Viral Injections in Zebrafish Retina

Viral injections were performed as previously described (Beier et al., 2016 (link); Ma et al., 2020 (link)). Briefly, VSV and lentivirus stock was diluted to final working concentrations (described in the "Results" section) with DMEM (11995073; Fisher Scientific), with Fast Green dye (BP123-10; Fisher Scientific) as the injection marker. Glass capillaries (TW100F-4; World Precision Instruments) were pulled into injection needles with a pipette puller (P-97; Sutter Instruments), and the tips were trimmed to create a ~10 μm opening. The injection needle was mounted into a microelectrode holder connected to a pneumatic PicoPump (World Precision Instruments). For retina injection, 3 dpf larvae were anesthetized in Tricaine (0.013% w/v, AC118000500; Fisher Scientific) and mounted laterally inside the center chamber of a glass-bottom dish (P50G-1.5-14-F; MatTek) with 1.5% low melting-point agarose (BP1360; Fisher Scientific). 0.5 nl of virus solution was injected inside the temporal retina.