Neurobiology of Aging 35 (2014) 936.e5e936.e12
Contents lists available at ScienceDirect
Neurobiology of Aging journal homepage: www.elsevier.com/locate/neuaging
Evaluation of late-onset Alzheimer disease genetic susceptibility risks in a Canadian population Ardeshir Omoumi a, Alice Fok a, Talitha Greenwood b, A. Dessa Sadovnick b, Howard H. Feldman a, Ging-Yuek R. Hsiung a, * a b
Division of Neurology, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, Canada Department of Medical Genetics, University of British Columbia, Vancouver, Canada
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 June 2013 Received in revised form 16 September 2013 Accepted 19 September 2013 Available online 28 October 2013
We performed case-control studies using 2 Canadian cohorts to examine the role of 10 promising Alzheimer’s disease (AD) loci identified in recent genomewide association studies. Patients age 65 years and older diagnosed with AD at baseline (prevalent cases) or who developed AD during follow-up assessments (incident cases) were compared with control subjects with no cognitive impairment. Our prevalent case study comparing prevalent AD cases (n ¼ 428) with participants with no cognitive impairment (n ¼ 524) revealed a significant association of rs6656401 and rs3818361 (CR1), rs2075650 (TOMM40), rs7561528 (BIN1), and rs3865444 (CD33) with late-onset AD that were robust to adjustment with age and apolipoprotein E ε4 genotype. The incident case study comparing patients who developed AD during longitudinal observation (n ¼ 152) with participants with no cognitive impairment found that rs2075650 (TOMM40) and rs3865444 (CD33) influence the risk of developing AD in this population. In addition, pooled analysis of our AD patients confirmed that CR1, TOMM40, BIN1, and CD33 contribute to late-onset AD susceptibility, in addition to apolipoprotein E. Ó 2014 Elsevier Inc. All rights reserved.
Keywords: CR1 TOMM40 BIN1 CD33 Alzheimer’s disease Canadian Cohorts
1. Introduction Alzheimer’s disease (AD) is the most common dementing disorder, with age as the strongest risk factor (Fratiglioni et al., 2000). The likelihood for people at age 65 to develop AD during their life span is 1 in 5 (Seshadri and Wolf, 2007), and increases to 1 in 2 if they reach the age of 85 (Avramopoulos, 2009). AD is a slowly progressive disease that usually manifests first with mild cognitive impairment before progressing to frank dementia, in which memory impairment is the most prominent cognitive deficit. AD can be classified based on the age of onset as early onset and late onset, with 65 years commonly used as the dividing threshold. Familial early-onset AD is often caused by autosomal dominant mutations in specific genes (amyloid precursor protein, presenilins 1 and 2) (Wu et al., 2012). In contrast, the majority of AD cases are late-onset AD (LOAD), which has a complex genetic role. The discovery of the genetic factors for LOAD can contribute to understanding the pathogenesis of disease and making prognostic predictions. Apolipoprotein E (APOE) is currently the strongest genetic risk factor associated with LOAD (Bertram et al., 2008; Farrer et al., 1997; * Corresponding author at: S162e2211 Wesbrook Mall, UBC Hospital, Vancouver BC, Canada V6T 2B5. Tel.: þ1 604 822 3610; fax: þ1 604 822 7177. E-mail address: [email protected] (G.-Y.R. Hsiung). 0197-4580/$ e see front matter Ó 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.neurobiolaging.2013.09.025
Strittmatter et al., 1993), with an approximate 3-fold increased risk in those who carry a copy of the APOE ε4 allele compared with noncarriers (Avramopoulos, 2009). Recently, genome-wide association studies (GWASs) have identified several additional genetic risk factors for LOAD in white populations, albeit with much lower odds ratios (Ors) than APOE. In a GWAS by Harold et al., (2009), several genetic variants were found to be associated significantly with LOAD, including rs3818361 (CR1), rs1136000 (CLU), rs3851179 (PICALM), and rs2075650 (TOMM40). In another study, Lambert et al. (2009) also reported a significant association of rs6656401 (CR1) with LOAD, in addition to rs1136000 (CLU) and rs3818361 (CR1). Moreover, a recent study reported an uncommon coding variant of rs4844609 (CR1) that was associated significantly with pathologically diagnosed AD, and a strong linkage disequilibrium was also found between this single nucleotide polymorphism (SNP) and rs6656401 (CR1) (Shulman et al., 2011). Additional genetic variants associated with risk of AD identified in recent GWASs are rs3865444 (CD33), rs11767557 (EPHA1), rs4938933 (MS4A4A), rs9349407 (CD2AP), rs7561528 (BIN1), and rs3764650 (ABCA7) (Hollingworth et al., 2011; Naj et al., 2011). Although these associated SNPs generally have small effect sizes with ORs in the range of 1.1e1.5 (Wijsman et al., 2011), a number of these novel AD loci have shown evidence for replication in different ethnicities or association with neuroimaging or neuropathological features of AD
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A. Omoumi et al. / Neurobiology of Aging 35 (2014) 936.e5e936.e12
Fig. 1. Defining the cohorts and comparison groups. Abbreviations: ACCORD, A Canadian Collaborative Cohort of Cognitive Impairment and Related Dementia; AD, Alzheimer’s Disease; CSHA, Canadian Study of Health and Aging; IC, incident case-control study; NCI, no cognitive impairment; PA, pooled analysis; PC, prevalence case-control study.
(Biffi et al., 2010; Carrasquillo et al., 2010; Chen et al., 2012; Kok et al., 2011; Lee et al., 2011; Yu et al., 2010). In this study, we investigated the role of the previously mentioned polymorphisms in CR1, CLU, PICALM, TOMM40, CD33, EPHA1, MS4A4A, CD2AP, BIN1, and ABCA7 in susceptibility to LOAD in prevalent cases, as well as the risk of progression to AD in incident cases, using 2 wellcharacterized Canadian cohorts. 2. Methods 2.1. Study design and subjects We identified prevalent and incident cases of LOAD in participants from two large Canadian cohorts: Canadian Study of Health and Aging (CSHA) and A Canadian Collaborative Cohort of Cognitive Impairment and Related Dementia (ACCORD). The CSHA (n ¼ 10,263) was a population-based longitudinal study of cognition in
aging for up to 10 years with an initial baseline in 1991 (phase 1) and follow-up assessments in 1996 (phase 2) and 2001 (phase 3). A total of 1728 participating individuals in the CSHA consented to DNA donation for genetic studies. Details of the CSHA study methodology have been published elsewhere (CSHA, 1994; CSHA, 2000; Graham et al., 1996; Hsiung et al., 2004). The ACCORD (n ¼ 1136) was a 7-year longitudinal cohort study that recruited subjects from 8 specialized dementia clinics across Canada, with DNA donation by 532 participants for genetic studies. The baseline assessment in the ACCORD was accomplished from 1997 to 1999, with 2 annual follow-ups, and a final follow-up after 5e7 years after the baseline assessment (Feldman et al., 2003). Both the CSHA and ACCORD studies consisted of subjects primarily of European ethnic background because of the requirement that all subjects be fluent in English or French to allow proper neuropsychological testing. The criteria used for diagnosis of cognitive impairment no dementia and AD in the 2 cohorts were adhered to without change
A. Omoumi et al. / Neurobiology of Aging 35 (2014) 936.e5e936.e12
936.e7
Table 1 SNPs used in this study Gene
CR1
BIN1 CD2AP EPHA1 PICALM MS4A4A CD33 ABCA7 TOMM40 CLU (APOJ)
Chromosome
1
2 6 7 11 11 19 19 19 8
Reference SNP no.
Minor allele
Description
rs6656401 rs3818361 rs4844609 rs7561528 rs9349407 rs11767557 rs3851179 rs4938933 rs3865444 rs3764650 rs2075650 rs1136000
A A A A C C T C T G G T
Intronic Intronic T1610S 5’ Intronic Intronic 5’ Intronic d Intronic Intronic Intronic
Original study of LOAD GWAS OR
Reference
1.21 1.17 d 1.16 1.12 0.87 0.85 0.88 0.89 1.23 2.53 0.84 0.86
Lambert et al. (2009) Harold et al. (2009) Keenan et al. (2011) Harold et al. (2009) Naj et al. (2011) Naj et al. (2011) Harold et al. (2009) Naj et al. (2011) Naj et al. (2011) Hollingworth et al. (2011) Harold et al. (2009) Harold et al. (2009) Lambert et al. (2009)
Key: GWAS, genomewide association studies; LOAD, late-onset Alzheimer’s disease; OR, odds ratio; SNP, single nucleotide polymorphism.
(Ebly et al., 1994; Graham et al., 1996). In brief, subjects were deemed as normal or no cognitive impairment (NCI) if they did not have any of the Diagnostic and Statistical Manual of Mental Disorders, version III, revised, criteria for dementia after clinical and neuropsychological assessments (American Psychiatric Association, 1987). AD was diagnosed by the Diagnostic and Statistical Manual of Mental Disorders, version III, revised, dementia criteria and the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association criteria, including both possible and probable AD (McKhann et al., 1984). Candidate SNPs showing significant association with LOAD in recent GWASs were examined. For the prevalence case-control study, patients age 65 years and older diagnosed with AD at the time of
enrollment were compared with control subjects who consisted of participants age 65 years and older who had NCI until the end of the study. For the incidence case-control study, patients who, initially, were not demented at the time of enrollment but later developed AD during longitudinal assessments were compared with those with NCI. Last, we performed a pooled analysis, comparing patients with AD diagnosed with AD at baseline or follow-up assessments with individuals with NCI who never developed dementia throughout the longitudinal observation period of the cohorts (Fig. 1). 2.2. SNP selection SNPs or SNPs tagging linkage disequilibrium blocks with the strongest statistical association from recent GWASs were selected
Table 2 Prevalence case-control study Control subjects (n ¼ 524)
AD patients (n ¼ 428)
Genotypic association General genetic model
Additive genetic model
Genotype frequencies (%)
p Valuea
p Valuea Adjusted OR (95% CI)b
Crude OR (95% CI) APOE Control subjects Patients with AD rs6656401 (CR1) Control subjects Patients with AD rs3818361 (CR1) Control subjects Patients with AD rs3851179 (PICALM) Control subjects Patients with AD rs2075650 (TOMM40) Control subjects
/ 79.0 49.5 AA 3.0 5.7 AA 3.7 6.8 CC 41.9 45.1 AA 78.8
/ε4 20.8 41.1 AG 26.1 31.3 AG 26.9 30.0 CT 41.9 43.3 AG 19.6
ε4/ε4 0.2 9.3 GG 70.9 63.0 GG 69.4 63.3 TT 16.2 11.6 GG 1.6
Patients with AD
56.9
36.6
6.5
rs7561528 (BIN1) Control subjects Patients with AD rs3865444 (CD33) Control subjects Patients with AD
GG 46.5 42.4 TT 10.7 9.3
AG 38.3 46.3 GT 48.5 39.5
AA 15.2 11.3 GG 40.8 51.2
Key: AD, Alzheimer’s disease; APOE, apolipoprotein E; CI, confidence interval; OR, odds ratio. a c2 test. p Values less than 0.05 are in bold type. b Adjusted for APOE and age. c ε4 present versus ε4 absent.
p Value
Contents lists available at ScienceDirect
Neurobiology of Aging journal homepage: www.elsevier.com/locate/neuaging
Evaluation of late-onset Alzheimer disease genetic susceptibility risks in a Canadian population Ardeshir Omoumi a, Alice Fok a, Talitha Greenwood b, A. Dessa Sadovnick b, Howard H. Feldman a, Ging-Yuek R. Hsiung a, * a b
Division of Neurology, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, Canada Department of Medical Genetics, University of British Columbia, Vancouver, Canada
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 June 2013 Received in revised form 16 September 2013 Accepted 19 September 2013 Available online 28 October 2013
We performed case-control studies using 2 Canadian cohorts to examine the role of 10 promising Alzheimer’s disease (AD) loci identified in recent genomewide association studies. Patients age 65 years and older diagnosed with AD at baseline (prevalent cases) or who developed AD during follow-up assessments (incident cases) were compared with control subjects with no cognitive impairment. Our prevalent case study comparing prevalent AD cases (n ¼ 428) with participants with no cognitive impairment (n ¼ 524) revealed a significant association of rs6656401 and rs3818361 (CR1), rs2075650 (TOMM40), rs7561528 (BIN1), and rs3865444 (CD33) with late-onset AD that were robust to adjustment with age and apolipoprotein E ε4 genotype. The incident case study comparing patients who developed AD during longitudinal observation (n ¼ 152) with participants with no cognitive impairment found that rs2075650 (TOMM40) and rs3865444 (CD33) influence the risk of developing AD in this population. In addition, pooled analysis of our AD patients confirmed that CR1, TOMM40, BIN1, and CD33 contribute to late-onset AD susceptibility, in addition to apolipoprotein E. Ó 2014 Elsevier Inc. All rights reserved.
Keywords: CR1 TOMM40 BIN1 CD33 Alzheimer’s disease Canadian Cohorts
1. Introduction Alzheimer’s disease (AD) is the most common dementing disorder, with age as the strongest risk factor (Fratiglioni et al., 2000). The likelihood for people at age 65 to develop AD during their life span is 1 in 5 (Seshadri and Wolf, 2007), and increases to 1 in 2 if they reach the age of 85 (Avramopoulos, 2009). AD is a slowly progressive disease that usually manifests first with mild cognitive impairment before progressing to frank dementia, in which memory impairment is the most prominent cognitive deficit. AD can be classified based on the age of onset as early onset and late onset, with 65 years commonly used as the dividing threshold. Familial early-onset AD is often caused by autosomal dominant mutations in specific genes (amyloid precursor protein, presenilins 1 and 2) (Wu et al., 2012). In contrast, the majority of AD cases are late-onset AD (LOAD), which has a complex genetic role. The discovery of the genetic factors for LOAD can contribute to understanding the pathogenesis of disease and making prognostic predictions. Apolipoprotein E (APOE) is currently the strongest genetic risk factor associated with LOAD (Bertram et al., 2008; Farrer et al., 1997; * Corresponding author at: S162e2211 Wesbrook Mall, UBC Hospital, Vancouver BC, Canada V6T 2B5. Tel.: þ1 604 822 3610; fax: þ1 604 822 7177. E-mail address: [email protected] (G.-Y.R. Hsiung). 0197-4580/$ e see front matter Ó 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.neurobiolaging.2013.09.025
Strittmatter et al., 1993), with an approximate 3-fold increased risk in those who carry a copy of the APOE ε4 allele compared with noncarriers (Avramopoulos, 2009). Recently, genome-wide association studies (GWASs) have identified several additional genetic risk factors for LOAD in white populations, albeit with much lower odds ratios (Ors) than APOE. In a GWAS by Harold et al., (2009), several genetic variants were found to be associated significantly with LOAD, including rs3818361 (CR1), rs1136000 (CLU), rs3851179 (PICALM), and rs2075650 (TOMM40). In another study, Lambert et al. (2009) also reported a significant association of rs6656401 (CR1) with LOAD, in addition to rs1136000 (CLU) and rs3818361 (CR1). Moreover, a recent study reported an uncommon coding variant of rs4844609 (CR1) that was associated significantly with pathologically diagnosed AD, and a strong linkage disequilibrium was also found between this single nucleotide polymorphism (SNP) and rs6656401 (CR1) (Shulman et al., 2011). Additional genetic variants associated with risk of AD identified in recent GWASs are rs3865444 (CD33), rs11767557 (EPHA1), rs4938933 (MS4A4A), rs9349407 (CD2AP), rs7561528 (BIN1), and rs3764650 (ABCA7) (Hollingworth et al., 2011; Naj et al., 2011). Although these associated SNPs generally have small effect sizes with ORs in the range of 1.1e1.5 (Wijsman et al., 2011), a number of these novel AD loci have shown evidence for replication in different ethnicities or association with neuroimaging or neuropathological features of AD
936.e6
A. Omoumi et al. / Neurobiology of Aging 35 (2014) 936.e5e936.e12
Fig. 1. Defining the cohorts and comparison groups. Abbreviations: ACCORD, A Canadian Collaborative Cohort of Cognitive Impairment and Related Dementia; AD, Alzheimer’s Disease; CSHA, Canadian Study of Health and Aging; IC, incident case-control study; NCI, no cognitive impairment; PA, pooled analysis; PC, prevalence case-control study.
(Biffi et al., 2010; Carrasquillo et al., 2010; Chen et al., 2012; Kok et al., 2011; Lee et al., 2011; Yu et al., 2010). In this study, we investigated the role of the previously mentioned polymorphisms in CR1, CLU, PICALM, TOMM40, CD33, EPHA1, MS4A4A, CD2AP, BIN1, and ABCA7 in susceptibility to LOAD in prevalent cases, as well as the risk of progression to AD in incident cases, using 2 wellcharacterized Canadian cohorts. 2. Methods 2.1. Study design and subjects We identified prevalent and incident cases of LOAD in participants from two large Canadian cohorts: Canadian Study of Health and Aging (CSHA) and A Canadian Collaborative Cohort of Cognitive Impairment and Related Dementia (ACCORD). The CSHA (n ¼ 10,263) was a population-based longitudinal study of cognition in
aging for up to 10 years with an initial baseline in 1991 (phase 1) and follow-up assessments in 1996 (phase 2) and 2001 (phase 3). A total of 1728 participating individuals in the CSHA consented to DNA donation for genetic studies. Details of the CSHA study methodology have been published elsewhere (CSHA, 1994; CSHA, 2000; Graham et al., 1996; Hsiung et al., 2004). The ACCORD (n ¼ 1136) was a 7-year longitudinal cohort study that recruited subjects from 8 specialized dementia clinics across Canada, with DNA donation by 532 participants for genetic studies. The baseline assessment in the ACCORD was accomplished from 1997 to 1999, with 2 annual follow-ups, and a final follow-up after 5e7 years after the baseline assessment (Feldman et al., 2003). Both the CSHA and ACCORD studies consisted of subjects primarily of European ethnic background because of the requirement that all subjects be fluent in English or French to allow proper neuropsychological testing. The criteria used for diagnosis of cognitive impairment no dementia and AD in the 2 cohorts were adhered to without change
A. Omoumi et al. / Neurobiology of Aging 35 (2014) 936.e5e936.e12
936.e7
Table 1 SNPs used in this study Gene
CR1
BIN1 CD2AP EPHA1 PICALM MS4A4A CD33 ABCA7 TOMM40 CLU (APOJ)
Chromosome
1
2 6 7 11 11 19 19 19 8
Reference SNP no.
Minor allele
Description
rs6656401 rs3818361 rs4844609 rs7561528 rs9349407 rs11767557 rs3851179 rs4938933 rs3865444 rs3764650 rs2075650 rs1136000
A A A A C C T C T G G T
Intronic Intronic T1610S 5’ Intronic Intronic 5’ Intronic d Intronic Intronic Intronic
Original study of LOAD GWAS OR
Reference
1.21 1.17 d 1.16 1.12 0.87 0.85 0.88 0.89 1.23 2.53 0.84 0.86
Lambert et al. (2009) Harold et al. (2009) Keenan et al. (2011) Harold et al. (2009) Naj et al. (2011) Naj et al. (2011) Harold et al. (2009) Naj et al. (2011) Naj et al. (2011) Hollingworth et al. (2011) Harold et al. (2009) Harold et al. (2009) Lambert et al. (2009)
Key: GWAS, genomewide association studies; LOAD, late-onset Alzheimer’s disease; OR, odds ratio; SNP, single nucleotide polymorphism.
(Ebly et al., 1994; Graham et al., 1996). In brief, subjects were deemed as normal or no cognitive impairment (NCI) if they did not have any of the Diagnostic and Statistical Manual of Mental Disorders, version III, revised, criteria for dementia after clinical and neuropsychological assessments (American Psychiatric Association, 1987). AD was diagnosed by the Diagnostic and Statistical Manual of Mental Disorders, version III, revised, dementia criteria and the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association criteria, including both possible and probable AD (McKhann et al., 1984). Candidate SNPs showing significant association with LOAD in recent GWASs were examined. For the prevalence case-control study, patients age 65 years and older diagnosed with AD at the time of
enrollment were compared with control subjects who consisted of participants age 65 years and older who had NCI until the end of the study. For the incidence case-control study, patients who, initially, were not demented at the time of enrollment but later developed AD during longitudinal assessments were compared with those with NCI. Last, we performed a pooled analysis, comparing patients with AD diagnosed with AD at baseline or follow-up assessments with individuals with NCI who never developed dementia throughout the longitudinal observation period of the cohorts (Fig. 1). 2.2. SNP selection SNPs or SNPs tagging linkage disequilibrium blocks with the strongest statistical association from recent GWASs were selected
Table 2 Prevalence case-control study Control subjects (n ¼ 524)
AD patients (n ¼ 428)
Genotypic association General genetic model
Additive genetic model
Genotype frequencies (%)
p Valuea
p Valuea Adjusted OR (95% CI)b
Crude OR (95% CI) APOE Control subjects Patients with AD rs6656401 (CR1) Control subjects Patients with AD rs3818361 (CR1) Control subjects Patients with AD rs3851179 (PICALM) Control subjects Patients with AD rs2075650 (TOMM40) Control subjects
/ 79.0 49.5 AA 3.0 5.7 AA 3.7 6.8 CC 41.9 45.1 AA 78.8
/ε4 20.8 41.1 AG 26.1 31.3 AG 26.9 30.0 CT 41.9 43.3 AG 19.6
ε4/ε4 0.2 9.3 GG 70.9 63.0 GG 69.4 63.3 TT 16.2 11.6 GG 1.6
Patients with AD
56.9
36.6
6.5
rs7561528 (BIN1) Control subjects Patients with AD rs3865444 (CD33) Control subjects Patients with AD
GG 46.5 42.4 TT 10.7 9.3
AG 38.3 46.3 GT 48.5 39.5
AA 15.2 11.3 GG 40.8 51.2
Key: AD, Alzheimer’s disease; APOE, apolipoprotein E; CI, confidence interval; OR, odds ratio. a c2 test. p Values less than 0.05 are in bold type. b Adjusted for APOE and age. c ε4 present versus ε4 absent.
p Value
