Recent studies support the notion that recurrent structural mutations may contribute substantially to the risks of psychiatric disorders such as autism12 and schizophrenia13. Recently, we found evidence suggesting that a recurrent deletion at 15q11.2 is associated with schizophrenia14. Assuming that association is real, the penetrance is not very high. In Iceland, a total of 63 carriers were observed: 4 in 648 schizophrenics, one in a parent of a schizophrenic, and 58 in 32,442 controls (OR ~ 3.5). Here we explore the inheritance of this deletion independent of its putative association with schizophrenia. Out of the 63 chromosomes with the deletion, 14 of the parents of origin were chip-typed. Twelve of these 14 parents also carry the deletion (i.e. part of the 63) and one does not, the latter points to a de novo event for the proband. Given that many of the deletion carriers do not have a ‘first-generation’ de novo mutation, we investigated the relationship between the 63 chromosomes with the deletion through long-range phasing. The deletion resides in a difficult region. Chromosome 15 has a very short p-arm.
