Fig. 1. slt-1, sax-3, egl-17 and egl-15 mutations enhanced the CAN migration defects of vab-8 and unc-34 mutant. (A) Merged fluorescence and Nomarski images of a newly hatched first larval stage ceh-23::gfp transgenic animal that expresses GFP in the CANs, as well as sensory neurons in the head and tail. Anterior is towards the left and dorsal is upwards. Only the left CAN is visible. Although the ceh-23::gfp transgenic animals shown are used to illustrate the normal positions of the CANs, this transgene sensitizes the background to CAN defects. To avoid this, we scored CAN positions by Nomarski optics in a background lacking this transgene. (B) In a schematic view of the region in which CAN positions were scored, the CAN is shown in a wild-type position and the arrow marks the path of CAN migration. The vertical marks define the positions of the landmark V cell and P cell nuclei, which are also shown in the diagram. (C) For each genotype, the percentage of CANs found in each position is noted along with the total number (n) of CANs scored. The shading of the box reflects the percentage of CANs in that position, with darker shading reflecting higher percentages. Single mutants of the tested guidance cues and receptors did not show CAN migration defects. slt-1(eh15), sax-3(ky200), egl-17(n1377) and several egl-15 mutants enhanced the CAN migration defects of vab-8(gm84) mutants (P<0.01), while unc-6(ev400), unc-40(e1430) and let-756(s2887) did not (P=0.65, P=0.14, P=0.26, respectively). A two-sample z-test on the proportion of CANs found in the most anterior CAN position was used to determine whether double mutants showed significant enhancement of CAN migration defects when compared with vab-8(gm84) single mutants. In particular, vab-8(gm84); slt-1(eh15) and vab-8(gm84); sax-3(ky200) displayed significant enhancement of vab-8(gm84) CAN migration defects with P<0.0001, while vab-8(gm84); egl-15(n484) and vab-8(gm84); egl-15(n1456) strains enhanced with P<0.001. vab-8(gm84); egl-17(n1377), egl-15(n484) mutants displayed CAN migration defects comparable with vab-8(gm84); egl-17(n1377) and vab-8(gm84); egl-15(n484) mutants (P=0.98 and P=0.31, respectively). egl-17(n1377) and egl-15(n1477ts) mutants also enhanced the CAN migration defects (P<0.01) of the unc-34(e951) null allele when using a two-sample z-test on the proportion of CANs found in the two most anterior CAN positions.