Figure 3.

Migration of the visceral branches is impaired in integrin mutants. We examined the tracheal mutant phenotypes by using either the mAb2A12 antibody, which recognizes the tracheal lumen in stage 15 embryos (A,D,G,J,K), or by using a combination of btlGAL4/UAS-tau-lacZ constructs and anti-FasIII antibody to analyze the relation between the tracheal cells and the mesoderm in stage 13 (B,E,H) and stage 15 embryos (C,F,I,L). (A–C) Wild-type embryos. (D) In mutant embryos for αPS1, the visceral branches (arrowhead) are shorter compared with the wild type, but they do have fine branches. Earlier in development, they reach and contact the visceral mesoderm (E), but then they do not migrate along the mesoderm (arrow) (F). (G–I) The same defects on visceral branch migration are observed in mutants for αPS2, although they are often milder. (J–L) Mutant embryos for βPS also exhibit a failure in visceral branch migration similar to those observed in αPS mutants. (L) In addition, visceral branches sometimes detach from the visceral mesoderm. (K) Some mutant embryos for βPS also show gaps in the dorsal trunk (arrow), and defects in the dorsal branch.