Reverse transcription-PCR combined with either (a) restriction enzyme digestion and repeat PCR or (b) ligase chain reaction has identified two new alternatively spliced transcripts of the adenomatous polyposis coli (APC) gene. In one of these transcripts exons 1–4 and the first 16 bases of exon 5 are deleted; in the other exons 2–4 and the first 16 bases of 5 are deleted. Both transcripts use an intraexonic splice acceptor in exon 5. These transcripts delete exons mutated in attenuated APC (3 and 4) and could account for the reduction in severity of this variant.
W.S.S. was supported by National Cancer Institute Grant CA 01755.