title: Programmed cell death in extraocular muscle tendon/sclera precursors.
abstract: OBJECTIVE
  This study was designed to examine the occurrence of natural cell death in the periocular mesenchyme of mouse embryos.
  
  
  METHODS
  Vital staining with LysoTracker Red and Nile blue sulfate as well as terminal nick end labeling (TUNEL) were utilized to identify apoptotic cell death in whole and histologicaly sectioned gestational day 10.5 to 14 mouse embryos. Laser scanning confocal microscopy was used to provide a three dimensional representation of the cell death pattern. Immunohistochemical staining for neural crest and myoblast populations was utilized to indicate the cell population undergoing apoptosis.
  
  
  RESULTS
  Programmed cell death was evident in the developing rectus muscle tendons/sclera on gestational days 11 through 12.5 (corresponding to the weeks 5-6 of human development). Although each of these peripheral periocular condensations has readily apparent amounts of apoptosis, the pattern of cell death varied among them. Cell death was most apparent in the superior rectus tendon primordium, while that for the lateral rectus had the least evidence of apoptosis.
  
  
  CONCLUSIONS
  Although apoptosis was readily evident in the periocular mesenchyme in distinct regions located medial and distal to the developing rectus muscles, programmed cell death in these sites has not previously been reported. New imaging techniques coupled with stains that evidence apoptotic cell death have made it possible to define this tissue as a prominent region of programmed cell death. Although neuronal tissues, including particular regions of the developing eye, are well recognized as sites of programmed cell death, description of this phenomenon in the extraocular tendon/sclera precursors is novel.
authors.affiliation: Department of Cell and Developmental Biology and Bowles Center for Alcohol Studies, The University of North Carolina, Chapel Hill, NC 27599, USA. mouse@med.unc.edu
authors.forename: K K
authors.initials: KK
authors.lastname: Sulik
authors.forename: D B
authors.initials: DB
authors.lastname: Dehart
authors.forename: C S
authors.initials: CS
authors.lastname: Johnson
authors.forename: S L
authors.initials: SL
authors.lastname: Ellis
authors.forename: S Y
authors.initials: SY
authors.lastname: Chen
authors.forename: W C
authors.initials: WC
authors.lastname: Dunty
authors.forename: R M
authors.initials: RM
authors.lastname: Zucker
mesh_terms: D000818:Animals; D017209:Apoptosis; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D007124:Immunoenzyme Techniques; D020287:In Situ Nick-End Labeling; D008648:Mesoderm / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D017570:MyoD Protein / Q000378:metabolism; D018008:Myogenin / Q000378:metabolism; D009432:Neural Crest / Q000166:cytology / Q000378:metabolism; D009801:Oculomotor Muscles / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D010078:Oxazines / Q000378:metabolism; D011247:Pregnancy; D012590:Sclera / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology*; D013710:Tendons / Q000166:cytology / Q000196:embryology* / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D017570:MyoD Protein; C503801:Myog protein, mouse; D018008:Myogenin; D010078:Oxazines; C008619:Nile Blue