title: Morphogenesis and morphometric scaling of lung airway development follows phylogeny in chicken, quail, and duck embryos.
abstract: BACKGROUND
  New branches within the embryonic chicken lung form via apical constriction, in which epithelial cells in the primary bronchus become trapezoidal in shape. These branches form at precise locations along the primary bronchus that scale relative to the size of the organ. Here, we examined the extent to which this scaling relationship and branching mechanism are conserved within lungs of three species of birds.
  
  
  RESULTS
  Analyzing the development of embryonic lungs from chicken, quail, and duck, as well as lungs explanted and cultured ex vivo, revealed that the patterns of branching are remarkably conserved. In particular, secondary bronchi form at identical positions in chicken and quail, the patterns of which are indistinguishable, consistent with the close evolutionary relationship of these two species. In contrast, secondary bronchi form at slightly different positions in duck, the lungs of which are significantly larger than those of chicken and quail at the same stage of development. Confocal analysis of fixed specimens revealed that each secondary bronchus forms by apical constriction of the dorsal epithelium of the primary bronchus, a morphogenetic mechanism distinct from that used to create branches in mammalian lungs.
  
  
  CONCLUSIONS
  Our findings suggest that monopodial branching off the primary bronchus is driven by apical constriction in lungs of chicken, quail, and duck. The relative positions at which these branches form are also conserved relative to the evolutionary relationship of these species. It will be interesting to determine whether these mechanisms hold in more distant species of birds, and why they differ so significantly in mammals.
authors.affiliation: Department of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544 USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Tzou
authors.affiliation: Department of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544 USA.
authors.forename: James
authors.initials: J
authors.lastname: W Spurlin
authors.affiliation: Department of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544 USA.
authors.forename: Amira L
authors.initials: AL
authors.lastname: Pavlovich
authors.affiliation: Department of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544 USA.
authors.forename: Carolyn R
authors.initials: CR
authors.lastname: Stewart
authors.affiliation: Department of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544 USA.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Gleghorn
authors.affiliation: Department of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544 USA ; Department of Molecular Biology, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544 USA.
authors.forename: Celeste M
authors.initials: CM
authors.lastname: Nelson
keywords: Allometry; Lateral branching; Morphodynamics; Patterning