We read the article by Fuse and associates with great interest. In their report, a variant (rs1048661, G allele) of lysyl oxidase–like 1 ( LOXL1 ) gene was associated with exudative age-related macular degeneration (AMD), but not with polypoidal choroidal vasculopathy (PCV). The LOXL1 polymorphisms (rs1048661:758G/T and rs3825942:794G/A) have been reported to be associated with pseudoexfoliation syndrome (XFS) through a genome-wide scanning study. However, there have been few reports suggesting that XFS could be one of the risk factors for AMD.
We further investigated their findings in a larger cohort of 401 participants composed of 89 patients with exudative AMD, 135 patients with PCV, and 177 controls. The genotyping of rs1048661 and rs3825942 was performed by restriction fragment length polymorphism assay, as we have described previously. Both variants were within the Hardy-Weinberg equilibrium in all 3 groups ( P > .65, Hardy-Weinberg exact test). Neither the frequencies of the T allele of rs1048661 (exudative AMD 56.2%, PCV 53.0%, and controls 55.1%) nor those of the G allele of rs3825942 (exudative AMD 82.6%, PCV 82.6%, and controls 85.6%) in exudative AMD were significantly different from PCV cases or controls ( P = .504 and P = .811, respectively for rs1048661 and P = .998 and P = .364 for rs3825942, χ 2 test). The statistical power was 93.7% and 79.2% to detect any significant differences of the frequencies of the T allele of rs1048661 and the G allele of rs3825942 between exudative AMD cases and controls, respectively (significance level α = 0.05).
The lysyl oxidases are a family of enzymes that play an important role in the formation of elastin polymer fibers. LOXL1 protein is essential for the maintenance of elastic fibers. Indeed, LOXL1-deficient mice develop larger laser-induced choroidal neovascular membranes compared with wild-type controls. It could easily be postulated that a variant of rs1048661 in the LOXL1 gene may be a susceptible variant for exudative AMD. However, a recent genome-wide association study did not reveal a positive association between exudative AMD and LOXL1 gene variants. Our results of a negative association between variants of the LOXL1 gene and exudative AMD suggest that the involvement of rs1048661 in the LOXL1 gene as a risk allele for exudative AMD might be small if present.