Splicing of wild-type and Arg134Xaa mutant mRNAs. (A) Schematic representation of the FGG gene showing the C>T change in the penultimate base of exon 4 that creates a premature termination codon (TGA) with the first base of exon 5. The horizontal arrows indicate the positions of the oligonucleotide primers used to produce the wild-type and mutant minigenomic constructs for mRNA analysis. (B) RT-PCR analysis of COS-7 cells transfected with wild-type (wt) and Arg134Xaa mutant (mut) minigenomic constructs followed by agarose gel electrophoresis indicates normal splicing for both constructs. The arrow indicates the normal mRNA product (expected size, 620 bp). Sequencing of these RT-PCR products confirmed normal splicing for both wild-type and mutant constructs. M indicates 1-kb DNA ladder marker; RT-, negative controls with heat-inactivated enzymes (“Patients, materials, and methods”).