Project description:Polycomb group (PcG) proteins are transcriptional repressors with a central role in the establishment and maintenance of gene expression patterns during development. We have investigated the role of Polycomb Repressive Complexes (PRCs) in hematopoietic stem cells (HSCs) and progenitor populations. We show that mice with loss of function mutations in PRC2 components display enhanced HSC/progenitor population activity, whereas mutations that disrupt PRC1 or PhoRC are associated with HSC/progenitor cell defects. Since the hierarchical model of PRC action would predict synergistic effects of PRC1 and PRC2 mutation, these opposing effects suggest this model does not hold true in HSC/progenitor cells. To investigate the molecular targets of each complex in HSC/progenitor cells, we measured genome-wide expression changes associated with PRC-deficiency, and identified transcriptional networks that are differentially regulated by PRC1 and PRC2. These studies provide new insights into the mechanistic interplay between distinct PRCs and have important implications for approaching PcG proteins as therapeutic targets. Total RNA obtained from foetal liver LSK cells from mouse embryos with genes from different polycomb repressive complexes mutated or knocked-out was compared with wild-type samples.
Project description:Nuclear pore complexes (NPCs) are established players in cell division and differentiation. However studies on the contribution of individual NPC subunits to these processes are still scarce. Here we have used mouse embryonic stem cells (mESCs) to characterize the role of structural components of the NPCs, focusing on the short arm of the Y-complex that comprises Nup85, Seh1 and Nup43. We show that Seh1 and Nup43, although dispensable at the pluripotent stage, are required for normal cell growth rates at that stage and for mESC viability upon differentiation. Lack of Seh1 or Nup43 in mESCs is associated with a mild reduction of NPC density that is also observed when Seh1 interaction with Nup85 is impaired. Nevertheless, mESC proliferation and differentiation are not altered in these ∆E2-GFP-Nup85 mutants, indicating that it is the integrity of the Y-complex, rather than the number of NPCs, that is critical to ensure these processes.
Project description:Polycomb group (PcG) proteins play a pivotal role in epigenetically silencing development-related genes, restricting their expression to appropriate tissues. However, in some instances PcG target genes must also be dynamically regulated in response to developmental signals encountered during morphogenesis. Here we examine the role of PcG factors in early forelimb bud patterning, a process that relies on various morphogenetic signals. Depletion of Ring1 proteins, which are essential components of Polycomb repressive complex-1 (PRC1), led to dramatic deficiencies in forelimb formation and proximal-distal regionalization. Gene expression analysis identified Meis2 and Meis1 as critical PRC1 targets genes in early distal specification, with PcG proteins counteracting retinoic acid (RA) signaling to control their expression. Importantly, in this system, PcG factors appear to function by adjusting the threshold for RA signaling, revealing an unexpected role of polycomb proteins in dynamic gene regulation during development. [Affymetrix] Mouse E10.5 forelimb buds of Ring1A-KO, Ring1A/B-dKO and RA-treated wild type were used for RNA extraction and hybridization on Affymetrix microarrays. [Agilent] ChIP analysis of mouse E10.5 whole forelimb buds against anti-H3K27me3 antibody.
Project description:Identification of gene expression changes in wild type versus mutant mouse hearts where Brg1 and Brm were knocked out in adult cardiomyocytes.
