RNA preparation and array hybridizations were performed at Rosetta Inpharmatics (Seattle, Washington, United States). The custom ink-jet microarrays used in this study (Agilent Technologies, previously described [21,34]) contain 2,186 control probes and 23,574 noncontrol oligonucleotides extracted from mouse UniGene clusters and combined with RefSeq sequences and RIKEN full-length clones.