title: Canonical WNT signaling enhances stem cell expression in the developing heart without a corresponding inhibition of cardiogenic differentiation.
abstract: WNT signaling has been shown to influence the development of the heart. Although recent data suggested that canonical WNTs promote the emergence and expansion of cardiac progenitors in the pregastrula embryo, it has long been accepted that once gastrulation begins, canonical WNT signaling needs to be suppressed for cardiac development to proceed. Yet, this latter supposition appears to be odds with the expression of multiple canonical WNTs in the developing heart. The present study examining the effect of ectopic canonical WNT signaling on cardiogenesis in the developing frog was designed to test the hypothesis that heart formation is dependent on the inhibition of canonical WNT activity at the onset of gastrulation. Here we report that cardiac differentiation of explanted precardiac tissue from the dorsal marginal zone was not suppressed by exposure to WNT1 protein, although expression of Tbx5, Tbx20, and Nkx2.5 was selectively reduced. Pharmacological activation of WNT signaling in intact embryos using the GSK3 inhibitor SB415286 did not prevent the formation of an anatomically normal and functionally sound heart, with the only defect observed being lower levels of the cardiac transcription factor Nkx2.5. In both the explant and whole embryo studies, expression of muscle genes and proteins was unaffected by ectopic canonical WNT signaling. In contrast, canonical Wnt signaling upregulated expression of the cardiac stem cell marker c-kit and pluripotency genes Oct25 and Oct60. However, this regulatory stimulation of stem cells did not come at the expense of blocking cardiac progenitors from differentiating.
authors.affiliation: Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina, USA.
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Martin
authors.forename: Nadejda V
authors.initials: NV
authors.lastname: Mezentseva
authors.forename: Momka
authors.initials: M
authors.lastname: Bratoeva
authors.forename: Ann F
authors.initials: AF
authors.lastname: Ramsdell
authors.forename: Carol A
authors.initials: CA
authors.lastname: Eisenberg
authors.forename: Leonard M
authors.initials: LM
authors.lastname: Eisenberg
mesh_terms: D000627:Aminophenols / Q000494:pharmacology; D000818:Animals; D000943:Antigens, Differentiation / Q000235:genetics / Q000378:metabolism; D036703:Blastula / Q000166:cytology / Q000378:metabolism; D002454:Cell Differentiation; D005260:Female; D054262:Gastrulation; D015870:Gene Expression; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors; D006321:Heart / Q000254:growth & development*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007814:Larva / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism; D012518:Sarcomeres / Q000378:metabolism; D015398:Signal Transduction; D013234:Stem Cells / Q000378:metabolism / Q000502:physiology*; D046509:Tissue Culture Techniques; D060449:Wnt Signaling Pathway; D051155:Wnt1 Protein / Q000494:pharmacology / Q000502:physiology; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
chemical_list: C417520:3-(3-chloro-4-hydroxyphenylamino)-4-(4-nitrophenyl)-1H-pyrrole-2,5-dione; D000627:Aminophenols; D000943:Antigens, Differentiation; D018398:Homeodomain Proteins; D008301:Maleimides; C093133:SIA1 protein, Xenopus; D051155:Wnt1 Protein; D029867:Xenopus Proteins; D038362:Glycogen Synthase Kinase 3; D018995:Myosin Heavy Chains