Fig. 5

Fig. 5 lazarus is required non-autonomously for nV axon pathfinding, and lazarus and hoxb1a are both required autonomously for nVII motor neuron migration. (A) Schematic of experimental design: cells from a lineage-labeled transgenic donor embryo were transplanted into the presumptive ventral hindbrain of an unlabeled, nontransgenic host embryo at 6 hpf. (B–F) Confocal images of 36-hpf host embryos. Anterior is to the left. (B) Control transplant of wild-type donor cells (red, yellow if GFP-expressing) into a wild-type host, showing normal development of donor-derived branchiomotor neurons. Arrowheads: trigeminal (nV) motor neurons in r2; arrows: facial (nVII) motor neurons in r5, r6, and r7. (C) lzr/pbx4^-/- nVII motor neurons (arrow) fail to migrate out of r4 in a wild-type host, while lzr/pbx4^-/- nV motor neurons (arrowheads) always extend axons correctly from lateral r2 when placed in a wild-type embryo. (D) In the reciprocal experiment, wild-type nVII motor neurons in a lzr/pbx4^-/- host migrate out of r4 and into more posterior rhombomeres (arrows), while wild-type nV axons (small arrowheads) often misroute from r4 with the nVII nerve. (E) Presumptive nVII motor neurons from a hoxb1aMO-injected donor fail to migrate in a wild-type host. (F) Wild-type nVII motor neurons migrate posteriorly in a hoxb1aMO-injected host. Scale bar, 100 μm.