Lateral view, immunostaining of severed pLL nerves proximal (A–D) and distal (A’–D’) to injury site, 3 hr post-injury; dotted line = nerve outline. (A,B) tRet immunostaining is not notably different between wild-type siblings (A,A’) and jip3nl7 mutants (B,B’) on either side of injury site. (C,D) p905Ret staining is mostly absent in wild-type siblings proximal to injury site (C) and jip3nl7 mutants on both sides of the injury site (D,D’). Scale bar = 10 μm. Stronger p905Ret staining signal is present in wild-type siblings distal to the injury site (C’), indicating presence of retrograde transport of activated Ret receptor in the axon. (E,F) Quantification of tRet (E; WT n = 12, jip3nl7 n = 14) and p905Ret (F; WT n = 12, jip3nl7 n = 12) staining following axon sever displayed by whisker plot (*=p < 0.05). Note p905Ret signal in wild-type siblings is significantly higher than in jip3nl7 mutants, suggesting a failure of retrograde transport of pRet receptor in mutants. (G–J) Kymographs of trafficking in individual pLLG axons of Ret51-mCherry (G,H; Ret51 construct trafficking further shown in Figure 5—figure supplement 1) and TrkB-mCherry fusions (I,J) in wild-type siblings and jip3nl7 mutants. (G’–J’) Kymograph traces of scored anterograde (blue) and retrograde (magenta) transported particles. (K) Quantification of normalized anterograde particle counts from kymograph analysis (wild type Ret51 = 5.93 ± 0.52 vs. jip3nl7 Ret51 = 5.53 ± 0.76, p=0.44 by Mann-Whitney U test; wild type TrkB = 3.58 ± 0.42 vs. jip3nl7 TrkB = 3.36 ± 0.86, p=0.82). (L) Quantification of normalized retrograde particle counts from kymograph analysis (wild type Ret51 = 7.33 ± 1.17 vs. jip3nl7 Ret51 = 4.73 ± 0.53, p=0.03; wild type TrkB = 3.07 ± 0.31 vs. jip3nl7 TrkB = 3.06 ± 0.75, p=1.00). jip3nl7 mutants show a significant decrease in the number of retrogradely transported Ret51-mCherry particles but no change in TrkB-mCherry particle counts or anterograde Ret51-mCherry particles. *=p < 0.05. Error bars represent S.E.M.