Purpose: While chronic glucocorticoid (GC) therapy leads to ocular hypertension in about one third of individuals, almost all primary open-angle glaucoma (POAG) patients show this response and are called "steroid responders." Two differentially spliced isoforms of the glucocorticoid receptor (GR), GRalpha and GRbeta, regulate GC responsiveness in trabecular meshwork (TM) cells. GRbeta acts as a dominant negative regulator of GC activity and is expressed at lower levels in glaucomatous TM cells, making them more sensitive to GCs. Several arginine/serine-rich splicing factor (SR) proteins have been implicated in alternative splicing of the GR. We have previously demonstrated that immunophilins FKBP5 and FKBP4 are required for GRalpha and GRbeta translocation into the nucleus, which is essential for their biologic activity. The purpose of the present study was to use single nucleotide polymorphism (SNP) genotyping to determine whether there are any allele frequency differences in GR, FKBP4/5, or SR genes between normal control, POAG, and steroid responder populations.
Methods: Clinically characterized individuals (400 normal controls, 197 POAG, and 107 steroid responders) were recruited from the U. Iowa Ophthalmology Clinics after IRB approved consent. Genotyping of DNA samples for 48 SNPs in SFRS3, SFRS5, SFRS9, FKBP4, FKBP5, and NR3C1 was done at GeneSeek using a mass spectroscopy based system.
Results: All 48 SNPs displayed high call rates (99%). There were no significant differences in allele frequencies or genotypes in SNPs for SFRS5, SFRS9, FKBP4, FKBP5, and NR3C1 between the 3 groups. Up to three SNPs in SFRS3 had p-values <0.05 when comparing controls to POAG or steroid responders, but this statistical significance was lost when the p values were adjusted for multiple measures.
Conclusions: Although these 6 genes may be involved in the pathogenesis of GC-induced ocular hypertension, it does not appear that major heritable risk alleles in these genes are responsible for the development of GC-induced ocular hypertension or POAG.