Fig. 1

Structure of PPP6R3-TENM4-NRG1 fusion transcripts expressed by MDA-MB-175. a Schematic of genes involved, showing hypothetical genomic structure deduced from the transcripts. Exons from PPP6R3 are shown in blue, TENM4 exons, red, NRG1 exons, green, with the transmembrane domain exon in black. Cryptic exon from TENM4 intron 15 in reverse orientation, orange. In grey, possible position of exon 16 of TENM4 for orientation, not present in fusion transcripts. NRG1 exons are numbered according to genome position. Exon 9 is the receptor-binding domain; exons 3 and 4 are the Ig-like domain. Exons 1, 2, 7, and 8 are omitted because they are normal transcription start sites and do not participate in the fusion. Where transcription terminates in exon 11, the exon is extended to give the β3 isoforms. Genomic positions are hg19. b Transcripts detected. In colour, transcripts amplified by PCR and cloned; grey, additional isoform that includes exon 17, inferred from successful amplification between primers shown. Asterisk marks transcript matching original cDNA of Schaefer et al. [11]. c Examples of confirmation of junctions by PCR, showing inclusion of cytoplasmic exons of NRG1 in fusion. Primer pairs are shown by arrows in a. HB4a is control normal breast cell line. d Sequences through junctions