Combined effect between two functional polymorphisms of SLC6A12 gene is associated with temporal lobe epilepsy.

Temporal lobe epilepsy (TLE) is the most common epilepsy subtype with complex genetic structure. A recent study in four populations (Ireland, UK, Australia and Finland) reported an allelic association between betaine/GABA transporter-1(BGT-1 or SLC6A12) and mesial temporal lobe epilepsy with hippocampal sclerosis. To demonstrate the association between SLC6A12 gene polymorphisms and TLE, TaqMan method was used to genotype five single-nucleotide polymorphisms of SLC6A12 gene in 358 TLE patients and 596 nonepileptic control subjects of Chinese Han origin. Real-time PCR was used to detect the effects of variations on gene expression associated with TLE. Though, the single-marker analysis did not demonstrate allelic association with TLE, rs542736-rs557881 interaction showed significant association. The SLC6A12 expression levels in peripheral blood mononuclear cells were significantly higher in TLE patients than in control subjects and were correlated to rs542736 G-rs557881 A haplotypes. Our preliminary results suggested combined effect of two common polymorphisms on SLC6A12 gene may be associated with TLE, but the precise mechanism needs further investigation.