Fig. 3. spn-4 is required for spindle rotation in two-cell stage par-3 mutant embryos. (A) Nomarski photomicrographs of par-3(it71) and par-3(it71);spn-4(RNAi) mutant embryos. Arrows point at the centrosomes. In par-3 embryos, both cells divide with longitudinally oriented spindles. In par-3; spn-4 double mutant embryos, both divide with transversely oriented spindles. In both par-3 and par-3; spn-4 embryos the two cells are similar in size and divide synchronously. (B) Schematic depiction of mitotic spindle orientations in two-cell stage in par-3 and par-3; spn-4 mutant embryos. In par-3 mutants, spindle angles range from 3° to 48° (n=7). Two allelic combinations of par-3; spn-4 double mutants were analyzed. In par-3(it71); spn-4(RNAi) spindle orientation ranges from 16° to 87° (n=7), in par-3(it71);spn-4(or191ts) from 20° to 89° (n=10).