To supplement fragmentary prior descriptions of the human tissue-specific expression of PPP3CA isoforms, we studied expression patterns in eight brain regions and nine peripheral tissues using relatively quantitative Taqman assays. MGB probes were designed according to junction sequences of two alternatively spliced exons [Figure 1(B) and S3] to avoid detecting genomic DNA. We selected CNEX1-3 expression in amygdala as “100%” reference, and compare isoform expression data from other brain regions and peripheral tissues to this value (Table 3). The most prominent isoforms, CNEX1-3 and 13-14, are expressed at the highest levels in caudate and putamen (200%–400% of amygdala levels), high levels in cortex, amygdala, cerebellum, and hippocampus (100%–200%), and lower levels in hypothalamus and substantia nigra (5%–20%). CNEX1-3 and 13-15 were expressed at intermediate levels in leukocytes, muscle, spleen, and testis (7%–36%). CNEX13-14 contains a 10 amino acid insertion [Figure 2(B), 427-ATVEAIEADE-436] as compared to CNEX13-15. CNEX13-14 is more concentrated in brain, whereas CNEX13-15 is more concentrated in peripheral tissues (Table 3). CNEX1-2, CNEX1-4, and CNEX9-11 with truncated N-terminus, partial deletion of phosphatase domain, and complete deletion of subunit b
