Microarray experimental design, analysis and validation. To induce AP-1 in the nervous system, 1–3 day old adult ElavGS-GAL4-AP1 flies were treated with the synthetic steroid hormone RU486 in 2% sucrose or sucrose alone for six hrs. Biotinylated RNA from heads was created and hybridized to Affymetrix Drosophila Genome1 GeneChip arrays. Gene expression changes between AP-1 induced and control samples were considered significant if they passed a statistical (P < 0.01, Student's t-test) and secondary filters looking at variance in untreated control samples from the same experiment. Validation of candidate gene expression changes was carried out using quantitative real-time RT-PCR and in situ hybridization experiments.