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Editors Selection IGR 24-1
Clinical Forms of Glaucoma: LOXL1 polymorphism and pseudoexfoliation in Chinese
Comment by Subhabrata Chakrabarti on:
24352 Association of LOXL1 polymorphisms with pseudoexfoliation in the Chinese, Lee KYC; Ho SL; Thalamuthu A et al., Molecular Vision, 2009; 15: 1120-1126
The variants in LOXL1 gene has been widely implicated in pseudoexfoliation (XFS) worldwide. Lee et al. (1165) screened two specific XFS-associated LOXL1 single nucleotide polymorphisms (SNPs) to understand their involvement in a Chinese cohort comprising XFS and pseudoexfoliation glaucoma (XFG). The authors compared allelic profile of the two associated SNPs, rs1048661 and rs3825942, and observed that the frequency of the 'G' allele of rs3825942 was similar, while that of the 'G' allele of rs1048661 was relatively lower in the Chinese cohort compared to most other populations. Haplotypes generated with these two SNPs indicated a risk haplotype 'G-G' that was significantly associated with the XFS/XFG cases. This is the first study on the involvement of LOXL1 in cases of XFS and XFG among the Chinese population. Despite a relatively smaller sample size (perhaps attributed to a low frequency of XFS in the Chinese), the genetic profile of LOXL1 with respect to the rs3825942 SNP and the risk haplotype was similar to most other populations with XFS and XFG. Due to the vagaries of power and sample size, the association with the rs1048661 could not be determined as it had a smaller effect size compared to rs3825942. While the data is sound, an additional meta analysis of the associated variants in multiple studies (Table 5) would have been useful. In the Asian context, the results were similar to an Indian cohort but somewhat discordant with respect to Japanese populations. Intriguingly, the studies in Japanese populations indicated a different genetic profile due to a flip of the associated allele (rs1048661). While the authors have provided some evolutionary insights, it would be worthwhile to explain these in the background of HAPMAP data and through an extended haplotype at the LOXL1 locus indicating their differentiation in populations from the ancestral haplotype over a period of time.
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