Kha CX , Tseng KA .

Figure 1. Restoration of visual function requires eye regrowth.(A) Representative images showing effects on eye regrowth after apoptosis inhibitor treatments (M50054 or NS3694) at 6 days post surgery (dps) as compared to a DMSO-vehicle control (n = 12 per condition). Green arrowhead indicates a DMSO-treated regrowing eye. Red arrowheads indicate regrowth-inhibited eyes. To assay for visual function of a single eye, the right contralateral eye was removed for all conditions (shown in bottom middle and right panels). Top panels: dorsal is up, and anterior is to the left. Bottom panels: anterior is up. Scale bar: 500 µm. (B) DMSO-treated tadpoles with either one normal or one regrown eye display white background preference. Tadpoles with an uninjured eye treated with an apoptosis inhibitor also showed white background preference (n = 12 per condition, P> 0.05). Tadpoles with a regrowth-inhibited eye resulting from treatment with an apoptosis inhibitor lost white background preference (n = 12 per condition, *P < 0.01).

Figure 2. Eye regrowth declines with increasing age.The Regrowth Index (RI) is a measure of eye regrowth quality (Kha et al., 2018). Each regrown eye is assigned to one of four phenotypes: full (comparable to an unoperated control eye), partial (minor abnormalities with some reduction in size), weak (no lens and small size), and none (no regrowth). To obtain the RI value, the number of tadpoles in each category is multiplied by: 3 (full), 2 (partial), 1 (weak), or 0 (none), added together, and then divided by total number of tadpoles. A value of 300 denotes full regrowth in all individuals in the group whereas a value of 0 denotes no regrowth in all individuals. (A) At 5 days post surgery (dps): developmental stage. 27, RI = 281 (n> 100); st. 28 RI = 251 (n = 67); st. 29–30, RI = 159 (n = 142); st. 31, RI = 82 (n = 106); st. 32, RI = 37 (n =113); and st. 33–34, RI = 10 (n = 70). *P < 0.01, vs. st. 27. (B) Representative images showing resulting eyes at 5 dps. Corresponding top and bottom panel show side and top views of the same tadpole. (B1, B1’) Unoperated control eye indicated by yellow arrowheads. (B2, B2’) st. 27. (B3, B3’) st. 28. (B4, B4’) st. 29–30. (B5, B5’) st. 31. (B6, B6’) st. 32. (B7, B7’) st. 33–34. Green arrowheads: Full regrown eyes; orange arrowheads: partial eye regrowth; red arrowheads: no regrowth. Top panels: dorsal is up and anterior is to the left. Bottom panels: anterior is up. Scale bar: 500 µm.

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