mem, a Temperature-Sensitive Mutant Defective in Fin Regeneration (A) Whole-mount images of adult mem/+ and mem fin regenerates at 4 and 7 dpa (days post-amputation). Red arrows indicate amputation plane. Scale bar, 1 mm. (B) Schematic timeline of three distinct phases during zebrafish fin regeneration. Green bar indicates the wound healing phase. Orange bar indicates the blastema formation phase. Blue bar indicates the regenerative outgrowth phase. (C) Measurement of mem fin regenerate length in fish maintained at 26°C at 4, 7, 14, and 28 dpa (n = 20 mem/+, 17 mem; mean ± SD; Student’s t test; NS, non-significant). (D) Measurement of mem fin regenerate length at 7 dpa. The 2nd lateral bony ray from the dorsal side was measured to represent tailfin length. After amputation, animals were shifted from the permissive temperature (26°C) to the restrictive temperature (33°C) at 0, 1, 2, or 4 dpa (n = 31 mem/+, 35 mem; 32 mem/+, 30 mem; 31 mem/+, 33 mem; and 31 mem/+, 32 mem; mean ± SD; Student’s t test; ∗∗∗p < 0.001). (E) Whole-mount images of mem fin regenerates at 21 dpa (n = 91 mem/+, 94 mem; mem regenerates were highly variable in shape and size). Animals were kept at the restrictive temperature from day 0 to 7 dpa. Red arrows indicate amputation plane. Scale bar, 1 mm. (F) Shape factors of mem regenerates at 21 dpa are shown in box and whisker plots. Left: aspect ratio was determined as the ratio of the major axis of the regenerate to the minor axis. Right: circularity index was determined as the ratio of the regenerate size to the area circled by a perimeter (n = 48 mem/+, 42 mem; median values are shown; boxes indicate the 25% and 75% percentiles; bars, the minimum and maximum values). (G) Top: schematic timeline of temperature shifts after fin amputation. Red bar indicates the period at 33°C. Bottom: measurement of mem fin regenerate sizes at 21, 60, 90, and 120 dpa are shown. After 7 days at the restrictive temperature, animals were maintained at the permissive temperature for a 4-month period (n = 24 mem/+, 22 mem). See also Figure S1.
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