Map of the human 15q11-q14 region. Location of NDNL2 was derived from the Ensembl Human Genome server http://www.ensembl.org/ and the physical location of APBA2, which is located on the same genomic clone as NDNL2. The large double-headed arrow indicates the common PWS/AS deletion, and BP2 and BP3 indicate the most common proximal and distal breakpoint regions. The breakpoint region for the largest inv dup (15) chromosome  and the autistic disorder susceptibility region  are also indicated. The physical distance between BP3 and APBA2/NDNL2 is as yet unknown due to the presence of repetitive elements in the intervening region.