(A) Cartoon representation of intron 6-intron 8 of the ERGIC-53 gene. The primers used for the RT-PCR analysis are indicated by an arrow and the asterisk indicates the position of the IVS7-1 mutation. Potential RT-PCR products resulting from normal splicing, inclusion of intron 7 or skipping of exon 7 are shown. (B) Agarose gel electrophoresis of the RT-PCR products after amplification of polyadenylated RNA with ERGIC-53 exon 6-exon 8 specific primers and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) specific primers. The GAPDH amplification was a control for mRNA integrity. The cDNA synthesis was primed with the exon 8 specific primer and oligo dT. Lane M, markers; lane 1, individual A2 (homozygous 822G > A); lane 2, individual A12 (homozygous 822G > A); lane 3, human endothelial cell line; lane 4, unaffected individual; lanes 5, 6, and 7, affected individuals with the M1T mutation; lane 8, no DNA control. The arrow marks the normally spliced product. The asterisk marks the incorrectly spliced product. (C) DNA sequence chromatograms of: 1, the incorrectly spliced product, resulting from skipping of exon 7, observed in RT-PCR of polyadenylated lymphoblastoid RNA from individual A12; 2, the major product observed in RT-PCR of polyadenylated RNA from a human endothelial cell line. The exon boundaries are indicated by an arrow.