title: HCN4 dynamically marks the first heart field and conduction system precursors.
abstract: BACKGROUND
  To date, there has been no specific marker of the first heart field to facilitate understanding of contributions of the first heart field to cardiac lineages. Cardiac arrhythmia is a leading cause of death, often resulting from abnormalities in the cardiac conduction system (CCS). Understanding origins and identifying markers of CCS lineages are essential steps toward modeling diseases of the CCS and for development of biological pacemakers.
  
  
  OBJECTIVE
  To investigate HCN4 as a marker for the first heart field and for precursors of distinct components of the CCS, and to gain insight into contributions of first and second heart lineages to the CCS.
  
  
  RESULTS
  HCN4CreERT2, -nuclear LacZ, and -H2BGFP mouse lines were generated. HCN4 expression was examined by means of immunostaining with HCN4 antibody and reporter gene expression. Lineage studies were performed using HCN4CreERT2, Isl1Cre, Nkx2.5Cre, and Tbx18Cre, coupled to coimmunostaining with CCS markers. Results demonstrated that, at cardiac crescent stages, HCN4 marks the first heart field, with HCN4CreERT2 allowing assessment of cell fates adopted by first heart field myocytes. Throughout embryonic development, HCN4 expression marked distinct CCS precursors at distinct stages, marking the entire CCS by late fetal stages. We also noted expression of HCN4 in distinct subsets of endothelium at specific developmental stages.
  
  
  CONCLUSIONS
  This study provides insight into contributions of first and second heart lineages to the CCS and highlights the potential use of HCN4 in conjunction with other markers for optimization of protocols for generation and isolation of specific conduction system precursors.
authors.affiliation: Skaggs School of Pharmacy and Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.|Key Laboratory of Arrhythmia, Ministry of Education, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.
authors.forename: Xingqun
authors.initials: X
authors.lastname: Liang
authors.affiliation: Skaggs School of Pharmacy and Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.affiliation: Skaggs School of Pharmacy and Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors.forename: Lizhu
authors.initials: L
authors.lastname: Lin
authors.affiliation: Skaggs School of Pharmacy and Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lowe
authors.affiliation: Key Laboratory of Arrhythmia, Ministry of Education, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.
authors.forename: Qingquang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Skaggs School of Pharmacy and Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Bu
authors.affiliation: Key Laboratory of Arrhythmia, Ministry of Education, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.
authors.forename: Yihan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Skaggs School of Pharmacy and Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors.forename: Ju
authors.initials: J
authors.lastname: Chen
authors.affiliation: Skaggs School of Pharmacy and Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.|Key Laboratory of Arrhythmia, Ministry of Education, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.
authors.forename: Yunfu
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Skaggs School of Pharmacy and Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors.forename: Sylvia M
authors.initials: SM
authors.lastname: Evans
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000235:genetics; D015415:Biomarkers / Q000378:metabolism; D019070:Cell Lineage; D005260:Female; D055879:Gene Knock-In Techniques; D006329:Heart Conduction System / Q000166:cytology* / Q000378:metabolism*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / Q000235:genetics / Q000378:metabolism*; D007763:Lac Operon / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D023421:Models, Animal; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*
chemical_list: D015415:Biomarkers; C578706:Hcn4 protein, mouse; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
keywords: HCN4; arrhythmias, cardiac; cardiac biomarkers; cardiac conduction system; cardiac development; cardiac lineage; heart field; transgenic model