FIGURE 5

FIGURE 5

Axon guidance and outgrowth are unaffected in olt mutant larvae. (A,B) Lateral view with anterior to the left of the hindbrains of 5 dpf Tg(zCREST1:mRFP) larvae. The morphologies of trigeminal (V) and FBM (VII) axons were analyzed and number of branches were calculated with Leica Application Suite X (LAS X) software. e, eye. (C) The total lengths of trigeminal motor axons and FBM axons and their branches were similar between olt mutants and wildtype siblings. (D) Trigeminal motor and FBM axon branching numbers showed no significant differences between wildtype siblings and olt mutants. Statistical analysis was performed with a two-tailed student t-test (C,D). NS, not significant. Pooled data from 4 experiments (number of larvae in parenthesis). (E,F) Ventral view with anterior to the left of the jaw musculature in 5 dpf Tg(zCREST1:mRFP); Tg(α-actin:GFP) larvae showing motor axons (magenta) and jaw and gill muscles (green). (E) Thick motor axon fascicles were seen on the ima/imp, ih, and hh muscles in wildtype siblings. This phenotype was defined as Normal Fasciculation (NF). (F) In olt mutants, these axon fascicles appeared thinner and were frequently defasciculated (arrowheads), especially on the ih muscle. This phenotype was defined as Defasciculation (DF). (G) There was a preponderance of the defasciculated axon (DF) phenotype in olt mutants, and the proportion of normal fasciculation (NF) to defasciculated (DF) axons was significantly different between wildtype siblings and olt mutants. Statistical analysis was performed using Fisher’s two-tailed exact test. Data pooled from 4 experiments (number of larvae in parenthesis). **p < 0.0001. ima/imp, intermandibularis anterior/intermandibularis posterior; ih, interhyal; hh, hyohal. Scale bar (A,E), 100 μm.