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Oncotarget. 2018 May 15;9(37):24590-24600. doi: 10.18632/oncotarget.25083. eCollection 2018 May 15.

Genome-wide significant risk factors on chromosome 19 and the APOE locus.

Author information

1
Research Center and Memory Clinic of Fundació ACE, Institut Català de Neurociències Aplicades, Univesitat Internacional de Catalunya, Barcelona, Spain.
2
Institute of Human Genetics, University of Bonn, Bonn, Germany.
3
Department of Genomics, Life & Brain Center, University of Bonn, Bonn, Germany.
4
Department of Psychiatry and Psychotherapy, University of Bonn, Bonn, Germany.
5
German Center for Neurodegenerative Diseases, DZNE, Bonn, Germany.
6
Department of Psychiatry and Psychotherapy, University of Cologne, Cologne, Germany.
7
Memory Unit, University Hospital La Paz-Cantoblanco, Madrid, Spain.
8
Dementia Unit, University Hospital Virgen de la Arrixaca, Murcia, Spain.
9
Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, CIBERDEM, Spain, Hospital Clínico San Carlos, Madrid, Spain.

Abstract

The apolipoprotein E (APOE) gene on chromosome 19q13.32, was the first, and remains the strongest, genetic risk factor for Alzheimer's disease (AD). Additional signals associated with AD have been located in chromosome 19, including ABCA7 (19p13.3) and CD33 (19q13.41). The ABCA7 gene has been replicated in most populations. However, the contribution to AD of other signals close to APOE gene remains controversial. Possible explanations for inconsistency between reports include long range linkage disequilibrium (LRLD). We analysed the contribution of ABCA7 and CD33 loci to AD risk and explore LRLD patterns across APOE region. To evaluate AD risk conferred by ABCA7 rs4147929:G>A and CD33 rs3865444:C>A, we used a large Spanish population (1796 AD cases, 2642 controls). The ABCA7 rs4147929:G>A SNP effect was nominally replicated in the Spanish cohort and reached genome-wide significance after meta-analysis (odds ratio (OR)=1.15, 95% confidence interval (95% CI)=1.12-1.19; P = 1.60 x 10-19). CD33 rs3865444:C>A was not associated with AD in the dataset. The meta-analysis was also negative (OR=0.98, 95% CI=0.93-1.04; P=0.48). After exploring LRLD patterns between APOE and CD33 in several datasets, we found significant LD (D' >0.20; P <0.030) between APOE-Ɛ2 and CD33 rs3865444C>A in two of five datasets, suggesting the presence of a non-universal long range interaction between these loci affecting to some populations. In conclusion, we provide here evidence of genetic association of the ABCA7 locus in the Spanish population and also propose a plausible explanation for the controversy on the contribution of CD33 to AD susceptibility.

KEYWORDS:

ABCA7; APOE; CD33; Gerotarget; late onset Alzheimer’s disease; linkage disequilibrium

Conflict of interest statement

CONFLICTS OF INTEREST None. The authors declare that they have no competing interest.

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