(A) fst(RNAi) animals did not form blastemas after amputation (left, arrowheads, n > 100) and did not regenerate a brain as assayed with an RNA probe for choline-acetyltransferase (chat, middle, arrowhead, n = 9/9). (B) fst(RNAi) animals did not form blastemas 8 days following excision of a wedge of lateral tissue (arrowhead, n = 14/14). (C) fst(RNAi) animals displayed no phenotype in the absence of amputation (right, n = 30/30, 123 days RNAi). (D) fst(RNAi) animals still produced new neurons 20 days after failing to regenerate (n = 8/8; cells that are SMEDWI protein+ and chat+ are newly differentiating neurons [Wagner et al., 2011]), demonstrating ongoing tissue turnover in old tissues. Scale bar 10 µm. (E) fst was expressed sparsely throughout the intact animal and at the anterior pole. Following head and tail amputation, robust fst expression occurred at both anterior and posterior wound sites, with peak expression 12 hr post-amputation. Scale bars = 100 µm for left of (A), (B), and (C); 200 µm for right of (A) and (E). Anterior up.