Deletions of the proximal long arm of chromosome 15 (bands 15q11q13) are found 
in the majority of patients with two distinct genetic disorders, Angelman 
syndrome (AS) and Prader-Willi syndrome (PWS). The deleted regions in the two 
syndromes, defined cytogenetically and by using cloned DNA probes, are similar. 
However, deletions in AS occur on the maternally inherited chromosome 15, and 
deletions in PWS occur on the paternally derived chromosome 15. This observation 
has led to the suggestion that one or more genes in this region show 
differential expression dependent on parental origin (genetic imprinting). No 
genes of known function have previously been mapped to this region. We show here 
that the gene encoding the GABAA (gamma-aminobutyric acid) receptor beta 3 
subunit maps to the AS/PWS region. Deletion of this gene (GABRB3) was found in 
AS and PWS patients with interstitial cytogenetic deletions. Evidence of beta 3 
gene deletion was also found in an AS patient with an unbalanced 13;15 
translocation but not in a PWS patient with an unbalanced 9;15 translocation. 
The localization of this receptor gene to the AS/PWS region suggests a possible 
role of the inhibitory neurotransmitter GABA in the pathogenesis of one or both 
of these syndromes.