Schizophrenia (SZ), bipolar disorder (BD) and recurrent major depressive disorder (rMDD) are common forms of serious mental illness, each with a strong and overlapping genetic component.1, 2, 3 Genome-wide linkage, association, cytogenetic, copy number variant and, more recently, sequencing studies establish that the genetic architecture of psychiatric illness is complex and that there is extensive genetic heterogeneity, which is incompletely defined or understood (reviewed in Sullivan et al.4). We previously reported a t(1;11) translocation in a single large Scottish family that showed genome-wide significant linkage for SZ, rMDD and jointly with BD.5 The t(1;11) translocation is balanced and structurally simple, but the outcome is genetically complex, disrupting the protein coding gene Disrupted in schizophrenia 1 (DISC1), the antisense non-coding gene Disrupted in schizophrenia 2 (DISC2) and the non-coding gene DISC1FP1, creating a DISC1/DISC1FP1 fusion transcript.6, 7, 8, 9, 10, 11
