title: Sequence of deposition of heterogeneous amyloid beta-peptides and APO E in Down syndrome: implications for initial events in amyloid plaque formation.
abstract: Patients with trisomy 21 [Down syndrome (DS)] progressively develop amyloid beta-protein (A beta) deposits and then other features of Alzheimer's disease (AD), apparently due to increased gene dosage and thus expression of the beta-amyloid precursor protein. Because the neuropathological phenotype in older DS subjects closely resembles that of AD, the examination of DS brains of increasing age provides a unique model of the progression of AD. Here, we characterized the deposition of several A beta peptides and apolipoprotein E in formalin-fixed brain sections from 29 DS subjects between 3 and 73 years old. Amyloid plaque number and the percentage of cortical area they occupied were quantified by computerized image analysis. A beta ending at amino acid 42 (A beta 42) was the earliest form of A beta deposited in DS cortex. It was observed in 7 of 16 young (3-30 years) subjects, with the earliest deposition occurring at age 12. A beta ending at residue 40 (A beta 40) was not detected until approximately age 30, a time when degenerating neurites around A beta immunoreactive (IR) plaques were first observed, and the frequency of A beta 40 IR plaques then rose with age. Even in old (51-73 years) DS subjects, A beta 42 IR plaques were always more abundant than A beta 40 IR plaques. A beta peptides starting at aspartate 1 or pyroglutamate 3 were detected in small subsets of compacted, neuritic plaques beginning around age 30 and rose with age, the latter species always exceeding the former. Thus, the N-termini of the A beta 42 peptides abundantly deposited in very young DS subjects remain unknown. Apo E was detectable in a small subset of A beta 42 IR plaques beginning at age 12 and rose steadily with age; it clearly followed the deposition of A beta. Our analysis of very young DS brains suggests that amyloid plaque formation begins with A beta 42-ending peptides, and the number and percentage of cortical area of A beta 42 plaques increase very little with advancing age, while other heterogeneous A beta species and Apo E progressively accrue onto plaques containing A beta 42.
authors.affiliation: Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Lemere
authors.forename: J K
authors.initials: JK
authors.lastname: Blusztajn
authors.forename: H
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: T
authors.initials: T
authors.lastname: Wisniewski
authors.forename: T C
authors.initials: TC
authors.lastname: Saido
authors.forename: D J
authors.initials: DJ
authors.lastname: Selkoe
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism; D000544:Alzheimer Disease / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism; D001057:Apolipoproteins E / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D004314:Down Syndrome / Q000150:complications / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016501:Neurites / Q000473:pathology; D016874:Neurofibrillary Tangles; D010446:Peptide Fragments / Q000378:metabolism; D013194:Staining and Labeling; D013702:Temporal Lobe / Q000098:blood supply / Q000378:metabolism / Q000473:pathology
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D001057:Apolipoproteins E; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)