The exon and junction probes are 30-mer oligonucleotides synthesized by Integrated DNA Technologies (Coralville, IA, USA) or Illumina/Invitrogen (San Diego, CA, USA) and printed on poly-L-lysine slides at 50 mM along with Human Cot-1 DNA (Invitrogen), which is enriched for repetitive sequences, and herring sperm DNA (Promega, Madison, WI, USA), which was used as nonspecific control. The printing procedure has been described and essentially follows the manual of the DeRisi arrayer with silicon microcontact printing pins (Parallel Synthesis Technologies, Inc. Santa Clara, CA, USA) (25) (26) (27) . Arrays were postprocessed with succinic anhydride-based method for blocking before hybridization as previously described (27) . The protocols related to array printing and hybridization in this article generally can be found in the following link: http://cat.ucsf.edu/equipment/arrayer/index.html.