Fig. 5.

Deletion of Fgfr2 disrupts epithelial cell shape, cytoskeletal organization, and cell adhesion. (A-D′) Ultrastructural analysis by TEM reveals aberrant cell shapes in Fgfr2^– genital tubercle epithelia; mutant basal cells fail to elongate perpendicular to the basement membrane in both Fgfr2^EndoΔ and Fgfr2^EctoΔ mutant epithelia. Diminished stratification is evident in the Fgfr2^EndoΔ urethra. Cells adjacent to basement membrane are pseudocolored cyan, those neighboring the lumen are magenta and intervening cells are yellow. Scale bars: 2 μm. (E-P) Fluorescent micrographs of control, Fgfr2^EndoΔ and Fgfr2^EctoΔ genital tubercles stained with phalloidin (E-J) or immunolabeled with an anti-β-catenin antibody (K-P). Note the long cell cortices stained with F-actin in E (white arrows) and short, hatched phalloidin domains in F (arrowheads). Punctate, basolateral foci of β-catenin are evident in control basal urethral cells (yellow arrows) but were not detected in Fgfr2^EndoΔ mutants. In controls, the ventral seam shows enriched actin stress fibers (white triangles) distally and increased β-catenin staining (yellow triangles) proximally. Elevated abundance of F-actin fibers is coincident with static levels of β-catenin intensity along the proximodistal ventral midline of Fgfr2^EctoΔ mutants. Asterisks mark urethral lumen, dotted lines outline the urethral and surface epithelia. Scale bars: 20 μm.