Biology subjects

Smeeton, J.

Publications and source records attributed to Smeeton, J..

6 recordsLinked to original sources

bioRxiv2026

Scarless regeneration requires post-translational proteolytic regulation via macrophage-derived Legumain

Macrophages express proteolytic factors in response to injury but how proteases are deployed and regulated during regeneration are incompletely defined. Beyond their transcriptomic expression, activity of individual proteases is defined both by their unique substrate specificity and post-translational modifications of their active forms. Here we show a key role for the lysosomal protease Legumain in controlling ECM dynamics and post-translational processing of the regenerative proteome. Injury interface-targeted Ctsla localization and post-translational processing requires Lgmn in macrophages. Extracellular cues from physical remodeling control differentiation state and injury response of ligament resident fibroblasts. Loss of ECM turnover, including localized Fibronectin 1a/b remodeling, impairs dedifferentiation in legumain mutants and leads to fibrotic scarring. Taken together, we demonstrate a role for macrophage-derived lysosomal proteases as specialized tools required to fine-tune proteome composition and function in regeneration.

cell biology↗

bioRxiv2024

Dynamic cell fate plasticity and tissue integration drive functional synovial joint regeneration

Adult mammalian synovial joints have limited regenerative capacity, where injuries heal with mechanically inferior fibrotic tissues. Here we developed a unilateral whole-joint resection model in adult zebrafish to advance our understanding of how to stimulate regrowth of native synovial joint tissues. Using a combination of microCT, histological, live imaging, and single-cell RNA sequencing (scRNAseq) approaches after complete removal of all joint tissues, we find de novo regeneration of articular cartilage, ligament, and synovium into a functional joint. Clonal lineage tracing and scRNAseq implicate a multipotent, neural crest-derived population in the adult skeleton as a cell source for these regenerating tissues. Together, our findings reveal latent molecular and cellular programs within the adult skeleton that are deployed to regenerate a complex joint with lubricated articular cartilage.

developmental biology↗

bioRxiv2024

Polyamines regulate cell fate by altering the activity of histone-modifying enzymes

Polyamines are polycationic alkyl-amines abundant in proliferating stem and cancer cells. How these metabolites influence numerous cellular processes remains unclear. Here we show that polyamine levels decrease during differentiation and that inhibiting polyamine synthesis leads to a differentiated-like cell state. Polyamines are enriched in the nucleus, where their loss drives changes in chromatin accessibility and histone post-translational modifications. Polyamines interact electrostatically with DNA on the nucleosome core, freeing histone tails to conformations accessible to chromatin-modifying enzymes. Consistent with their role in increasing histone-tail accessibility, polyamines are able to replace MYCs role in reprogramming to pluripotency. These data reveal a mechanism by which an abundant metabolite influences chromatin structure and function in a direct but sequence independent manner, facilitating chromatin remodeling during reprogramming and limiting it during fate commitment.

cell biology↗

bioRxiv2023

Ligament injury in adult zebrafish triggers ECM remodeling and cell dedifferentiation for scar-free regeneration

After traumatic injury, healing of mammalian ligaments is typically associated with fibrotic scarring as opposed to scar-free regeneration. In contrast, here we show that the ligament supporting the jaw joint of adult zebrafish is capable of rapid and complete scar-free healing. Following surgical transection of the jaw joint ligament, we observe breakdown of ligament tissue adjacent to the cut sites, expansion of mesenchymal tissue within the wound site, and then remodeling of extracellular matrix (ECM) to a normal ligament morphology. Lineage tracing of mature ligamentocytes following transection shows that they dedifferentiate, undergo cell cycle re-entry, and contribute to the regenerated ligament. Single-cell RNA sequencing of the regenerating ligament reveals dynamic expression of ECM genes in neural-crest-derived mesenchymal cells, as well as diverse immune cells expressing the endopeptidase-encoding gene legumain. Analysis of legumain mutant zebrafish shows a requirement for early ECM remodeling and efficient ligament regeneration. Our study establishes a new model of adult scar-free ligament regeneration and highlights roles of immune-mesenchyme cross-talk in ECM remodeling that initiates regeneration. HighlightsO_LIRapid regeneration of the jaw joint ligament in adult zebrafish C_LIO_LIDedifferentiation of mature ligamentocytes contributes to regeneration C_LIO_LIscRNAseq reveals dynamic ECM remodeling and immune activation during regeneration C_LIO_LIRequirement of Legumain for ECM remodeling and ligament healing C_LI

molecular biology↗

bioRxiv2021

Lifelong single-cell profiling of cranial neural crest diversification

The cranial neural crest generates a huge diversity of derivatives, including the bulk of connective and skeletal tissues of the vertebrate head. How neural crest cells acquire such extraordinary lineage potential remains unresolved. By integrating single-cell transcriptome and chromatin accessibility profiles of cranial neural crest-derived cells across the zebrafish lifetime, we observe region-specific establishment of enhancer accessibility for distinct fates. Neural crest-derived cells rapidly diversify into specialized progenitors, including multipotent skeletal progenitors, stromal cells with a regenerative signature, fibroblasts with a unique metabolic signature linked to skeletal integrity, and gill-specific progenitors generating cell types for respiration. By retrogradely mapping the emergence of lineage-specific chromatin accessibility, we identify a wealth of candidate lineage-priming factors, including a Gata3 regulatory circuit for respiratory cell fates. Rather than multilineage potential being an intrinsic property of cranial neural crest, our findings support progressive and region-specific chromatin remodeling underlying acquisition of diverse neural crest lineage potential. HighlightsO_LISingle-cell transcriptome and chromatin atlas of cranial neural crest C_LIO_LIProgressive emergence of region-specific cell fate competency C_LIO_LIChromatin accessibility mapping identifies candidate lineage regulators C_LIO_LIGata3 function linked to gill-specific respiratory program C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=173 SRC="FIGDIR/small/456710v1_ufig1.gif" ALT="Figure 1"> View larger version (69K): org.highwire.dtl.DTLVardef@1c4ca91org.highwire.dtl.DTLVardef@cf0d10org.highwire.dtl.DTLVardef@162bfe9org.highwire.dtl.DTLVardef@2565fd_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2019

nkx3.2 mutant zebrafish accommodate the jaw joint loss through a phenocopy of the head shapes of Paleozoic agnathans

The vertebrate jaw is a versatile feeding apparatus that facilitated explosive diversification. To function, it requires a joint between the upper and lower jaws, so jaw joint defects - such as osteoarthritis or even ankylosis - are often highly disruptive and difficult to study. To describe consequences of jaw-joint dysfunction, we engineered two independent null alleles of a single jaw-joint marker gene, nkx3.2, in zebrafish. These mutations caused zebrafish to become functionally jawless via fusion of the upper and lower jaw cartilages (ankylosis). Despite lacking jaw joints, nkx3.2 mutants survive to adulthood and accommodate this defect by: a) remodeling their skulls; and b) altering their behavior from suction feeding to ram feeding. As a result of remodeling, nkx3.2 mutants developed superficial similarities to the skull shapes observed in two lineages of ancient jawless vertebrates (anaspids and furcacaudiid thelodonts), including: a fixed open gape, reduced snout, and enlarged branchial region. However, no homology exists in individual skull elements between these taxa, and most of the modified elements in the mutant zebrafish occur outside known expression domains of nkx3.2. Therefore, we interpret the adult nkx3.2 phenotype not as a reversal to an ancestral state, but as convergence due to similar functional requirement of feeding without moveable jaws. This remarkable convergence strongly suggests that jaw movements themselves dramatically influence the development of jawed vertebrate skulls, which implies that functionally viable skull morphologies are finite, with or without functional jaws. Because nkx3.2 null zebrafish display prominent joint ankylosis, drastically modified skull shape, and altered feeding behaviors, these mutants provide a unique model with which to investigate mechanisms of skeletal remodeling and joint diseases.

evolutionary biology↗