Genetic variants associated with susceptibility to psychosis in late-onset Alzheimer’s disease families

Neurobiology of Aging 36 (2015) 3116.e9e3116.e16

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Genetic variants associated with susceptibility to psychosis in late-onset Alzheimer’s disease families Sandra Barral a, b, c, Badri N. Vardarajan a, b, c, Dolly Reyes-Dumeyer a, b, c, Kelley M. Faber d, Thomas D. Bird e, f, Debby Tsuang e, f, David A. Bennett g, Roger Rosenberg h, Bradley F. Boeve i, Neill R. Graff-Radford j, Alison M. Goate k, Martin Farlow l, Rafael Lantigua a, m, Martin Z. Medrano n, Xinbing Wang o, p, M. Ilyas Kamboh o, Mahmud Muhiedine Barmada o, Daniel J. Schaid q, Tatiana M. Foroud d, Elise A. Weamer r, Ruth Ottman b, c, s, t, Robert A. Sweet u, v, Richard Mayeux a, b, c, *, for the NIA-LOAD/NCRAD Family Study Group a

Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Columbia University Medical Center and New York Presbyterian Hospital, New York, NY, USA Gertrude H. Sergievsky Center, Columbia University Medical Center and New York Presbyterian Hospital, New York, NY, USA c Department of Neurology, Columbia University Medical Center and New York Presbyterian Hospital, New York, NY, USA d Department of Medical and Molecular Genetics, Indiana University, Indianapolis, IN, USA e Department of Neurology, University of Washington, Seattle, WA, USA f Department of Medicine, University of Washington, Seattle, WA, USA g Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, IL, USA h Department of Neurology and Neurotherapeutics, The University of Texas Southwestern Medical Center, Dallas, TX, USA i Department of Neurology, Mayo Clinic, Rochester, MN, USA j Department of Neurology, Mayo Clinic, Jacksonville, FL, USA k Icanhn School of Medicine at Mount Sinai, New York, NY, USA l Department of Neurology, Indiana University Center for Alzheimer’s Disease and Related Disorders, Indianapolis, IN, USA m Department of Medicine, Columbia University Medical Center and New York Presbyterian Hospital, New York, NY, USA n Department of Geriatrics, Pontificia Universidad Católica Madre y Maestra, Santiago, Dominican Republic o Department of Human Genetics, University of Pittsburgh, Pittsburgh, PA, USA p Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA, USA q Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA r Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA s Department of Epidemiology, Columbia University Medical Center and New York Presbyterian Hospital, New York, NY, USA t Division of Epidemiology, New York State Psychiatric Institute, New York, NY, USA u Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA v VISN 4 Mental Illness Research, Education and Clinical Center (MIRECC), VA Pittsburgh Healthcare System, Pittsburgh, PA, USA b

a r t i c l e i n f o Article history: Received 20 April 2015 Received in revised form 1 July 2015 Accepted 8 August 2015

Keywords: Late-onset Alzheimer’s disease Psychosis Genome-wide linkage analysis Association analysis Non-Hispanic Caucasian and Caribbean Hispanic ancestry populations

a b s t r a c t Psychotic symptoms are frequent in late-onset Alzheimer’s disease (LOAD) patients. Although the risk for psychosis in LOAD is genetically mediated, no genes have been identified. To identify loci potentially containing genetic variants associated with risk of psychosis in LOAD, a total of 263 families from the National Institute of Aging-LOAD cohort were classified into psychotic (LOADþP, n ¼ 215) and nonpsychotic (LOADeP, n ¼ 48) families based on the presence/absence of psychosis during the course of LOAD. The LOADþP families yielded strong evidence of linkage on chromosome 19q13 (two-point [2-pt] logarithm of odds [LOD] ¼ 3.8, rs2285513 and multipoint LOD ¼ 2.7, rs541169). Joint linkage and association in 19q13 region detected strong association with rs2945988 (p ¼ 8.7  107). Linkage results for the LOADeP families yielded nonsignificant 19q13 LOD scores. Several 19q13 single-nucleotide polymorphisms generalized the association of LOADþP in a Caribbean Hispanic (CH) cohort, and the strongest signal was rs10410711 (pmeta ¼ 5.1  105). A variant located 24 kb upstream of rs10410711 and rs10421862 was strongly associated with LOADþP (pmeta ¼ 1.0  105) in a meta-analysis of the CH cohort and an additional

* Corresponding author at: G.H. Sergievsky Center and the Department of Neurology, Columbia University Medical Center and New York Presbyterian Hospital, New York, NY 10032, USA. Tel.: (212) 305-2391; fax: 212-305-2518. E-mail address: [email protected] (R. Mayeux). 0197-4580/Ó 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). http://dx.doi.org/10.1016/j.neurobiolaging.2015.08.006

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non-Hispanic Caucasian dataset. Identified variants rs2945988 and rs10421862 affect brain gene expression levels. Our results suggest that genetic variants in genes on 19q13, some of which are involved in brain development and neurodegeneration, may influence the susceptibility to psychosis in LOAD patients. Ó 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

2. Materials and methods

participants. Recruitment for the National Institute of Aging (NIA)LOAD study was approved by the relevant institutional review boards of the participating centers. The study was conducted according to the principles expressed in the Declaration of Helsinki. Description of the recruitment, diagnostic procedures, and the approach to characterization of psychotic symptoms for the NIALOAD cohort has been described previously (Sweet et al., 2010). In brief, qualifying families required a proband and a full sibling, each with a diagnosis of definite or probable Alzheimer’s disease (McKhann et al., 1984) with onset after 60 years of age and at least 1 additional biologically related family member who was 60 years or older if unaffected or 50 years or older if diagnosed as having AD or mild cognitive impairment (Petersen et al., 1999). Psychosis was assessed by interview of a knowledgeable informant and rated on the Consortium to Establish a Registry for Alzheimer’s Disease Behavioral Rating Scale 1996 version (Mack et al., 1999), the Neuropsychiatric Inventory (Cummings et al., 1994), and the Neuropsychiatric Inventory Questionnaire (Kaufer et al., 2000), with slight modification as described previously (Sweet et al., 2010). We have previously established excellent interrater reliability of psychosis using this approach to assessment in this cohort (Sweet et al., 2010). Delusions were defined as persistent false beliefs based on incorrect inference about external reality, resistant to persuasion or contrary evidence, and not attributable to social or cultural mores. Hallucinations were defined as sensory perceptions for which there was no basis in reality. Discrete hypnagogic and hypnopompic hallucinations, as well as symptoms occurring only during an episode of delirium, were not rated. To avoid phenocopies because of momentary confusion or misinterpretation by the observer, a delusion or hallucination was defined by its persistence over time. Thus, a given Consortium to Establish a Registry for Alzheimer’s Disease Behavioral Rating Scale item is considered evidence of a delusion or hallucination when it was rated as occurring (at least) 3 times in the past month at any visit. Because the frequency of psychosis in LOAD increases in individuals with a Clinical Dementia Rating (CDR) Scale score >1 (Sweet et al., 2010), classification as not psychotic required individuals to be free of delusions and hallucinations throughout their illness and to have a CDR >1. Using this definition, we found that LOADþP is a highly heritable trait (h2 ¼ 0.61, standard error ¼ 0.31) in the NIA-LOAD cohort (for a description of heritability analysis, see Supplementary Methods), supporting its use for the gene-mapping analyses we conducted. For the present analysis, we used a sample of 607 families from the NIA-LOAD cohort that was previously used in a genome-wide analysis of familial LOAD (Wijsman et al., 2011). We furthermore restricted the analysis to families where members had psychosis assessments and also available genome-wide data, leading to a final sample of 1279 subjects from 263 families. The families were divided into 2 subgroups based on the presence or absence of psychosis symptoms in LOAD family members. Families with at least 1 LOAD family member with psychosis were classified as LOADþP families (n ¼ 215). Families without any LOAD members with psychosis were classified as LOADP families (n ¼ 48).

2.1. Study participants

2.2. Statistical analyses

2.1.1. National Institute of Aging LOAD Cohort 2.1.1.1. Standard protocol approvals, registrations, and patient consents. Informed consent for the study was obtained for all

2.2.1. Genome-wide genotyping of NIA-LOAD cohort Genotyping of the study participants was performed using Illumina Human610Quadv1_B BeadChips (Illumina, San Diego, CA,

1. Introduction Psychotic symptoms, hallucinations and delusions, are frequent in patients with late-onset Alzheimer’s disease (LOAD). Multiple studies suggest that the frequency of psychosis in patients with LOAD (LOADþP) is close to 50%. With estimates of >13 million Americans affected by LOAD by 2050 (Thies and Bleiler, 2013), LOADþP would be among the most prevalent psychotic disorders in the United States. Compared with LOAD patients without psychosis (LOADeP), patients with LOADþP demonstrate more severe cognitive and functional deficits (Scarmeas et al., 2005), more rapid cognitive decline (Sweet et al., 2012), and more prone aggressive behaviors (Sweet et al., 2000). Patients with LOADþP progress to more advanced stages of disease with worse general health (Bassiony et al., 2000), greater rates of institutionalization (Lopez et al., 1999), and increased mortality (Wilson et al., 2006). There is strong evidence for familial aggregation of psychosis in patients with LOAD. In a previous study of familial aggregation of LOADþP in a cohort of patients and their siblings with AD (Sweet et al., 2002), we showed that the occurrence of psychotic symptoms in siblings with LOAD was 3 times that of the siblings of patients without psychosis. Additional studies have supported the familial aggregation of LOADþP (Hollingworth et al., 2007). The estimated heritability of psychosis in LOAD is 61% when psychosis is defined by the presence of multiple or recurrent psychotic symptoms and is 30% for any single occurrence of a symptom (Bacanu et al., 2005). Subsequent linkage and association studies to identify genetic variants associated with the combined LOADþP phenotype have detected linkage to chromosomes 2p, 6q, 7q, and 15q (Avramopoulos et al., 2005; Bacanu et al., 2002; Go et al., 2005; Hollingworth et al., 2007). Initial efforts to identify genetic variants contributing to LOADþP used a candidate gene approach, focused on the APOE locus and on genes implicated in alterations in the serotonergic, dopaminergic, and catecholaminergic neurotransmission systems (DeMichele-Sweet and Sweet, 2010). Results for the APOE locus have been inconsistent but predominantly negative (DeMichele-Sweet and Sweet, 2010). More recently, the first genome-wide association study (GWAS) of LOADþP was reported (Hollingworth et al., 2012), a meta-analysis of 3 LOAD GWAS datasets comprising 1299 cases with LOADþP, 735 with LOADeP, and 5659 unaffected controls. This analysis identified several loci with strong evidence of association with LOADþP, although no single locus reached the threshold for genome-wide significance. We hypothesized that a distinct genetic mechanism raises risk for LOAD with an increased likelihood of comorbid psychosis. To test this hypothesis, we divided a large set of LOAD families into 2 groups based on the presence/absence of psychosis during the course of LOAD in at least 1 individual. Then, we carried out linkage analysis separately within each set of families.

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USA) (Wijsman et al., 2011). Genome-wide linkage analysis was restricted to single-nucleotide polymorphism (SNP) markers with minor allele frequencies of 5%. 2.2.2. Linkage analysis To evaluate the evidence for linkage in the LOADþP and LOADP families, we performed nonparametric two-point (2-pt) genomewide linkage analysis using the Kong and Cox linear model implemented in multipoint engine for rapid likelihood inference (Abecasis et al., 2002). Linkage analyses performed in both LOADþP and LOADP families were carried out using sex, age, education, and CDR as covariates. We have included CDR score because functional severity of dementia has been associated with the presence of psychosis in patients with LOAD (Sweet et al., 2010). Evidence for linkage was considered statistically significant in the 2-pt analysis if the 2-pt LOD score was 3.6 (Lander and Kruglyak, 1995). We performed multipoint (mpt) linkage analysis in regions with significant linkage evidence in the 2-pt analysis. Because the presence of linkage disequilibrium among SNPs violates an underlying assumption of mpt linkage analysis software, SNPs were pruned on the basis of a correlation coefficient, r2, of 0.2 using PLINK software (http://pngu.mgh.harvard.edu/wpurcell/plink/index.shtml). 2.2.3. Test of linkage heterogeneity To test for linkage heterogeneity between the LOADþP and LOADP families, we used an approach based on the heterogeneity test of Morton (1956). First, we performed linkage analysis in all LOADþP and LOADP families combined, to obtain the maximum LOD score under the null hypothesis of homogeneity (Zmax, combined). Second, we performed linkage analysis within each family subgroup separately, obtained the maximum LOD score for each SNP, Zmax, LOADþP and Zmax, and LOADP, and then summed these 2 maximum values. The chi-square statistic for the test for heterogeneity was computed as c2(1) ¼ 4.6  ([Zmax, LOADþP þ Zmax, LOADP]  Zmax, combined). 2.2.4. Linkage power calculation To estimate the power of our LOADeP families in detecting linkage, we performed simulations of genotypes for 100 replicates using SLINK (Ott, 1989). We assumed an autosomal dominant inheritance model, recombination fraction ranging from 0.0 to 0.45 and minor allele frequencies ranging from 10% to 40%. 2.2.5. Joint linkage and association analysis For chromosomal regions that yielded significant 2-pt LOD scores and mpt LOD scores 2.5, we carried out joint linkage and association analysis in a 50-kb region encompassing the linkage peaks using PSEUDOMARKER software (Gertz et al., 2014). Adjustment for multiple testing based on the 157 SNPs tested on 19q13.12 was carried out using Bonferroni correction (significance threshold p  3.7  104). 2.2.6. Generalization cohort Because the frequencies of genetic variants can differ substantially between different ethnic groups, it is important to assess whether results obtained in populations of European ancestry can be extended to populations of different ancestry. Hence, we assessed whether our results can be generalized using a Caribbean Hispanic (CH) sample, Estudio Familiar de Influencia Genetica en Alzheimer (EFIGA), and Washington Heights-Inwood Columbia Aging Project (WHICAP). Unrelated CH subjects were selected from the WHICAP study and the EFIGA. WHICAP is a population-based study of elderly individuals residing in New York, and EFIGA study recruited CH families with multiple members affected with LOAD. Both studies followed the same clinical diagnostic methods,

and both cohorts have been described elsewhere (Mayeux et al., 2001; Vardarajan et al., 2014). For analysis purposes, we identified unrelated individuals as psychotic based on the presence of one or more of the following rated as present on the medical history form: (1) psychosis identified as the first symptom of dementia; (2) hallucinations (visual, auditory, olfactory, or tactile); (3) delusions; and (4) receipt of anti-psychotic medication. In this analysis, we have included 4917 study’s participants from 3 different and independent recruitment waves (CH1, CH2, and CH3). 2.2.7. Genome-wide genotyping Genome-wide genotyping was done using 2 high-throughput SNP genotyping platforms: Illumina HumanHap 650Y platform and Omni Express. 2.2.8. Test of SNP association in the CH sample For generalization purposes, the 19q13.12 region was defined by a total of 246 SNPs that were within the region of interest and genotyped in the 3 CH datasets. To account for the effects of population substructure, we performed a principal components analysis using EIGENSTRAT software (http://genepath.med.harvard. edu/wreich/EIGENSTRAT.htm). Logistic regression models were conducted using PLINK software (http://pngu.mgh.harvard.edu/ wpurcell/plink/index.shtml). All analyses were adjusted for sex, age, and the first 10 principal components derived from the EIGENSTRAT analysis. 2.2.9. Meta-analysis of the CH datasets The 3 independent datasets were combined into a meta-analysis taking into account study-specific sample size and direction of the association effect using METAL software (http://www.sph.umich. edu/csg/abecasis/metal/). Adjustment for multiple testing was carried out using Bonferroni correction. 2.2.10. Replication cohort: University of Pittsburgh Alzheimer Disease Research Center To further replicate associations in an independent dataset, we used a non-Hispanic Caucasian (NHC) cohort recruited from the University of Pittsburgh Alzheimer Disease Research Center. Characterization of the psychotic symptoms and quality control of the Alzheimer Disease Research Center genomic data has been described in detail elsewhere (Hollingworth et al., 2012). For analysis purposes, a total of 496 LOADþP and 156 LOADP subjects were included. 2.2.11. Brain expression Quantitative Trait Loci (eQTL) analyses To further determine whether associated SNPs affect gene expression levels, we used the publically available dataset from the UK Brain Expression Consortium that is based on tissue from 12 brain regions from 134 individuals free of neurodegenerative disorders analyzed using the Affymetrix Exon 1.0 ST Array (http:// www.braineac.org/). 3. Results Characteristics of the different study cohorts (NIA-LOAD, CH1, CH2, CH3, and NHC) are provided in Supplementary Table 1. The LOADþP families used for the linkage analysis consisted of 981 individuals from 215 families, including 264 LOAD patients with psychotic symptoms and 279 without psychosis. The average age at evaluation and standard deviation of the LOADþP family members was 76  7 years, and 55% were women. The LOADP families consisted of 298 individuals from 48 families, including 139 LOAD patients without psychotic symptoms. The age at evaluation of the LOADP family members was 76  8 years, and 53% were females.

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Genome-wide linkage analysis of the LOADþP families identified several regions with 2-pt LOD scores 3.6. The maximum 2-pt LOD score was observed on chromosome 18q21.32, with LOD ¼ 4.9 at rs2332026 (90.18 cM); however, mpt linkage analysis of the region did not yield significant evidence of linkage (maxLOD ¼ 2.0 at rs7069001). There were 3 different chromosomal regions, 14q32, 16q21, and 19q13.12, that yielded 2-pt LOD scores 3.6 and mpt LOD scores 2.5 that were prioritized for additional analysis (Fig. 1A and B, Table 1). Joint linkage and association analysis of these 3 candidate regions (Fig. 1C, Table 1) identified SNP marker rs2945988 at 19q13.12 as strongly associated with psychosis (p ¼ 8.7  107) even after Bonferroni adjustment. Although additional SNPs showed also nominal association with psychosis within the 2 other regions, rs10139111 at 14q32 (p ¼ 0.005) and rs9927943 at 16q21 (p ¼ 0.003), they did not survive correction for multiple testing. We focused on 19q13.12 signal because of its strong evidence of linkage and association and tested linkage heterogeneity. We found statistical evidence for the existence of heterogeneity between LOADþP and LOADP families (p ¼ 0.011), further supporting the need for stratifying the family cohort based on the presence or absence of psychotic symptoms among the LOAD patients. Our simulation results shown that when the linked allele frequency is 37%, the frequency of the minor allele of SNP rs2945988 in the LOADP cohort of families, we will have 93% power to detect

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LOD scores exceeding the Lander and Kruglyak threshold for significant linkage (LOD  3.6). To test whether our findings can be generalizable to another ethnic group, we used a sample of unrelated subjects with CH ancestry (CH1, CH2, and CH3) that included 231 LOAD patients with psychotic symptoms and 1943 without psychosis. Logistic regression analysis (age, sex, and population stratification adjusted) identified several SNPs as strongly associated with the LOADþP phenotype after adjustment for multiple testing with Bonferroni correction (Fig. 2 and Supplementary Table 2). The strongest signal with the same effect direction in all 3 CH datasets was found for SNP rs10410711 (pmeta ¼ 5  105), an intronic variant in ZNF566 gene. Additional variants in this gene also survived multiple testing corrections and achieved significant LOADþP association: rs10421862, located 24 kb downstream (pmeta ¼ 5  105) showed same direction of the association in the 3 CH cohorts and rs10419962 (pmeta ¼ 4.7  105), 234 kb upstream, showed same direction of the association in CH1 and CH2. We interrogated 19q13.12 region, defined by a total of 246 SNPs, in an independent NHC dataset. First, we analyzed the results from CH and NHC datasets via trans-ethnic meta-analysis using MANTRA software (Morris, 2011). Results from MANTRA revealed little evidence of heterogeneity in allelic effects of the SNPs (posterior probability of heterogeneity <50%) between the different populations, that is, the most heterogeneous SNP in terms of allelic

Fig. 1. Results of the genome-wide linkage and association analyses. (A) Genome-wide nonparametric 2-point (2-pt) linkage analysis in late-onset Alzheimer’s disease patients with psychosis (LOADþP) (right panel) and late-onset Alzheimer’s disease patients without psychosis (LOADP) (left panel) families; x-axis represents each of the analyzed chromosomes, and y-axis corresponds to the individual single-nucleotide polymorphism (SNP)’s LOD score. (B) Multipoint (mpt) linkage analysis in chromosomal regions with genomewide significant evidence of linkage (2-pt LOD scores 3.6) in the LOADþP families (right panel) and mpt linkage analysis of the same chromosomes in the LOADP families; x-axis represents physical location in base pair, and y-axis represents the individual SNP’s LOD score. (C) Joint linkage and association analysis in 50 kb region encompassing the linkage peak for chromosomal regions mpt LOD scores 2.5 in the LOADþP families; x-axis represents base pair position (Mb) along the chromosome, the left y-axis corresponds to the recombination rate (cM/Mb), and the right y-axis corresponds to the logarithm of the p value.

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Fig. 2. Generalization of 19q13.12 region in Caribbean Hispanic (CH) cohorts. Multivariate regression results from 3 independent CH replication cohorts and their meta-analysis; x-axis represents physical location of the single-nucleotide polymorphism markers in kilobases, and y-axis represents logarithm of the p value obtained in the analyses.

effect, rs7249613, has a posterior probability of heterogeneity of 34%. As SNPs in CH and NCH cohorts share a common effect size, we meta-analyzed the results with a fixed-effect model approach using METAL software (http://www.sph.umich.edu/csg/abecasis/metal/). The strongest association with LOADþP phenotype corresponds to rs10421862 (pmeta ¼ 1.0  105), with the same effect direction in CH and NHC datasets (data not shown). SNP rs2945988 identified in the NIA-LOAD cohort was not statistically significant in the CH meta-analysis (p ¼ 0.063). However, SNPrs2945988 in NIA-LOAD and its closest variant in CH, rs10421862, located 45 kb apart, are in low linkage disequilibrium (r2 ¼ 0.10), which would be expected based on the different linkage disequilibrium patterns within this chromosomal region between European and Hispanics ancestry populations (Supplementary Fig. 1). Nevertheless, the location would suggest that a gene or set of genes in this region are likely to underlie psychosis in patients with LOAD. Results from eQTL analyses using BRAINEAC showed that 73 genes within the 19q13.12 region had also altered brain expression because of these 2 19q13.12 variants, rs2945988 and rs10421862

Table 1 Candidate regions from genome-wide linkage and association analyses of the LOADþP families Band

SNP

2-pt LOD SNP

14q32 rs3742339 4.4 16q21 rs1867612 3.6 19q13.12 rs2285513 3.8

mpt LOD SNP

rs5508 2.5 rs9302724 2.6 rs541169 2.7

pjoint

rs10139111 0.005 rs9927943 0.003 rs2945988 8.7  107

LOADþP, late-onset Alzheimer’s disease patients with psychosis; SNP, singlenucleotide polymorphism.

(Supplementary Table 3). After Bonferroni multiple testing adjustment (p  6.8  104), rs2945988 is a significant gene-level ciseQTL for ZNF461 (p ¼ 2.2  105) and ZFP82 (p ¼ 8.0  105). Both genes are expressed in brain and codify Krüppel-associated boxcontaining zinc-finger proteins, the largest family of transcriptional regulators in the human genome (Urrutia, 2003). 4. Discussion To identify loci potentially containing genetic variants associated with higher risk of developing psychosis in subjects affected by LOAD, we performed a genome-wide linkage analysis in a sample of NIA-LOAD families in which some members with LOAD also exhibited psychosis symptoms. We observed significant evidence for 2-pt and mpt linkages on chromosome 19q13.12 (2-pt LOD ¼ 3.8 and mpt LOD ¼ 2.7). Further investigation of the linkage signal using joint linkage and association analyses identified SNP rs2945988 as strongly associated with psychosis (pjoint ¼ 8.7  107). The 19q13.12 association with psychosis was generalized to a sample of unrelated Alzheimer’s patients and controls of CH ancestry rs10410711 (pmeta ¼ 5  105). Further evidence was achieved through the metaanalysis of the CHs and an independent NHC cohorts, where another 19q13.12 variant located 24 kb upstream rs10410711, rs10421862, appeared strongly associated with LOADþP (pmeta ¼ 1.0  105) with the same effect direction in all datasets. In the most recent genome-wide linkage analysis of LOADþP up to date, Hollingworth et al. (2007) reported chromosome- and genomewide significant linkage peaks on chromosomes 7 and 15. Despite the differences in their study design (linkage analysis was restricted to affected relative pairs) and clinical assessment of psychosis (limited data were available covering the presence, type, and severity of

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psychotic symptoms), they reported suggestive linkage (LOD ¼ 1.86) to chromosome 19 at 50 cM, being the nearest marker D19S433 (30,417,027e30,417,232), w5 Mb upstream 19q13.12 region. Recent studies evaluating the genetic contributions to LOADþP have consisted of GWAS approaches. Hollingworth et al. (2012) undertook a meta-analysis of 3 GWASs to identify loci LOADþP loci. The possible association between chromosome 19 and LOADþP is limited to APOE locus (located >10 Mb apart from the identified 19q13.12 region). However, as previously reported (Demichele-Sweet et al., 2011), no evidence of association was observed at the APOE locus when analyzing LOADþP versus LOADeP. They also identified genetic variants/genes revealed overlap with other psychiatric disorders with psychotic features. In the first genome-wide study of copy number variation to date, Zheng et al. (2015) identified a significant duplication in the APC2 gene on 19p13, which was protective against developing LOADþP. Their results also suggested that the same genetic variants (SNPs and copy number variations) may be implicated in different psychiatric disorders (schizophrenia, autism, and LOADþP). To that end, the identified 19q13.12 variants in this study, rs2945988 and rs10421862, are located within zinc-finger binding proteins, ZNF260 and ZNF566, respectively, with a plausible role as regulators of gene expression. Of interest, several recent genetic association studies have reported that variants in a zinc-finger protein gene, ZNF804A, strongly influence susceptibility to psychosis, schizophrenia, and bipolar disorder (Steinberg et al., 2011). Additional studies have implicated genomic variation in 19q13.12 as risk factor for neuropsychiatric disorders. Xu et al. (2008) reported a de novo deletion on chromosome 19q13.12 with relatively high penetrance that contributes to the genetic component of schizophrenia. A multistage schizophrenia GWAS (Schizophrenia Working Group of the Psychiatric Genomics Consortium, 2014) identified 128 independent associations spanning 108 conservatively defined loci. Among the significant loci was an SNP on chromosome 19q13.12, mapping 13 Mb upstream of our identified region. Brain eQTL analyses revealed that SNP rs2945988 significantly affects gene expression of 2 Krüppel-associated box-containing zinc-finger genes (ZNF461 and ZFP82), suggesting transcriptional regulation as possible functional mechanism. Although they represent plausible a priori functional candidates for LOADþP, there is no guarantee that they are the causal genes; thus, it is likely that other loci within this region contribute to psychosis risk in LOAD (for genes in the 19q13.12 linkage region, see Supplementary Fig. 2). Among other potential candidate genes within this region (Supplemental Fig. 2) are WDR62 and SNX26, both expressed in brain and highly conserved. Assessment of brain expression patterns also revealed that rs2945988 and rs10421862 nominally affect the expression levels of the proteins encoded by WDR62 (p ¼ 0.012) and SNX26 (p ¼ 0.006) genes, respectively. Mutations in the WD repeatecontaining protein 62 gene WDR62 have been reported as the cause of a wide spectrum of severe cerebral cortical malformations. Experiments in human and mouse embryonic brain found that its expression was restricted to neural precursors undergoing mitosis, suggesting that WDR62 is a key protein in neural precursor generation, a process that is uniquely vital to human cerebral cortex growth (Nicholas et al., 2010). The sorting nexin 26 gene (SNX26), a brain-enriched Rho GTPase-activating protein, is involved in the regulation of dendritic branching and neuronal complexity in the developing brain and also affects synaptic plasticity in mature neurons. Dendritic spines changes are closely associated with various neurologic diseases (Kim et al., 2013). Our results suggest that the locus at 19q13.12 may influence the risk of developing a form of LOAD associated with psychosis. Our

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generalization sample consisted of a population-based cohort of CH subjects. Because of differences in genetic ancestry between European and Hispanic populations, we would not necessarily expect the same SNPs to be associated with LOADþP in both populations, although different SNPs in the same region might show association. Our observation of association of LOADþP with several SNPs in the same region in CHs and NHC, despite the differences between European and Hispanic samples in environmental and genetic factors, strengthens the evidence for 19q13.12 as susceptibility locus for psychosis in LOAD patients. Similar generalization approaches have been previously reported in the literature. Graff et al. (2013) used Hispanic population to investigate common adiposityrelated genetic loci previously reported in European descent populations and provided evidence for the generalization of several body mass index and central adiposity loci in Hispanic women. Although a potential limitation of our study was the lack of detailed assessments of the psychosis phenotype in the CH cohort, the evidence for generalization of the linkage signal indicates that the findings were robust and not related to the method of identification of the phenotype. Some of the subjects from the NIA-LOAD family cohort were included in the GWAS meta-analysis conducted by Hollingworth et al. (2012). The fact that the identified LOADþP variants affect the brain expression levels of the several genes in 19q13.12 region suggests that their expression might be transcriptionally regulated. Whether these variants are associated with the development of psychosis in LOAD specifically or are associated also with psychosis in the absence of LOAD is an interesting question that remains to be investigated. Sequencing of the 19q13.12 region using the most informative families may help to identify variants contributing to susceptibility to LOAD and psychosis. Disclosure statement S.B. is funded by NIH grants U01 AG023749, 1U01AG032984, UF1AG047133 and P50 AG08702; B.N.V. receives support from NIMH TRANSFORM K12 Mentored Career Development Award; K.M.F. has received research support from the NIH through U24AG021886 and U01AG032984; T.D.B. receives support from NIH grant P50AG005136 and from the Department of Veterans Affairs, the McCaffrey Foundation; D.T. is supported by NIH/NIA U0 AG032984 and P50AG05136-22 and also receives support from the Research and Development, VA Puget Sound Health Care System; D.A.B. is supported by NIH R01AG017917, P30AG010161, R01AG015819, U01AG46152, R01AG036042 and Zinfandel, Inc. He serves on the editorial board of Neurology, Current Alzheimer’s Research, and Neuroepidemiology; has received honoraria for nonindustry sponsored lectures; serves on the adjudication committee for Takeda, Inc., and has served as a consultant to Enzymotic, Ltd., and Vigorous Minds, Inc.; R.R. discloses he is PI on the NIH/NIA Alzheimer’s Disease Center Grant P30AG12300-20. He is Editor of JAMA Neurology and Editorial Board Member of JAMA. He is listed as Inventor on the US Patent for “Amyloid Beta Gene Vaccines”; B.F.B has served as an investigator for a clinical trial sponsored by GE Healthcare. He receives royalties from the publication of a book entitled Behavioral Neurology Of Dementia (Cambridge Medicine, 2009). He has received honoraria from the American Academy of Neurology. He serves on the Scientific Advisory Board of the Tau Consortium. He receives research support from the NIH (U01 AG045390, P50 AG016574, U01 AG006786, RO1 AG032306, RO1 AG041797) and the Mangurian Foundation.; N.R.G. is taking part in a multicenter study for treatment of mild Alzheimer disease funded by Eli Lilly. He is taking part in a treatment of bvFTD study funded by TauRx and has consulted for Cytox. He is funded by NIH grants U01AG24904, P50AG 16574, U01AG032438, R01AG041797 and

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R01AG039389; A.M.G. is funded by NIHNIA grants: R01AG041797, U24AG026395, R37AG015473, and U24AG21886. She also serves as consultant for Cognition Therapeutics and receives license income from Taconic Industries; M.F. receives research support from Accera, Biogen, Chase Pharmaceuticals, Eisai, Eli Lilly, Genentech, Lundbeck, MedAvante/AstraZeneca, Navidea and Roche. He also receives research support from the following NIH/NIA grants: U24AG021886, P30AG10133, U01AG042791, UL1RR001106-01NIH, KL2TR025760-01, TL1RR025759-01, U24AG021886, R01AG041797, P30AG10133, U01AG024904; he is part of the speaker’s bureau of Eisai, Pfizer, Forest, Novartis, Eli Lilly & Company, serves on the consultant/advisory boards at Accera, Alltech, Avanir, Eisai Med Res, Inc., EnVivo Pharmaceuticals, Grifols, Helicon, Inc Research, Medavante, Medivation, Inc., Merck and Co. Inc., Novartis, Pfizer, Prana Biotech, QR Pharma, Roche, Sanofi-Aventis, Schering-Plough, Toyama Pharm., Lilly, UCB Pharma and Elan; X.W., M.I.K. and M.M.B. receive support from NIH grants AG030653, AG041718 and AG005133. D.J.S. receives support from NIH grant 5R01GM06545011; T.M.F. is funded by NIH grants R01AG041797 and U24AG0218860. She is a member of the Washington University Alzheimer’s Disease Research Center External Advisory Board; E.A.W. is supported by NIH grants AG026395, AG05133 and AG027224; RO serves on the scientific advisory board for and holds stock options in Trigeminal Solutions, Inc; received funding for travel from the École des Hautes Etudes en Santé Publique, the University of Bologna, and the University of Calgary; and receives research support from the NIH through U01NS077276, U01NS077367, R01NS078419, P50 HG007257, R01NS073872 and R01AG041797; R.A.S. receives support from USPHS grants MH071533, AG027224, AG041797, AG05133, MH094564, HHS N271201300032C, MH103204 and VHA grant 1BX000452; RM receives support from the NIH/NIA through P50AG0870, U01AG023749-05, R37 AG015473-12, 1R01AG036040-01, 1U01A G032984-01, R01AG037212, R01AG035020-01, R01AG041797. He is also funded by the Department of Defense W81XWH. Acknowledgements Study participants were enrolled under federal grants R01AG041797, U24AG026395, R37AG015473, AG030653, AG0 41718, AG005133, U24AG21886, and AG027224 from the National Institute on Aging. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health, the Department of Veterans Affairs, or the US Government. We would like to acknowledge Dr Andrew P. Morris for his useful contribution, assisting with the analysis, and interpretation of the MANTRA results and Dr. Jurg Ott for his contribution to evaluate linkage heterogeneity. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.neurobiolaging. 2015.08.006. References Abecasis, G.R., Cherny, S.S., Cookson, W.O., Cardon, L.R., 2002. Merlindrapid analysis of dense genetic maps using sparse gene flow trees. Nat. Genet. 30, 97e101. Avramopoulos, D., Fallin, M.D., Bassett, S.S., 2005. Linkage to chromosome 14q in Alzheimer’s disease (AD) patients without psychotic symptoms. Am. J. Med. Genet. B Neuropsychiatr. Genet. 132B, 9e13. Bacanu, S.A., Devlin, B., Chowdari, K.V., DeKosky, S.T., Nimgaonkar, V.L., Sweet, R.A., 2002. Linkage analysis of Alzheimer disease with psychosis. Neurology 59,118e120.

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