Biology subjects

Guzman, S. D.

Publications and source records attributed to Guzman, S. D..

3 recordsLinked to original sources

bioRxiv2026

Nuclear Speckles Regulate Splicing During Muscle Stem Cell Activation and Aging

Skeletal muscle contains a population of adult stem cells called satellite cells or muscle stem cells (MuSCs) that are responsible for regeneration after injury. MuSCs utilize gene expression programs to maintain quiescence and differentiate after injury and a key regulator of gene expression is splicing, which uniquely changes when transcripts interact with nuclear speckles (NS). NS are membrane-less biomolecular condensates that phase separate proteins, RNAs and chromatin, but how these organelles regulate molecular processes in MuSCs remains unknown. Herein, we build a comprehensive and systems-level understanding of NS influence on alternative splicing, transcriptional regulation and stem cell function before and after injury and in aging. We establish that NS increased in size and number in MuSCs following injury and influence MuSC activation dynamics. We generated a catalog of isoform-resolved splicing events and linked how RNA interactions with NS amplify splicing completion during the injury response. In old age, MuSCs lose NS, yet shifted towards longer, more completely spliced isoforms enriched for RNA binding protein motifs and multivalency. Our studies unveil evidence that RNA interactions with NS shape stem cell state and regenerative responses but are attenuated in old age. HIGHLIGHTSO_LI3D super-resolution imaging of nuclear speckles in muscle stem cells before and after muscle injury shows intricate relationship with activation C_LIO_LIIsoform-resolved profiling of muscle stem cells shows increases in gene expression and splicing during injury response C_LIO_LIMapping RNA interactions with nuclear speckles shows RNAs undergo strongest splicing when proximal to nuclear speckles C_LIO_LIOld aged muscle stem cells lose nuclear speckles and display aberrant splicing, with longer transcripts, more exons, and increased RNA binding protein motifs C_LI

genomics↗

bioRxiv2026

Longitudinal Single-Cell RNA-seq Profiling of Lung Cell Phenotypes, Signaling, and Cross-talk During Fibrosis Resolution

Resolution of fibrosis following lung injury is distinguished from persistent/progressive parenchymal scarring through the timely clearance of aberrant cell types, removal of excess collagens, and regeneration of alveolar structure. The requisite signaling pathways, cellular cross-talk, and phenotypic shifts associated with, and required for, resolution of established lung fibrosis have not been well characterized. To address this critical knowledge gap, we performed longitudinal single-cell RNA sequencing of whole mouse lung digests obtained during spontaneously resolving fibrosis. We observed a putatively pro-fibrotic macrophage population emerge during peak fibrosis and undergo partial clearance during resolution. Our study also revealed conspicuous shifts in well-established pathways associated with tissue repair and fibrosis among immune, mesenchymal, and epithelial cells during spontaneous resolution. In addition to a decline in pro-fibrotic driver pathways, the putative anti-fibrotic pathways cAMP, HGF/MET, and TWEAK were enriched in several cell types during spontaneous resolution. CellChat analysis was used to predict the cellular senders and recipients of each pathway and characterize their longitudinal changes. Our characterization of the cellular and molecular dynamics in whole lungs during spontaneous fibrosis resolution provides a foundation for the identification of endogenous pathways that might be leveraged to treat pulmonary fibrosis.

cell biology↗

bioRxiv2023

Decoding muscle-resident Schwann cell dynamics during neuromuscular junction remodeling

This investigation leverages single-cell RNA sequencing (scRNA-Seq) to delineate the contributions of muscle-resident Schwann cells to neuromuscular junction (NMJ) remodeling by comparing a model of stable innervation with models of reinnervation following partial or complete denervation. The study discovered multiple distinct Schwann cell subtypes, including a novel terminal Schwann cell (tSC) subtype integral to the denervation-reinnervation cycle, identified by a transcriptomic signature indicative of cell migration and polarization. The data also characterizes three myelin Schwann cell subtypes, which are distinguished based on enrichment of genes associated with myelin production, mesenchymal differentiation or collagen synthesis. Importantly, SPP1 signaling emerges as a pivotal regulator of NMJ dynamics, promoting Schwann cell proliferation and muscle reinnervation across nerve injury models. These findings advance our understanding of NMJ maintenance and regeneration and underscore the therapeutic potential of targeting specific molecular pathways to treat neuromuscular and neurodegenerative disorders.

neuroscience↗