Effect of light on gene expression in the zebrafish pineal gland

Microarray data allowed detection of genes that are induced by light in the zebrafish pineal gland Adult (0.5-1.5 years old) transgenic zebrafish, Tg(aanat2:EGFP)Y8, which express enhanced green fluorescent protein (EGFP) in the pineal gland under the control of the aanat2 regulatory regions, were used. Fish were raised under 12-hr light:12-hr dark (LD) cycles, in a temperature controlled room. Fish were transferred to constant darkness (DD) at the end of the day prior to the experiment. Fish were exposed to a 1-hr light pulse (light intensity of 12 W/m2) prior to sampling (light treatment) or kept under constant darkness for control (dark treatment). The tissues were collected from light- and dark-treated fish at 6 time points with 4-hr intervals throughout one daily cycle, corresponding to CT2, 6, 10, 14, 18 and 22. Fish were anesthetized in 1.5 mM Tricane (Sigma), sacrificed by decapitation, and pineal glands were removed under a fluorescent dissecting microscope. Pools of 12 pineal glands were prepared at each condition and total RNA was extracted using the RNeasy Lipid Tissue Mini Kit (QIAGEN), according to the manufacturer's instructions.