title: A common Shox2-Nkx2-5 antagonistic mechanism primes the pacemaker cell fate in the pulmonary vein myocardium and sinoatrial node.
abstract: In humans, atrial fibrillation is often triggered by ectopic pacemaking activity in the myocardium sleeves of the pulmonary vein (PV) and systemic venous return. The genetic programs that abnormally reinforce pacemaker properties at these sites and how this relates to normal sinoatrial node (SAN) development remain uncharacterized. It was noted previously that Nkx2-5, which is expressed in the PV myocardium and reinforces a chamber-like myocardial identity in the PV, is lacking in the SAN. Here we present evidence that in mice Shox2 antagonizes the transcriptional output of Nkx2-5 in the PV myocardium and in a functional Nkx2-5(+) domain within the SAN to determine cell fate. Shox2 deletion in the Nkx2-5(+) domain of the SAN caused sick sinus syndrome, associated with the loss of the pacemaker program. Explanted Shox2(+) cells from the embryonic PV myocardium exhibited pacemaker characteristics including node-like electrophysiological properties and the capability to pace surrounding Shox2(-) cells. Shox2 deletion led to Hcn4 ablation in the developing PV myocardium. Nkx2-5 hypomorphism rescued the requirement for Shox2 for the expression of genes essential for SAN development in Shox2 mutants. Similarly, the pacemaker-like phenotype induced in the PV myocardium in Nkx2-5 hypomorphs reverted back to a working myocardial phenotype when Shox2 was simultaneously deleted. A similar mechanism is also adopted in differentiated embryoid bodies. We found that Shox2 interacts with Nkx2-5 directly, and discovered a substantial genome-wide co-occupancy of Shox2, Nkx2-5 and Tbx5, further supporting a pivotal role for Shox2 in the core myogenic program orchestrating venous pole and pacemaker development.
authors.affiliation: Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA.
authors.forename: Wenduo
authors.initials: W
authors.lastname: Ye
authors.affiliation: Department of Molecular Physiology and Biophysics, Baylor College of Medicine and the Texas Heart Institute, Houston, TX 77030, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA Southern Center for Biomedical Research and Fujian Key Laboratory of Developmental and Neural Biology, College of Life Science, Fujian Normal University, Fuzhou, Fujian 350108, P.R. China.
authors.forename: Yingnan
authors.initials: Y
authors.lastname: Song
authors.affiliation: Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA.
authors.forename: Diankun
authors.initials: D
authors.lastname: Yu
authors.affiliation: Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA.
authors.forename: Cheng
authors.initials: C
authors.lastname: Sun
authors.affiliation: Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA.
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA.
authors.forename: Fading
authors.initials: F
authors.lastname: Chen
authors.affiliation: Southern Center for Biomedical Research and Fujian Key Laboratory of Developmental and Neural Biology, College of Life Science, Fujian Normal University, Fuzhou, Fujian 350108, P.R. China.
authors.forename: Yanding
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Center for Cancer and Stem Cell Biology, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX 77030, USA.
authors.forename: Fen
authors.initials: F
authors.lastname: Wang
authors.affiliation: Developmental and Stem Cell Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia St. Vincent's Clinical School and School of Biological and Biomolecular Sciences, University of New South Wales, Kensington, New South Wales 2052, Australia.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Harvey
authors.affiliation: Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Schrader
authors.affiliation: Department of Molecular Physiology and Biophysics, Baylor College of Medicine and the Texas Heart Institute, Houston, TX 77030, USA.
authors.forename: James F
authors.initials: JF
authors.lastname: Martin
authors.affiliation: Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA Southern Center for Biomedical Research and Fujian Key Laboratory of Developmental and Neural Biology, College of Life Science, Fujian Normal University, Fuzhou, Fujian 350108, P.R. China ychen@tulane.edu.
authors.forename: YiPing
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000818:Animals; D001683:Biological Clocks; D002454:Cell Differentiation; D019070:Cell Lineage; D002469:Cell Separation; D004562:Electrocardiography; D058732:Embryoid Bodies / Q000378:metabolism; D005434:Flow Cytometry; D018507:Gene Expression Regulation, Developmental; D016678:Genome; D006321:Heart / Q000196:embryology; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010641:Phenotype; D017434:Protein Structure, Tertiary; D011667:Pulmonary Veins / Q000378:metabolism*; D012849:Sinoatrial Node / Q000378:metabolism*; D020825:T-Box Domain Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C484469:Nkx2-5 protein, mouse; C484663:Shox2 protein, mouse; D020825:T-Box Domain Proteins; C103172:T-box transcription factor 5; D014157:Transcription Factors
keywords: Atrial fibrillation; Cell fate; Human; Mouse; Nkx2-5; Pulmonary vein; Shox2; Sinoatrial node