Four lysyl oxidase family genes (LOXL1, LOXL2, LOXL3, and LOXL4), which catalyze cross-linking of collagen and elastin, were considered to be functional candidates for intracranial aneurysms (IA) and were extensively screened for genetic susceptibility in Japanese IA patients. Total RNA was isolated from four paired ruptured IA and superficial temporal artery (STA) tissue and examined by real-time RT-PCR. The expression of LOXL2 in the paired IA and STA tissues was elevated in the IA tissue. A total of 55 single nucleotide polymorphisms (SNPs) of LOXL1-4 were genotyped for an allelic association study in 402 Japanese IA patients and 462 Japanese non-IA controls. Allelic associations were evaluated with the chi-square test and the permutation test especially designed for adjustment of multiple testing. SNPs of LOXL1 and LOXL4 were not significantly associated with IA, while several SNPs of LOXL2 and LOXL3 showed nominally significant associations in IA patients. We detected an empirically significant association with one SNP of LOXL2 in familial IA patients after adjustment for multiple testing [X2 = 10.23, empirical P = 0.023, OR (95% CI) = 1.49 (1.17, 1.90)]. Furthermore, multilocus interaction was evaluated by multifactor dimensionality reduction analysis. We found that the SNPs of LOXL2 have an interactive effect with elastin (ELN) and LIM kinase 1 (LIMK1) that have been previously found to be associated with IA. In conclusion, one SNP of LOXL2 showed a significant association with IA individually, and we also detected a gene-gene interaction of LOXL2 with ELN LIMK1, which may play an important role in susceptibility to IA.
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