Discovery of novel genes based on trapclusters. The figure shows six examples of novel multiexon genes predicted using gene trap data verified by RT-PCR on ES-cell RNA as well as CpG island and Eponine transcription start site annotation. TCLG1417 is a transcript without an ORF found in reverse orientation and partial overlap with the Trpm3 gene with seven out of 10 predicted exons confirmed to be transcribed in ES cells (more expression info in Fig. 4). TCLG1647 is also found in opposite orientation to a known gene, Tcf15, but it is actually larger and contains the known gene within its intron. This trapcluster gene was predicted to contain seven exons, but PCR verification resulted in the merge of two proximal exons, the addition of a novel exon that was not present in the gene trap collection, and two exons that could not be linked to this transcript. TCLG400 is also opposite and in partial overlap to a known gene, Ngfr, and all its four exons were confirmed by RT-PCR. Only three out of five exons of TCLG1753 were connected in a single, large transcript that contains the Prkci gene on the opposite strand. TCLG2423 is found opposite to the 1110032O16Rik gene, and all its four exons were confirmed by RT-PCR. TCLG4470 is a compact three-exon transcript found opposite and nested to the Oprd1 gene, confirmed by RT-PCR.
