Figure 2

PDE axon pathfinding defects in arx mutants. (A-D) Shown are fluorescent micrographs of larval or young adult animals with osm-6::gfp expression in the PDE neurons. (A) A wild-type PDE neuron extended a single unbranched axon (arrow) straight ventrally to the ventral nerve cord (VNC), which is out of focus but represented by a dashed line. (B-D) PDE axons were misguided in arx-2, arx-4, and arx-7 mutants. The axons failed to reach the VNC and wandered laterally (B, C) or wandered laterally before extending to the VNC (D). In all micrographs, anterior is to the left and dorsal is up; dashed lines represent the location of the out-of-focus VNC, and scale bars = 10 μm. In genotypes, 'M+' denotes that the animal had wild-type maternal arx contribution. (E-G) Quantification of PDE axon guidance defects. Genotypes are along the x-axis, and proportion of misguided PDE axons is on the y-axis. The numbers of PDE axons scored for each genotype is listed above the graph. In (E), Ex [arx(+)] indicates that the animals harbored a wild-type arx(+) transgene, and Ex [Posm-6::arx-4] indicates that the animals harbored a transgene that expressed the arx-4(+) gene specifically in the PDEs. The differences between arx mutants alone and those harboring transgenes were significant in all cases (P ≤ 0.0001, indicated by an asterisk).