Fig. 6

Fate determinant expression during regeneration does not recapitulate developmental sequence after different injuries. a, b) In uninjured control, a prolonged BrdU pulse labels neurons in the peripheral ciliary margin zone, which results in a stripe of BrdU positive cells after BrdU withdrawal, as BrdU negative cells continue to be added from the ciliary margin. This BrdU stripe is observed in micrographs from control (b). There are no BrdU cells in the mature retina found more centrally. c-h) Using prolonged exposure, BrdU labelled cells observed in this central mature retina region reflects regeneration. Micrographs show retinal sections from 14 days post-injury (dpi). The proportion of BrdU positive GCL cells after mechanical injury (n = 17 larvae - 10 dpi, 9 larvae −14 dpi, 12 larvae - 17 dpi) is higher compared to genetic injury (n = 8 larvae - 10 dpi, 15 larvae - 14 dpi, 19 larvae - 17 dpi) at 10 and 14 dpi. The firstborn ganglion cell marker Tg(atoh7:GFP) shows more co-labelling after mechanical injury. A large proportion of BrdU positive labelled cells in the bipolar layer (outer half of INL) show high expression of Tg(vsx1:GFP) indicative of bipolar differentiation (last born during development) after both injuries, starting earlier after mechanical (n = 13 larvae - 10 dpi, 24 larvae - 14 dpi, 21 larvae - 17 dpi) than genetic (n = 14 larvae - 10 dpi, 21 larvae - 14 dpi, 11 larvae - 17 dpi) injury. For both injuries, strongly labelled Vsx1 cells are observed prior to strongly labelled Atoh7 GCL cells. Results are mean ± SEM ONL: outer nuclear layer; OPL: outer plexiform layer; INL: inner nuclear layer; IPL: inner plexiform layer; GCL: ganglion cell layer. Scale bar B = 100 μm, scale bar C (for c, d, f, g) = 50 μm, scale bar in insets C (for insets in c, d, f, g) = 20 μm