- Email: [email protected]
Genetic variation in PLXNA4 associated with susceptibility of Alzheimer’s disease through tau phosphorylation
P692
Oral Sessions: O4-06: Basic Science: Genetics III—Common Variation and Risk for Alzheimer’s Disease
ORAL SESSIONS: O4-06: BASIC SCIENCE: GENETICS III—COMMON VARIATION AND RISK FOR ALZHEIMER’S DISEASE O4-06-01
GENETIC MODIFIERS IN EARLY-ONSET FAMILIAL ALZHEIMER’S DISEASE IN CARIBBEAN HISPANICS
Joseph Lee1, Rong Cheng1, Ward Ortmann2, Rafael Lantigua3, Robert Graham2, Tushar Bhangale2, Gilberto Perez-Horta4, Martin Medrano5, Timothy Behrens2, Richard Mayeux3, 1Columbia University, College of Physicians and Surgeons, New York, New York, United States; 2Genentech, South San Francisco, California, United States; 3 Columbia University, New York, New York, United States; 4University of Puerto Rico, San Juan, Puerto Rico; 5Pontificia Universidad Catolica Madre y Maestra, Santiago, Dominican Republic. Contact e-mail: JHL2@ columbia.edu Background: We identified the G206A mutation in PSEN1 in 2001, and observed that this mutation was highly penetrant, but it was associated with a wide range of age at onset. Carriers of the mutation ranged as much as 20+ years in age at onset. The observed variation in age at onset was explained by neither APOE-ε4 nor known environmental risk factors (e.g., levels of education). Methods: To identify variants that influence age at onset of AD, we investigated five families that had familial EOAD and carried the G206A variant in PSEN1. We performed a linkage analysis to identify candidate regions that may harbour variants, and then conducted a joint linkage and association analysis with additional 543 unaffected Hispanics as controls. We then performed whole exome sequencing (WES) on a subset of individuals to identify genetic variants that are associated with variable age at onset. Multiple regression was used to assess mean age at onset by genotype. Results: The linkage analysis revealed that 2p25 and 4q35 had LOD scores>3, and additional loci elsewhere in the genome had suggestive linkage. For nine top linkage signals, we performed a joint linkage and association analysis to ensure that there exist candidate variants that are associated with AD under the linkage peaks. Subsequently, we selected 27 individuals from the same set of families and performed exome sequencing to identify variants that are associated with variable age at onset. This analysis identified multiple loci – specifically, 1p13.1, 2q13, 4q25, 17p11 – that were significant at p
O4-06-02
GENETIC VARIATION IN PLXNA4 ASSOCIATED WITH SUSCEPTIBILITY OF ALZHEIMER’S DISEASE THROUGH TAU PHOSPHORYLATION
Gyungah Jun1, Hirohide Asai1, Elodie Drapeau2, Jong-Ho Park3, Ella Zeldich4, Ci-Di Chen4, Sehwa Kim5, Tatiana Foroud6, Kathryn Lunetta7, Jong-Won Kim3, Joseph Buxbaum8, Carmela Abraham4, Tsuneya Ikezu4, Richard Mayeux9, Lindsay Farrer5, 1Boston University School of Medicine, Boston, Massachusetts, United States; 2Mount Sinai School of Medicine, New York, New York, United States; 3Sungkyunkwan University, Seoul, South Korea; 4Boston University, Boston, , Massachusetts, United States; 5Sungkyunkwan University School of Medicine, Seoul, South Korea; 6Indiana University School of Medicine, Indianapolis, Indiana, United States; 7Boston University School of Public Health, Boston, Massachusetts, United States; 8Mount Sinai Hospital, New York, New York, United States; 9Columbia University, New York, New York, United States. Contact e-mail: [email protected]
Background: Common variants explain <50% of the genetic component of Alzheimer’s disease (AD). We sought to identify associations in families including infrequent variants (minor allele frequency, 0.01 MAF<0.10) using a novel family-based approach. Methods: Association of AD with 341,492 genotyped SNPs was evaluated in the Framingham Heart Study (FHS) comprising 61 incident cases and 2,530 cognitively normal relatives using an approach accounting for family structure. Top-ranked genes were examined in 1,840 cases and 1,988 unaffected relatives in the NIA-LOAD Study. We examined impact of the top-ranked gene on amyloid precursor protein (APP) processing and tau phosphorylation in cell lines, rat primary hippocampal neurons, and RNA expression in autopsy brain tissue from 14 AD cases and 5 controls and in blood from 116 population controls ages 11-45 years. Results: Genome-wide significant associations were identified with infrequent genotyped SNPs in ITIH3 (rs9311482, p¼4.6x10-9), PLXNA4 (rs277484, p¼9.0x10-10) and MYO18B (rs13057714, p¼8.9x10-9). Although none of these SNPs were replicated in the NIA-LOAD, ten other PLXNA4 SNPs were significant after multiple testing correction in the propensity score model (best p for rs10236235: FHS¼0.11, NIA-LOAD¼9.6x10-6, combined¼4.4x10-7). Association of PLXNA4 was corroborated by a gene-based test (p: FHS¼0.004, NIA-LOAD¼0.03, combined ¼ 3.6x10-4). The top PLXNA4 SNPs flank an alternatively spliced exon present only in a shorter isoform (TS3). Transfection of SH-SY5Y cells or primary rat neurons with the full-length (TS1) of PLXNA4 increased tau phosphorylation when stimulated by sema3A ligand, while the shorter isoforms (TS2 and TS3) decreased tau phosphorylation. However, all three isoforms failed to show differential effects on APP processing or beta-amyloid production. The AD cases had 6.5-fold increased expression of TS1 (P¼0.041) and 1.8-fold increased expression of TS3 (P¼0.001) compared to controls. Risk alleles from all top SNPs were correlated with elevated expression of both isoforms in the population controls (best p¼0.02 for TS1). Conclusions: Our results show that variants in PLXNA4 surrounding an alternatively spliced exon influence risk of AD and suggest that the mechanism underlying this association is related to differential effects of Plexin-A4 isoforms on tau phosphorylation. PLXNA4 or its binding partners can be served as biomarkers or novel drug targets for AD.
O4-06-03
GENOTYPE-PHENOTYPE STUDIES EXAMINING THE CD33 LOCUS AND AMYLOID BIOLOGY
Elizabeth Bradshaw1, Lori Chibnik1, Brendan Keenan1, Linda Ottoboni1, Towfique Raj1, Anna Tang1, Laura Rosenkrantz1, Selina Imboywa2, Michelle Lee1, Alina Von Korff1, Alzheimer’s Disease Neuroimaging Initiative (ADNI)3, Martha Clare Morris4, Denis Evans5, Keith Johnson1, Reisa Sperling6, Julie Schneider5, David Bennett7, Philip De Jager1, 1 Brigham and Women’s Hospital, Boston, Massachusetts, United States; 2 Brigham and Womens’ Hospital, Belmont, Massachusetts, United States; 3 Alzheimer’s Disease Neuroimaging Initiative (ADNI) University of California San Diego, LaJolla, California, United States; 4Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, Illinois, United States; 5Rush University Medical Center, Chicago, Illinois, United States; 6Center for Alzheimer Research and Treatment, Brigham and Women’s Hospital, Boston, Massachusetts, United States; 7Rush University, Chicago, Illinois, United States. Contact e-mail: [email protected]. harvard.edu Background: Alzheimer’s disease (AD) is an age-related neurodegenerative disease characterized by progressive cognitive decline and dementia. Recent genome-wide studies have identified nine AD susceptibility loci in addition to APOE- ε4, including ABCA7, BIN1, CD2AP, CD33, CLU, CR1, EPHA1, MS4A4/MS4A6E and PICALM. The identification of the CD33 locus directly implicates the innate immune system in AD susceptibility. CD33 is a putative inhibitory protein expressed at high levels on the cell surface of myeloid cells and is a member of the siglec family of
Oral Sessions: O4-06: Basic Science: Genetics III—Common Variation and Risk for Alzheimer’s Disease
ORAL SESSIONS: O4-06: BASIC SCIENCE: GENETICS III—COMMON VARIATION AND RISK FOR ALZHEIMER’S DISEASE O4-06-01
GENETIC MODIFIERS IN EARLY-ONSET FAMILIAL ALZHEIMER’S DISEASE IN CARIBBEAN HISPANICS
Joseph Lee1, Rong Cheng1, Ward Ortmann2, Rafael Lantigua3, Robert Graham2, Tushar Bhangale2, Gilberto Perez-Horta4, Martin Medrano5, Timothy Behrens2, Richard Mayeux3, 1Columbia University, College of Physicians and Surgeons, New York, New York, United States; 2Genentech, South San Francisco, California, United States; 3 Columbia University, New York, New York, United States; 4University of Puerto Rico, San Juan, Puerto Rico; 5Pontificia Universidad Catolica Madre y Maestra, Santiago, Dominican Republic. Contact e-mail: JHL2@ columbia.edu Background: We identified the G206A mutation in PSEN1 in 2001, and observed that this mutation was highly penetrant, but it was associated with a wide range of age at onset. Carriers of the mutation ranged as much as 20+ years in age at onset. The observed variation in age at onset was explained by neither APOE-ε4 nor known environmental risk factors (e.g., levels of education). Methods: To identify variants that influence age at onset of AD, we investigated five families that had familial EOAD and carried the G206A variant in PSEN1. We performed a linkage analysis to identify candidate regions that may harbour variants, and then conducted a joint linkage and association analysis with additional 543 unaffected Hispanics as controls. We then performed whole exome sequencing (WES) on a subset of individuals to identify genetic variants that are associated with variable age at onset. Multiple regression was used to assess mean age at onset by genotype. Results: The linkage analysis revealed that 2p25 and 4q35 had LOD scores>3, and additional loci elsewhere in the genome had suggestive linkage. For nine top linkage signals, we performed a joint linkage and association analysis to ensure that there exist candidate variants that are associated with AD under the linkage peaks. Subsequently, we selected 27 individuals from the same set of families and performed exome sequencing to identify variants that are associated with variable age at onset. This analysis identified multiple loci – specifically, 1p13.1, 2q13, 4q25, 17p11 – that were significant at p
O4-06-02
GENETIC VARIATION IN PLXNA4 ASSOCIATED WITH SUSCEPTIBILITY OF ALZHEIMER’S DISEASE THROUGH TAU PHOSPHORYLATION
Gyungah Jun1, Hirohide Asai1, Elodie Drapeau2, Jong-Ho Park3, Ella Zeldich4, Ci-Di Chen4, Sehwa Kim5, Tatiana Foroud6, Kathryn Lunetta7, Jong-Won Kim3, Joseph Buxbaum8, Carmela Abraham4, Tsuneya Ikezu4, Richard Mayeux9, Lindsay Farrer5, 1Boston University School of Medicine, Boston, Massachusetts, United States; 2Mount Sinai School of Medicine, New York, New York, United States; 3Sungkyunkwan University, Seoul, South Korea; 4Boston University, Boston, , Massachusetts, United States; 5Sungkyunkwan University School of Medicine, Seoul, South Korea; 6Indiana University School of Medicine, Indianapolis, Indiana, United States; 7Boston University School of Public Health, Boston, Massachusetts, United States; 8Mount Sinai Hospital, New York, New York, United States; 9Columbia University, New York, New York, United States. Contact e-mail: [email protected]
Background: Common variants explain <50% of the genetic component of Alzheimer’s disease (AD). We sought to identify associations in families including infrequent variants (minor allele frequency, 0.01 MAF<0.10) using a novel family-based approach. Methods: Association of AD with 341,492 genotyped SNPs was evaluated in the Framingham Heart Study (FHS) comprising 61 incident cases and 2,530 cognitively normal relatives using an approach accounting for family structure. Top-ranked genes were examined in 1,840 cases and 1,988 unaffected relatives in the NIA-LOAD Study. We examined impact of the top-ranked gene on amyloid precursor protein (APP) processing and tau phosphorylation in cell lines, rat primary hippocampal neurons, and RNA expression in autopsy brain tissue from 14 AD cases and 5 controls and in blood from 116 population controls ages 11-45 years. Results: Genome-wide significant associations were identified with infrequent genotyped SNPs in ITIH3 (rs9311482, p¼4.6x10-9), PLXNA4 (rs277484, p¼9.0x10-10) and MYO18B (rs13057714, p¼8.9x10-9). Although none of these SNPs were replicated in the NIA-LOAD, ten other PLXNA4 SNPs were significant after multiple testing correction in the propensity score model (best p for rs10236235: FHS¼0.11, NIA-LOAD¼9.6x10-6, combined¼4.4x10-7). Association of PLXNA4 was corroborated by a gene-based test (p: FHS¼0.004, NIA-LOAD¼0.03, combined ¼ 3.6x10-4). The top PLXNA4 SNPs flank an alternatively spliced exon present only in a shorter isoform (TS3). Transfection of SH-SY5Y cells or primary rat neurons with the full-length (TS1) of PLXNA4 increased tau phosphorylation when stimulated by sema3A ligand, while the shorter isoforms (TS2 and TS3) decreased tau phosphorylation. However, all three isoforms failed to show differential effects on APP processing or beta-amyloid production. The AD cases had 6.5-fold increased expression of TS1 (P¼0.041) and 1.8-fold increased expression of TS3 (P¼0.001) compared to controls. Risk alleles from all top SNPs were correlated with elevated expression of both isoforms in the population controls (best p¼0.02 for TS1). Conclusions: Our results show that variants in PLXNA4 surrounding an alternatively spliced exon influence risk of AD and suggest that the mechanism underlying this association is related to differential effects of Plexin-A4 isoforms on tau phosphorylation. PLXNA4 or its binding partners can be served as biomarkers or novel drug targets for AD.
O4-06-03
GENOTYPE-PHENOTYPE STUDIES EXAMINING THE CD33 LOCUS AND AMYLOID BIOLOGY
Elizabeth Bradshaw1, Lori Chibnik1, Brendan Keenan1, Linda Ottoboni1, Towfique Raj1, Anna Tang1, Laura Rosenkrantz1, Selina Imboywa2, Michelle Lee1, Alina Von Korff1, Alzheimer’s Disease Neuroimaging Initiative (ADNI)3, Martha Clare Morris4, Denis Evans5, Keith Johnson1, Reisa Sperling6, Julie Schneider5, David Bennett7, Philip De Jager1, 1 Brigham and Women’s Hospital, Boston, Massachusetts, United States; 2 Brigham and Womens’ Hospital, Belmont, Massachusetts, United States; 3 Alzheimer’s Disease Neuroimaging Initiative (ADNI) University of California San Diego, LaJolla, California, United States; 4Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, Illinois, United States; 5Rush University Medical Center, Chicago, Illinois, United States; 6Center for Alzheimer Research and Treatment, Brigham and Women’s Hospital, Boston, Massachusetts, United States; 7Rush University, Chicago, Illinois, United States. Contact e-mail: [email protected]. harvard.edu Background: Alzheimer’s disease (AD) is an age-related neurodegenerative disease characterized by progressive cognitive decline and dementia. Recent genome-wide studies have identified nine AD susceptibility loci in addition to APOE- ε4, including ABCA7, BIN1, CD2AP, CD33, CLU, CR1, EPHA1, MS4A4/MS4A6E and PICALM. The identification of the CD33 locus directly implicates the innate immune system in AD susceptibility. CD33 is a putative inhibitory protein expressed at high levels on the cell surface of myeloid cells and is a member of the siglec family of