Project description:Bmi1 is a component of the Polycomb-repressive complexes (PRC) and essential for maintaining the pool of adult stem cells. PRC are key regulators for embryonic development by modifying chromatin architecture and maintaining gene repression. To assess the role of Bmi1 in pluripotent stem cells and upon exit from pluripotency during differentiation, we studied forced Bmi1 expression in mouse embryonic stem cells (ESC). We found that ESC do not express detectable levels of Bmi1 RNA and protein and that forced Bmi1 expression had no obvious influence on ESC self-renewal. However, upon ESC differentiation Bmi1 effectively enhanced development of hematopoietic cells. Global transcriptional profiling identified a large array of genes that were differentially regulated during ESC differentiation by Bmi1. Importantly, we found that Bmi1 induced a prominent up-regulation of Gata2, a zinc finger transcription factor, which is essential for primitive hematopoietic cell generation from mesoderm. In addition, Bmi1 caused sustained growth and a more than 100-fold expansion of ESC-derived hematopoietic stem/progenitor cells within 2-3 weeks of culture. The enhanced proliferative capacity was associated with reduced Ink4a/Arf expression in Bmi1-transduced cells. Taken together, our experiments demonstrate distinct activities of Bmi1 in ESC and ESC-derived hematopoietic progenitor cells. In addition, Bmi1 enhances the propensity of ESC in differentiating towards the hematopoietic lineage. Thus, Bmi1 could be a candidate gene for engineered adult stem cell derivation from ESC. 8 samples in total. Bmi1 embryonic stem cells sample_1 (Bmi1_ESC_1) Bmi1 embryonic stem cells sample_2 (Bmi1_ESC_2) Untreated CCE embryonic stem cells (CCE_ESC_Control) Empty vector CCE embryonic stem cells (CCE_ESC_Vector) Bmi1 embryoid body sample_1 (Bmi1_EB_1) Bmi1 embryoid body sample_2 (Bmi1_EB_2) Empty vector control embryoid body sample_1 (Vector_EB_1) Empty vector control embryoid body sample_2 (Vector_EB_2)
Project description:NguyenLK2011 - Ubiquitination dynamics in
Ring1B-Bmi1 system
This theoretical model investigates the
dynamics of Ring1B/Bmi1 ubiquitination to identify bistable
switch-like and oscillatory behaviour in the
system. Michaelis-Menten (MM) equations are used to formulate
the model. However, the authors show that the dynamics persist even
for Mass-Action kinetics. This SBML file is the MM version of the
model.
This model is described in the article:
Switches,
excitable responses and oscillations in the Ring1B/Bmi1
ubiquitination system.
Nguyen LK, Muñoz-García J,
Maccario H, Ciechanover A, Kolch W, Kholodenko BN.
PLoS Comput. Biol. 2011 Dec; 7(12):
e1002317
Abstract:
In an active, self-ubiquitinated state, the Ring1B ligase
monoubiquitinates histone H2A playing a critical role in
Polycomb-mediated gene silencing. Following ubiquitination by
external ligases, Ring1B is targeted for proteosomal
degradation. Using biochemical data and computational modeling,
we show that the Ring1B ligase can exhibit abrupt switches,
overshoot transitions and self-perpetuating oscillations
between its distinct ubiquitination and activity states. These
different Ring1B states display canonical or multiply branched,
atypical polyubiquitin chains and involve association with the
Polycomb-group protein Bmi1. Bistable switches and oscillations
may lead to all-or-none histone H2A monoubiquitination rates
and result in discrete periods of gene (in)activity. Switches,
overshoots and oscillations in Ring1B catalytic activity and
proteosomal degradation are controlled by the abundances of
Bmi1 and Ring1B, and the activities and abundances of external
ligases and deubiquitinases, such as E6-AP and USP7.
This model is hosted on
BioModels Database
and identified by:
BIOMD0000000622.
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:The polycomb protein Bmi1 restricts adipogenic differentiation of mesenchymal stromal cells to maintain the integrity of hematopoietic stem cell niche.
Project description:Bmi1 is a component of the Polycomb-repressive complexes (PRC) and essential for maintaining the pool of adult stem cells. PRC are key regulators for embryonic development by modifying chromatin architecture and maintaining gene repression. To assess the role of Bmi1 in pluripotent stem cells and upon exit from pluripotency during differentiation, we studied forced Bmi1 expression in mouse embryonic stem cells (ESC). We found that ESC do not express detectable levels of Bmi1 RNA and protein and that forced Bmi1 expression had no obvious influence on ESC self-renewal. However, upon ESC differentiation Bmi1 effectively enhanced development of hematopoietic cells. Global transcriptional profiling identified a large array of genes that were differentially regulated during ESC differentiation by Bmi1. Importantly, we found that Bmi1 induced a prominent up-regulation of Gata2, a zinc finger transcription factor, which is essential for primitive hematopoietic cell generation from mesoderm. In addition, Bmi1 caused sustained growth and a more than 100-fold expansion of ESC-derived hematopoietic stem/progenitor cells within 2-3 weeks of culture. The enhanced proliferative capacity was associated with reduced Ink4a/Arf expression in Bmi1-transduced cells. Taken together, our experiments demonstrate distinct activities of Bmi1 in ESC and ESC-derived hematopoietic progenitor cells. In addition, Bmi1 enhances the propensity of ESC in differentiating towards the hematopoietic lineage. Thus, Bmi1 could be a candidate gene for engineered adult stem cell derivation from ESC.
Project description:PCGF6, a polycomb group protein, regulates mesodermal lineage differentiation in murine ES cells and functions in iPS reprogramming
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:Polycomb group (PcG) proteins play important roles in hematopoietic stem cell (HSC) self-renewal. Mel18 and Bmi1 are homologs of the PCGF subunit within the Polycomb repressive complex 1 (PRC1). Bmi1 (PCGF4) enhances HSC self-renewal and promotes terminal differentiation. However, the role of Mel18 (PCGF2) in hematopoiesis is not fully understood and how Mel18 regulates gene transcription in HSCs remains elusive. We found that acute deletion of Mel18 in the hematopoietic compartment significantly increased the frequency of functional HSCs in the bone marrow. Furthermore, we demonstrate that Mel18 inhibits HSC self-renewal and proliferation. RNA-seq studies revealed that HSC self-renewal and proliferation gene signatures are enriched in Mel18-/- hematopoietic stem and progenitors (HSPCs) compared to Mel18+/+ HSPCs. Notably, ATAC-seq revealed increased chromatin accessibility at genes important for HSC self-renewal, whereas CUT&RUN showed decreased enrichment of H2AK119ub1 at genes important for proliferation, leading to increased expression of both Hoxb4 and Cdk4 in Mel18-/- HSPCs. Furthermore, leukemia stem cells and several types of acute leukemia gene signatures are enriched in Mel18-/- HSCs compared to WT HSCs. Thus, we demonstrate that Mel18 inhibits hematopoietic stem cell self-renewal through repressing the transcription of genes important for HSC self-renewal and proliferation.