Exon-centric microarrays detect Ca2+-mediated changes in transcript and exon abundance. (a) Potassium chloride (KCl)-induced membrane depolarization and thapsigargin (TPG) treatment increase intracellular calcium (Ca2+) concentrations via extracellular Ca2+ influx through plasma membrane channels and via release of Ca2+ from intracellular stores, respectively. Ca2+ (green) acts as a second messenger to effect gene expression. (b) Whole transcripts (i) and individual exons (ii) that exhibit a change in abundance in response to KCl or TPG can be identified because of the distribution of probes selection regions (PSRs; purple) into exonic regions (orange indicates a change in abundance). All of the PSRs of a transcript are used to determine transcript abundance, whereas the PSRs of an exon are used to determine exon abundance. The inclusion of an exon or transcript into one of two separate datasets (transcript or exon) was determined using a combination of fold change and statistical significance cut-offs (see text).