Fig. 1

A. RPA strategy. 1. Structure of the region covering exons 6, 7 and 8 in Axin and Axin^Fu DNA. 2. Wild type and alternative transcripts from Axin and Axin^Fu, respectively. Wavy lines represent exons beyond the region of interest. As the exact features of the alternative transcript for Axin^Fu are unknown, the alternative transcript described here represents only one possibility. 3. Antisense RNA probe transcribed from the cDNA template T3 promoter. Area of hybridization between probe and target indicated by dashed lines. 4. Double stranded hybrids protected from RNase digestion. When the antisense probe hybridizes wild type transcript, it protects a full length 286 bp fragment, being the sum of the regions of exons 6, 7 and 8 covered by the probe. When the antisense probe hybridizes an alternative transcript where exon 6 is no longer adjacent to exons 7 and 8, the probe protects a 238-bp fragment, being the sum of exons 7 and 8 only. A 48-bp fragment is also expected from the alternative transcript representing a protected fragment from exon 6 only (not shown). B. Sense strand of the cDNA template used for transcription of probe in RPA. Standard font, 3′ portion of exon 6 (48 bp); underlined, the entire exon 7 (171 bp); italic, 5′ portion of exon 8 (67 bp). C. 5% polyacrylamide gel of RNase protection assay. Lane 1, Axin^Fu+/Axin^Fu+ homozygote; Lane 2, Axin^Fu+/+tf heterozygote; Lane 3, +tf/+tf.