Project description:mRNAs associated with microtubules during interphase, metaphase and the midbody stage of cytokinesis were sequenced. Selective midbody-localized RNAs were identified and their translational characteristics were studied.
Project description:The compartmentalisation of distinct organelles within eukaryotic cells is essential for their diverse functions, however, how their structures and functions depend on each other has not been systematically explored. We combined a fluorescent reporter of mitochondrial stress with genome-wide CRISPR knockout screening and identified networks of genes involved in the biogenesis and metabolism of diverse organelles. Targeted organelle gene knockouts identified that defects in peroxisomes, Golgi, and ER cause mitochondrial fragmentation and dysfunction. Correlative light and electron microscopy analysed using artificial intelligence-directed voxel extraction revealed in unprecedented detail how impaired mitochondrial interactions with diverse organelles caused cell-wide defects in their morphology and biogenesis. Multi-omics analyses identified a unified proteome stress response and global shifts in lipid and glycoprotein homeostasis that are elicited when organelle biogenesis is compromised. Our comprehensive resource has defined metabolic and morphological interactions between organelles that can be mined to understand how changes in organelle components drive diverse cellular pathologies.
Project description:Eukaryotic cells contain several membrane-separated organelles to compartmentalize distinct metabolic reactions. However, it has remained unclear how these organelle systems are coordinated, when cells adapt metabolic pathways to support their development, survival or effector functions. Here we present OrgaPlexing, a multispectral organelle imaging approach for the comprehensive mapping of six key metabolic organelles and their interactions. We use this analysis on macrophages, immune cells that undergo rapid metabolic switches upon sensing bacterial and inflammatory stimuli. Our results identify lipid droplets (LDs) as primary inflammatory responder organelle, which forms three- and four-way interactions with other organelles. While clusters with endoplasmic reticulum (ER) and mitochondria (M-ER-LD unit) help supply fatty acids for LD growth, the additional recruitment of peroxisomes (M-ER-P-LD unit) supports fatty acid efflux from LDs. Interference with individual components of these units has direct functional consequences for inflammatory lipid synthesis. Together, we show that macrophages form functional multi-organellar units (MOUs) to support metabolic adaptation, and provide an experimental strategy to identify organelle-metabolic signaling hubs.
Project description:We report that the PRC1 component polycomb group ring finger 6 (Pcgf6) is required to maintain embryonic stem cell (ESC) identity. In contrast to canonical PRC1, Pcgf6 acts as a positive regulator of transcription and binds predominantly to promoters bearing active chromatin marks. Pcgf6 is expressed at high levels in ESCs, and knockdown reduces the expression of the core ESC regulators Oct4,Sox2, and Nanog. Conversely, Pcgf6 overexpression prevents downregulation of these factors and impairs differentiation. In addition, Pcgf6 enhanced reprogramming in both mouse and human somatic cells. The genomic binding profile of Pcgf6 is highly similar to that of trithorax group proteins, but not of PRC1 or PRC2 complexes, suggesting that Pcgf6 functions atypically in ESCs. Our data reveal novel roles for Pcgf6 in directly regulating Oct4, Nanog, Sox2, and Lin28 expression to maintain ESC identity. To identify Pcgf6-bound genomic DNA regions in mouse embryonic stem cells, we fixed mouse ESCs and isolated Pcgf6-bound genomic DNA regions for deep sequencing analysis.
Project description:Loss of organelle homeostasis is a hallmark of aging. However, it remains elusive how this occurs at transcriptional levels. Here, we report that human mesenchymal stem cell (hMSC) aging is associated with dysfunction of double-membrane organelles and downregulation of transcription factor ATF6. CRISPR/Cas9-mediated inactivation of ATF6 in hMSCs, not in human embryonic stem cells (hESCs), resulted in premature cellular aging, characteristic of loss of endomembrane homeostasis. Comparative transcriptomic analyses in hMSCs identify 145 constitutive and 112 tunicamycin-induced ATF6-regulated genes implicated in different layers of cellular homeostasis regulation. Notably, FOS was identified as one of the constitutive ATF6 responsive genes, downregulation of which contributes to accelerated hMSC senescence. Our study identifies a novel transcriptional program related to homeostatic regulation of membrane organelles, and provides mechanistic insights into aging-associated attrition of human stem cells.