Abstract
The prevalence of Alzheimer’s disease (AD) is increasing rapidly worldwide due to an ageing population and a lack of disease modifying therapeutics. In monogenic forms of AD mutations lead to the accumulation of neurotoxic peptides called beta-amyloid. Beta-amyloid accumulation is also postulated to precipitate sporadic AD although the pathogenesis of this common form remains largely unknown. The two leading risk factors for sporadic AD are ageing and the possession of the APOE epsilon 4 allele. Changes in APOE expression that are independent of the epsilon genotype have also been described in the AD brain including a recent RNA-Seq analysis that showed upregulation of a rare alternative splice isoform (APOE-005). To replicate these RNA-Seq findings we used quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) to compare APOE-005 and total APOE expression in the superior temporal gyrus of 14 AD cases and 16 neurologically normal controls. In AD, this area shows prominent beta-amyloid deposition but few neurofibrillary tangles and only moderate neuronal loss. As poorer RNA quality among the AD cases was a likely confounder in this study, the analysis was repeated in a RIN-matched sub-cohort of 17 individuals. Contrary to the original RNA-Seq study, we found no difference in total APOE, APOE-005 or the common isoform, APOE-001, between AD cases and controls. Our findings are consistent with ApoE acting largely at the protein level to increase the risk for sporadic AD.
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Abbreviations
- Aβ:
-
Amyloid-beta
- ACTB:
-
Beta-actin
- AD:
-
Alzheimer’s disease
- ANOVA:
-
Analysis of variance
- APOE:
-
Apolipoprotein E
- APP:
-
Amyloid precursor protein
- AT8:
-
A phospho-tau antibody
- BACE1:
-
Beta-site APP-cleaving enzyme 1
- BLAST:
-
Basic Local Alignment Search Tool
- cDNA:
-
Copy DNA
- Cq :
-
Quantification cycle
- CLU:
-
Clusterin
- DAB:
-
3,3′-Diaminobenzidine
- DNA:
-
Deoxyribonucleic acid
- FFPE:
-
Formalin-fixed paraffin-embedded
- GAPDH:
-
Glyceraldehyde 3-phosphate dehydrogenase
- GFAP:
-
Glial fibrillary acidic protein
- GOI:
-
Gene of interest
- HMBS:
-
Hydroxymethylbilane synthase
- HPRT1:
-
Hypoxanthine phosphoribosyltransferase 1
- mRNA:
-
Messenger RNA
- HRP:
-
Horseradish peroxidase
- MAPT:
-
Microtubule associated protein tau
- NCBI:
-
National Center for Biotechnology Information
- NFT:
-
Neurofibrillary tangle
- NSWBB:
-
New South Wales Brain Banks
- PMI:
-
Post mortem interval
- PSEN1:
-
Presenilin-1
- RG:
-
Reference gene
- RNA:
-
Ribonucleic acid
- RNA-Seq:
-
Next generation sequencing of the transcriptome
- RT-qPCR:
-
Quantitative reverse transcriptase polymerase chain reaction
- SDHA:
-
Succinate dehydrogenase complex, subunit A
- STG:
-
Superior temporal gyrus
- SNP:
-
Single nucleotide polymorphism
- TSS:
-
Transcriptional start site
- UBC:
-
Ubiquitin C
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Acknowledgments
The authors would like to thank the donors and their families for their kind gift that has allowed this research to be undertaken. A special thanks to A/Prof David Sullivan and Terrance Foo from Department of Clinical Biochemistry, Royal Prince Alfred Hospital, Sydney, for the APOE genotyping. We also thank the New South Wales Brain Bank Network for providing tissue samples and assistance with clinical and pathological data. The Network is made up of the Sydney Brain Bank (SBB) and NSW Tissue Resource Centre (NSW TRC). The SBB is supported by Neuroscience Research Australia, the University of New South Wales, the National Health and Medical Research Council (NHMRC) and the Australian Brain Bank Network. NSW TRC is supported by the University of Sydney, NHMRC (#605210), the Schizophrenia Research Institute and the National Institutes of Alcoholism and Alcohol Abuse (NIAAA; R24 AA012725).
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James D. Mills and Pamela J. Sheahan have contributed equally to this work.
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11033_2014_3516_MOESM1_ESM.xls
Supplementary Table S1. This table contains all demographic, clinical, pathological, RNA quality and RT-qRCR raw and normalized data (GFAP as the reference gene) for the total cohort (n = 29)
11033_2014_3516_MOESM2_ESM.xls
Supplementary Table S2. This table contains all demographic, clinical, pathological, RNA quality and RT-qRCR raw and normalized data (GFAP as the reference gene) in a RIN-matched sub-cohort of 17 AD cases and controls
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Mills, J.D., Sheahan, P.J., Lai, D. et al. The alternative splicing of the apolipoprotein E gene is unperturbed in the brains of Alzheimer’s disease patients. Mol Biol Rep 41, 6365–6376 (2014). https://doi.org/10.1007/s11033-014-3516-8
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DOI: https://doi.org/10.1007/s11033-014-3516-8