The GABAA receptor subunit gene expression was detected from mouse A9 hybrids containing a single
human paternal chromosome 15, but not from cells containing a maternal chromosome 15, leading to the
conclusion that human GABRB3, GABRA5, GABRG3 are imprinted (paternally expressed). Unexpectedly
there was evidence of paternal methylation at the 5’ end of GABRB3 (Meguro
M et al, 1997).
Previously Kubota T et al (1994)
reported possible paternal silencing of GABRB3 on the basis of undetectable expression in a single
Presence of a 50-60 kb domain of allele-specific replication between the
γ-aminobutyric acid receptor subunit β3 (GABRB3) and α5 (GABRA5) genes were reported (LaSalle
M J and Lalande M, 1994)
All three genes were biallelically expressed in 21 brain samples (Hogart
A et al, 2007).
Reduced expression levels of GABRA5 and GABRB3, measured by microarray and quantitative RT-PCR,
were noted in cells from PWS with maternal UPD suggesting higher expression levels from the paternal
DC et al, 2003).
GABRB3 showed significantly reduced expression in
multiple Rett, Angelman and autism human brain samples and in Mecp2 deficient mice, by quantitative
immunoblot suggesting that the reduced levels of GABRB3 were attributable to altered neuronal
function rather than imprinting (Samaco
RC et al, 2005).
Transmission disequilibrium test analysis has provided evidence for
paternal (but not maternal) transmission of GABRA5 and GABRB3 in association with alcoholism (P <
0.004 and P < 0.007 respectively) (Jiuzhou
S et al, 2003). In contrast others have failed to confirm any parent-or-origin effects for
alcoholism at this locus (Dick DM et al, 2004).
Morcos L et al (2011) found no evidence of
allelic expression bias in fibroblast cell lines for GABRB3 and GABRA5 and for GABRG3 no evidence
of imprinting was found in the lymphoblast cell lines investigated.