Apoptosis in the developing mouse heart

Authors

  • Laura Barbosky,

    1. Department of Pediatrics, Rainbow Babies and Children's Hospital, Case Western Reserve University School of Medicine, Cleveland, Ohio
    Current affiliation:
    1. Pediatrics/Neonatology Division, Neonatal/Perinatal Research Institute, Duke University Medical Center, Bell Research Drive, Box 3179 DUMC, Durham, NC 27710
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  • David K. Lawrence,

    1. Department of Pediatrics, Rainbow Babies and Children's Hospital, Case Western Reserve University School of Medicine, Cleveland, Ohio
    Current affiliation:
    1. 3104 Mineral Ridge Lane, Stone Mountain, GA 30087
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  • Ganga Karunamuni,

    1. Department of Pediatrics, Rainbow Babies and Children's Hospital, Case Western Reserve University School of Medicine, Cleveland, Ohio
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  • Jamie C. Wikenheiser,

    1. Department of Pediatrics, Rainbow Babies and Children's Hospital, Case Western Reserve University School of Medicine, Cleveland, Ohio
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  • Yong-Qiu Doughman,

    1. Department of Pediatrics, Rainbow Babies and Children's Hospital, Case Western Reserve University School of Medicine, Cleveland, Ohio
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  • Richard P. Visconti,

    1. Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, South Carolina
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  • John B.E. Burch,

    1. Department of Cell and Developmental Biology, Fox Chase Cancer Center, Philadelphia, Pennsylvania
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  • Michiko Watanabe

    Corresponding author
    1. Department of Pediatrics, Rainbow Babies and Children's Hospital, Case Western Reserve University School of Medicine, Cleveland, Ohio
    • Department of Pediatrics, Rainbow Babies & Children's Hospital, 11100 Euclid Avenue, Cleveland, OH 44106-6011
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Abstract

Apoptosis occurs at high frequency in the myocardium of the developing avian cardiac outflow tract (OFT). Up- or down-regulating apoptosis results in defects resembling human conotruncal heart anomalies. This finding suggested that regulated levels of apoptosis are critical for normal morphogenesis of the four-chambered heart. Recent evidence supports an important role for hypoxia of the OFT myocardium in regulating cell death and vasculogenesis. The purpose of this study was to determine whether apoptosis in the outflow tract myocardium occurs in the mouse heart during developmental stages comparable to the avian heart and to determine whether differential hypoxia is also present at this site in the murine heart. Apoptosis was detected using a fluorescent vital dye, Lysotracker Red (LTR), in the OFT myocardium of the mouse starting at embryonic day (E) 12.5, peaking at E13.5–14.5, and declining thereafter to low or background levels by E18.5. In addition, high levels of apoptosis were detected in other cardiac regions, including the apices of the ventricles and along the interventricular sulcus. Apoptosis in the myocardium was detected by double-labeling with LTR and cardiomyocyte markers. Terminal deoxynucleotidyl transferase–mediated deoxyuridinetriphosphate nick end-labeling (TUNEL) and immunostaining for cleaved Caspase-3 were used to confirm the LTR results. At the peak of OFT apoptosis in the mouse, the OFT myocardium was relatively hypoxic, as indicated by specific and intense EF5 staining and HIF1α nuclear localization, and was surrounded by the developing vasculature as in the chicken embryo. These findings suggest that cardiomyocyte apoptosis is an evolutionarily conserved mechanism for normal morphogenesis of the outflow tract myocardium in avian and mammalian species. Developmental Dynamics 235:2592–2602, 2006. © 2006 Wiley-Liss, Inc.

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