Decreased binding of [11C]flumazenil in Angelman syndrome patients with GABA(A) receptor beta3 subunit deletions.

We used positron emission tomography (PET) to study brain [11C]flumazenil (FMZ) binding in four Angelman syndrome (AS) patients. Patients 1 to 3 had a maternal deletion of 15q11-q13 leading to the loss of beta3 subunit of gamma-aminobutyric acidA/benzodiazepine (GABA(A)/BZ) receptor, whereas Patient 4 had a mutation in the ubiquitin protein ligase (UBE3A) saving the beta3 subunit gene. [11C]FMZ binding potential in the frontal, parietal, hippocampal, and cerebellar regions was significantly lower in Patients 1 to 3 than in Patient 4. We propose that the 15q11-q13 deletion leads to a reduced number of GABA(A)/BZ receptors, which could partly explain the neurological deficits of the AS patients.