Rarity of the Alzheimer disease-protective APP A673T variant in the United States.

Authors:
Li-San Wang Adam C Naj Robert R Graham Paul K Crane Brian W Kunkle Carlos Cruchaga Josue D Gonzalez Murcia Lisa Cannon-Albright Clinton T Baldwin Henrik Zetterberg Kaj Blennow Walter A Kukull Kelley M Faber Nicole Schupf Maria C Norton JoAnn T Tschanz Ronald G Munger Christopher D Corcoran Ekaterina Rogaeva Chiao-Feng Lin Beth A Dombroski Laura B Cantwell Amanda Partch Otto Valladares Hakon Hakonarson Peter St George-Hyslop Robert C Green Alison M Goate Tatiana M Foroud Regina M Carney Eric B Larson Timothy W Behrens John S K Kauwe Jonathan L Haines Lindsay A Farrer Margaret A Pericak-Vance Richard Mayeux Gerard D Schellenberg Marilyn S Albert Roger L Albin Liana G Apostolova Steven E Arnold Robert Barber Michael Barmada Lisa L Barnes Thomas G Beach James T Becker Gary W Beecham Duane Beekly David A Bennett Eileen H Bigio Thomas D Bird Deborah Blacker Bradley F Boeve James D Bowen Adam Boxer James R Burke Joseph D Buxbaum Nigel J Cairns Chuanhai Cao Chris S Carlson Steven L Carroll Helena C Chui David G Clark David H Cribbs Elizabeth A Crocco Charles DeCarli Steven T DeKosky F Yesim Demirci Malcolm Dick Dennis W Dickson Ranjan Duara Nilufer Ertekin-Taner Kenneth B Fallon Martin R Farlow Steven Ferris Matthew P Frosch Douglas R Galasko Mary Ganguli Marla Gearing Daniel H Geschwind Bernardino Ghetti John R Gilbert Jonathan D Glass Neill R Graff-Radford John H Growdon Ronald L Hamilton Kara L Hamilton-Nelson Lindy E Harrell Elizabeth Head Lawrence S Honig Christine M Hulette Bradley T Hyman Gail P Jarvik Gregory A Jicha Lee-Way Jin Gyungah Jun Gyungah Jun M Ilyas Kamboh Anna Karydas Jeffrey A Kaye Ronald Kim Edward H Koo Neil W Kowall Joel H Kramer Frank M LaFerla James J Lah James B Leverenz Allan I Levey Gei Li Andrew P Lieberman Oscar L Lopez Kathryn L Lunetta Constantine G Lyketsos Wendy J Mack Daniel C Marson Eden R Martin Frank Martiniuk Deborah C Mash Eliezer Masliah Wayne C McCormick Susan M McCurry Andrew N McDavid Ann C McKee W Marsel Mesulam Bruce L Miller Carol A Miller Joshua W Miller Thomas J Montine John C Morris Jill R Murrell John M Olichney Joseph E Parisi William Perry Elaine Peskind Ronald C Petersen Aimee Pierce Wayne W Poon Huntington Potter Joseph F Quinn Ashok Raj Murray Raskind Eric M Reiman Barry Reisberg Christiane Reitz John M Ringman Erik D Roberson Howard J Rosen Roger N Rosenberg Mary Sano Andrew J Saykin Julie A Schneider Lon S Schneider William W Seeley Amanda G Smith Joshua A Sonnen Salvatore Spina Robert A Stern Rudolph E Tanzi Tricia A Thornton-Wells John Q Trojanowski Juan C Troncoso Debby W Tsuang Vivianna M Van Deerlin Linda J Van Eldik Badri N Vardarajan Harry V Vinters Jean Paul Vonsattel Sandra Weintraub Kathleen A Welsh-Bohmer Jennifer Williamson Sarah Wishnek Randall L Woltjer Clinton B Wright Steven G Younkin Chang-En Yu Lei Yu

JAMA Neurol 2015 Feb;72(2):209-16

Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia.

Importance: Recently, a rare variant in the amyloid precursor protein gene (APP) was described in a population from Iceland. This variant, in which alanine is replaced by threonine at position 673 (A673T), appears to protect against late-onset Alzheimer disease (AD). We evaluated the frequency of this variant in AD cases and cognitively normal controls to determine whether this variant will significantly contribute to risk assessment in individuals in the United States.

Objective: To determine the frequency of the APP A673T variant in a large group of elderly cognitively normal controls and AD cases from the United States and in 2 case-control cohorts from Sweden.

Design, Setting, And Participants: Case-control association analysis of variant APP A673T in US and Swedish white individuals comparing AD cases with cognitively intact elderly controls. Participants were ascertained at multiple university-associated medical centers and clinics across the United States and Sweden by study-specific sampling methods. They were from case-control studies, community-based prospective cohort studies, and studies that ascertained multiplex families from multiple sources.

Main Outcomes And Measures: Genotypes for the APP A673T variant were determined using the Infinium HumanExome V1 Beadchip (Illumina, Inc) and by TaqMan genotyping (Life Technologies).

Results: The A673T variant genotypes were evaluated in 8943 US AD cases, 10 480 US cognitively normal controls, 862 Swedish AD cases, and 707 Swedish cognitively normal controls. We identified 3 US individuals heterozygous for A673T, including 1 AD case (age at onset, 89 years) and 2 controls (age at last examination, 82 and 77 years). The remaining US samples were homozygous for the alanine (A673) allele. In the Swedish samples, 3 controls were heterozygous for A673T and all AD cases were homozygous for the A673 allele. We also genotyped a US family previously reported to harbor the A673T variant and found a mother-daughter pair, both cognitively normal at ages 72 and 84 years, respectively, who were both heterozygous for A673T; however, all individuals with AD in the family were homozygous for A673.

Conclusions And Relevance: The A673T variant is extremely rare in US cohorts and does not play a substantial role in risk for AD in this population. This variant may be primarily restricted to Icelandic and Scandinavian populations.

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Source
http://dx.doi.org/10.1001/jamaneurol.2014.2157DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4324097PMC
February 2015
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