Fig. 2.

Confirmation of the origin of the isolated sequences. A. Determination of genomic DNA contamination. DNase I digested RNA samples were tested by direct PCR amplification of beta-actin genomic DNA with primers spanning an intron. The amplicons from genomic DNA will be 329 bps, whereas that from mRNA will be 234 bp. 1. RT-PCR with RNA samples. 2. PCR with RNase A digested RNA samples. 3. Negative control without RNA. B. RT-PCR confirmation of detected sequences. A total of 30 isolated sequences were selected for the confirmation. Sense primer and antisense primer were designed based on each sequence. For antisense confirmation, antisense primer was used for cDNA synthesis; for other types of confirmation, oligo dT was used for cDNA synthesis. No. 1, 2, 3, 4, and 5 are the antisense confirmation. The order of the tested sequences is the same as listed in the Supplementary table 1. (+): positive control with beta-actin transcripts; (-): negative control with RNase A digested RNA samples. Most of the sequences, except for a few cases, were detected in both RNA samples with similar size distribution.