Abstract
Purpose:
ARMS2 gene is the second major risk allele for AMD, contributing independently of complement factor H to disease risk. The rs10490924 (A69S) SNP in ARMS2 accounts for approximately 35% of the population-attributable risk for the development of AMD. However, there are controversies regarding its function, localization, expression and whether it is a real gene or pseudo gene. The present study was undertaken to gain an understanding of ARMS2 transcripts in human and macaque retina.
Methods:
Total RNA from human and macaque retinas was reverse transcribed and PCR and qPCR were performed using custom designed primers and probes. For macaque, primers were designed based on homologous human sequence. The cDNAs of various human tissues including placenta were purchased from Zyagen. The PCR products of interest were purified and sequenced to confirm the authenticity of the amplified products.
Results:
PCR and qPCR results showed that two splice variants of ARMS2 mRNAs are expressed in human retina. DNA sequencing results of PCR products revealed that a larger splice variant of ARMS2 (designated as variant A) was detected in 5 human retinas with more common alleles at R38 and A69, whereas, a shorter splice variant of ARMS2 (designated as variant B) was detected in 7 human retinas and all of them showed “C to T” SNP at rs2736911. Quantitative RT-PCR results suggested that expression level of variant B was much higher than the variant A (the Δcycle is about 4-5). In macaque retina, only variant A was detected. In human, ARMS2 expression was detected only in placenta besides retina.
Conclusions:
Two ARMS2 splice variants are expressed in human retina, whereas, only variant A is expressed in macaque retina. Variant B is the major transcript of ARMS2 in human retina. Our results suggest that variant A carried more common alleles at both, R38 and A69 positions, whereas, variant B always carried R38X SNP and common allele at A69 suggesting that R38X variation may be a prerequisite for variant B splicing. Further studies are required to understand the function, cellular localization, and the pathogenic role of ARMS2 splice variants in the development of AMD.
Keywords: 412 age-related macular degeneration •
533 gene/expression •
738 transcription