RT-PCR of UROS mRNAs from lymphoblasts. RT-PCR analysis of the UROS mRNAs from lymphoblasts of patients 3 and 6, their parents, and a normal person demonstrated that the presence of additional sequences between exons 9 and 10 was responsible for the larger mRNAs. (A) Schematic overview of the RT-PCR analysis of alternative splicing in intron 9. The sequences of primers S3 and AS3 are provided in supplemental Table 2. (B) Agarose gel electrophoresis and ethidium bromide staining of UROS RT-PCR products revealed the 4 longer products. Sequencing the longer amplicons in patients 3 and 6 determined their location in intron 9 and their sizes of 236, 401, 513, and 678 bp in addition to the normal 155-bp product.