The Arctic Alzheimer mutation facilitates early intraneuronal Aβ aggregation and senile plaque formation in transgenic mice
Introduction
Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive decline, abundant senile plaque and neurofibrillary tangle formation in the brain. Aβ peptides aggregate into crossed β-sheet fibrils which accumulate in the extracellular space as highly protease resistant material with distinct tinctorial properties. The “amyloid cascade hypothesis”, which states that Aβ is central to the disease, has been criticized for its inability to explain how Aβ confer neurodegeneration and dementia. Cognitive decline correlates better with synapse loss or tau pathology than with Aβ plaque burden [2], [39]. A possible explanation could be that soluble Aβ, rather than insoluble Aβ, confer neurotoxicity [24]. Indeed, certain species of soluble Aβ, e.g. Aβ oligomers, Aβ diffusible ligands (ADDLs), Aβ protofibrils and amylospheroids are neurotoxic in vitro or disrupt long-term potentiation (LTP) [13], [19], [40], [41]. The accumulation of Aβ oligomers has recently been reported to occur inside neurons in association with morphological abnormalities [37]. The Arctic mutation, which leads to AD, could be an excellent tool to better understand Aβ oligomerization, since Arctic Aβ peptides more easily form soluble Aβ protofibrils in vitro [30]. The Arctic mutation is located within the Aβ domain, in contrast to other APP mutations linked to AD which frame the Aβ sequence. We sought to use the Arctic mutation in transgenic mice to study its pathogenic mechanism and the role of soluble Aβ aggregates in vivo. Our idea was that the Arctic and Swedish mutations, when used together, would give rise to high levels of Arctic Aβ peptides resulting in an abundance of Aβ protofibrils. Human APP containing the Swedish (KM670/671NL) and Arctic (E693G) mutations was inserted into a Thy-1 expression vector [26], [30], [36]. Here, we show that young tg-APPArcSwe mice develop strong intraneuronal Aβ aggregation prior to extracellular Aβ deposition and that tg-APPArcSwe show much earlier onset of senile plaque formation than tg-APPSwe. The intraneuronal Aβ aggregates in APPArcSwe mice did not stain with thioflavine S and Aβ antibodies reacted differently with intraneuronal Aβ than with fibrillar Aβ in extracellular senile plaques. This suggests that intraneuronal Aβ aggregates predate Aβ fibrils and that the structure of these species differ from those of fibrillar Aβ. Further investigation of intraneuronal Aβ could improve our understanding of early stage AD and the mechanistic links between intraneuronal Aβ and tau pathology, neurodegeneration and dementia.
Section snippets
Expression vectors, transgenic mice and tissue preparation
Human APP cDNA clones (3′-UTR extended to SmaI at +3100) with the Swedish mutation (KM670/671NL) and with or without the Arctic mutation (E693G) were generated, attached to a modified Kozak sequence, inserted into the murine Thy-1323-cassette and sequenced [22]. The constructs were linearized with NotI and purified with β-agarase, microinjected (2 μg/ml) into pronuclear oocytes of C57BL/6-CBA-F1 mice and implanted into pseudopregnant foster mothers at the two-cell stage. Founders were screened
Strong intraneuronal Aβ immunostaining in young tg-APPArcSwe mice
Founder mice were initially screened with PCR using two sets of primer pairs that framed the Thy-1 basal promoter region and the APP coding region. We identified one founder line with both Swedish and Arctic mutations (called tg-APPArcSwe mice) and two founder lines with Swedish mutation alone (called tg-APPSwe mice). Brain tissue of 1-month-old mice was examined for APP protein expression. Human APP expression was measured with the 6E10 antibody (epitope 1–16 in Aβ) and total (human + murine)
Discussion
The most prominent phenotype in tg-APPArcSwe mice, as compared to tg-APPSwe mice, is strong intraneuronal Aβ aggregation which is associated with an early onset of parenchymal amyloid deposition. The Arctic mutation does not appear to alter Aβ levels when measured with ELISA in young mice. It should be noted that our Aβ analysis was limited to ELISA measurements of 2-month-old mice with C-terminal directed Aβ antibodies. Thus, C-terminal truncated/modified Aβ peptides will not be detected by
Acknowledgements
We thank Dr. Herman van der Putten at Novartis for providing the murine Thy-1 expression cassette. Aβ40- and Aβ42-specific antibodies were generously provided by Dr. Jan Näslund (Karolinska Institutet) and the 3D6 antibody by Dr. Dale Schenk (Elan Pharmaceuticals). Support by Uppsala University Transgenic Facility for this project is greatly acknowledged. The research was funded by grants from Uppsala University, Landstinget i Uppsala län, Alzheimerfonden, Hjärnfonden, Bertil Hållstens
References (45)
- et al.
Immunochemical identification of the serine protease inhibitor alpha 1-antichymotrypsin in the brain amyloid deposits of Alzheimer's disease
Cell
(1988) - et al.
Time sequence of maturation of dystrophic neurites associated with Abeta deposits in APP/PS1 transgenic mice
Exp Neurol
(2003) - et al.
Massive CA1/2 neuronal loss with intraneuronal and N-terminal truncated Abeta42 accumulation in a novel Alzheimer transgenic model
Am J Pathol
(2004) - et al.
Early-onset and robust cerebral microvascular accumulation of amyloid beta-protein in transgenic mice expressing low levels of a vasculotropic Dutch/Iowa mutant form of amyloid beta-protein precursor
J Biol Chem
(2004) - et al.
Time course of the development of Alzheimer-like pathology in the doubly transgenic PS1 + APP mouse
Exp Neurol
(2002) - et al.
Intraneuronal Abeta42 accumulation in human brain
Am J Pathol
(2000) - et al.
Visualization of A beta 42(43) and A beta 40 in senile plaques with end-specific A beta monoclonals: evidence that an initially deposited species is A beta 42(43)
Neuron
(1994) - et al.
Seeding “one-dimensional crystallization” of amyloid: a pathogenic mechanism in Alzheimer's disease and scrapie?
Cell
(1993) - et al.
Subcellular topography of neuronal Abeta peptide in APP × PS1 transgenic mice
Am J Pathol
(2004) - et al.
Neurotoxicity and physicochemical properties of Abeta mutant peptides from cerebral amyloid angiopathy: implication for the pathogenesis of cerebral amyloid angiopathy and Alzheimer's disease
J Biol Chem
(2003)
Apolipoprotein E immunoreactivity in cerebral amyloid deposits and neurofibrillary tangles in Alzheimer's disease and kuru plaque amyloid in Creutzfeldt–Jakob disease
Brain Res
Abeta immunotherapy leads to clearance of early, but not late, hyperphosphorylated tau aggregates via the proteasome
Neuron
The human amyloid-beta precursor protein 770 mutation V717F generates peptides longer than amyloid-beta-(40–42) and flocculent amyloid aggregates
J Biol Chem
Intraneuronal Alzheimer abeta42 accumulates in multivesicular bodies and is associated with synaptic pathology
Am J Pathol
Amyloid beta-protein fibrillogenesisStructure and biological activity of protofibrillar intermediates
J Biol Chem
Amyloid beta-protein fibrillogenesisDetection of a protofibrillar intermediate
J Biol Chem
Neurofibrillary tangles but not senile plaques parallel duration and severity of Alzheimer's disease
Neurology
Epitope and isotype specificities of antibodies to beta-amyloid peptide for protection against Alzheimer's disease-like neuropathology
Proc Natl Acad Sci USA
Aggressive amyloidosis in mice expressing human amyloid peptides with the Arctic mutation
Nat Med
Evidence that neurones accumulating amyloid can undergo lysis to form amyloid plaques in Alzheimer's disease
Histopathology
The ubiquitin-proteasome proteolytic pathway: destruction for the sake of construction
Physiol Rev
Intraneuronal abeta-amyloid precedes development of amyloid plaques in Down syndrome
Arch Pathol Lab Med
Cited by (211)
Passive and receptor mediated brain delivery of an anti-GFAP nanobody
2022, Nuclear Medicine and BiologySynthesis and evaluation of fluorine-18 labelled tetrazines as pre-targeting imaging agents for PET
2024, EJNMMI Radiopharmacy and ChemistryAltered amyloid-β structure markedly reduces gliosis in the brain of mice harboring the Uppsala APP deletion
2024, Acta Neuropathologica CommunicationsCritical thinking of Alzheimer’s transgenic mouse model: current research and future perspective
2023, Science China Life Sciences