Investigating APOE, APP-A beta metabolism genes and Alzheimer's disease GWAS hits in brain small vessel ischemic disease
SCIENTIFIC REPORTS
Authors: Blumenau, Sonja; Foddis, Marco; Mueller, Susanne; Holtgrewe, Manuel; Bentele, Kajetan; Berchtold, Daniel; Beule, Dieter; Dirnagl, Ulrich; Sassi, Celeste
Abstract
Alzheimer's disease and small vessel ischemic disease frequently co-exist in the aging brain. However, pathogenic links between these 2 disorders are yet to be identified. Therefore we used Taqman genotyping, exome and RNA sequencing to investigate Alzheimer's disease known pathogenic variants and pathways: APOE epsilon 4 allele, APP-A beta metabolism and late-onset Alzheimer's disease main genome-wide association loci (APOE, BIN1, CD33, MS4A6A, CD2AP, PICALM, CLU, CR1, EPHA1, ABCA7) in 96 early-onset small vessel ischemic disease Caucasian patients and 368 elderly neuropathologically proven controls (HEX database) and in a mouse model of cerebral hypoperfusion. Only a minority of patients (29%) carried APOE epsilon 4 allele. We did not detect any pathogenic mutation in APP, PSEN1 and PSEN2 and report a burden of truncating mutations in APP-A ss degradation genes. The single-variant association test identified 3 common variants with a likely protective effect on small vessel ischemic disease (0.54>OR>0.32, adj. p-value <0.05) (EPHA1 p.M900V and p.V160A and CD33 p.A14V). Moreover, 5/17 APP-A catabolism genes were significantly upregulated (LogFC>1, adj. p-val<0.05) together with Apoe, Ms4a cluster and Cd33 during brain hypoperfusion and their overexpression correlated with the ischemic lesion size. Finally, the detection of A oligomers in the hypoperfused hippocampus supported the link between brain ischemia and Alzheimer's disease pathology.
Alzheimer risk genes modulate the relationship between plasma apoE and cortical PiB binding
NEUROLOGY-GENETICS
Authors: Lazaris, Andreas; Hwang, Kristy S.; Goukasian, Naira; Ramirez, Leslie M.; Eastman, Jennifer; Blanken, Anna E.; Teng, Edmond; Gylys, Karen; Cole, Greg; Saykin, Andrew J.; Shaw, Leslie M.; Trojanowski, John Q.; Jagust, William J.; Weiner, Michael W.; Apostolova, Liana G.
Abstract
Objective: We investigated the association between apoE protein plasma levels and brain amyloidosis and the effect of the top 10 Alzheimer disease (AD) risk genes on this association. Methods: Our dataset consisted of 18 AD, 52 mild cognitive impairment, and 3 cognitively normal Alzheimer's Disease Neuroimaging Initiative 1 (ADNI1) participants with available [C-11]-Pittsburgh compound B (PiB) and peripheral blood protein data. We used cortical pattern matching to study associations between plasma apoE and cortical PiB binding and the effect of carrier status for the top 10 AD risk genes. Results: Low plasma apoE was significantly associated with high PiB SUVR, except in the sensorimotor and entorhinal cortex. For BIN1 rs744373, the association was observed only in minor allele carriers. For CD2AP rs9349407 and CR1 rs3818361, the association was preserved only in minor allele noncarriers. We did not find evidence for modulation by CLU, PICALM, ABCA7, BIN1, and MS4A6A. Conclusions: Our data show that BIN1 rs744373, CD2AP rs9349407, and CR1 rs3818361 genotypes modulate the association between apoE protein plasma levels and brain amyloidosis, implying a potential epigenetic/downstream interaction.