- Email: [email protected]
P4-061 Better memory in young APOE4 carriers
$490
Poster Session P4: Genetic Factors of Alzheimer's Disease
The only replicated genetic risk factor is the 84 allele of the apolipoprotein E (APOE) gene, but this gene is thought to contribute less than 50% of the genetic component. Several genome scans of AD sib pairs have shown convergent evidence for a susceptibility gene on the q arm of chromosome 10. Myers et al. 2000 found broad linkage to markers on 10q with lod scores greater than 3 between the markers D10S1220 and D10S1670 at 52 Mb and 68.2 Mb respectively. Due to the nature of complex disease, it is likely that allelic or locus heterogeneity will have a confounding effect on the exact location of the linkage peak. The phosphatase and tensin homolog gene (PTEN) is located at 89.3 Mb on chromosome 10, close enough to be a candidate. The protein encoded by this gene is a phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase and it dephosphorylates phosphatidylinositol-3-phosphate (PIP3) resulting in antagonism of PI-3 kinase activity. Inhibition of PI-3 kinase activity leads to the overactivation of GSK-3 which in turn causes the hyperphosphorylation of tan and the impairment of spatial memory (Liu et al 2003). This makes PTEN both a positional and biological candidate for an AD risk loci. Objective(s): To determine the evidence for association of a candidate gene, PTEN, with LOAD. Methods: Nine polymorphisms spanning 99.4kb of the 102.9kb PTEN gene were selected for genotyping in pools of 366 cases and controls using the SNaPshot methodology. Additionally, individual samples were genotyped to examine linkage disequilibrium across the gene. Results: In preliminary analyses, strong linkage disequilibrium was found, with D' values approaching one between adjacent markers. In the markers genotyped so far little evidence has been found for association with the disease state (p = 0.708, 0.652, 0.359 and 0.941). Markers closer to the 5 ~ end of the gene have still to be genotyped. Conelusious: At present there is no evidence of association of PTEN with disease.
~ C D C 2 AS A CANDIDATE FOR LATE-ONSET ALZHEIMER'S DISEASE Victoria L. Busby* 1, Gillian Hamilton 1, Sarah Walter 1, Catherine Foy 1, Nicola Archer 1, Dragana Turic 2, Luke Jehu 2, Paul Hollingworth 2, Pare Moore 2, Sue Jones 2, Leslie Jones 2, Jnlie Williams 2, Michael Owen 2, John Powell 1, Simon Lovestone I . 1Institute of Psychiatry, London, United
Kingdom; 2 University of Wales College of Medicine, Cardiff, United Kingdom. Contact e-maiL" spjuvlb@ iop.kcl.ac.uk
Background: Currently the only known genetic risk factor for late-unset Alzheimer's disease (LOAD) is the APOE 8 4 allele, but this only accounts for less than 50% of the genetic variance. A number of genome scans have highlighted a region on chromosome 10 which shows strong evidence of linkage to LOAD (LOD score on chromosome 10 of 3.5, as compared to the LOD score on chromosome 19 of 1.79 for ApoE). Within this region is the cell division cycle 2 (CDC2) gene, which is also a good functional candidate. It is a protein kinase which is involved in regulation of the cell cycle and also in neuronal differentiation. CDC2 is expressed in neurons, and in AD brains it iis found in an active form in neurons containing NFTs, implicating it in the Oathogenesis of AD. Objective: To identify SNPs within this gene and genotype a sample of AD cases and controls to determine whether this gene is the susceptibility gene identifed on chromosome 10. Methods: We sequenced all exons and 5 ~- and 3~-untranslated regions in a set of cases and did not identify any polymorphisms that affected the coding sequence, though we identified two rare non coding polymorphisms (Exonl111 C>G, Exon 5+5 ins C). We genotyped two validated SNPs from the NCBI SNP database which were approximately 6kb apart within this 16kb gene. The analysis was done on a sample of approximately 200 cases and controls using dynamic allele specific hybridisation (DASH). Conclusions: No association was found between these SNPs and LOAD (rs2170007 p = 0.825, rs1871447 p = 0.595). Haplotype analysis using the EH Plus program was also negative (p = 0.599). A recent study (Johansson et al, Neuroscience Letters 340:69-73) identified other polymorphisms flanked by these SNPs that were implicated in AD and fronto-temporal dementia (FTD). The two SNPs that we genotyped are in linkage disequilibrium (r2 = 0.179) but the degree of disequilibrium with the polymorphisms identified by Johansson et al is unknown. A further 9 polymorphisms have been selected across CDC2 for genotyping with an average spacing of 4.9kb.
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U N I Q U E APOLIPOPROTEIN E A L L E L E (APOE4 YORUBA)F O U N D IN IBADAN POPULATION
Jill R. Murrell* 1, Brandon M. Price 1, Reid G. Gibson 1 Olusegun Baiyewu z, Oye Gureje 2, Mark Deeg 1, Hugh Hendrie I , Adesola Ogunniyi z, Kathleen Hall 1. 1Indiana University School of
Medicine, Indianapolis, IN, USA; 2 University of lbadan, lbadan, Nigeria. Contact e-maiL"jrmurrel@ iupui, edu
Background: Apolipoprotein E functions in lipoprotein metabolism and lipid transport. APOE has three common alleles, APOE2, APOE3, APOE4. Each isoform functions differently and thus vary as risk factors for disease susceptibility, apoE3 has a cysteine at residue 112 and arginine at 158. apoE2 (cysteine 112/158) has been associated with type lII hyperlipidemia. apoE4 (arginine 112/158), encoded by ancestral allele APOE4, is associated with increased risk for coronary artery disease and Alzheimer disease (AD). Objective: One aim of the Indianapolis-Ibadan Dementia Study is to identify risk factors for dementia in elderly African-Americans and Nigerian Yoruba. Since there is evidence that APOE4 increases the risk of AD in some populations, APOE was genotyped in our cohort. Methods: Informed consent was obtained from participants. Genomic DNA was isolated from blood. APOE was genotyped by amplification followed by Hhal digestion and gel electrophoresis. Amplification products were sequenced. Levels of cholesterol, triglycerides, high-density lipoproteins, glucose, insulin and thyrotropinstimulating hormone were determined. Lipoproteins were fractionated by gel filtration and electrophoresis. Results: One lbadan subject had a unique HhaI pattern. Sequencing revealed one allele as APOE4 and the other allele as a unique apoE with arginine 112 and cysteine 158. This allele has been named APOE4 Yoruta (APOE4Y). The individual is a 70 year-old female with no history of illness, cognitively intact and functioning independently. Apart from hypertension her physical, neurological and neuropsychological examinations were normal. All biological measurements were within normal limits. A normal lipoprotein profile was seen. Additional family members were identified: a 67 year-old brother who appears to have APOE2/E4 and a 34 year-old son with the mother's genotype (APOE4/E4Y). HhaI digestion cannot distinguish APOE2/E4 from APOE4Y/E2 or APOE4Y/E3. Direct sequencing cannot distinguish APOE2/E4 from APOE31E4Y so SSCP gel electrophoresis will be done for all Ibadan APOE2/E4 samples. Conclusion: We report, for the first time, a new APOE allele in a Yoruba family. Presently, the frequency of APOE4Y and function of apoE4Y are unknown. APOE4Y does not appear to lead to abnormal biological measurements or health problems. How APOE4Y relates as a risk factor for dementia needs to be determined in subsequent studies.
•
BETTER MEMORY IN YOUNG APOE4 CARRIERS
Andreas Papassotiropoulos*, M. Axel Wollmer, Katharina Henke, Christoph Hock, Roger M. Nitsch, Dominique J. de Quervaiu. University of
Zurich, Zurich, Switzerland. Contact e-mail: [email protected]
Background: The 84 allele of the apolipoprotein E (APOE) gene is associated with increased risk for the development of dementia and with impaired memory in elderly non-demented individuals. Objective: To investigate the role of the APOE e4 allele on memory in young adults. Methods: We recruited 340 genetically homogeneous healthy young adults (mean age, 22.8). Genetic homogeneity was assessed by genotyping each subject for 27 non-functional single nucleotide polymorphisms. Thorough neuropsychological testing was used to quantify verbal and figural episodic memory performance. Results: The APOE 84 allele was associated, in a dose-dependent manner, with better memory performance. Conclusions: These results suggest that the APOE 84 allele favours memory processes in young age and that its deleterious effect on memory later in life might result from distinct, age-related pathological processes. Supported by the Swiss
National Science Foundation (A.P and D.Q.)
Poster Session P4: Genetic Factors of Alzheimer's Disease
The only replicated genetic risk factor is the 84 allele of the apolipoprotein E (APOE) gene, but this gene is thought to contribute less than 50% of the genetic component. Several genome scans of AD sib pairs have shown convergent evidence for a susceptibility gene on the q arm of chromosome 10. Myers et al. 2000 found broad linkage to markers on 10q with lod scores greater than 3 between the markers D10S1220 and D10S1670 at 52 Mb and 68.2 Mb respectively. Due to the nature of complex disease, it is likely that allelic or locus heterogeneity will have a confounding effect on the exact location of the linkage peak. The phosphatase and tensin homolog gene (PTEN) is located at 89.3 Mb on chromosome 10, close enough to be a candidate. The protein encoded by this gene is a phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase and it dephosphorylates phosphatidylinositol-3-phosphate (PIP3) resulting in antagonism of PI-3 kinase activity. Inhibition of PI-3 kinase activity leads to the overactivation of GSK-3 which in turn causes the hyperphosphorylation of tan and the impairment of spatial memory (Liu et al 2003). This makes PTEN both a positional and biological candidate for an AD risk loci. Objective(s): To determine the evidence for association of a candidate gene, PTEN, with LOAD. Methods: Nine polymorphisms spanning 99.4kb of the 102.9kb PTEN gene were selected for genotyping in pools of 366 cases and controls using the SNaPshot methodology. Additionally, individual samples were genotyped to examine linkage disequilibrium across the gene. Results: In preliminary analyses, strong linkage disequilibrium was found, with D' values approaching one between adjacent markers. In the markers genotyped so far little evidence has been found for association with the disease state (p = 0.708, 0.652, 0.359 and 0.941). Markers closer to the 5 ~ end of the gene have still to be genotyped. Conelusious: At present there is no evidence of association of PTEN with disease.
~ C D C 2 AS A CANDIDATE FOR LATE-ONSET ALZHEIMER'S DISEASE Victoria L. Busby* 1, Gillian Hamilton 1, Sarah Walter 1, Catherine Foy 1, Nicola Archer 1, Dragana Turic 2, Luke Jehu 2, Paul Hollingworth 2, Pare Moore 2, Sue Jones 2, Leslie Jones 2, Jnlie Williams 2, Michael Owen 2, John Powell 1, Simon Lovestone I . 1Institute of Psychiatry, London, United
Kingdom; 2 University of Wales College of Medicine, Cardiff, United Kingdom. Contact e-maiL" spjuvlb@ iop.kcl.ac.uk
Background: Currently the only known genetic risk factor for late-unset Alzheimer's disease (LOAD) is the APOE 8 4 allele, but this only accounts for less than 50% of the genetic variance. A number of genome scans have highlighted a region on chromosome 10 which shows strong evidence of linkage to LOAD (LOD score on chromosome 10 of 3.5, as compared to the LOD score on chromosome 19 of 1.79 for ApoE). Within this region is the cell division cycle 2 (CDC2) gene, which is also a good functional candidate. It is a protein kinase which is involved in regulation of the cell cycle and also in neuronal differentiation. CDC2 is expressed in neurons, and in AD brains it iis found in an active form in neurons containing NFTs, implicating it in the Oathogenesis of AD. Objective: To identify SNPs within this gene and genotype a sample of AD cases and controls to determine whether this gene is the susceptibility gene identifed on chromosome 10. Methods: We sequenced all exons and 5 ~- and 3~-untranslated regions in a set of cases and did not identify any polymorphisms that affected the coding sequence, though we identified two rare non coding polymorphisms (Exonl111 C>G, Exon 5+5 ins C). We genotyped two validated SNPs from the NCBI SNP database which were approximately 6kb apart within this 16kb gene. The analysis was done on a sample of approximately 200 cases and controls using dynamic allele specific hybridisation (DASH). Conclusions: No association was found between these SNPs and LOAD (rs2170007 p = 0.825, rs1871447 p = 0.595). Haplotype analysis using the EH Plus program was also negative (p = 0.599). A recent study (Johansson et al, Neuroscience Letters 340:69-73) identified other polymorphisms flanked by these SNPs that were implicated in AD and fronto-temporal dementia (FTD). The two SNPs that we genotyped are in linkage disequilibrium (r2 = 0.179) but the degree of disequilibrium with the polymorphisms identified by Johansson et al is unknown. A further 9 polymorphisms have been selected across CDC2 for genotyping with an average spacing of 4.9kb.
•
U N I Q U E APOLIPOPROTEIN E A L L E L E (APOE4 YORUBA)F O U N D IN IBADAN POPULATION
Jill R. Murrell* 1, Brandon M. Price 1, Reid G. Gibson 1 Olusegun Baiyewu z, Oye Gureje 2, Mark Deeg 1, Hugh Hendrie I , Adesola Ogunniyi z, Kathleen Hall 1. 1Indiana University School of
Medicine, Indianapolis, IN, USA; 2 University of lbadan, lbadan, Nigeria. Contact e-maiL"jrmurrel@ iupui, edu
Background: Apolipoprotein E functions in lipoprotein metabolism and lipid transport. APOE has three common alleles, APOE2, APOE3, APOE4. Each isoform functions differently and thus vary as risk factors for disease susceptibility, apoE3 has a cysteine at residue 112 and arginine at 158. apoE2 (cysteine 112/158) has been associated with type lII hyperlipidemia. apoE4 (arginine 112/158), encoded by ancestral allele APOE4, is associated with increased risk for coronary artery disease and Alzheimer disease (AD). Objective: One aim of the Indianapolis-Ibadan Dementia Study is to identify risk factors for dementia in elderly African-Americans and Nigerian Yoruba. Since there is evidence that APOE4 increases the risk of AD in some populations, APOE was genotyped in our cohort. Methods: Informed consent was obtained from participants. Genomic DNA was isolated from blood. APOE was genotyped by amplification followed by Hhal digestion and gel electrophoresis. Amplification products were sequenced. Levels of cholesterol, triglycerides, high-density lipoproteins, glucose, insulin and thyrotropinstimulating hormone were determined. Lipoproteins were fractionated by gel filtration and electrophoresis. Results: One lbadan subject had a unique HhaI pattern. Sequencing revealed one allele as APOE4 and the other allele as a unique apoE with arginine 112 and cysteine 158. This allele has been named APOE4 Yoruta (APOE4Y). The individual is a 70 year-old female with no history of illness, cognitively intact and functioning independently. Apart from hypertension her physical, neurological and neuropsychological examinations were normal. All biological measurements were within normal limits. A normal lipoprotein profile was seen. Additional family members were identified: a 67 year-old brother who appears to have APOE2/E4 and a 34 year-old son with the mother's genotype (APOE4/E4Y). HhaI digestion cannot distinguish APOE2/E4 from APOE4Y/E2 or APOE4Y/E3. Direct sequencing cannot distinguish APOE2/E4 from APOE31E4Y so SSCP gel electrophoresis will be done for all Ibadan APOE2/E4 samples. Conclusion: We report, for the first time, a new APOE allele in a Yoruba family. Presently, the frequency of APOE4Y and function of apoE4Y are unknown. APOE4Y does not appear to lead to abnormal biological measurements or health problems. How APOE4Y relates as a risk factor for dementia needs to be determined in subsequent studies.
•
BETTER MEMORY IN YOUNG APOE4 CARRIERS
Andreas Papassotiropoulos*, M. Axel Wollmer, Katharina Henke, Christoph Hock, Roger M. Nitsch, Dominique J. de Quervaiu. University of
Zurich, Zurich, Switzerland. Contact e-mail: [email protected]
Background: The 84 allele of the apolipoprotein E (APOE) gene is associated with increased risk for the development of dementia and with impaired memory in elderly non-demented individuals. Objective: To investigate the role of the APOE e4 allele on memory in young adults. Methods: We recruited 340 genetically homogeneous healthy young adults (mean age, 22.8). Genetic homogeneity was assessed by genotyping each subject for 27 non-functional single nucleotide polymorphisms. Thorough neuropsychological testing was used to quantify verbal and figural episodic memory performance. Results: The APOE 84 allele was associated, in a dose-dependent manner, with better memory performance. Conclusions: These results suggest that the APOE 84 allele favours memory processes in young age and that its deleterious effect on memory later in life might result from distinct, age-related pathological processes. Supported by the Swiss
National Science Foundation (A.P and D.Q.)