Fig. 5: Light-controlled elimination of a specific embryonic cell population by expression of a toxic protein.

Zebrafish embryos were injected with mRNA encoding for the Kid toxin (blue), and with the standard translation-blocking morpholino (black) only (a) or with the same mix together with the cPMO2 (yellow with black stripes and pink shapes) (b, c). Embryos were then allowed to develop for 12 h. At this stage, some embryos (b - b”’) were kept in the dark, such that the translation of the mRNA was blocked by the translation-blocking morpholino, and no toxin was produced. Other embryos (a– a”’, c–c”’) were subjected to 405 nm laser irradiation at a specific region of the embryo (red dotted boxes). Laser irradiation in the absence of the PMO2 had no effect (a–a”’). Irradiation in the presence of the PMO2 (c–c”’) resulted in the photolysis of PMO2’s light-sensitive moieties, sequestration of the translation-blocking morpholino, translation of the RNA, and production of the toxin. Cell apoptosis was detected only in the irradiated region by 1 hour post-irradiation (c” red box, and c”’). (a”’, b”’, c”’) Embryos were subjected to immunostaining for the active caspase-3, a marker of apoptosis. The embryos in these panels are not the same as those presented in the bright-field panels left of them. Scale bar 150 μm.