Article Figures & Data
Figures
- Fig. 1.
Schematic representation of the netrin UNC-6 protein and UNC-6 derivatives used in this study. UNC-6 comprises an N-terminal domain VI (residues 1–268) similar to the N-terminal domain VI of laminin subunits, three cysteine-rich repeats (residues 269–437) similar to those of domain V of laminin subunits, and a C-terminal domain named C (residues 438–591) that is not found in laminins but is phylogenetically conserved among other extracellular proteins. An epitope tag comprising three tandem copies of the HA epitope was engineered into a site immediately after the predicted signal peptide (SP).
- Fig. 2.
Summary of cell and axon positions.A, Cell bodies and axons of representative sensory and motor neurons. The migration of the axons of DA and DB motor neurons and of SDQR were assayed to measure the ability of unc-6mutations and transgenes to guide dorsal axon migrations. Only DA motor neurons are represented for simplicity. PVCL and AVM axons were assayed to measure ventral axon migrations. B, Migrating mesodermal cells, the distal tip cells, and the anchor cell were assayed to measure dorsal and ventral cell migrations, respectively. Details of the phenotypes of these cells in unc-5, unc-6, and unc-40 mutants were reported byHedgecock et al. (1990). Anterior is to the left; dorsal is at top.
- Fig. 3.
Dorsal axon migrations of DA and DB motor neurons.A, In wild-type animals, the DA and DB cell bodies (arrowheads) are positioned along the ventral nerve cord, and each has an axon that migrates longitudinally along the ventral nerve cord (vc) and an axon that migrates circumferentially to the dorsal nerve cord (dc). B, In some mutants, the dorsal circumferential migration defects are relatively mild. In thisunc-40 mutant, a single axon (arrows) has abnormally migrated at the dorsal sublateral position and fails to reach the dorsal nerve cord. C, In unc-6mutants, the axons rarely reach the dorsal nerve cord. In thisunc-6 mutant, most axons turn and migrate at the ventral sublateral and lateral positions (arrows). Anterior is to the left; dorsal is at top. Scale bars, 25 μm.
- Fig. 4.
Ventral axon migrations of PVC in the tail region.A, In wild-type animals, the PVC neurons extend an axon ventrally along the lumbar commissure to the ventral nerve cord (vc). The left PVC neuron (PVCL) is shown. B, In unc-6 mutants, the PVC axons often migrate at the lateral position instead of directly entering the ventral nerve cord. In this animal, the axon from the left PVC neuron (PVCL) has migrated laterally, whereas the axon from the right PVC neuron (PVCR) has correctly migrated to the ventral nerve cord. Anterior is to the left; dorsal is at top. Scale bars, 10 μm.
- Fig. 5.
A summary of the proposed function for each of the UNC-6 domains. The combination of domains elicits parallel signals that together mediate the different cytoskeletal changes necessary for guidance.
Tables
unc-6 transgene Genetic background Dorsal guidance (% defective) Ventral guidance (% defective) Axon guidance Cell guidance Axon guidance Cell guidance DA, DB1-a SDQR1-b DTC1-canterior DTC1-cposterior PVCL1-d AVM1-e EGL1-f Wild type 0 2 ± 1 0 0 0 0 0 unc-6(+) unc-6(ev400) ND 3 ± 1 0 0 ND 0 0 unc-6(ev400) 98 ± 2 91 ± 3 38 ± 1 62 ± 3 39 ± 2 27 ± 2 55 ± 2 unc-40(e1430) 25 ± 1 57 ± 4 9 ± 3 25 ± 2 26 ± 1 15 ± 2 49 ± 1 unc-5(e53) 99 ± 1 95 ± 2 40 ± 3 64 ± 1 0 0 0 unc-40(e1430); unc-6(ev400) 99 ± 1 94 ± 3 43 ± 3 65 ± 4 30 ± 2 25 ± 3 73 ± 3 unc-5(e53); unc-6(ev400) 99 ± 1 93 ± 4 45 ± 3 73 ± 3 35 ± 2 25 ± 1 58 ± 2 unc-6ΔV-1 unc-6(ev400) 0 3 ± 1 0 0 0 0 0 unc-6ΔV-2 unc-6(ev400) 99 ± 2 85 ± 3 43 ± 2 61 ± 2 5 ± 2 14 ± 3 34 ± 1 unc-6(rh204) 94 ± 1 88 ± 4 40 ± 3 57 ± 5 0 11 ± 2 16 ± 2 unc-6V-1-3-3 unc-6(ev400) 98 ± 3 89 ± 2 40 ± 4 64 ± 4 13 ± 3 10 ± 1 37 ± 3 unc-6ΔV-3 unc-6(ev400) 95 ± 2 89 ± 2 35 ± 2 65 ± 3 16 ± 2 8 ± 3 50 ± 3 unc-6(e78) 90 ± 2 80 ± 2 0 15 ± 1 0 0 10 ± 1 unc-6ΔC unc-6(ev400) 9 ± 2 56 ± 4 3 ± 3 13 ± 2 4 ± 1 18 ± 2 30 ± 2 ↵F1-a The DA, DB motor neuronal cell bodies are located along the ventral nerve cord, and from each an axon migrates dorsally to the dorsal nerve cord.
↵F1-b The SDQR neuron cell body is located laterally, and the axon migrates dorsally to the dorsal sublateral nerve in the larva.
↵F1-c The hermaphrodite gonad is created by the migrations of the two distal tip cells, which at one point migrate dorsally. In the mutants, the distal tip cells may fail to migrate dorsally and instead migrate along the ventral muscle quadrant.
↵F1-d The PVCL neuron cell body is located posteriorly, and the axon migrates ventrally into the ventral nerve cord.
↵F1-e The AVM neuronal cell body is located laterally, and the axon migrates ventrally to the ventral nerve cord.
↵F1-f L4 stage hermaphrodites were placed individually onto seeded plates and examined at 12 hr intervals to determine whether any eggs were laid. Animals were scored as abnormal if they were incapable of egg laying. Three independently derivedunc-6 transgenic strains were counted for each phenotype.n = 100. Mean ± SEM.
unc-6 transgene Genetic background Axon guidance (% defective) Cell Guidance (% defective) DA, DB SDQR DTC anterior DTC posterior Temperature (°C) 15 20 25 15 20 25 15 20 25 15 20 25 unc-6(ev400) 97 97 98 90 91 93 33 38 40 65 62 64 unc-40(e1430) 23 25 24 54 57 55 8 9 8 20 25 23 unc-5(e53) 98 99 99 90 95 92 41 40 43 65 64 67 unc-40(e1430); unc-6(ev400) 99 99 99 92 94 93 42 43 45 66 65 67 unc-5(e53); unc-6(ev400) 98 99 99 95 93 95 46 45 47 74 73 75 unc-6(rh46 ev436) 4 10 95 48 63 90 3 8 15 10 36 45 unc-6(rh46) 48 94 98 67 93 95 25 44 47 45 75 78 unc-6ΔVI8β unc-6(ev400) 51 98 98 70 90 95 32 41 40 50 73 71 unc-6ΔVI unc-6(ev400) 98 98 99 90 93 92 46 45 46 73 72 75 unc-6 transgene Genetic background Axon guidance (% defective) Cell guidance (% defective) PVCL AVM EGL Temperature (°C) 15 20 25 15 20 25 15 20 25 unc-6(ev400) 36 39 39 25 27 25 54 55 56 unc-40(e1430) 23 26 28 16 15 17 48 49 50 unc-5(e53) 0 0 0 0 0 0 0 0 0 unc-40(e1430); unc-6(ev400) 32 30 35 26 25 27 72 73 75 unc-5(e53); unc-6(ev400) 36 35 39 25 25 23 60 58 61 unc-6(rh46 ev436) 0 3 25 0 15 20 15 43 55 unc-6(rh46) 20 38 48 13 23 30 32 51 77 unc-6ΔV18β unc-6(ev400) 16 30 59 12 25 32 23 58 80 unc-6ΔVI unc-6(ev400) 53 55 58 36 35 37 75 78 79
