title: Actin and type I collagen propeptide distribution in the developing chick cornea.
abstract: OBJECTIVE
  To determine the organization of actin filaments and distribution of type I procollagen during the development of the chick corneal stroma.
  
  
  METHODS
  Embryonic chicken corneas of ages 6 to 18 days and 18 days posthatch were cryosectioned and fluorescently labeled for filamentous actin with phalloidin and for the N-and C-terminal propeptides of type I procollagen with specific monoclonal antibodies. Tissue sections were examined by fluorescence and confocal microscopy.
  
  
  RESULTS
  Prominent actin filament bundles were present at all embryonic stages, arranged in orthogonal arrays. Type I collagen propeptides were also present, with the C-propeptide visible as small foci, often associated with the actin label. The N-propeptide was also detected in the stromal matrix, especially in Bowman's layer. Actin filaments were also prominent in the corneal epithelium, along with collagen propeptide labeling, up to embryonic day 14.
  
  
  CONCLUSIONS
  Actin filament bundles are abundant in the stroma, presumably in the keratocytes of the developing chick cornea, and are arranged in an orthogonal manner suggesting a possible role in cell and matrix organization in this tissue. Filament bundles appear to be closely associated with the foci of type I procollagen label, suggesting a possible association between the actin cytoskeleton and the trafficking of collagen. The presence of the N-propeptide of type I collagen in the extracellular matrix and the restricted distribution of the C-propeptide suggest differential processing of these molecules after secretion. The persistence of the N-propeptide implies a role in development, possibly in association with control of collagen fibril diameter and spacing.
authors.affiliation: Connective Tissue Biology Laboratories, School of Biosciences, Cardiff University, Cardiff, United Kingdom.
authors.forename: Claire
authors.initials: C
authors.lastname: Gealy
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Hayes
authors.forename: Rebecca
authors.initials: R
authors.lastname: Buckwell
authors.forename: Robert D
authors.initials: RD
authors.lastname: Young
authors.forename: Bruce
authors.initials: B
authors.lastname: Caterson
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Quantock
authors.forename: James R
authors.initials: JR
authors.lastname: Ralphs
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002642:Chick Embryo; D003319:Corneal Stroma / Q000196:embryology* / Q000254:growth & development / Q000378:metabolism; D005456:Fluorescent Dyes; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D010446:Peptide Fragments / Q000378:metabolism*; D010748:Phosphopeptides / Q000378:metabolism*; D011347:Procollagen / Q000378:metabolism*
chemical_list: D000199:Actins; D005456:Fluorescent Dyes; C062121:N-propeptide type I collagen; D010446:Peptide Fragments; D010748:Phosphopeptides; D011347:Procollagen; C042813:procollagen type I carboxy terminal peptide