Fig. 2

The pac mutation affects cell-cell adhesion in the midbrain-hindbrain region. (A-C) Bodipy ceramide staining; 24 hpf; confocal microscopic cross sections at hindbrain levels; (A) wild-type sibling, (B,C) pac^fr7 mutant. Red arrowheads indicate rounded cells, blue arrows indicate ectopic rosette-like structures in dorsal regions of the pac mutant, and white arrows indicate ventricle lumen of the neural tube and ectopic lumina in dorsal rosette-like structures in pac. Insets in A,B show longitudinal sections through the mid- and hindbrain. The midbrainhindbrain boundary (mhb) is indicated by white arrowheads and levels at which the crosssections are taken are indicated by white arrows. Note the less pronounced mhb in pac mutant (B). (D-K) Chimeric embryos after transplantation of wild-type or pac mutant cells into wildtype or pac mutant hosts, as indicated: 24 hpf; lateral view of the mid- and hindbrain (D-F) and transverse sections at midbrain-hindbrain level (G-K). Note the tighter organization of the aggregate in I compared with K. Arrows in E,F,J,K indicate isolated cells. Note that in K, isolated pac mutant cells have a rounded shape, in contrast to their elongated wild-type neighbors (compare with alar wild-type cells in G).