| 1. |
- Karlsson, Ida K., et al.
(författare)
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Measuring heritable contributions to Alzheimer's disease : polygenic risk score analysis with twins
- 2022
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Ingår i: Brain Communications. - : Oxford University Press. - 2632-1297. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- The heritability of Alzheimer's disease estimated from twin studies is greater than the heritability derived from genome-based studies, for reasons that remain unclear. We apply both approaches to the same twin sample, considering both Alzheimer's disease polygenic risk scores and heritability from twin models, to provide insight into the role of measured genetic variants and to quantify uncaptured genetic risk. A population-based heritability and polygenic association study of Alzheimer's disease was conducted between 1986 and 2016 and is the first study to incorporate polygenic risk scores into biometrical twin models of Alzheimer's disease. The sample included 1586 twins drawn from the Swedish Twin Registry which were nested within 1137 twin pairs (449 complete pairs and 688 incomplete pairs) with clinically based diagnoses and registry follow-up (M-age = 85.28, SD = 7.02; 44% male; 431 cases and 1155 controls). We report contributions of polygenic risk scores at P < 1 x 10(-5), considering a full polygenic risk score (PRS), PRS without the APOE region (PRS.no.APOE) and PRS.no.APOE plus directly measured APOE alleles. Biometric twin models estimated the contribution of environmental influences and measured (PRS) and unmeasured genes to Alzheimer's disease risk. The full PRS and PRS.no.APOE contributed 10.1 and 2.4% to Alzheimer's disease risk, respectively. When APOE e4 alleles were added to the model with the PRS.no.APOE, the total contribution was 11.4% to Alzheimer's disease risk, where APOE e4 explained 9.3% and PRS.no.APOE dropped from 2.4 to 2.1%. The total genetic contribution to Alzheimer's disease risk, measured and unmeasured, was 71% while environmental influences unique to each twin accounted for 29% of the risk. The APOE region accounts for much of the measurable genetic contribution to Alzheimer's disease, with a smaller contribution from other measured polygenic influences. Importantly, substantial background genetic influences remain to be understood. Karlsson et al. report that measured polygenic scores from genome-based studies, including an outsized role for APOE, explain only a fraction of the heritability indicated by twin models of Alzheimer's disease, leaving most genetic risk for Alzheimer's disease unexplained. Sensitive designs are needed to capture all the genetic influences.
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| 2. |
- Kumar, Atul, et al.
(författare)
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Genetic effects on longitudinal cognitive decline during the early stages of Alzheimer’s disease
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Cognitive decline in early-stage Alzheimer’s disease (AD) may depend on genetic variability. In the Swedish BioFINDER study, we used polygenic scores (PGS) (for AD, intelligence, and educational attainment) to predict longitudinal cognitive change (measured by mini-mental state examination (MMSE) [primary outcome] and other cognitive tests) over a mean of 4.2 years. We included 260 β-amyloid (Aβ) negative cognitively unimpaired (CU) individuals, 121 Aβ-positive CU (preclinical AD), 50 Aβ-negative mild cognitive impairment (MCI) patients, and 127 Aβ-positive MCI patients (prodromal AD). Statistical significance was determined at Bonferroni corrected p value < 0.05. The PGS for intelligence (beta = 0.1, p = 2.9e−02) was protective against decline in MMSE in CU and MCI participants regardless of Aβ status. The polygenic risk score for AD (beta = − 0.12, p = 9.4e−03) was correlated with the rate of change in MMSE and was partially mediated by Aβ-pathology (mediation effect 20%). There was no effect of education PGS on cognitive measures. Genetic variants associated with intelligence mitigate cognitive decline independent of Aβ-pathology, while effects of genetic variants associated with AD are partly mediated by Aβ-pathology.
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| 3. |
- Kumar, Atul, et al.
(författare)
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Genetic influence during the early phases of Alzheimer's disease on longitudinal cognitive impairment
- 2021
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Ingår i: Alzheimer's & dementia : the journal of the Alzheimer's Association. - 1552-5279. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The rate of cognitive decline in the early stages of Alzheimer's disease (AD) is variable, which may be partly due to genetic factors. We therefore investigated genetic predictors of longitudinal cognitive decline in AD. METHOD: In the Swedish BioFINDER study, we used polygenic scores (PGS) (of AD, intelligence and educational attainment), and genetic variants (in a genome-wide association study [GWAS]) to predict longitudinal change in cognition (measured by MMSE) over a mean of 4.2 years. We included 555 b-amyloid (Aβ) negative cognitively unimpaired (CU) individuals, 206 Aβ-positive CU (preclinical AD), 110 Aβ-negative mild cognitive impairment (MCI) patients, and 146 Aβ-positive MCI patients (prodromal AD). Mixed-effect models were fitted with longitudinal MMSE data as dependent variable. Random slopes and intercepts were extracted and were rank-based inverse normal transformed (INT) to be used as dependent variables in linear regression models. RESULT: AD polygenic risk score (PRS) and intelligence PGS (but not education PGS) were associated with rate of cognitive decline (Figure 1). The AD PRS was only associated with decline in Ab-positive individuals, but the intelligence PGS was protective irrespective of Ab-status (Figure 2). The model containing only the APOE burden (ε4 and ε2 counts) was associated with cognitive decline with a nominal level of significance, whereas this was not found for the early-stage AD cohort (Figure 1 and 2). Our GWAS identified 8 genes (out of which 3 genes independent of Aβ-status) associated with rate of cognitive decline at a p-value ≤ 5e-05 (Table 1). CONCLUSION: An a priori defined genetic risk score for AD was only associated with rate of cognitive decline in early stage AD (Aβ+ CU and Aβ+ MCI) and not in an unselected population, while a polygenic score for intelligence was protective irrespective of Aβ status. Together with novel genetic associations for rate of cognitive decline in AD, this may provide new insights into the pathophysiology of AD and new therapeutic development targets.
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| 4. |
- Kumar, Atul, et al.
(författare)
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Genetic interaction study of Alzheimer's disease quantitative biomarkers : A polygenic risk score analysis and evaluation
- 2021
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Ingår i: Alzheimer's & dementia : the journal of the Alzheimer's Association. - 1552-5279. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Relationship between genetic factors and pathological features of Alzheimer's disease (AD) may be studied with biomarker, using both polygenic risk scores (PRSs), as well as individual genetic variants in genome-wide association studies (GWAS). METHOD: In the Swedish BioFINDER study, we used a priori PRS for AD based on findings in recent GWAS, and AD related biomarkers in cerebrospinal fluid (CSF) in cognitively unimpaired individuals (n = 751), Mild Cognitive Impairment (n = 212), and AD (n = 150) patients. AD related biomarkers were rank-based inverse normal transformed to be used as dependent variables in linear regression models adjusted for age, gender, education, APOE ε4, ε2 count and significant principal components. We also tested individual genetic variants in GWAS for each biomarker. Analyses were performed in the total sample, and after stratification on MMSE results. RESULT: The PRS was associated with higher CSF P-tau 181 (p ≤1.2e-05) and T-tau (p ≤ 8.14e-05) and lower CSF Aβ42/40 (p ≤ 0.006) and Aβ42 (p ≤ 0.04) (Figure 1, 2). Gene Enrichment of PRS 5 genes [containing 1850 genetic variants mapped to 1607 genes] for Tau biomarker showed 13 Gene Ontology (GO) Biological Process (BP) terms at p-value < e-03 ("Dendrite Morphogenesis": top hit; p-value ≤ 9.20e-06) and 16 KEGG pathway term enriched for genes of PRS 5 ("Phosphatidylinositol signaling system": top hit; p-value ≤ 5.5e-06) (Figure 3, 4). Gene enrichment of PRS 7 [containing 62 genetic variants mapped to 58 genes] for Aβ biomarker returned 12 GO terms ("Integrin-Mediated Signaling Pathway": top hit; p-value ≤1.20e-03) and 1 term enriched for KEGG pathway (Hematopoietic cell lineage). In our predefined list of genes interacting with MAPT (22 genes) and APP (69 genes) we found 3 genes from MAPT and APP set that were involved in PRS 5 and PRS 7 respectively. We also found 9 genes from APP set that was involved in PRS 5. CONCLUSION: Elevated levels of AD related biomarkers are associated with polygenic risk scores in AD. These findings further strengthens the link between genetic and biomarker disease predictors and indicate a potential role for these markers in disease prediction and patient stratification in AD.
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| 5. |
- Sproviero, William, et al.
(författare)
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ATXN2 trinucleotide repeat length correlates with risk of ALS
- 2017
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Ingår i: Neurobiology of Aging. - : Elsevier BV. - 0197-4580 .- 1558-1497. ; 51, s. 178.e1-178.e9
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Tidskriftsartikel (refereegranskat)abstract
- We investigated a CAG trinucleotide repeat expansion in the ATXN2 gene in amyotrophic lateral sclerosis (ALS). Two new case-control studies, a British dataset of 1474 ALS cases and 567 controls, and a Dutch dataset of 1328 ALS cases and 691 controls were analyzed. In addition, to increase power, we systematically searched PubMed for case-control studies published after 1 August 2010 that investigated the association between ATXN2 intermediate repeats and ALS. We conducted a meta-analysis of the new and existing studies for the relative risks of ATXN2 intermediate repeat alleles of between 24 and 34 CAG trinucleotide repeats and ALS. There was an overall increased risk of ALS for those carrying intermediate sized trinucleotide repeat alleles (odds ratio 3.06 [95% confidence interval 2.37-3.94]; p = 6 × 10(-18)), with an exponential relationship between repeat length and ALS risk for alleles of 29-32 repeats (R(2) = 0.91, p = 0.0002). No relationship was seen for repeat length and age of onset or survival. In contrast to trinucleotide repeat diseases, intermediate ATXN2 trinucleotide repeat expansion in ALS does not predict age of onset but does predict disease risk.
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