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Fig. 2 The Initial Scale Osteoblast Pool Regenerates by De Novo Differentiation (A–E) A single scale was cleared of overlapping scales (A and A’), osteoblasts were photoconverted to red (B and B’), and the scale was removed (C and C’). One day later, all osteoblasts present had no detectable photoconverted protein (D–E’). (A)–(D) were acquired with a fluorescence dissecting scope (scale bar represents 250 μm); (E) was acquired with a confocal microscope (scale bar represents 50 μm). (F–H) Scales were allowed to regenerate to 24, 30, and 36 hpp and then photoconverted and imaged again at 36 (F and F’), 42 (G and G’), and 48 hpp (H and H’), respectively. The average fraction of red-expressing area for each time point is indicated in the bottom left corner of each image (n = 6 scales per time point). Scale bar represents 100 μm. (I–K) Representative pictures from a video of scale regeneration in osx:H2A-mCherry fish, acquired from 23 to 43 hpp. Colored nuclear outlines indicate tracked nuclei. Outlines present in (J) and (K), but not in (I), represent nuclei first detected later in the video; outlines of the same color indicate daughter nuclei of a dividing nucleus. Scale bar represents 10 μm. (L) Fluorescence levels of tracked nuclei. Line colors correspond to outlines in (I)–(K). Splitting of one line into two denotes mitosis. (M) Average fluorescence level of 91 tracked nuclei relative to their peak from 60 min before to 60 min after anaphase. By 60 min post-anaphase, nuclear fluorescence decreased 36.1% from its peak but increased 12.5% from the start of tracking.