title: Loss of Wnt5a disrupts second heart field cell deployment and may contribute to OFT malformations in DiGeorge syndrome.
abstract: Outflow tract (OFT) malformation accounts for ∼30% of human congenital heart defects and manifests frequently in TBX1 haplo-insufficiency associated DiGeorge (22q11.2 deletion) syndrome. OFT myocardium originates from second heart field (SHF) progenitors in the pharyngeal and splanchnic mesoderm (SpM), but how these progenitors are deployed to the OFT is unclear. We find that SHF progenitors in the SpM gradually gain epithelial character and are deployed to the OFT as a cohesive sheet. Wnt5a, a non-canonical Wnt, is expressed specifically in the caudal SpM and may regulate oriented cell intercalation to incorporate SHF progenitors into an epithelial-like sheet, thereby generating the pushing force to deploy SHF cells rostrally into the OFT. Using enhancer trap and Cre transgenes, our lineage tracing experiments show that in Wnt5a null mice, SHF progenitors are trapped in the SpM and fail to be deployed to the OFT efficiently, resulting in a reduction in the inferior OFT myocardial wall and its derivative, subpulmonary myocardium. Concomitantly, the superior OFT and subaortic myocardium are expanded. Finally, in chick embryos, blocking the Wnt5a function in the caudal SpM perturbs polarized elongation of SHF progenitors, and compromises their deployment to the OFT. Collectively, our results highlight a critical role for Wnt5a in deploying SHF progenitors from the SpM to the OFT. Given that Wnt5a is a putative transcriptional target of Tbx1, and the similar reduction of subpulmonary myocardium in Tbx1 mutant mice, our results suggest that perturbing Wnt5a-mediated SHF deployment may be an important pathogenic mechanism contributing to OFT malformations in DiGeorge syndrome.
authors.affiliation: Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Alabama, USA.
authors.forename: Tanvi
authors.initials: T
authors.lastname: Sinha
authors.affiliation: Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Alabama, USA.
authors.forename: Ding
authors.initials: D
authors.lastname: Li
authors.affiliation: Aix Marseille Université, CNRS, IBDM UMR 7288, Marseille 13288, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Théveniau-Ruissy
authors.affiliation: Department of Pediatrics, Duke University School of Medicine, Durham, North Carolina.
authors.forename: Mary R
authors.initials: MR
authors.lastname: Hutson
authors.affiliation: Aix Marseille Université, CNRS, IBDM UMR 7288, Marseille 13288, France.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Kelly
authors.affiliation: Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Alabama, USA, j18wang@uab.edu.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Wang
mesh_terms: D000818:Animals; D002642:Chick Embryo; D004062:DiGeorge Syndrome / Q000209:etiology / Q000235:genetics*; D053595:Embryonic Stem Cells / Q000473:pathology*; D017353:Gene Deletion; D006321:Heart / Q000196:embryology*; D051379:Mice; D018345:Mice, Knockout; D009206:Myocardium / Q000473:pathology; D051153:Wnt Proteins / Q000235:genetics*; D000071818:Wnt-5a Protein
chemical_list: D051153:Wnt Proteins; D000071818:Wnt-5a Protein; C438615:Wnt5a protein, mouse