Association Analysis of a Polymorphism of Interleukin 1β (IL-1β) Gene with Temporal Lobe Epilepsy in a Chinese Population

Purpose: Temporal lobe epilepsy with hippocampal sclerosis (TLE-HS ⁺) is one of the most common medically intractable epilepsies. Although the pathogenesis of HS⁺ still remains highly controversial, genetics may play a role as a predisposing factor. Previous evidence in a Japanese population shows that the homozygotes for allele 2 at position -511 of the interleukin (IL)-1β gene promoter region (IL-1β-511*2/2) confers susceptibility to the development of HS. However, this result has not been confirmed in populations of European ancestry. Given that the discrepancy may be attributed to ethnic differences, our aim in this study was to test the validity of a previous report in another Asian population. Methods: This study consisted of total 112 nonlesional TLE patients of Chinese ancestry, and 115 ethnically matched control subjects. A 304-base pair fragment in position of IL-1β-511 was amplified by polymerase chain reaction (PCR). The PCR products were digested with restriction enzyme AvaI, and run on a 12% polyacrylamide gel. We compared the frequency of this gene variation among 67 refractory TLE-HS⁺ patients, 45 patients without HS (TLE-HS-), and normal control subjects. Results: The heterozygous type (-511*1/2) is the most common genotype in our patient groups and controls. Allele 1 (-511C) and allele 2 (-511T) showed equal frequency (∼50%), which is similar to that (46%) in Japanese. Analysis of genotype and allele distribution showed no significant difference among the three groups (p > 0.05). Conclusions: In contrast with the lower frequency in the white population (35 and 34%) and higher rate in the population of African ancestry (60%), the allele -511T frequency in our present study is ∼50%, indicating differences in the distribution of allele frequencies in IL-1β-511 among different ethnic groups. In this Chinese population, however, we still did not find a strong association between IL-1β-511 polymorphism and the development of HS.