Abstract
Genetic variation within the apolipoprotein E gene (APOE) locus is associated with late-onset Alzheimer's disease risk and quantitative traits as well as apoE expression in multiple tissues. The aim of this investigation was to explore the influence of APOE locus cis-regulatory element enhancer region genetic variation on regional gene promoter activity. Luciferase reporter constructs containing haplotypes of APOE locus gene promoters; APOE, APOC1 and TOMM40, and regional putative enhancers; TOMM40 intervening sequence (IVS)2-4, TOMM40 IVS6 poly-T, as well as previously described enhancers; multienhancer 1 (ME1), or brain control region (BCR), were evaluated for their effects on luciferase activity in three human cell lines. Results of this investigation demonstrate that in SHSY5Y cells, the APOE promoter is significantly influenced by the TOMM40 IVS2-4 and ME1, and the TOMM40 promoter is significantly influenced by the TOMM40 IVS6 poly-T, ME1 and BCR. In HepG2 cells, theTOMM40 promoter is significantly influenced by all four enhancers, whereas the APOE promoter is not influenced by any of the enhancers. The main novel finding of this investigation was that multiple APOE locus cis-elements influence both APOE and TOMM40 promoter activity according to haplotype and cell type, suggesting that a complex transcriptional regulatory structure modulates regional gene expression.
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Acknowledgements
This work was supported in part by the US Department of Veterans Affairs, Office of Research and Development Biomedical Laboratory Research Program and the National Institutes of Health/National Institutes on Aging Grant 1K99AG034214-01A1. We thank J Anthony Gill for the editing of the manuscript.
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Bekris, L., Lutz, F. & Yu, CE. Functional analysis of APOE locus genetic variation implicates regional enhancers in the regulation of both TOMM40 and APOE. J Hum Genet 57, 18–25 (2012). https://doi.org/10.1038/jhg.2011.123
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DOI: https://doi.org/10.1038/jhg.2011.123
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