome-wide binding patterns of transcriptional regulators and their associated epigenetic marks in hematopoietic cell lineages. In order to determine how epigenetic marks are established and maintained during developmental progression, we have generated long-term cultures of hematopoietic progenitors by enforcing the expression of the E-protein antagonist Id2. Hematopoietic progenitors that express Id2 are multipotent and readily differentiate upon withdrawal of Id2 expression into committed B lineage cells, thus indicating a causative role for E2A in promoting the B cell fate. Genome-wide analyses revealed that a substantial fraction of lymphoid and myeloid enhancers are pre-marked by H3K4me1 in multipotent progenitors. However, H3K4me1 levels at a subset of enhancers are elevated during developmental progression, resulting in evolving enhancer repertoires that we propose orchestrate the myeloid and B cell fates.
Project description:Recent studies have documented genome-wide binding patterns of transcriptional regulators and their associated epigenetic marks in hematopoietic cell lineages. In order to determine how epigenetic marks are established and maintained during developmental progression, we have generated long-term cultures of hematopoietic progenitors by enforcing the expression of the E-protein antagonist Id2. Hematopoietic progenitors that express Id2 are multipotent and readily differentiate upon withdrawal of Id2 expression into committed B lineage cells, thus indicating a causative role for E2A in promoting the B cell fate. Genome-wide analyses revealed that a substantial fraction of lymphoid and myeloid enhancers are pre-marked by H3K4me1 in multipotent progenitors. However, H3K4me1 levels at a subset of enhancers are elevated during developmental progression, resulting in evolving enhancer repertoires that we propose orchestrate the myeloid and B cell fates.