Fig. 7. ß-Spectrin affects the guidance of the Apterous (Ap) neurons. (A-E) All embryos have AptGal4, UAS-TauMycGFP in the background. (F,G) Embryos have AptGal4; UAS-TauGFP in the background. (A) Wild-type embryos have no `thick' bundles of Ap neurons crossing the midline. (B) slit/+ heterozygous embryos have less than one thick bundle of Ap neurons crossing the midline (arrow). (C) ß-spectrin mutant embryos have approximately one to two thick Ap bundles crossing the midline (arrow). (D) Ap neuron guidance defects in a slit/+ heterozygous background are enhanced by removing ß-spectrin (arrows). (E) The genetic interaction seen in D cannot be rescued by expressing UAS-ß-Spectrin in the Ap neurons (arrows). (F) In robo mutants, Ap neurons in every segment cross and recross the midline (starred arrowheads). (G) Unlike what is observed in the ß-spectrin background, Ap neuron defects seen in robo1 mutants can be rescued by expressing UAS-RoboMyc specifically in the Ap neurons themselves (arrowheads). (H) Quantification of genotypes: a, AptTMG/+ (n=12); b, slit, AptTMG/+ (n=14); c, em6/Y; AptTMG (n=10); d, em6/Y; slit, AptTMG/+ (n=16); e, em6/Y; slit, AptTMG/UAS-ßSpec (n=20); f, G0198/Y; AptTMG/+ (n=14); g, G0198/Y; slit, AptTMG/+ (n=13). Asterisk denotes a significant difference between genotypes d and c (P=0.0144; two-sample Student's t-test). There is no significant difference between genotypes d and e. Double asterisk denotes a significant difference between genotypes g and f (P=0.00139; two-sample Student's t-test). AptTMG, ApterousGal4, UAS-TauMycGFP.