ORCID Profile
0000-0002-6754-9730
Current Organisations
University of Zurich
,
Universität Zürich
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Publisher: eLife Sciences Publications, Ltd
Date: 28-01-2022
DOI: 10.7554/ELIFE.68000
Abstract: Advancing age causes reduced hippoc al neurogenesis, associated with age-related cognitive decline. The spatial relationship of age-induced alterations in neural stem cells (NSCs) and surrounding cells within the hippoc al niche remains poorly understood due to limitations of antibody-based cellular phenotyping. We established iterative indirect immunofluorescence imaging (4i) in tissue sections, allowing for simultaneous detection of 18 proteins to characterize NSCs and surrounding cells in 2-, 6-, and 12-month-old mice. We show that reorganization of the dentate gyrus (DG) niche already occurs in middle-aged mice, paralleling the decline in neurogenesis. 4i-based tissue analysis of the DG identifies changes in cell-type contributions to the blood-brain barrier and microenvironments surrounding NSCs to play a pivotal role to preserve neurogenic permissiveness. The data provided represent a resource to characterize the principles causing alterations of stem cell-associated plasticity within the aging DG and provide a blueprint to analyze somatic stem cell niches across lifespan in complex tissues.
Publisher: Cold Spring Harbor Laboratory
Date: 17-05-2021
DOI: 10.1101/2021.05.17.444432
Abstract: Unlike its DNA template, RNA abundance and synthesis rates increase with cell size, as part of a mechanism of cellular RNA concentration homeostasis. Here, we study this scaling phenomenon in human cells by combining genome-wide perturbations with quantitative single-cell measurements. Despite relative ease in perturbing RNA synthesis, we find that RNA concentrations remain highly constant. Systems-level analysis indicates that perturbations that would lead to increased nuclear mRNA abundance result in downregulation of mRNA synthesis. This is associated with reduced levels of several transcription-associated proteins and protein states that are normally coordinated with RNA production in single cells, including RNA polymerase II (Pol II) itself. Acute shut-down of nuclear RNA degradation, elevation of nuclear mRNA levels, and mathematical modelling indicate that mammalian cells achieve RNA concentration homeostasis by an mRNA-based negative feedback on transcriptional activity in the nucleus. Ultimately, this acts to robustly scale Pol II abundance with cell volume and coordinate mRNA synthesis and degradation.
Publisher: Cold Spring Harbor Laboratory
Date: 25-05-2022
DOI: 10.1101/2022.05.25.493370
Abstract: Arrayed CRISPR libraries extend the scope of gene-perturbation screens but require large numbers of efficacious sgRNA-expressing vectors. Using a newly invented liquid-phase plasmid cloning methodology, we constructed genome-wide arrayed libraries for human gene ablation (19,936 plasmids), activation, and epigenetic silencing (22,442 plasmids). At least 76% of each plasmid preparation encoded an intact array of 4 non-overlapping sgRNAs designed to tolerate most human DNA polymorphisms. We achieved perturbation efficacies of 75-99%, 76-92% and up to 10,000x in deletion, silencing and activation experiments, respectively. Upon conversion into massively parallel lentiviral vectors, an arrayed activation screen of 1,634 human transcription factors yielded 11 novel regulators of the cellular prion protein PrP C . Furthermore, a screen using a pooled version of the ablation library identified 5 novel modifiers of autophagy that went undetected with either of two 1sgRNA libraries. The CRISPR libraries described here represent a powerful resource for the targeted perturbation of human protein-coding genes.
Publisher: Cold Spring Harbor Laboratory
Date: 08-05-2022
DOI: 10.1101/2022.05.07.490900
Abstract: Highly multiplexed quantitative subcellular imaging holds enormous promise for understanding how spatial context shapes the activity of our genome and its products at multiple scales. Yet unbiased analysis of subcellular organisation across experimental conditions remains challenging, because differences in molecular profiles between conditions confound differences in molecular profiles across space. Here, we introduce a deep-learning framework called CAMPA (Conditional Autoencoder for Multiplexed Pixel Analysis), which uses a variational autoencoder conditioned on cellular states and perturbations to learn consistent molecular signatures. Clustering the learned representations into subcellular landmarks allows quantitative comparisons of landmark sizes, shapes, molecular compositions and relative spatial organisation between conditions. By performing high-resolution multiplexed immunofluorescence on human cells, we use CAMPA to reveal how subnuclear organisation changes upon different perturbations of RNA production or processing, and how different membraneless organelles scale with cell size. Furthermore, by integrating information across the cellular and subcellular scales, we uncover new links between the molecular composition of membraneless organelles and bulk RNA synthesis rates of single cells. We anticipate that CAMPA will greatly accelerate the systematic mapping of multiscale atlases of biological organisation to identify the rules by which context shapes physiology and disease.
No related grants have been discovered for Lucas Pelkmans.