Fig. 4.

Neuroblasts with reduced Gαi levels can recruit Pins/Insc but not Mud to the apical cortex and have spindle alignment defects. (A and B Top) Gαi apical cortical protein levels are reduced in Gαi zygotic mutant larval neuroblasts (B) compared with WT (A). (A and B Lower) Same neuroblast labeled for α-tubulin (tub) and Pins. Strong Pins crescents were observed in both WT (Left) and zygotic Gαi mutant (Right) metaphase neuroblasts. (C and D) Strong Insc crescents were observed in both WT (C) and zygotic Gαi mutant (D) metaphase neuroblasts (cortical fluorescence intensities Insc 84% of WT; see Methods for details). (E–I) Gαi zygotic mutant larval neuroblasts have robust Pins apical crescents but a loss of Mud apical protein crescents (cortical fluorescence intensities of Pins 90% of WT; see Methods for details). (E and F) WT larval neuroblasts have apical crescents of Pins and Mud at prophase (pro) and metaphase (meta) (arrowheads), as well as strong Mud staining on centrosomes and at the basal cortex (arrows). (G–I) Gαi mutant larval neuroblasts show Pins apical crescents but have defects in forming Mud apical protein crescents at prophase and metaphase (arrowheads), although Mud at the basal cortex is unaffected (arrows). (Scale bar: E–I, 5 μm.) (J) Quantification of apical crescent formation at metaphase in WT and Gαi mutant neuroblasts (see Methods for details). The number in each bar represents the number of neuroblasts examined. (K) Gαi zygotic mutant neuroblasts show spindle alignment defects. Quantification of apical spindle pole alignment (red ticks) relative to the center of the Pins cortical crescent (vertical line). WT spindles are tightly aligned, but Gαi mutant spindles are frequently misaligned.