RNase protection assay analysis of zfper4 (410-nt protected fragment, amino acid positions 88–225) and β-actin (282-nt protected fragment) was performed with RNA harvested at the indicated zeitgeber times (ZT0 is lights-on, ZT12 is lights-off) or CT. (A) Whole brain from adult zebrafish maintained in LD. (B) Six-day-old larvae raised in LD. (C) PAC-2 cells were maintained in LD for 5 days. Cells were entrained in LD and harvested in DD (D)orinLL(E). (F) Peak and trough samples from the LD, DD, and LL sets of PAC-2 cells (C–E) assayed together to allow comparison of the relative expression levels. (G) Larvae raised for 6 days in DD and then exposed to light for the indicated times (hours; + Light). Control larvae remained in DD and were harvested in parallel. (H) Analysis of PAC-2 cells equivalent to G.