(A–D) Immunohistochemical detection of proliferating cells (H3P-positive) 24 h (A, C) and 48 h (B, D) after proximal amputation. (A, B) control fin; (C, D) V-ATPase knocked down fin. (E) Quantification of H3P-positive cells in the blastema. *statistical significant results (p<0.05). (F–U) In situ hybridization for mkp3 (F-M) and aldh1a2 (N-U), after proximal amputation (F, H, J, L; N, P, R, T) and distal amputation (G, I, K, M; O, Q, S, U): (F–G; N–O) control fin, 24 hpa; (H–I; P–Q) V-ATPase knocked down fin, 24 hpa; (J–K; R–S) control fin, 48 hpa; (L–M; T–U) V-ATPase knocked down fin, 48 hpa. Control fin: caudal fin from AB wild type fish, non-treated. V-ATPase knockdown procedure: atp6v1e1b vivo-MO delivered to the caudal fin of atp6v1e1bhi577aTg/+ (AB) fish, 2 hpa. hpa: hours post amputation. For each panel, n = 3.