Fig. 5. Fgf20a and Mps1 are required for homeostatic regeneration in zebrafish fins. (A,B) In situ hybridization for fgf20a and mps1 during regeneration and priming. fgf20a and mps1 expression is increased upon recovery of Fgf signaling (arrowheads), as described for mkp3 and msxb. Expression is undetectable by this method in wild-type fins. (C) Images of wild-type, fgf20a and mps1 mutant fins at day 0, day 30 and day 60 at the restrictive temperature (33°C). Both mutants exhibited a significant loss in distal tissue that was not seen in wild-type controls maintained at the restrictive temperature. (D) Quantification of length changes in centrally located rays of fgf20a and mps1 mutants. Both mutant strains showed a significant reduction in fin length after 30 and 60 days at the restrictive temperature, whereas wild-type controls maintained fin length (mean±s.e.m., Student's t-test, ^*P<0.001 at days 30 and 60).