Possible dosage effect of maternally expressed genes on visual recognitionmemory in Prader-Willi syndrome

Seventeen patients with Prader-Willi syndrome (7 with paternal deletion of chromosome 15q11-q13 and 10 with maternal uniparental disomy [UPD]), and 9 controls performed a computerized visual recognition task. A series of colo r digital photographs were presented; most were presented twice, but the re mainder appeared only once. Photographs presented twice were separated in t heir presentation by either 0, 10, 30, 50 or 100 intervening photographs. S ubjects indicated whether each photograph had been presented previously. Th is procedure was implemented twice, once using photographs of foods, and on ce using photographs of nonfood objects. As the number of intervening photo graphs between the first and second presentation increased, subjects were l ess likely to remember having seen the photograph before. Performance by UP D subjects was less affected by increasing the number of intervening photog raphs relative to the other two groups, suggesting they had superior visual recognition memory. This raises the possibility of a beneficial effect of having two copies maternally expressed genes on chromosome 15. UBE3A is sug gested as a possible candidate for this effect. Am. J. Med. Genet. (Neurops ychiatr. Genet.) 105: 71-75, 2001. (C) 2001 Wiley-Liss, Inc.