Tension Creates an Endoreplication Wavefront that Leads Regeneration of Epicardial Tissue

Abstract

SUMMARY Mechanisms that control cell cycle dynamics during tissue regeneration require elucidation. Here we find in zebrafish that regeneration of the epicardium, the mesothelial covering of the heart, is mediated by two phenotypically distinct epicardial cell subpopulations. These include a front of large, multinucleate leader cells, trailed by follower cells that divide to produce small, mononucleate daughters. By live imaging of cell cycle dynamics, we show that leader cells form by spatiotemporally regulated endoreplication, caused primarily by cytokinesis failure. Leader cells display greater velocities and mechanical tension within the epicardial tissue sheet, and experimentally induced tension anisotropy stimulates ectopic endoreplication. Unbalancing epicardial cell cycle dynamics with chemical modulators indicated autonomous regenerative capacity in both leader and follower cells, with leaders displaying an enhanced capacity for surface coverage. Our findings provide evidence that mechanical tension can regulate cell cycle dynamics in regenerating tissue, stratifying the source cell features to improve repair.

Keratin 14-dependent disulfides regulate epidermal homeostasis and barrier function via 14-3-3σ and YAP1

“…Third, the nucleus is known to function as a mechanosensor (Cao et al 2017 University School of Medicine for the production of krt14 C373A mice. This work was supported by grant AR042047 to P.A.C.…”

“…YAP is a key effector of mechanosensing and mechanotransduction (Dupont et al 2011;Benham-Pyle et al 2015;Panciera et al 2017), while K14 has been shown to provide vital mechanical support in basal keratinocytes of the epidermis Vassar et al 1991;Fuchs and Coulombe 1992). Cells experiencing tension typically respond by forming more Factin stress fibers heightened acto-myosin contraction, enhanced recruitment of α-catenin and vinculin to AJs (Leckband and de Rooij 2014;Yap et al 2018), enhanced expression of lamin A/C (Swift et al 2013), and increased frequency of binucleated cells (Cao et al 2017). We next assessed the status of these mechanosensitive markers in skin tissue and in keratinocytes in primary culture.…”

In Toto Imaging of Dynamic Osteoblast Behaviors in Regenerating Skeletal Bone

“…The H2A-mCherry-SV40 polyA sequence was obtained from a plasmid constructed by Dr. Jingli Cao, amplified by PCR using the primers 5’-TTTTTGGATCCGCCGCCACCATGGCAGGTGGAAAAGCAGG-3’ and 5’-TTTTTCTCGAGTTACTTGTACAGCTCGTCCATGC-3’, digested using XhoI, then partially digested using BamHI due to the presence of a BamHI site in the ORF [40]. The fragment was then ligated into a pBluescript SK plasmid that had been modified to contain ISceI sites in the MCS and into which osx:mCherry had already been subcloned.…”

A Regeneration Toolkit

“…How these ancillary cell types themselves regenerate or fail to regenerate upon depletion is also, in and of itself, fascinating biology. For instance, the depleted epicardium quickly regenerates back over the naked cardiac surface from spared cells, in a wave that requires both cell division and generation of a leading front of polyploid cells (Cao et al, 2017) (Figure 2D, E). A broadened panel of cell type-specific, inducible ablation strains would be a powerful addition to the vertebrate regeneration toolkit.…”

“…Images in (D) are adapted from Wang et al, 2015. Image in (E) is adapted from Cao et al, 2017. Image in (F) is adapted from He et al, 2017.…”