bioRxiv Science⌕ Search

Biology subjects

Bowness, J.

Publications and source records attributed to Bowness, J..

4 recordsLinked to original sources

Spatially resolved, multimodal in vivo Perturb-seq using antibody-based cell hashing

Large-scale perturbation screens have begun to map cell intrinsic gene-function relationships, yet how genes shape tissue architecture remains largely unexplored. To address this gap, we developed PerturbSpace, a novel approach that integrates CRISPR perturbations with spatially hashed single-cell multiomics. This approach enables the first high-throughput, spatially resolved Perturb-seq analysis across complex tissue architecture in vivo. Notably, PerturbSpace enables spatial transcriptome-wide perturbation readouts at organ scale and can be seamlessly integrated with orthogonal modalities. We combine PerturbSpace with surface proteomics and expressed lineage tracing barcodes to demonstrate multimodal compatibility. We use PerturbSpace to study the genetic determinants of tissue architecture. First, we map how 40 transcriptional regulators determine the size and lineage composition of colonies in the spleen during regenerative hematopoiesis. Second, we characterize immune-niche interactions in the liver by dissecting the extrinsic effects mediated by cytokine-secreting immune cells on their neighboring cells. Collectively, our work establishes PerturbSpace as a scalable and cost-effective approach for transcriptome-wide spatial profiling of whole cells while remaining compatible with the single-cell multiomics workflows that the field has already adopted at scale.

genomics↗

Lentiviral single-cell MPRA of synthetic enhancers reveals motif affinity-based encoding of cell type specificity

Cell-state-specific gene expression programs emerge from the interplay between cis-regulatory elements (CREs), such as enhancers, and transcription factors (TFs). Massively parallel reporter assays (MPRAs) have enabled large-scale dissection of CRE design principles, but bulk approaches cannot resolve cell state-specific regulatory logic on continuous trajectories of cellular differentiation, and existing single-cell MPRAs are not readily applicable to primary cell differentiation models. Here, we developed a single-cell lentiviral Massively Parallel Reporter Assay (sc-lentiMPRA) that overcomes these limitations and enables parallel quantification of enhancer activity and cellular transcriptome. Applying sc-lentiMPRA in blood stem differentiation, we profiled the activity and specificity of ~160 fully synthetic enhancers with controlled motif composition and affinities across ~190,000 single cells. Focusing on Trp53 and Cebpa, we show that enhancers with high and low affinity motifs differ qualitatively and quantitatively in their responses to TF expression gradients. For Trp53, low-affinity motifs exhibited near-linear correlation with TF expression, whereas high-affinity motifs showed reduced sensitivity to TF levels and a potential contribution of cofactor availability. In contrast, Cebpa-associated enhancers displayed nonlinear behaviors. Together, sc-lentiMPRA establishes a powerful framework for systematically relating enhancer architecture and TF expression to regulatory output at single-cell resolution during cellular differentiation.

genomics↗

YY1 binding is a gene-intrinsic barrier to Xist-mediated gene silencing

X chromosome inactivation (XCI) in mammals is mediated by Xist RNA which functions in cis to silence genes on a single X chromosome in XX female cells, thereby equalising levels of X-linked gene expression relative to XY males. XCI progresses over a period of several days, with some X-linked genes silencing faster than others. Chromosomal location of a gene is an important determinant of silencing rate, but uncharacterised gene-intrinsic features also mediate resistance or susceptibility to silencing. In this study, we integrate time-course data of gene silencing and decreasing inactive X (Xi) chromatin accessibility in mouse embryonic stem cell lines with an inducible Xist allele (iXist-ChrX mESCs). Our analysis reveals that motifs bound by the transcription factor YY1 are associated with persistently accessible regulatory elements, including many promoters and enhancers of slow-silencing genes. We further show that YY1 is evicted relatively slowly from target sites on Xi, and that silencing of X-linked genes is increased upon YY1 degradation. Together our results indicate that YY1 acts as barrier to Xist-mediated silencing that is removed only at late stages of the XCI process.

genomics↗

Time-resolved structured illumination microscopy reveals key principles of Xist RNA spreading

Xist RNA directs the process of X-chromosome inactivation in mammals by spreading in cis along the chromosome from which it is transcribed and recruiting chromatin modifiers to silence gene transcription. To elucidate mechanisms of Xist RNA cis-confinement, we established a sequential dual color labeling, super-resolution imaging approach to trace individual Xist RNA molecules over time, enabling us to define fundamental parameters of spreading. We demonstrate a feedback mechanism linking Xist RNA synthesis and degradation, and an unexpected physical coupling between preceding and newly synthesized Xist RNA molecules. Additionally, we show that the protein SPEN, a key factor for Xist-mediated gene-silencing, has a distinct function in Xist RNA localization, stability and in coupling behavior. Our results provide important insights towards understanding the unique dynamic properties of Xist RNA. One Sentence SummaryVisualizing Xist RNA dynamics in single cells during X chromosome inactivation

developmental biology↗