Project description:FOXO transcription factors are central regulators of longevity from worms to humans. FOXO3 – the FOXO isoform associated with exceptional human longevity – preserves adult neural stem cell pools. Here we identify FOXO3 direct targets genome-wide in primary cultures of adult neural progenitor cells (NPCs). Interestingly, FOXO3-bound sites are enriched for motifs for bHLH transcription factors and FOXO3 shares common targets with the pro-neuronal bHLH transcription factor ASCL1/MASH1 in NPCs. Analysis of the chromatin landscape reveals that FOXO3 and ASCL1 are particularly enriched at the enhancers of genes involved in neurogenic pathways. Intriguingly, FOXO3 inhibits ASCL1-dependent neurogenesis in NPCs and direct neuronal conversion in fibroblasts. FOXO3 also restrains neurogenesis in vivo. Our study identifies a genome-wide interaction between the pro-longevity transcription factor FOXO3 and the cell fate determinant ASCL1, and raises the possibility that FOXO3’s ability to restrain ASCL1-dependent neurogenesis may help preserve the neural stem cell pool. ChIP-seq profiles of two transcription factors (FOXO3 and ASCL1) and three histone marks (H3K4me1, H3K4me3 and H3K27me3) in adult mouse neural progenitor cells.
Project description:FOXO transcription factors are central regulators of longevity from worms to humans. FOXO3 – the FOXO isoform associated with exceptional human longevity – preserves adult neural stem cell pools. Here we identify FOXO3 direct targets genome-wide in primary cultures of adult neural progenitor cells (NPCs). Interestingly, FOXO3-bound sites are enriched for motifs for bHLH transcription factors and FOXO3 shares common targets with the pro-neuronal bHLH transcription factor ASCL1/MASH1 in NPCs. Analysis of the chromatin landscape reveals that FOXO3 and ASCL1 are particularly enriched at the enhancers of genes involved in neurogenic pathways. Intriguingly, FOXO3 inhibits ASCL1-dependent neurogenesis in NPCs and direct neuronal conversion in fibroblasts. FOXO3 also restrains neurogenesis in vivo. Our study identifies a genome-wide interaction between the pro-longevity transcription factor FOXO3 and the cell fate determinant ASCL1, and raises the possibility that FOXO3’s ability to restrain ASCL1-dependent neurogenesis may help preserve the neural stem cell pool.
Project description:ASCL1, a basic helix-loop-helix family transcription factor, is a master regulator of developmental neurogenesis and a crucial component of transcription factor cocktails that can convert heterologous cell types such as fibroblasts into neurons. The ability of ASCL1 to drive neuronal differentiation is controlled by multi-site phosphorylation but how this modification controls the genome-wide transcriptional activity of ASCL1 is unknown. Using human neuroblastoma cells that maintain a rapidly dividing neuroblastic phenotype yet retain the ability to undergo differentiation as a model system, we find that phosphorylation of ASCL1 has limited effect on target gene promoter association, but predominantly regulates its binding to a subset of distal enhancer regions, resulting in extensive differences in target control by activation, as well as direct and indirect gene repression. These genome-wide analyses reveal how post-translational modification of ASCL1 can change its structure and function, driving it to differential regulatory elements to change cell fate, and controlling ASCL1’s activity as a master transcription regulator of neurogenesis. Using functional mutational and pharmacological approaches, we find that preventing CDK-dependent phosphorylation of ASCL1 in neuroblastoma cells results in co-ordinated suppression of the MYC-driven core circuit supporting neuroblast identity and proliferation, while simultaneously activating a gene programme driving neuronal differentiation. Thus, we show targeting the post-translational modification of a key developmental regulator can re-engage a latent genome-wide programme forcing mitotic exit and differentiation in cancer cells.
Project description:The roles of neurogenic pioneer transcription factors and chromatin remodelers have been characterized in that process in developing animal models and cancers. However how these factors interact with each other to regulate cell state transitions in human neurogenesis remains unclear. Here we investigated the activity of the pioneer proneural factor ASCL1 in an in vitro model of human neurogenesis. We found that ASCL1 expression characterizes a transitional state from cycling neural progenitor to post-mitotic neuron, and ASCL1 knockout impedes progenitor neuronal differentiation. ASCL1 binds to genomic targets to regulate loci promoting differentiation by different mechanisms. Acting as a classical pioneer transcription factor, its binding to compacted chromatin is required to induce transcriptional activity. At other loci, it acts as a non-pioneer chromatin remodeler, accessing permissive chromatin to further increase chromatin accessibility. We show that ASCL1 interacts with ATPase-active BAF mSWI/SNF chromatin remodelers at cis-regulatory elements, altering the chromatin regulatory landscape at a subset of target genes. This cooperative function is predominant at sites of non-pioneer chromatin remodeler function where ASCL1 requires mSWI/SNF for DNA binding while ASCL1 classical pioneer activity does not involve significant mSWI/SNF binding. Our work establishes novel roles for ASCL1 and for an interaction with mSWI/SNF in regulating epigenetic states in human neurogenesis.
Project description:The proper balance of excitatory and inhibitory neurons is crucial to normal processing of somatosensory information in the dorsal spinal cord. Two neural basic helix-loop-helix transcription factors, Ascl1 and Ptf1a, are essential for generating the correct number and sub-type of neurons in multiple regions of the nervous system. M-BM- In the dorsal spinal cord, Ascl1 and Ptf1a have contrasting functions in specifying inhibitory versus excitatory neurons. To understand how Ascl1 and Ptf1a function in these processes, we identified their direct transcriptional targets genome-wide in the embryonic mouse neural tube using ChIP-Seq and RNA-Seq. We show that Ascl1 and Ptf1a regulate the specification of excitatory and inhibitory neurons in the dorsal spinal cord through direct regulation of distinct homeodomain transcription factors known for their function in neuronal sub-type specification. Besides their roles in regulating these homeodomain factors, Ascl1 and Ptf1a each function differently during neuronal development with Ascl1 directly regulating genes with roles in several steps of the neurogenic program including, Notch signaling, neuronal differentiation, axon guidance, and synapse formation. In contrast, Ptf1a directly regulates genes encoding components of the neurotransmitter machinery in inhibitory neurons, and other later aspects of neural development distinct from those regulated by Ascl1. Moreover, Ptf1a represses the excitatory neuronal fate by directly repressing several targets of Ascl1. Examination of the Ascl1 and Ptf1a bound sequences shows they are enriched for a common E-Box with a GC core and with additional motifs used by Sox, Rfx, Pou, and Homeodomain factors. Ptf1a bound sequences are uniquely enriched in an E-Box with a GA/TC core and in the binding motif for its co-factor Rbpj, providing two keys to specificity of Ptf1a binding. The direct transcriptional targets identified for Ascl1 and Ptf1a provide a molecular understanding for how they function in neuronal development, particularly as key regulators of homeodomain transcription factors required for neuronal sub-type specification. Examination of Ascl1 and Ptf1a genome-wide binding in developing neural tube.
Project description:These findings suggest that physical interactions between Gsx2 and Ascl1 limit Ascl1:Ascl1 and Ascl1:Tcf3 interactions, and thereby inhibit Ascl1-dependennt neurogenesis and allow for progenitor expansion within the LGE.
Project description:Neuroblastoma is an embryonic malignancy originating from early nerve cells. Neuroblastoma retains plasticity, interconverting between the mesenchymal (MES) and adrenergic (ADRN) states, which are controlled by different sets of transcription factors forming the core regulatory circuit (CRC). However, their functional roles and cooperative mechanisms in neuroblastoma pathogenesis are poorly understood. Here, we demonstrate that overexpression of ASCL1 in MES neuroblastoma cells opens closed chromatin at the promoters of key ADRN genes, accompanied by epigenetic activation and establishment of enhancer-promoter interactions, thereby initiating subtype switching. ASCL1 inhibits the TGFb-SMAD2/3 pathway but activates the BMP-SMAD1-ID3/4 pathway, serving as negative feedback to balance the function of ASCL1-TCF12 dimers. ASCL1 and other ADRN CRC members potentiate each other’s activity, increasing the expression of the original targets and inducing a new set of genes, thereby promoting conversion to ADRN neuroblastoma. Thus, via its pioneer factor function, ASCL1 serves as a master regulator that characterizes ADRN neuroblastoma.
Project description:The proper balance of excitatory and inhibitory neurons is crucial to normal processing of somatosensory information in the dorsal spinal cord. Two neural basic helix-loop-helix transcription factors, Ascl1 and Ptf1a, are essential for generating the correct number and sub-type of neurons in multiple regions of the nervous system. M-BM- In the dorsal spinal cord, Ascl1 and Ptf1a have contrasting functions in specifying inhibitory versus excitatory neurons. To understand how Ascl1 and Ptf1a function in these processes, we identified their direct transcriptional targets genome-wide in the embryonic mouse neural tube using ChIP-Seq and RNA-Seq. We show that Ascl1 and Ptf1a regulate the specification of excitatory and inhibitory neurons in the dorsal spinal cord through direct regulation of distinct homeodomain transcription factors known for their function in neuronal sub-type specification. Besides their roles in regulating these homeodomain factors, Ascl1 and Ptf1a each function differently during neuronal development with Ascl1 directly regulating genes with roles in several steps of the neurogenic program including, Notch signaling, neuronal differentiation, axon guidance, and synapse formation. In contrast, Ptf1a directly regulates genes encoding components of the neurotransmitter machinery in inhibitory neurons, and other later aspects of neural development distinct from those regulated by Ascl1. Moreover, Ptf1a represses the excitatory neuronal fate by directly repressing several targets of Ascl1. Examination of the Ascl1 and Ptf1a bound sequences shows they are enriched for a common E-Box with a GC core and with additional motifs used by Sox, Rfx, Pou, and Homeodomain factors. Ptf1a bound sequences are uniquely enriched in an E-Box with a GA/TC core and in the binding motif for its co-factor Rbpj, providing two keys to specificity of Ptf1a binding. The direct transcriptional targets identified for Ascl1 and Ptf1a provide a molecular understanding for how they function in neuronal development, particularly as key regulators of homeodomain transcription factors required for neuronal sub-type specification. Examination of gene expression in Ascl1 and Ptf1a lineage cells in the developing neural tube.
Project description:Forkhead box O transcription factors are important downstream targets of AKT signalling. In the human Multiple Myeloma celline MM1.S, AKT inhibtion leads to cell death in a FOXO3 dependent fashion. We used microarrays to asses which genes are up- or downregulated by FOXO3 after AKT inhibition by MK2206.
Project description:Forkhead box O transcription factors are important downstream targets of AKT signalling. In the human Multiple Myeloma celline XG-3, AKT inhibtion leads to cell death in a FOXO3 dependent fashion. We used microarrays to asses which genes are up- or downregulated by FOXO3 after AKT inhibition by MK2206.