Fig. 6.
Motor axons stall in shot mutant embryos. A, A dorsal section of three abdominal hemisegments in a late stage 16 embryo stained with mAb 1D4 (Van Vactor et al., 1993) to visualize the motor axons. Motor axons in the ISN (arrows) form three terminal arborizations over the dorsal muscles. T, Trachea. B, A ventrolateral section of three abdominal hemisegments in a late stage 16 embryo stained with mAb 1D4. The ISN extends dorsally. The SNa motor axons contact lateral muscles and bifurcate into dorsal (arrow) and lateral (arrowhead) branches. The ISNb motor axons (concave arrow) make contacts with muscles 12 and 13 and the cleft between muscles 6 and 7.C, ISN motor axons (arrow) typically stall at variable positions in the dorsal muscle field inshot3/Df(2R)CX1 mutant embryos, but generally form the third arborization. D, The SNa (arrowhead) and ISNb motor axons (concave arrow) stall before reaching their muscle targets in a late stage 16 shot3 mutant embryo.WT, Wild type.