| First Author | Tian M | Year | 2012 |
| Journal | J Neurosci | Volume | 32 |
| Issue | 17 | Pages | 5937-52 |
| PubMed ID | 22539854 | Mgi Jnum | J:184596 |
| Mgi Id | MGI:5425158 | Doi | 10.1523/JNEUROSCI.5332-11.2012 |
| Citation | Tian M, et al. (2012) The intronic GABRG2 mutation, IVS6+2T->G, associated with childhood absence epilepsy altered subunit mRNA intron splicing, activated nonsense-mediated decay, and produced a stable truncated gamma2 subunit. J Neurosci 32(17):5937-52 |
| abstractText | The intronic GABRG2 mutation, IVS6+2T-->G, was identified in an Australian family with childhood absence epilepsy and febrile seizures (Kananura et al., 2002). The GABRG2 intron 6 splice donor site was found to be mutated from GT to GG. We generated wild-type and mutant gamma2 subunit bacterial artificial chromosomes (BACs) driven by a CMV promoter and expressed them in HEK293T cells and expressed wild-type and mutant gamma2 subunit BACs containing the endogenous hGABRG2 promoter in transgenic mice. Wild-type and mutant GABRG2 mRNA splicing patterns were determined in both BAC-transfected HEK293T cells and transgenic mouse brain, and in both, the mutation abolished intron 6 splicing at the donor site, activated a cryptic splice site, generated partial intron 6 retention, and produced a frameshift in exon 7 that created a premature translation termination codon (PTC). The resultant mutant mRNA was either degraded partially by nonsense-mediated mRNA decay or translated to a stable, truncated subunit (the gamma2-PTC subunit) containing the first six GABRG2 exons and a novel frameshifted 29 aa C-terminal tail. The gamma2-PTC subunit was homologous to the mollusk AChBP (acetylcholine binding protein) but was not secreted from cells. It was retained in the ER and not expressed on the surface membrane, but it did oligomerize with alpha1 and beta2 subunits. These results suggested that the GABRG2 mutation, IVS6+2T-->G, reduced surface alphabetagamma2 receptor levels, thus reducing GABAergic inhibition, by reducing GABRG2 transcript level and producing a stable, nonfunctional truncated subunit that had a dominant-negative effect on alphabetagamma2 receptor assembly. |
