Cited by 244Alzheimer's disease research and treatmentsDown syndrome and intellectual disability researchDementia and Cognitive Impairment Research

Down Syndrome, Partial Trisomy 21, and Absence of Alzheimer’s Disease: The Role of APP

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Doran, Eric, Keator, David, Head, Elizabeth, Phelan, Michael J., Kim, Ron, Totoiu, Minodora, Barrio, Jorge R., Small, Gary W. +2 more·2017·Journal of Alzheimer’s Disease

Abstract

Overexpression of the amyloid precursor protein (APP) gene on chromosome 21 in Down syndrome (DS) has been linked to increased brain amyloid levels and early-onset Alzheimer’s disease (AD). An elderly man with phenotypic DS and partial trisomy of chromosome 21 (PT21) lacked triplication of APP affording an opportunity to study the role of this gene in the pathogenesis of dementia. Multidisciplinary studies between ages 66–72 years comprised neuropsychological testing, independent neurological exams, amyloid PET imaging with 11 C-Pittsburgh compound-B (PiB), plasma amyloid-β (Aβ) measurements, and a brain autopsy examination. The clinical phenotype was typical for DS and his intellectual disability was mild in severity. His serial neuropsychological test scores showed less than a 3% decline as compared to high functioning individuals with DS who developed dementia wherein the scores declined 17–28% per year. No dementia was detected on neurological examinations. On PiB-PET scans, the patient with PT21 had lower PiB standard uptake values than controls with typical DS or sporadic AD. Plasma Aβ 42 was lower than values for demented or non-demented adults with DS. Neuropathological findings showed only a single neuritic plaque and neurofibrillary degeneration consistent with normal aging but not AD. Taken together the findings in this rare patient with PT21 confirm the obligatory role of APP in the clinical, biochemical, and neuropathological findings of AD in DS.

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Crossref · 10.3233/jad-160836

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  • DSAD is in part a result of triplication of the APP gene on Hsa21, which results in increased production of amyloid-β peptide and other APP gene products.

    “and is in part a result of triplication of the amyloid precursor protein gene (APP) on Hsa21, which results in the increased production of the amyloid-β peptide and other APP gene products [12, 54].”

    From Apolipoprotein E abundance is elevated in the brains of individuals with Down syndrome–Alzheimer’s disease (2025) · cites this paper as [12]

    The Introduction (page unavailable) states that APP triplication in Down syndrome increases brain Aβ levels, and the Discussion links increased APP copy number to Alzheimer’s disease in Down syndrome. Our copy does not state that triplication increases production of other APP gene products. (LLM, conf=0.83)

    Experimental — accuracy not yet measured
  • DSAD is the most commonly occurring single genetic cause of AD.

    “Down syndrome–Alzheimer’s disease (DSAD) is the most commonly occurring single genetic cause of AD”

    From Apolipoprotein E abundance is elevated in the brains of individuals with Down syndrome–Alzheimer’s disease (2025) · cites this paper as [12]

    The Introduction links trisomy 21 and increased APP dosage in Down syndrome to Alzheimer’s disease, and the Discussion describes APP copy number as central to Alzheimer’s disease in Down syndrome. Neither section compares Down syndrome with other genetic causes or establishes that it is the most common single genetic cause. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • Raised APP abundance in the DSAD cases is driven by the additional copy of APP on Hsa21.

    “Importantly here, we know that raised APP abundance in our DSAD cases is driven by the additional copy of APP on Hsa21, as indicated by both human-genetics studies and preclinical modelling [12, 54, 58].”

    From Apolipoprotein E abundance is elevated in the brains of individuals with Down syndrome–Alzheimer’s disease (2025) · cites this paper as [12]

    The Introduction links APP triplication in Down syndrome to increased brain Aβ, and the Discussion reports that a patient without APP triplication had very low amyloid levels and no Alzheimer’s disease. These passages support the importance of APP copy number, but the paper does not measure APP abundance in the citing authors’ DSAD cases or establish what drives it in those cases. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • Early onset AD invariably develops in Down syndrome due mainly to a third copy of APP present on trisomic chromosome 21.

    “a disorder in which an early onset form of AD invariably develops due mainly to a third copy of APP present on trisomic chromosome 21 (Korbel et al., 2009;Doran et al., 2017;Colacurcio et al., 2018).”

    From Lysosomal Dysfunction in Down Syndrome Is APP-Dependent and Mediated by APP-βCTF (C99) (2019) · cites this paper as Doran et al., 2017

    The Introduction links APP triplication in Down syndrome to increased brain amyloid, and the Discussion describes increased APP copy number as central to AD pathogenesis. But the Introduction distinguishes ubiquitous AD-like neuropathology from dementia: dementia prevalence varies from 30–75% at age 65. The paper therefore does not support the claim that early-onset AD invariably develops. (LLM, conf=0.90)

    Experimental — accuracy not yet measured
  • The strong gene-dosage effect in trisomy 21 reinforces the amyloid cascade hypothesis and provides a natural human model of genetically driven amyloidopathy.

    “This strong gene-dosage effect reinforces the amyloid cascade hypothesis and provides a natural human model of genetically driven amyloidopathy [152, 153].”

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Cites

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Research works printed but not linked: 3

  1. [28]Sparrow S Cicchetti D Balla D 2005 Vineland adaptive behavior scales: (Vineland II), survey interview form/caregiver rating form Livonia, MN Pearson Assessments
  2. [37]Jenkinson M Beckmann CF Behrens TE Woolrich MW Smith SM 2012 FSL Neuroimage 62 782 790 21979382
  3. [67]Jenkins EC Schupf N Genovese M Ye LL Kapell D Canto B Harris M Devenny D Lee JH Brown WT 1997 Increased low-level chromosome 21 mosaicism in older individuals with Down syndrome Am J Med Genet 68 147 151 9028448

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Authors
Doran, E., Keator, D., Head, E., Phelan, M. J., Kim, R., Totoiu, M., Barrio, J. R., Small, G. W., Potkin, S. G., & Lott, I. T.
Affiliations
  • University of California, Irvine Medical Center (US)
  • University of California, Irvine (US)
  • University of Kentucky (US)
  • University of California, Los Angeles (US)
Corresponding author
Lott, Ira T.
Venue
Journal of Alzheimer’s Disease
Published
2016-12-09
Volume
56
Issue
2
Pages
459-470
ISSN
  • 1387-2877 (ISSN-L)
  • 1875-8908
OpenAlex
W2567009735
Cited by
244
References
68
Citations by year
2026: 16 · 2025: 45 · 2024: 35 · 2023: 25 · 2022: 31 · 2021: 28 · 2020: 21 · 2019: 27 · 2018: 11 · 2017: 5
FWCI
11.53
Type
journal article
Language
en
Open access
Locations
  • Journal of Alzheimer s Disease (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
  • eScholarship (California Digital Library) (submittedVersion)
Funders
  • National Institutes of Health (UL1TR000153)
  • National Institute on Aging (P50AG016573, R01AG021912, U01AG051412, R01AG033015, U19AG068054, U24AG021886)
  • National Institute of Mental Health (U01MH097435)
  • National Center for Research Resources (U24RR021992, P20RR020837)
  • National Center for Advancing Translational Sciences
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01HD065160, R01HD064993)
Topics
  • Health Sciences › Medicine › Physiology › Alzheimer's disease research and treatments
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Down syndrome and intellectual disability research
  • Health Sciences › Medicine › Psychiatry and Mental health › Dementia and Cognitive Impairment Research
Keywords
Down syndrome, partial trisomy 21
MeSH terms
Aged, Alzheimer Disease, Brain, Down Syndrome, Humans, Male, Phenotype, Amyloid beta-Protein Precursor

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