Identification of genes whose expression is affected by Delta RNAi in spider embryos

In the spider Parasteatoda tepidariorum embryo, Delta-Notch signaling plays a key role in early development of the opisthosomal region by regulating the balance between the caudal ectoderm and mesoderm fates (Oda et al., 2007, Development 134, 2195-2205). In this microarray experiment, we attempted to identify candidate genes whose expressions are regulated by Delta-Notch signaling during early phases of the caudal development. The objective of this experiment was a screen for genes whose expressions might be affected by parental RNA interference (pRNAi) against Pt-Delta in spider embryos. Oligonucleotide probes were designed based on accumulated P. tepidariorum EST and cDNA sequences and embedded in a custom microarray (12K). Total RNA was extracted from late stage 5 embryos derived from a mated female before and after injection of dsRNA targeted for Pt-Delta. Gene expression levels were compared between the untreated (normal) and the Pt-Delta pRNAi-treated samples. Probes for a homolog of Drosophila caudal, Pt-cad (GB_ACC: AB096075.1; GI: LOC107437910), served as positive controls to validate this experiment.