A Wnt-and beta-catenin-dependent pathway for mammalian cardiac myogenesis. Proc Natl Acad Sci U S A

Department of Biochemistry & Molecular Biology, Baylor College of Medicine, Houston, Texas, United States
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 06/2003; 100(10):5834-9. DOI: 10.1073/pnas.0935626100
Source: PubMed


Acquisition of a cardiac fate by embryonic mesodermal cells is a fundamental step in heart formation. Heart development in frogs and avians requires positive signals from adjacent endoderm, including bone morphogenic proteins, and is antagonized by a second secreted signal, Wnt proteins, from neural tube. By contrast, mechanisms of mesodermal commitment to create heart muscle in mammals are largely unknown. In addition, Wnt-dependent signals can involve either a canonical beta-catenin pathway or other, alternative mediators. Here, we tested the involvement of Wnts and beta-catenin in mammalian cardiac myogenesis by using a pluripotent mouse cell line (P19CL6) that recapitulates early steps for cardiac specification. In this system, early and late cardiac genes are up-regulated by 1% DMSO, and spontaneous beating occurs. Notably, Wnt3A and Wnt8A were induced days before even the earliest cardiogenic transcription factors. DMSO induced biochemical mediators of Wnt signaling (decreased phosphorylation and increased levels of beta-catenin), which were suppressed by Frizzled-8Fc, a soluble Wnt antagonist. DMSO provoked T cell factor-dependent transcriptional activity; thus, induction of Wnt proteins by DMSO was functionally coupled. Frizzled-8Fc inhibited the induction of cardiogenic transcription factors, cardiogenic growth factors, and sarcomeric myosin heavy chains. Likewise, differentiation was blocked by constitutively active glycogen synthase kinase 3beta, an intracellular inhibitor of the Wntbeta-catenin pathway. Conversely, lithium chloride, which inhibits glycogen synthase kinase 3beta, and Wnt3A-conditioned medium up-regulated early cardiac markers and the proportion of differentiated cells. Thus, Wntbeta-catenin signaling is activated at the inception of mammalian cardiac myogenesis and is indispensable for cardiac differentiation, at least in this pluripotent model system.

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    • "In cultured ventral telencephalic slices, where Wnt/b-catenin signalling was activated by inhibition of Gsk3b activity (van Noort et al. 2002), Lef1 expression increased with an increased inhibition of this activity. The high levels of Lef1 expression in DMSO-treated slices have been previously observed in other culture systems suggesting that DMSO per se may activate Wnt/b-catenin signalling (Nakamura et al. 2003; Peng et al. 2002). However, these were significantly lower than the number of Lef1-expressing cells observed with even the lowest concentration of drug activator, confirming that the significant increase in Lef1-expressing cells in the ventral telencephalon was the result of a specific activation of the Wnt/b-catenin pathway. "
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    ABSTRACT: The mammalian eminentia thalami (EmT) (or thalamic eminence) is an embryonic forebrain structure of unknown function. Here, we examined the molecular and cellular properties of the mouse EmT. We first studied mRNA expression of signalling molecules and found that the EmT is a structure, rich in expression of secreted factors, with Wnts being the most abundantly detected. We then examined whether EmT tissue could induce cell fate changes when grafted ectopically. For this, we transplanted EmT tissue from a tau-GFP mouse to the ventral telencephalon of a wild type host, a telencephalic region where Wnt signalling is not normally active but which we showed in culture experiments is competent to respond to Wnts. We observed that the EmT was able to induce in adjacent ventral telencephalic cells ectopic expression of Lef1, a transcriptional activator and a target gene of the Wnt/β-catenin pathway. These Lef1-positive;GFP-negative cells expressed the telencephalic marker Foxg1 but not Ascl1, which is normally expressed by ventral telencephalic cells. These results suggest that the EmT has the capacity to activate Wnt/β-catenin signalling in the ventral telencephalon and to suppress ventral telencephalic gene expression. Altogether, our data support a role of the EmT as a signalling centre in the developing mouse forebrain.
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    • "LiCl can activate Wnt signaling selectively via the b-catenin/TCF pathway (Moon et al. 2002). Fz-8/Fc, an antagonist for Wnt8A and potentially for other Wnts, was shown to decrease b-catenin down to the basal level (Nakamura et al. 2003). We found that WIF1 expression alone in WIF1 mice or in H9c2 cells decreases the accumulation of b-catenin in cytoplasm and the nucleus, consistent with a decrease in c-myc expression as well as nppb and acta1 expression. "
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    ABSTRACT: Wnt activity is a key regulator of cardiac progenitor cell self-renewal, differentiation and morphogenesis. However, Wnt inhibitory factor 1 (WIF1), a antagonists of Wnt signaling activity, its potential effects on heart development has not yet been approached by either in vivo or in vitro studies. Here, the expression of WIF1 was regulated in a different way in the dilated and hypertrophic cardiomyopathy heart from transgenic mice by mutations in cardiac troponin T, cTnTR141W and cTnTR92Q. The heart tissue specific transgenic mice of WIF1 was studied using M-mode echocardiography and histologic analyses. Production levels of an array of effectors and transcription factors that impact cellular organization and tissue morphology were measured. The effects of WIF1 on β-catenin pathway could be reversed by LiCl regarding signaling pathways and effector and respondent molecules in H9c2 cells, consistent with the expression levels of c-myc, natriuretic peptide precursor type B and skeletal muscle actin α1. Among the most noteworthy findings were that WIF1 impaired the function and structure of heart, and the effects on β-catenin pathway maybe the course of the former. It is anticipated that our findings will contribute to expansion of our understanding of WIF1 biological function on heart development and possible modes of treatment of heart diseases. Electronic supplementary materialThe online version of this article (doi:10.1007/s11248-013-9738-z) contains supplementary material, which is available to authorized users.
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    • "Canonical Wnt signaling exhibits biphasic and antagonistic effects on cardiomyogenesis and hematopoiesis/vasculogenesis, depending on the stage of development. [15], [16], [17], [18], [19], [20], [21] Also, some researchers showed biphasic and antagonistic effects on apoptosis in cardiac cells and stem cells. Studies using mesenchymal stem cells (MSC) demonstrated that Wnt3a, a canonical Wnt, reversed acetylsalicylic acid-induced MSC apoptosis. "
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    ABSTRACT: Because of their regenerative and paracrine abilities, cardiac stem cells (CSCs) are the most appropriate, optimal and promising candidates for the development of cardiac regenerative medicine strategies. However, native and exogenous CSCs in ischemic hearts are exposed to various pro-apoptotic or cytotoxic factors preventing their regenerative and paracrine abilities. We examined the effects of H2O2 on mouse CSCs (mCSCs), and observed that hydrogen peroxide (H2O2) treatment induces mCSCs apoptosis via the caspase 3 pathway, in a dose-dependent manner. We then examined the effects of Wnt1 over-expression on H2O2-induced apoptosis in mCSCs and observed that Wnt1 significantly decreased H2O2-induced apoptosis in mCSCs. On the other hand, inhibition of the canonical Wnt pathway by the secreted frizzled related protein 2 (SFRP2) or knockdown of β-catenin in mCSCs reduced cells resistance to H2O2-induced apoptosis, suggesting that Wnt1 predominantly prevents H2O2-induced apoptosis through the canonical Wnt pathway. Our results provide the first evidences that Wnt1 plays an important role in CSCs' defenses against H2O2-induced apoptosis through the canonical Wnt1/GSK3β/β-catenin signaling pathway.
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