Rarity of the Alzheimer Disease–Protective<i>APP</i>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, M. 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, M. Ilyas Kamboh, Anna Karydas, Jeffrey A. Kaye, Ronald Kim, Edward H. Koo, Neil W. Kowall, Joel H. Kramer, Patricia Kramer, Frank M. LaFerla, James J. Lah, James B. Leverenz, Allan I. Levey, Ge 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, M. 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
Journal: JAMA Neurology (2014)

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