Figure 1. UNC-6/Netrin signaling is required for contact-dependent self-avoidance.

(a) Fluorescent image of PVD neuron labeled with GFP to show the non-overlapping pattern of PVD dendrites. Arrowheads denote gaps between 3⁰ dendrites of adjacent menorahs. The single PVD axon (arrow) marks the location of the ventral nerve cord. (b) Tracing of PVD branches to show numbering scheme. (c) Tracings of 3^o dendrites from dorsal (D) and ventral (V) regions of ten individual PVD neurons are denoted with matching colors. Note that 3^o dendrites do not terminate at specific anatomical regions or exhibit a single length as would be expected if outgrowth were governed by external landmarks or limited by an intrinsic mechanism of length determination. (d) egl-46 mutants show fewer 2^o branches and longer 3^o dendrites (arrows). (e) PVD neurons have fewer 2^o branches in egl-46 (n1076) mutants (32.3 + 5.3) than wild type (wt) (38.9 + 5.4). Despite the consequent reduction in the overall number of 3^o branches in egl-46 mutants, the normal distance between the tips of adjacent 3^o dendrites is maintained by extending the average outgrowth length of 3^o dendrites. Error bars represent s.d.