Two patients with balanced translocations and autistic disorder: CSMD3 as a candidate gene for autism found in their common 8q23 breakpoint area

Recent studies estimated a rate of 3-5% of cytogenetic abnormalities involving many different chromosomes in autistic spectrum disorders (ASDs). Here, we report on two unrelated male patients with de novo translocations, autistic behaviour and psychomotor delay. These two patients carry a balanced chromosome translocation t(5; 8)(q14.3; q23.3) and t(6; 8)(q13; q23.2), respectively. A detailed physical map covering the regions involved in the translocations was constructed using BAC clones mapping on chromosomes 5q14.3, 6q13 and 8q23. Fluorescence in situ hybridisation (FISH) analyses were carried out using these genomic clones. We fine mapped the two translocation breakpoints on chromosomes 8 identifying their position within a short 5 Mb genomic region. Breakpoints on chromosomes 8 in both patients do not interrupt any known gene but both map in a region containing the CSMD3 gene, which thereby can be considered as a candidate for ASDs.