Fig. 1

Loss of wnt11r and wnt4a phenocopies musk (unp) mutant. (A-K) Lateral view of trunk (top, dorsal; left, anterior) stained for AChR clusters (bungarotoxin, red) and motor axons (znp-1, green) in 20-somite and 26 hpf zebrafish embryos. (A,B) Three hemisegments in a wild-type embryo (hemisegment boundaries marked with dashed lines) with pre-patterned AChR clusters along the center of each hemisegment (cluster width marked by bracket; A) and three wild-type hemisegments in which motor axons have made synaptic contacts along the length of the trunk (B). (C,D) Three hemisegments in a musk (unp) mutant showing the absence of clustered AChRs, resulting in a complete dispersion of AChRs (C) and axon guidance errors in 26 hpf musk (unp) mutants (arrow points to axon branch) which occur in 85% of axons (D). (E-G) A single hemisegment from a wnt11r embryo showing an expanded AChR pre-pattern (width bracketed, 61% occurrence; E), and a single hemisegment showing a complete loss of AChR pre-pattern (39% of occurrence; F). Three hemisegments in a 26 hpf wnt11r mutant showing musk (unp)-like axon branching (arrow) in 26% of axons (G). (H,I) Three hemisegments in a wild-type embryo injected with 10 ng of wnt4a morpholino showing wild-type-like pre-patterning (H) and wild-type-like axons with only 6% guidance errors (I). (J,K) Three hemisegments from a wnt11r mutant injected with 10 ng of wnt4a morpholino showing musk (unp)-like AChR dispersal in all hemisegments (J) and guidance errors in 70% of axons (K). (L) Quantification of increase in AChR pre-pattern width in wnt11r mutants compared with wild type or wnt4a morpholino injected (P=0.01 for wild type vs wnt11r mutant, P=0.02 for wnt11r mutant vs wnt4a morpholino injected and P=0.38 for wild type vs wnt4a morpholino injected; Student’s two-tailed t-test, unequal variance; error bars indicate s.e.m.). Scale bars: 10 μm.