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Matthias Zenkel, Francesca Pasutto, Jasmine Onderka, Anita Krysta, Angelika Moessner, Friedrich Kruse, Ursula Schlotzer-Schrehardt; Candidate regulatory lysyl oxidase-like 1 (LOXL1) variants in pseudoexfoliation syndrome/glaucoma are associated with differential LOXL1 expression. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6243.
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© ARVO (1962-2015); The Authors (2016-present)
Candidate regulatory single nucleotide polymorphisms (SNPs) in the lysyl oxidase-like 1 (LOXL1) gene, the main genetic risk factor for pseudoexfoliation (PEX) syndrome/glaucoma, have been identified and suggested to influence expression and/or splicing of LOXL1 mRNA. To determine the role of these SNPs in PEX pathophysiology, we investigated the expression and size of LOXL1 mRNA in ocular tissues of PEX and control patients in correlation with the individual SNP genotypes.
Total RNA and genomic DNA were isolated simultanously from iridal tissue specimens, obtained from donor eyes with PEX syndrome and age-matched normal donor eyes (n=20 for each group). The mRNA expression of LOXL1 was measured by quantitative real-time PCR assays. LOXL1 mRNA size was analyzed by reverse transcription (RT-)PCR using primers located in the 5’- and 3’- untranslated regions of the LOXL1 mRNA. SNPs located in the promotor region (rs12914489 and rs16958477) and the first intron (rs1992314 and rs2028387) of the LOXL1 gene were genotyped by direct sequencing and correlated to LOXL1 expression.
The frequencies of the risk G-allele of rs12914489 and the risk C-allele of rs16958477 were 49% and 31% in PEX cases, and 42% and 24% in control cases, respectively. The frequencies of the risk C-allele of rs1992314 and the risk A-allele of rs2028387 were 43% and 42% in PEX cases, and 30% and 32% in control cases. The risk alleles of rs12914489 and rs16958477 were not significantly associated with alterations in LOXL1 expression levels. In contrast, the expression of LOXL1 displayed a significant increase by 40% (p<0.02) with two copies of the risk alleles of rs1992314 (CC) and rs2028387 (AA), as compared to the heterozygous alleles as well as to the homozygous non-risk alleles of rs1992314 (GG) and 2028387 (CC). This increase was strongly correlated (r=0.99, p<0.0001) with the presence of a risk-conferring haplotype C-A. RT-PCR analysis resulted in a single LOXL1 transcript in PEX and control cases arguing against alternative splicing events of LOXL1 mRNA in ocular tissues.
These data suggest, that the two intronic variants rs1992314 and rs2028387, which are associated with PEX syndrome in both Caucasian and black South African populations, are potentially functional variants for the disease by affecting LOXL1 gene expression in ocular tissues.
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