Unique maternal deletion of 15q in a patient with some symptoms of Prader-Willi syndrome.

BACKGROUND Human chromosome 15q11-q13 is a critical region for Prader-Willi syndrome (PWS) and Angelman syndrome (AS) and most of the genes are under the condition of imprinting mechanism. PWS results from the loss of expression of paternally expressed genes and AS of maternally expressed genes. In this study molecular studies about a patient with congenital anomalies and mental retardation are analyzed. METHODS Highly polymorphic microsatellite markers were analyzed by PCR. These markers exist within 15q11-q13 and distal to 15q13. RESULTS Only the maternal D15S986 locus within 15q11-q13 was deleted and other markers were biallelic. CONCLUSIONS The result of maternal small region deletion in this patient is different from the typical PWS with paternal chromosome deletion and it suggests that nearby the deleted region there exists a gene (genes) which is not imprinted but needs biallelic expression.