Equal expression was observed in brain from mice with either a paternally or maternally derived
deletion that included Gabrb3(Nicholls
RD et al, 1993). In addition no difference in Gabrb3 expression levels was detected between mice
with paternal and maternal uniparental disomies for this region (Cattanach
BM et al, 1992).
Biallelic expression of Gabrb3 in mice with uniparental duplications of proximal chromosome 7 was
shown by microarray analysis and by quantitative RT-PCR of RNA from cerebellum, cortex, and the
hippocampal pyramidal cell layer (Buettner
VL et al, 2004).
GABRB3 showed significantly reduced expression in Mecp2 deficient mice, and in
multiple Rett, Angelman and autism human brain samples, by quantitative immunoblot, suggesting that
the reduced levels of GABRB3 is a consequence of the abnormal neuronal function, rather than
attributable to imprinting (Samaco
RC et al, 2005).
In contrast, in heterozygous Gabrb3 (GABAA receptor beta 3 subunit) knockout mice, some phenotypes
were influenced by the parent-of-origin of the mutant, suggesting partial genomic imprinting. The
affected phenotypes were: EEG slow wave activity; protein expression levels in 6-8 week whole brain;
qualitative assessment of EEGs; EEG responses to carbamazepine administration (Liljelund
P et al, 2005). Their results suggest preferential paternal expression (maternal repression) of
Gabrb3 in mice.