LGALS4 and retinal degeneration: To confirm that the effect of C9orf72 RNA on the retrograde transport can be related to its ability to generate DPRs, we downregulated either ArfGAP-1 or ERGIC-53 in flies expressing 36 repeats of the GR dipeptide late during eye development under GMR-GAL4 at 25 °C [27], a condition that is sufficient to induce massive retina degeneration.