AMD-Associated Variants at the Chromosome 10q26 Locus and the Stability of<i>ARMS2</i>Transcripts

Abstract

PURPOSE: To analyze the effect of variants including age-related macular degeneration (AMD)-associated combinative insertion/deletion polymorphism (indel) at 3'UTR of ARMS2 and possibly associated R38X on the stability of ARMS2 transcripts. METHODS: ARMS2 transcription from minigene vectors carrying different alleles at variants R38X and the indel were assessed in mouse embryonic fibroblasts (MEFs). Dual luciferase assays were applied to evaluate the effect of the indel on gene expression. RT-PCR and quantitative RT-PCR (qRT-PCR) were used to measure the two ARMS2 transcripts (isoform A and isoform B) in MEFs and human retina-RPE-choroid samples (n = 83). RESULTS: Allele X at variant R38X decreased exogenous ARMS2 transcripts in MEFs compared to allele R. In contrast, the indel did not change the level of exogenous ARMS2 transcripts. After blocking transcription by actinomycin D, R38X appeared to accelerate the degradation of ARMS2 transcripts, while the indel did not obviously affect the stability of ARMS2 transcripts compared to the wild-type (WT) allele. Dual luciferase assays further indicated that the indel did not influence gene expression. Quantitative RT-PCR results showed that there was no significant difference in two ARMS2 transcript splice isoforms among retina-RPE-choroid samples carrying different genotypes at variants R38X and the indel. CONCLUSIONS: Variant R38X, not the indel, decreases the stability of ARMS2 transcripts in vitro. However, genotypes at R38X and the indel do not obviously affect the level of ARMS2 transcripts in retina-RPE-choroid samples. These results suggest that variants R38X and the indel are less likely to play a pathogenic role in AMD by changing the level of ARMS2 transcripts.