Figure 2.

Intergenic trans-splicing events. A. Nested RT-PCR experiments revealed MLL-AF4 fusion transcripts in 10 different healthy volunteers (1-10). Sequence analysis of these PCR amplimers revealed exon-exon fusions between MLL exon 9 and AF4 exon 4 (A). In patient 8, MLL exon 8 was fused to AF4 exon 4 (B). W: water control; -RT: minus RT control; a 100 bp ladder was used as size marker. B. Nested RT-PCR experiments revealed no AF4-MLL fusion transcripts in the same volunteers (1-10). W: water control; P: positive control (C). C. 3-RACE experiments were used to identify intergenic transplicing products. For 3 out of the 5 tested genes trans-splicing products were identified. Left: trans-splicing donor gene; middle: identified trans-splicing partner, listing the gene name (chromosome) and panel; the exon-exon-fusions between the trans-splicing partners are indicated by “::"; lower dashes between single exons indicate regularly spliced exon-exon boundaries in the identified transcripts. Exons designated with “a” or “b” represent cryptic exons normally not used for regular splicing events; right panels I-VII: RT-PCR experiments to validate the presence of the identified intergenic trans-splicing events in 3 additional healthy volunteers (a-c); M: size marker (100 bp ladder). D. Presence of the NPM-ALK fusion transcript in investigated healthy volunteers (1-10; D).