Distinct phases of Wnt/β-catenin signaling direct cardiomyocyte formation in zebrafish

Abstract

Normal heart formation requires reiterative phases of canonical Wnt/β-catenin (Wnt) signaling. Understanding the mechanisms by which Wnt signaling directs cardiomyocyte (CM) formation in vivo is critical to being able to precisely direct differentiated CMs from stem cells in vitro. Here, we investigate the roles of Wnt signaling in zebrafish CM formation using heat-shock inducible transgenes that increase and decrease Wnt signaling. We find that there are three phases during which CM formation is sensitive to modulation of Wnt signaling through the first 24 hours of development. In addition to the previously recognized roles for Wnt signaling during mesoderm specification and in the pre-cardiac mesoderm, we find a previously unrecognized role during CM differentiation where Wnt signaling is necessary and sufficient to promote the differentiation of additional atrial cells. We also extend the previous studies of the roles of Wnt signaling during mesoderm specification and in pre-cardiac mesoderm. Importantly, in pre-cardiac mesoderm we define a new mechanism where Wnt signaling is sufficient to prevent CM differentiation, in contrast to a proposed role in inhibiting cardiac progenitor (CP) specification. The inability of the CPs to differentiate appears to lead to cell death through a p53/Caspase-3 independent mechanism. Together with a report for an even later role for Wnt signaling in restricting proliferation of differentiated ventricular CMs, our results indicate that during the first 3 days of development in zebrafish there are four distinct phases during which CMs are sensitive to Wnt signaling.

Quantitative proteomics identify DAB2 as a cardiac developmental regulator that inhibits WNT/β-catenin signaling

“…Thus, the role of DAB2 in the whole organism is broad. Given that the heart is the first vertebrate organ to form and function, and requires tight regulation of WNT/β-catenin signaling (6,25), knowledge of which proteins promote or repress WNT/β-catenin signaling is crucial for identifying regulators of cardiac development. Our work demonstrates that DAB2 is dynamically expressed in human stem cells, and supports cardiomyocyte development in vivo in part by suppressing WNT/β-catenin signaling.…”

High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance of Intact Zebrafish Embryos Detects Metabolic Changes Following Exposure to Teratogenic Polymethoxyalkenes from Algae

“…27 Consistent with a possible role of the Wnt pathway is not only PMA teratogenicity in general but also specific inhibition of organogenesis observed in prior studies; more specifically, exposure to PMAs was found to inhibit the formation of both the eye and heart in developing embryos, 14 and both cardiac and ocular development in the zebrafish are, indeed, linked to Wnt. 28,29 It is tempting, therefore, to hypothesize a role for inositol through Wnt pathways in the observed teratogenicity of PMAs.…”

Uncovering the Molecular and Cellular Mechanisms of Heart Development Using the Zebrafish

“…Other studies have revealed interesting temporal roles for these signaling pathways. For example, activation of Wnt signaling at pregastrulation stages increases progenitor numbers, whereas activation an hour after the onset of gastrulation significantly decreases their numbers, possibly through induction of programmed cell death in cardiac progenitors (26,124). Though the heat-shock inducible transgenic animals used in these studies allowed for temporal analysis of Wnt signaling in cardiac specification, genetic loss-of-function studies are needed to dissect the role of this pathway in this process.…”