title: Common genetic variants on 6q24 associated with exceptional episodic memory performance in the elderly.
abstract: OBJECTIVE
  There are genetic influences on memory ability as we age, but no specific genes have been identified.
  
  
  OBJECTIVE
  To use a cognitive endophenotype, exceptional episodic memory (EEM) performance, derived from nondemented offspring from the Long Life Family Study (LLFS) to identify genetic variants that may be responsible for the high cognitive performance of LLFS participants and further replicate these variants using an additional 4006 nondemented individuals from 4 independent elderly cohorts.
  
  
  METHODS
  A total of 467 LLFS participants from 18 families with 2 or more offspring that exhibited exceptional memory performance were used for genome-wide linkage analysis. Adjusted multivariate linear analyses in the 40-megabase region encompassing the linkage peak were conducted using 4 independent replication data sets that included 4006 nondemented elderly individuals. Results of the individual replication cohorts were combined by meta-analysis.
  
  
  METHODS
  Episodic memory scores computed as the mean of the 2 standardized measures of Logical Memory IA and IIA.
  
  
  RESULTS
  Heritability estimates indicated a significant genetic component for EEM (h2 = 0.21; SE = 0.09). Genome-wide linkage analysis revealed that EEM was linked to the 6q24 region (maximum logarithm of odds score, 3.64). Association analysis in LLFS families identified single-nucleotide polymorphisms (SNPs) nominally associated with EEM in the 40-megabase window encompassing the linkage peak. Replication in one cohort identified a set of 26 SNPs associated with episodic memory (P ≤ .05). Meta-analysis of the 26 SNPs using the 4 independent replication cohorts found SNPs rs9321334 and rs6902875 to be nominally significantly associated with episodic memory (P = .009 and P = .013, respectively). With meta-analysis restricted to individuals lacking an APOE ε4 allele, SNP rs6902875 became statistically significant (meta-analysis, P = 6.7 × 10-5). Haplotype analysis incorporating the 2 SNPs flanking rs6902875 (rs9321334 and rs4897574) revealed that the A-A-C haplotype was significantly associated with episodic memory performance (P = 2.4 × 10-5). This genomic region harbors monooxygenase dopamine β-hydroxylase-like 1 gene (MOXD1), implicated in the biosynthesis of norepinephrine, which is prominently involved in cognitive functions.
  
  
  CONCLUSIONS
  The results provide strong evidence for potential candidate genes related to EEM on 6q24. Identifying the genes will help in understanding the biological basis of memory performance and allow interventions for enhancement of cognitive function.
authors.affiliation: G. H. Sergievsky Center, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Department of Neurology, Columbia University Medical Center, New York, New York.
authors.forename: Sandra
authors.initials: S
authors.lastname: Barral
authors.affiliation: G. H. Sergievsky Center, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Department of Neurology, Columbia University Medical Center, New York, New York.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Cosentino
authors.affiliation: The Danish Aging Research Center, University of Southern Denmark, Odense, Denmark3Department of Clinical Genetics, Odense University Hospital, Odense, Denmark4Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Odense, Denmar.
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
authors.affiliation: Department of Epidemiology, Graduate School of Public Health, Pittsburgh, Pennsylvania.
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
authors.affiliation: Section of Geriatrics, Department of Medicine, Boston University School of Medicine, Boston Medical Center, Boston, Massachusetts.
authors.forename: Thomas T
authors.initials: TT
authors.lastname: Perls
authors.affiliation: Data Management Coordinating Center, Division of Statistical Genomics, Washington University School of Medicine, St Louis, Missouri.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Province
authors.affiliation: G. H. Sergievsky Center, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Department of Neurology, Columbia University Medical Center, New York, New York.
authors.forename: Richard
authors.initials: R
authors.lastname: Mayeux
mesh_terms: D002896:Chromosomes, Human, Pair 6 / Q000235:genetics*; D015331:Cohort Studies; D058068:Endophenotypes; D014644:Genetic Variation; D055106:Genome-Wide Association Study; D006801:Humans; D061212:Memory, Episodic; D010375:Pedigree; D020641:Polymorphism, Single Nucleotide