Biology subjects

Koth, J.

Publications and source records attributed to Koth, J..

3 recordsLinked to original sources

bioRxiv2024

Injured endocardium obtains characteristics of haemogenic endothelium during adult zebrafish heart regeneration

Reactivation of embryonic developmental pathways during regeneration aims to restore tissue architecture and functionality. We previously reported that following cryoinjury, a heterogeneous population of Runx1-expressing endocardial cells differentially upregulates genes associate with scarring and myofibroblast identity. Further analysis of our published RNAseq data alongside 5 publicly available datasets now identifies additional heterogeneity in the Runx1-positive injured endocardium. Here, we show that the endocardium also reactivates a dormant endocardial-to-haematopoietic transition (EHT) mechanism. Runx1-expressing endocardial cells upregulate genes associated with haemogenesis and morphologically display features of EHT. Live imaging shows cells budding off the endocardium and lineage analysis identifies overlap with leukocyte markers. Ablation of runx1 function further shifts differentiation of the endocardium towards the EHT fate. The identification of transient runx1-expressing cells transitioning towards myofibroblast or haemogenic endocardium identities demonstrates the complexity of the zebrafish endocardial injury response and highlights the role of Runx1 in regulating cell fate decisions in the endocardium.

developmental biology↗

bioRxiv2022

Clonal behaviour of myogenic precursor cells throughout the vertebrate lifespan.

To address questions of stem cell diversity during skeletal myogenesis, a Brainbow-like genetic cell lineage tracing method, dubbed Musclebow, was derived by enhancer trapping in zebrafish. It is shown that at least 15 muscle precursor cells (mpcs) seed each somite, where they proliferate but contribute little to muscle growth prior to hatching. Thereafter, dermomyotome-derived mpc clones rapidly expand while some progeny undergo terminal differentiation, leading to stochastic clonal drift. No evidence of cell lineage-based clonal fate diversity was obtained. Neither fibre nor mpc death was observed in uninjured animals. Individual marked muscle fibres persist across much of the lifespan indicating low rates of nuclear turnover. In adulthood, early-marked mpc clones label stable blocks of tissue comprising a significant fraction of either epaxial or hypaxial somite. Fusion of cells from separate early-marked clones occurs in regions of clone overlap. Wounds are regenerated from many/most local mpcs; no evidence for specialised stem mpcs was obtained. In conclusion, our data indicate that most mpcs in muscle tissue contribute to local growth and repair and suggest that cellular turnover is low in the absence of trauma. Summary StatementMusclebow clonal cell lineage analysis is introduced to reveal the cellular dynamics of skeletal muscle formation, repair and maintenance throughout the life of zebrafish.

developmental biology↗

bioRxiv2019

Runx1 promotes scar deposition and inhibits myocardial proliferation and survival during zebrafish heart regeneration

Runx1 is a transcription factor that plays a key role in determining the proliferative and differential state of multiple cell-types, during both development and adulthood. Here, we report how runx1 is specifically upregulated at the injury site during zebrafish heart regeneration, but unexpectedly, absence of runx1 results in enhanced regeneration. Using single cell sequencing, we found that the wild-type injury site consists of Runx1-positive endocardial cells and thrombocytes that induce expression of smooth muscle and collagen genes without differentiating into myofibroblasts. Both these populations are absent in runx1 mutants, resulting in a less collagenous and fibrinous scar. The reduction in fibrin in the mutant is further explained by reduced myofibroblast formation and by upregulation of components of the fibrin degradation pathway, including plasminogen receptor Annexin 2A as well as downregulation of plasminogen activator inhibitor serpine1 in myocardium and endocardium, resulting in increased levels of Plasminogen. In addition, we find enhanced myocardial proliferation as well as increased myocardial survival in the mutant. Our findings suggest that Runx1 controls the regenerative response of multiple cardiac cell-types and that targeting Runx1 is a novel therapeutic strategy to induce endogenous heart repair.

developmental biology↗