CLK GP50 antibody only detects oscillator cells in adult brains. Brains were dissected from adults collected at ZT21, immunostained with CLK GP50 and PER antisera, and imaged by confocal microscopy. (A-C) A 66 μm projected Z-series image of a wild-type adult fly brain, where lateral is left and dorsal is top. CLK (A), PER (B) and CLK + PER (C) IR is detected in dorsal neurons (DN1s, DN2s, DN3s), lateral posterior neurons (LPNs), and lateral neurons (s-LNvs + l-LNvs). Co-localization of CLK (red) and PER (green) is shown as yellow. (D) A 64 μm projected Z-series image of a ClkJrk adult fly brain, where lateral is left and dorsal is top. No CLK or PER staining is detected. All images are representative of three or more independent experiments.