Detection of SMN1/2 transcripts containing exons 6 and 7a and the effect of CHX on expression. (a) Scheme of the transcript and positions of RT–PCR primers. (b) Nucleotide sequence analysis of the PCR product from control fibroblasts. Uppercase letters indicate exon 7a nucleotides, and lowercase letters indicate nucleotides from flanking introns. Red letters indicate premature termination codons. (+504) and (+654) mean c.834+504 and c.834+654, which represent the locations of the first and last nucleotide in the table. (c) Semi-quantitative analysis using an Agilent 2100 Bioanalyzer. First, RT–PCR products for SMN1/2 transcripts with exons 6 and 7a were separated by agarose gel electrophoresis. Then, SMN1/2 transcripts with exons 6 and 7a (SMN exon 7a-containing transcript) were semi-quantified using a DNA 7500 LabChip Kit with an Agilent 2100 Bioanalyzer (Agilent Technologies, Inc., Santa Clara, CA, USA). In this study, ‘the relative expression level of the SMN exon 7a-containing transcript’ refers to the relative RT–PCR product ratio of the SMN exon 7a-containing transcript to the GAPDH transcript. The relative expression level of the exon 7a-containing SMN transcript in CHX-treated cells was significantly higher than that in non-treated control fibroblast cells (‘Mock’) (single-factor analysis of variance, P<0.001). The difference between them was almost fourfold.