Fig. 2
lrp4 is required non-cell-autonomously for axonal growth during regeneration. a Lateral view of a wild-type motor nerve labeled with GFP before laser transection at 5 dpf, with transection site marked by yellow box. Scale bar is 10?µm. b Six hours post transection (hpt), motor axons distal to the transection site have fully degenerated. c Forty-eight hours post transection, motor axons have regrown along their original path; green arrowheads indicate multiple regenerated fascicles; this representative nerve received a score of ?best? regeneration. d Lateral view of lrp4 mutant motor nerve labeled with GFP before laser transection at 5 dpf, with transection site marked by yellow box. e Six hours post transection, distal motor axons have fully degenerated. f Forty-eight hours post transection, motor axons have sprouted from the proximal stump but most fail to cross the injury site (open blue arrowheads); green arrowhead indicates stalled fascicle; this representative nerve received a score of ?worst? regeneration. g Quantification of nerve regeneration in wild type and lrp4 mutant larvae. In wild type, 85% of nerves regenerate ?best? with two or more distinct fascicles (n?=?26 nerves from 13 larvae). In lrp4 mutants, 70% of nerves regenerate zero or one fascicle (n?=?28 nerves from 13 larvae) by 48?h post transection. Wild-type siblings regenerate significantly better than lrp4 mutants (?2-test p?<?0.0001, ?2?=?18.48, df?=?2). h Quantification of nerve regeneration in lrp4 mutant larvae and lrp4 mutant larvae expressing the motor neuron-specific mnx1:Lrp4-GFP transgene. At 48 hpt, lrp4 mutant larvae expressing Tg(mnx1:Lrp4-GFP) regenerate poorly (n?=?15 nerves from 6 larvae), like lrp4 mutant larvae (n?=?9 nerves from 4 larvae; ?2-test p?=?0.9266, ?2?=?0.1524, df?=?2)