Project description:The most common genetic mutation found in familial and sporadic amyotrophic lateral sclerosis (ALS), as well as fronto-temporal dementia (FTD), is a repeat expansion in the C9orf72 gene. C9orf72 is highly expressed in human myeloid cells, and although neuroinflammation and microglial pathology are widely found in ALS/FTD, the underlying mechanisms are poorly understood. Here, using human induced pluripotent stem cell-derived microglia-like cells (hiPSC-MG) harbouring C9orf72 mutation (mC9-MG) together with gene-corrected isogenic controls (isoC9-MG) and C9ORF72 knock-out hiPSC-MG (C9KO-MG), we show that reduced C9ORF72 protein is associated with impaired phagocytosis and an exaggerated inflammatory response upon stimulation with lipopolysaccharide, driven by sustained activation of NLRP3 inflammasome and NF-kB signalling. Analysis of the hiPSC-MG C9ORF72 interactome revealed an association of C9ORF72 with key regulators of autophagy, a process involved in the homeostatic regulation of the innate immune response. We found impaired initiation of autophagy in C9KO-MG and mC9-MG. Furthermore, through motor neuron-microglial (MN-MG) co-culture studies, we identified that autophagy deficit in mC9-MG led to increased vulnerability of C9 MNs to excitotoxic stimulus. Pharmacological activation of autophagy ameliorated the sustained activation of NLRP3 inflammasome and NF-B signalling, reversed the phagocytic deficit found in mC9-MG and also reduced MN death in MN-MG co-cultures. We validated these findings in blood-derived macrophages from people with C9orf72 mutation. Our results reveal an important role for C9ORF72 in regulating microglial immune homeostasis and identify dysregulation in human myeloid cells as a contributor to neurodegeneration in ALS/FTD
Project description:Meningiomas are mostly benign brain tumors, with a potential for becoming atypical or malignant. Based on comprehensive genomic, transcriptomic and epigenomic analyses of meningiomas, we compared benign tumors to atypical ones. We show that the vast majority of primary (de novo) atypical meningiomas display loss of NF2, which co-occurs either with genomic instability or recurrent mutations in SMARCB1. These tumors harbor increased H3K27me3 repressive signal and a hypermethylated phenotype, mainly occupying the polycomb repressive complex 2 (PRC2) binding sites in human embryonic stem cells (hESCs), thereby phenocopying a more primitive cellular state. Consistent with this observation, and based on differential gene expression analysis as well as correlation of mRNA:miRNA regulatory networks, atypical meningiomas exhibit up-regulation of EZH2, the catalytic subunit of the PRC2 complex, well as the E2F2 and FOXM1 transcriptional networks that promote proliferation through activation of the cell cycle pathways. In addition, based on H3K27ac ChIP-seq analysis, we show atypical tumors to display an activated super-enhancer near the meningeal identity transcription factor ZIC1, leading to its transcriptional upregulation. The H3k27ac ChIP-seq data for 15 benign meningiomas and 2 dura samples listed below were created by Dr. Justin Cotney in Dr. James Noonan’s lab at Yale and previously published in a paper by our group with Drs. Cotney and Noonan as co-authors (Clark et al. Science, 2013). Sample IDs: MN-297, MN-288, MN-292, MN-163, MN-1037, MN-105, MN-201, MN-249, MN-191, MN-1066, MN-169, MN-291, MN-24, MN-79, MN-1044, CONTROL1, CONTROL2. In this study, we used these benign meningioma H3k27ac ChIP-seq data as controls and compared them to the newly created ChIP-seq data. Sample IDs: MN-54, MN-97 and MN-171. This GEO entry contains ChIP-seq results for both data sets.
Project description:Motor neurons (MNs) are the final output of circuits driving fundamental behaviors, such as respiration and locomotion. Hox proteins are essential in generating the MN diversity required for accomplishing these functions, but the transcriptional mechanisms that enable Hox paralogs to assign distinct MN subtype identities despite their promiscuous DNA binding motif are not well understood. Here we show that Hoxa5 can modify chromatin accessibility in all mouse spinal cervical MN subtypes and engages TALE co-factors to directly bind and regulate subtype-specific genes. We identify a paralog-specific interaction of Hoxa5 with the phrenic MN-specific transcription factor Scip and show that heterologous expression of Hoxa5 and Scip is sufficient to suppress limb-innervating MN identity. We also demonstrate that phrenic MN identity is stable after Hoxa5 downregulation and identify Klf proteins as potential regulators of phrenic MN maintenance. Our data identify multiple modes of Hoxa5 action that converge to induce and maintain MN identity.
Project description:Motor neurons (MNs) are the final output of circuits driving fundamental behaviors, such as respiration and locomotion. Hox proteins are essential in generating the MN diversity required for accomplishing these functions, but the transcriptional mechanisms that enable Hox paralogs to assign distinct MN subtype identities despite their promiscuous DNA binding motif are not well understood. Here we show that Hoxa5 can modify chromatin accessibility in all mouse spinal cervical MN subtypes and engages TALE co-factors to directly bind and regulate subtype-specific genes. We identify a paralog-specific interaction of Hoxa5 with the phrenic MN-specific transcription factor Scip and show that heterologous expression of Hoxa5 and Scip is sufficient to suppress limb-innervating MN identity. We also demonstrate that phrenic MN identity is stable after Hoxa5 downregulation and identify Klf proteins as potential regulators of phrenic MN maintenance. Our data identify multiple modes of Hoxa5 action that converge to induce and maintain MN identity.