Fig. 1

Intron 1 retention in C9orf72 transcripts in lymphoblasts. C9orf72 transcripts were analyzed in lymphoblasts from C9orf72 G₄C₂ expansion carriers and control individuals. a RT-PCR analysis of poly(A)⁺ RNA using primers spanning the 5’ splice site (left) or the 3’ splice site (right) of intron 1 demonstrating retention of intron 1in polyadenylated RNA. The position of the primers is indicated on the diagram above the gels. GAPDH was used as a loading control. b Correctly spliced transcripts detected in controls and expansion carrier cells using primers in exons 1a and 2. c Quantitative analysis of intron retention by real-time PCR. Levels of C9orf72 transcripts spliced or unspliced at the 5’ and 3’ end of intron 1 were determined by real-time qRT-PCR. Data are shown as means ± SEM. Each data point represents an individual case, n=15 (C9^-); 15 (C9⁺). No significant differences were observed between the C9⁻ and C9⁺ groups. d Sequencing of the 3’ PCR product demonstrates an exact intron 1-exon 2 boundary. C9⁻, controls; C9⁺, expansion carriers