Project description:[original Title] Rapid and synchronous clearance of PcG histone modifications from Hox genes anticipates motor neuron differentiation. Hox genes are expressed in patterns that are spatially and temporally collinear with their chromosomal organization. This feature is an evolutionarily conserved hallmark of embryonic development, and in vertebrates it is critical, among others, for the specification of motor neuron subtypes and the wiring of sensory-motor circuits. We show here that the differentiation of motor neurons from stem cells is accompanied by a synchronous, domain-wide clearance of M-bM-^@M-^\repressiveM-bM-^@M-^] Polycomb (PcG)-dependent histone methylation from Hox gene chromatin domains. These findings argue against the idea, advanced recently, that the collinear dynamics of Hox gene expression invariably reflects the progressive clearance of repressive chromatin modifications. The rapid establishment of stable chromatin domains in response to a transient patterning signal likely serves as a molecular correlate of enduring rostro-caudal neural identity, which underlies the specification of postmitotic motor neuron subtype diversity and neuronal circuit assembly. The differentiation of ventral motor neurons is induced by treating embryonic stem cell cultures with retinoic acid and hedgehog agonist. Here, ChIP-chip using a custom Agilent array is used to profile the occupancy of H3K27me3, H3K4me3, and H3K79me2 at various defined stages during the differentiation process.
Project description:[original Title] Rapid and synchronous clearance of PcG histone modifications from Hox genes anticipates motor neuron differentiation. Hox genes are expressed in patterns that are spatially and temporally collinear with their chromosomal organization. This feature is an evolutionarily conserved hallmark of embryonic development, and in vertebrates it is critical, among others, for the specification of motor neuron subtypes and the wiring of sensory-motor circuits. We show here that the differentiation of motor neurons from stem cells is accompanied by a synchronous, domain-wide clearance of “repressive” Polycomb (PcG)-dependent histone methylation from Hox gene chromatin domains. These findings argue against the idea, advanced recently, that the collinear dynamics of Hox gene expression invariably reflects the progressive clearance of repressive chromatin modifications. The rapid establishment of stable chromatin domains in response to a transient patterning signal likely serves as a molecular correlate of enduring rostro-caudal neural identity, which underlies the specification of postmitotic motor neuron subtype diversity and neuronal circuit assembly.
2013-07-04 | GSE19447 | GEO
Project description:Rapid and synchronous clearance of PcG histone modifications from Hox genes anticipates motor neuron differentiation
Project description:To dissect the significance underlying the delay between Hox transcription and translation, we profiled global Hox gene expression using an in vitro ESC-derived motor neuron differentiation system
Project description:We aim to understand the role that Cdx2 plays in specifying the rostro-caudal identity of differentiating motor neurons. We find that expressing Cdx2 in combination with FGF signaling is sufficient to produce motor neurons with a more caudal identity. ChIP-seq analysis of Cdx2 finds that it binds extensively throughout the Hox regions in progenitor motor neurons. Analysis of polycomb-associated chromatin over Hox regions in the subsequently generated motor neurons finds that Cdx2 binding corresponds to chromatin domains encompassing de-repressed caudal Hox genes. These results suggest a direct role for Cdx2 in specifying caudal motor neuron identity. Expression studies: Affymetrix arrays are used to profile gene expression in ES cells, RA/Hh-derived Day 5 motor neurons, and RA/Hh-derived motor neurons that have also been exposed to Dox (to activate iCdx2) and FGF.
Project description:We aim to understand the role that Cdx2 plays in specifying the rostro-caudal identity of differentiating motor neurons. We find that expressing Cdx2 in combination with FGF signaling is sufficient to produce motor neurons with a more caudal identity. ChIP-seq analysis of Cdx2 finds that it binds extensively throughout the Hox regions in progenitor motor neurons. Analysis of polycomb-associated chromatin over Hox regions in the subsequently generated motor neurons finds that Cdx2 binding corresponds to chromatin domains encompassing de-repressed caudal Hox genes. These results suggest a direct role for Cdx2 in specifying caudal motor neuron identity. ChIP-seq studies: We characterize the binding of Cdx2 in progenitor motor neurons using a V5 tagged doxycycline inducible Cdx2 ESC line (iCdx2). Progenitor motor neurons were generated after 4 days of in vitro differentiation of mouse embryonic stem cells using retinoic acid (RA) and hedgehog (Hh) signaling exposure at day 2. On day 3, the cells are exposed to Dox with and without accompanying FGF signaling. The genome-wide binding of the induced Cdx2 transcription factor is profiled using ChIP-seq with an anti-V5 antibody. An appropriate whole-cell extract control experiment for these ChIP-seq experiments is also included. We also examine the effect of induced Cdx2 expression on polycomb-associated chromatin structure in the resulting cellular populations by profiling the H3K27me3 chromatin mark using ChIP-seq. H3K27me3 experiments were performed after 5 days of in vitro differentiation using cells exposed to either: 1) RA & Hh to derive progenitor motor neurons, followed by Dox & FGF; 2) Dox & FGF alone; or 3) RA and Hh alone. There are 6 Illumina sequencing datasets included in this submission: two biological replicates of iCdx2 ChIP-seq in the presence of FGF; one sample of iCdx2 ChIP-seq in the absence of FGF; one H3K27me3 ChIP-seq in the presence of RA, Hh, Dox, and FGF; one H3K27me3 ChIP-seq in the presence of Dox and FGF; and one H3K27me3 ChIP-seq in the presence of RA and Hh.
Project description:We aim to understand the role that Cdx2 plays in specifying the rostro-caudal identity of differentiating motor neurons. We find that expressing Cdx2 in combination with FGF signaling is sufficient to produce motor neurons with a more caudal identity. ChIP-seq analysis of Cdx2 finds that it binds extensively throughout the Hox regions in progenitor motor neurons. Analysis of polycomb-associated chromatin over Hox regions in the subsequently generated motor neurons finds that Cdx2 binding corresponds to chromatin domains encompassing de-repressed caudal Hox genes. These results suggest a direct role for Cdx2 in specifying caudal motor neuron identity.
Project description:We aim to understand the role that Cdx2 plays in specifying the rostro-caudal identity of differentiating motor neurons. We find that expressing Cdx2 in combination with FGF signaling is sufficient to produce motor neurons with a more caudal identity. ChIP-seq analysis of Cdx2 finds that it binds extensively throughout the Hox regions in progenitor motor neurons. Analysis of polycomb-associated chromatin over Hox regions in the subsequently generated motor neurons finds that Cdx2 binding corresponds to chromatin domains encompassing de-repressed caudal Hox genes. These results suggest a direct role for Cdx2 in specifying caudal motor neuron identity.
Project description:During Drosophila development, Polycomb-group and Trithorax-group proteins function to ensure correct maintenance of transcription patterns by epigenetically repressing or activating target gene expression. To get a deep insight into the PcG and trxG pathways, we investigated a BRCT domain-containing protein called PTIP, which was generally identified as a transcriptional coactivator and belongs to the TRR complex. At the genome scale, we sorted given PTIP binding peaks into two groups: PTIP/TRR-cobound and PTIP/PC-cobound peaks. In particular, we found that PTIP mediates the molecular switch between H3K4me3/H3K27ac and H3K27me3 histone modifications at TRR or PC occupied regions. Thus, we suggest that PTIP is a mediator rather than a dedicated co-activator along PcG and trxG pathways. Our hypothesis is further supported by the genetic assay: PTIP interacts genetically with either PcG or TrxG in a dosage-dependent manner, suggesting that PTIP functions as a co-factor of PcG/TrxG proteins. In addition, in accordance with the analysis of ChIP-seq, these genetic interactions correlate with modified ectopic HOX protein levels in imaginal discs, which reveals an essential role for PTIP in PcG-mediated Hox gene repression. Hence, we reveal a novel role for PTIP in the epigenetic regulation of gene expression along PcG and trxG pathways.
Project description:The motor neuron (MN)–hexamer complex consisting of LIM homeobox 3, Islet-1, and nuclear LIM interactor is a key determinant of motor neuron specification and differentiation. To gain insights into the transcriptional network in motor neuron development, we performed a genome-wide ChIP-sequencing analysis and found that the MN–hexamer directly regulates a wide array of motor neuron genes by binding to the HxRE (hexamer response element) shared among the target genes. Interestingly, STAT3-binding motif is highly enriched in the MN–hexamer–bound peaks in addition to the HxRE. We also found that a transcriptionally active form of STAT3 is expressed in embryonic motor neurons and that STAT3 associates with the MN–hexamer, enhancing the transcriptional activity of the MN–hexamer in an upstream signal-dependent manner. Correspondingly, STAT3 was needed for motor neuron differentiation in the developing spinal cord. Together, our studies uncover crucial gene regulatory mechanisms that couple MN–hexamer and STAT-activating extracellular signals to promote motor neuron differentiation in vertebrate spinal cord. To explain our experimental scheme briefly, we are interested in finding target sites for the dimer of transcription factors Isl1 and Lhx3. To mimic the biological activity of Isl1/Lhx3 dimer, we made Isl1-Lhx3 fusion and found that Isl1-Lhx3 has a potent biological activity in multiple systems (i.e. generation of ectopic motor neurons). Then we made ES cell line that induces Flag-tagged Isl1-Lhx3 expression upon Dox treatment. These *mouse* ES cells differentiate to motor neurons (iMN-ESCs) when treated with Dox following EB formation. To identify genomic binding sites of Isl1-Lhx3 (Flag-tagged), we performed ChIP with Flag antibody (pull down of Flag-Isl1-Lhx3) in ES cells treated with Dox. ChIP with Flag antibody in ES cells treated with vehicle (no Dox) was done as a negative control in parallel, and sequenced along with +Dox sample. We have done these experiments twice (two sets).