Fig. 6. Mouse Pins fulfills all aspects of the Drosophila pins function. (A,B) mitotic spindle in the cells of mitotic domain 9 is visualized by anti-ß-tubulin staining. In pins null mutants, mitotic spindles fail to reorient by 90° as in WT and consequently are all aligned parallel to the surface of the embryo (A). Ectopically expressed mouse PINS in pins mutant embryos can restore this 90° spindle reorientation in cell of mitotic domain 9, causing the mitotic spindles to be aligned perpendicular to the surface of the embryo as in WT (B). (C-E) In pins mutant embryos, Miranda localization is defective in the form of uniform cortical localization or misplaced cortical crescents (Schaefer et al., 2000; Yu et al., 2000; data not shown); ectopic expression of PINS results in its apical cortical localization (PINS apical crescent in green, C) and can also restore basal cortical localization of Miranda (basal crescents in red, D) in mitotic NBs. Panel E is a merged image of panels C and D. (F-H): One Eve-expressing RP2 neuron can be found at a characteristic position in each WT hemisegment (arrow, F); RP2 neurons are duplicated in a high proportion of hemisegments in pins mutants embryos (G); expression of PINS protein in pins mutant embryos can restore the WT situation in the great majority of hemisegments (H).