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Vinny Keshav, Lilla Simon, Connor Baharozian, Rebecca Regan, Sharmila Masli, Hyunjoo Jean Lee; THBS1 polymorphism associated with increased risk of pterygium and altered thrombospondin 1 expression. Invest. Ophthalmol. Vis. Sci. 2018;59(9):6054.
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© ARVO (1962-2015); The Authors (2016-present)
The pathogenesis of pterygium and risk factors beyond that of UV exposure are poorly understood. A thrombospondin 1 gene (THBS1) single nucleotide polymorphism (SNP) (rs1478604) was previously found to confer increased risk of post-LASIK dry eye syndrome (DES) and was associated with decreased ocular surface glycoprotein thrombospondin 1 expression. Our aims were to determine if rs1478604 is also associated with increased risk of pterygium and whether the associated decreased THBS1 expression can be observed in peripheral blood.
Peripheral blood was obtained from 39 normal subjects without pterygium. Portions of pterygium tissue were obtained from 42 patients undergoing pterygium excision. Genomic DNA was isolated for each subject, and THBS1 SNP rs1478604 was genotyped. The rs1478604 genotypes were compared between pterygium and normal subjects. RNA was isolated from peripheral blood samples and qRT-PCR was performed. The normal subjects were divided by rs1478604 genotype according to a recessive model (TT+TC vs CC), and the relative expression of THBS1 mRNA was compared between the 2 groups.
The minor allele of THBS1 SNP rs1478604 was associated with increased odds of having pterygium. Using a recessive model, the frequency of minor allele (CC) homozygosity was 35% in subjects with pterygium, compared to 7.6% in normal subjects (odds ratio [OR] = 6.667; 95% confidence interval [CI] = 1.752-25.37; p = 0.003) (Figure 1). Using an allele model, OR = 1.964, 95% CI = 1.046-3.690 (p = 0.0405). There was a trend toward decreased peripheral blood THBS1 mRNA expression in subjects carrying the minor allele of rs1478604, but was not statistically significant (14.23 ± 3.684 in TT+TC vs 8.924 ± 1.540 in CC; p = 0.1966) (Figure 2). Enrollment and data collection are on-going.
The minor allele of THBS1 SNP rs1478604 was associated with an increased risk of pterygium formation and with a trend toward decreased THBS1 mRNA expression in peripheral blood, although the latter was not statistically significant. Further investigation is warranted to determine the influence of THBS1 SNP rs1478604 on pterygium formation, as well as to elucidate the relationship between THBS1 SNP rs1478604 and THBS1 expression.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Figure 1: Frequency of THBS1 SNP rs1478604 genotypes in control blood and pterygium samples
Figure 2: Relative expression of rs1478604 in peripheral blood samples
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