1. Abt Entwicklungsbiochemie, Junior group SFB 271, Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany
2. Abt Biochemie, Universität Ulm, Albert-Einstein-Allee-11, D-89081 Ulm, Germany
3. Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, South Carolina 29425, USA

Correspondence to: Michael Kühl^1,2 Correspondence and requests for material should be addressed to M.K. (e-mail: Email: wnt_signaling@web.de).

Abstract

Formation of the vertebrate heart requires a complex interplay of several temporally regulated signalling cascades¹. In Xenopus laevis, cardiac specification occurs during gastrulation and requires signals from the dorsal lip and underlying endoderm². Among known Xenopus Wnt genes, only Wnt-11 shows a spatiotemporal pattern of expression that correlates with cardiac specification, which indicates that Wnt-11 may be involved in heart development^{3, 4}. Here we show, through loss- and gain-of-function experiments, that XWnt-11 is required for heart formation in Xenopus embryos and is sufficient to induce a contractile phenotype in embryonic explants. Treating the mouse embryonic carcinoma stem cell line P19 with murine Wnt-11 conditioned medium triggers cardiogenesis, which indicates that the function of Wnt-11 in heart development has been conserved in higher vertebrates. XWnt-11 mediates this effect by non-canonical Wnt signalling, which is independent of -catenin and involves protein kinase C and Jun amino-terminal kinase. Our results indicate that the cardiac developmental program requires non-canonical Wnt signal transduction.