title: Tissue-Specific Cell Cycle Indicator Reveals Unexpected Findings for Cardiac Myocyte Proliferation.
abstract: BACKGROUND
  Discerning cardiac myocyte cell cycle behavior is challenging owing to commingled cell types with higher proliferative activity.
  
  
  OBJECTIVE
  To investigate cardiac myocyte cell cycle activity in development and the early postnatal period.
  
  
  RESULTS
  To facilitate studies of cell type-specific proliferation, we have generated tissue-specific cell cycle indicator BAC transgenic mouse lines. Experiments using embryonic fibroblasts from CyclinA2-LacZ-floxed-EGFP, or CyclinA2-EGFP mice, demonstrated that CyclinA2-βgal and CyclinA2-EGFP were expressed from mid-G1 to mid-M phase. Using Troponin T-Cre;CyclinA2-LacZ-EGFP mice, we examined cardiac myocyte cell cycle activity during embryogenesis and in the early postnatal period. Our data demonstrated that right ventricular cardiac myocytes exhibited reduced cell cycle activity relative to left ventricular cardiac myocytes in the immediate perinatal period. Additionally, in contrast to a recent report, we could find no evidence to support a burst of cardiac myocyte cell cycle activity at postnatal day 15.
  
  
  CONCLUSIONS
  Our data highlight advantages of a cardiac myocyte-specific cell cycle reporter for studies of cardiac myocyte cell cycle regulation.
authors.affiliation: From the Skaggs School of Pharmacy and Pharmaceutical Sciences (M.H., S.M.E.), Department of Medicine (J.C., S.M.E.), and Department of Pharmacology (S.M.E.), University of California, San Diego, La Jolla.
authors.forename: Maretoshi
authors.initials: M
authors.lastname: Hirai
authors.affiliation: From the Skaggs School of Pharmacy and Pharmaceutical Sciences (M.H., S.M.E.), Department of Medicine (J.C., S.M.E.), and Department of Pharmacology (S.M.E.), University of California, San Diego, La Jolla.
authors.forename: Ju
authors.initials: J
authors.lastname: Chen
authors.affiliation: From the Skaggs School of Pharmacy and Pharmaceutical Sciences (M.H., S.M.E.), Department of Medicine (J.C., S.M.E.), and Department of Pharmacology (S.M.E.), University of California, San Diego, La Jolla. syevans@ucsd.edu.
authors.forename: Sylvia M
authors.initials: SM
authors.lastname: Evans
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D049109:Cell Proliferation / Q000502:physiology*; D002478:Cells, Cultured; D056751:Cyclin A2 / Q000172:deficiency / Q000235:genetics; D005260:Female; D049452:Green Fluorescent Proteins / Q000172:deficiency / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D032383:Myocytes, Cardiac / Q000502:physiology*; D011247:Pregnancy
chemical_list: C508184:CCNA2 protein, mouse; D056751:Cyclin A2; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins
keywords: cardiac myocyte; cell cycle; cyclins; heart development; proliferation