For EdU pulse labeling, EdU from the Click-iT Alexa Fluor 647 Imaging Kit (Life Technologies #C10340) was diluted to 2.5 mg/ml for retro-orbital injection. Each killed fish examined at 5 wpf was injected with 1 μl EdU solution, whereas 1.5 μl was used for 6 wpf fish. Fish were fixed 2  h post injection for cryo-sectioning; EdU detection was performed according to the manufacturer’s protocol.
Cryo-sectioning and immunofluorescence staining were performed as previously described.44 (link) Antibodies against EGFP (Life Technologies #A6455 and #A11120), Fib (Abcam #ab4566) and activated caspase-3 (BD Biosciences #559565) were used as primary antibodies. Secondary antibodies were conjugated with Alexa 488, 568, 647 (Life Technologies). DAPI (Life Technologies #S36973) was used for nuclear staining. Fluorescent images were taken by a Leica SP5X scanning confocal microscope at the Confocal and Light Microscopy core facility at Dana-Farber Cancer Institute.
Paraffin sectioning, H&E staining and immunohistochemistry with primary antibodies against TH (Pel-Freez #P40101, Rogers, AR, USA), HuC/D (Life Technologies #A-21271) and synaptophysin (Millipore #MAB5258, Billerica, MA, USA) were performed at the DF/HCC Research Pathology Core, and fluorescence-activated cell sorting at DFCI Flow Cytometry Core according to standard protocols.