Schematic diagram of the calpastatin (CAST) type II, type III ex2-ex4, and type III ex3 mRNA splice variants. Truncated mRNA transcripts are depicted. Exon numbers are marked within the boxes, including the exon 1 splice variants (1xb, 1xu, 1xy, 1xz). The arrows at the 5′ end of each variant indicate the location of the transcript-specific PCR primers. The arrows above exons 27 and 28 mark the location of the primers that were used to measure “total” calpastatin mRNA levels. The positioning of the pA1 and pA2 polyadenylation signals and the distance between them in kb are marked on the 3′ untranslated region (3’UTR). The location of the CAST:c.2832A > G SNP is shown and the arrows upstream of the pA1 and pA2 sites mark the locations of the CASTpA1 and CASTpA2 primers, respectively.