a–d, Representative transverse sections of the morpholino-electroporated/protein-injected blastemas that were used for quantification of BrdU incorporation in Fig. 4d. Rhodamine was co-injected with the protein samples. e, Quantification of BrdU+ cells in blastema sections of morpholino-electroporated/protein-injected tails at 3 dpa (n = 4: biological replicates; centre values as median; points represent each sample). f, The length of the blastema during tail regeneration. The data at 6 dpa were plotted in Fig. 4c. By 14 days the difference in total regenerate length among the samples was not statistically significant. g–j, The same experimental scheme (shown in Fig. 4a) as was used for AxMLP morpholino 1 was implemented for a second specific morpholino (AxMLP-specific morpholino 2). g, Bright-field images of the morpholino-2-electroporated/protein-injected tails at 6 dpa. Red bars indicate amputation planes. Dashed lines delineate the shape of the mesenchymal blastema. h, Blastema length at 6 dpa (n = 4: biological replicates; centre values as median; points represent each sample). i, The length of the blastema during tail regeneration. The data at 6dpa were plotted in h. j, Transverse sections immunostained for BrdU from morpholino-electroporated/protein-injected tails at 3 dpa. AxMLP-specific morpholino 2 combined with flow-through (FT) injection shows reduction of BrdU incorporation, whereas AxMLP protein injection rescues the phenotype. The corresponding five-mismatch control morpholino does not affect BrdU incorporation. Yellow circles indicate spinal cord (top) and notochord/cartilage (bottom). NS, not significant; **P < 0.005, ***P < 0.0005, ****P < 0.00005 with Student’s t-test. Scale bars, 200 μm (a–d, j); 500 μm (g).