Progressive neuropathology and cognitive decline in a single Arctic APP transgenic mouse model.

The Arctic APP mutation (E693G) leads to dementia with clinical features similar to Alzheimer disease (AD), but little is known about the pathogenic mechanism of this mutation. To address this question, we have generated a transgenic mouse model, TgAPParc, with neuron-specific expression of human APP with the Arctic mutation (hAPParc). Heterozygous mice from two separate founder lines with different levels of expression of hAPParc were analyzed with respect to brain morphology and behavior every 3 months until the age of 18 months. Standard histological stainings and immunohistochemistry using a panel of Aβ antibodies showed an age- and dose-dependant progression of amyloid deposition in the brain, starting in the subiculum and spreading to the thalamus. Cognitive behavioral testing revealed deficits in hippocampus-dependent spatial learning and memory in the Barnes maze test. This study demonstrates that the Arctic APP mutation is sufficient to cause amyloid deposition and cognitive dysfunction, and thus the TgAPParc mouse model provides a valuable tool to study the effect of the Arctic mutation in vivo without possible confounding effect of other APP mutations.

Rönnbäck A ，Zhu S ，Dillner K ，Aoki M ，Lilius L ，Näslund J ，Winblad B ，Graff C ... -  《-》

Amyloid neuropathology in the single Arctic APP transgenic model affects interconnected brain regions.

The Arctic APP mutation (E693G) within the amyloid β (Aβ) domain of amyloid precursor protein (APP) leads to dementia with clinical features similar to Alzheimer's disease (AD), which is believed to be mediated via increased formation of protofibrils. We have generated a transgenic mouse model, TgAPParc, with neuron-specific expression of human amyloid precursor protein with the Arctic mutation (hAPParc), showing mild amyloid pathology with a relatively late onset. Here we performed a detailed analysis of the spatiotemporal progression of neuropathology in homozygous TgAPParc, focusing on intracellular Aβ and diffuse Aβ aggregates rather than amyloid plaques. We show that the neuropathology in homozygous TgAPParc mice starts with intracellular Aβ aggregates, which is followed by diffuse extracellular Aβ deposits in subiculum that later expands to brain regions receiving neuronal projections from regions already affected. Together this suggests that the pathology in TgAPParc mice affects interconnected brain regions and may represent a valuable tool to study the spread and progression of neuropathology in Alzheimer's disease.

Rönnbäck A ，Sagelius H ，Bergstedt KD ，Näslund J ，Westermark GT ，Winblad B ，Graff C ... -  《-》

Progressive cognitive impairment and anxiety induction in the absence of plaque deposition in C57BL/6 inbred mice expressing transgenic amyloid precursor protein.

Numerous transgenic mouse models for Alzheimer's disease (AD) have been generated to recapitulate the histological pathogenesis and behavioral phenotypes of AD brain. However, none of the existing models exhibits the full spectrum of AD symptoms, nor have all of the traits mimicked by the developed animal models been successfully represented within a single mouse line, indicating that the development of transgenic lines showing new features of the AD-like brain should be explored. Here we report on a transgenic mouse line, named Tg-APP (Sw, V717F)/B6, that expresses the human amyloid precursor protein (APP) containing the Swedish and the V717F Indiana mutations in the brains of inbred C57BL/6 mice, designed to eliminate the potential phenotypic variations attributed to the compound genetic backgrounds adopted in most AD mouse models. The Tg-APP (Sw, V717F)/B6 mice expressed the transgene transcript, in the heterozygote state, at a level of 2.6 +/- 0.1 fold higher than that of endogenous mouse APP. However, no Abeta-plaque deposition was produced in the brain of the Tg-APP (Sw, V717F)/B6 mice up to 18 months of age. The Tg-APP(Sw, V717F)/B6 mice at 13-15 months showed reduced expression of calbindin and c-Fos in the brain. The Tg-APP (Sw, V717F)/B6 mice at 11-14 months displayed decreased motor coordination, learning and memory deficits, and severely increased anxiety. These phenotypes were not observed in the Tg-APP (Sw, V717F)/B6 mice at 5-7 months. Microarray analysis revealed altered expression, in the amygdala of the Tg-APP (Sw, V717F)/B6 mice, of genes previously implicated in anxiety. Taken together, these results suggest that the transgenic APP, or its derivatives, produces the age-dependent pathophysiology of the AD-like brain and that the progressive cognitive impairment and anxiety induction can proceed in the absence of visible Abeta-plaque deposition.

Lee KW ，Lee SH ，Kim H ，Song JS ，Yang SD ，Paik SG ，Han PL ... -  《JOURNAL OF NEUROSCIENCE RESEARCH》

RAGE does not affect amyloid pathology in transgenic ArcAbeta mice.

Alzheimer's disease (AD) is characterized by brain accumulation of the amyloid-beta peptide (Abeta) that triggers a cascade of biochemical and cellular alterations resulting in the clinical phenotype of the disease. While numerous experiments addressed Abeta toxicity, the mechanisms are still not fully understood. The receptor for advanced glycation end products (RAGE) binds Abeta and was suggested to be involved in the pathological processes of AD. Our purpose was to assess the effect of RAGE deletion on Abeta-related pathology. We crossed RAGE knockout (RAGE(-/-)) mice with transgenic mice harboring both the Swedish and Arctic Abeta precursor protein mutations (arcAbeta mice). We assessed Abeta levels, Abeta brain deposition, Abeta-degrading enzyme activities, Abeta precursor protein expression and processing, number and morphology of microglia as well as cognitive performance of 6- and 12-month-old RAGE(-/-)/arcAbeta, RAGE(-/-), arcAbeta and wild-type mice. RAGE(-/-)/arcAbeta mice had significantly lower levels of SDS- and formic-acid-extracted Abeta in the cortex and hippocampus, with concomitantly increased activity of insulin-degrading enzyme at the age of 6 months. However, RAGE deletion could neither prevent the decline in cognitive performance nor the age-related cerebral accumulation of Abeta peptide. Furthermore, histological analysis revealed no difference in the microglia-occupied brain areas or microglial morphologies between RAGE(-/-)/arcAbeta and arcAbeta mice. Together, our results indicate that while the absence of RAGE was associated with increased insulin-degrading enzyme activity in the brain, it was not sufficient to prevent or ameliorate cognitive deterioration, Abeta accumulation and microglial activation in the arcAbeta mouse model of AD.

Vodopivec I ，Galichet A ，Knobloch M ，Bierhaus A ，Heizmann CW ，Nitsch RM ... -  《-》

Mitochondrial amyloid-beta levels are associated with the extent of mitochondrial dysfunction in different brain regions and the degree of cognitive impairment in Alzheimer's transgenic mice.

Dragicevic N ，Mamcarz M ，Zhu Y ，Buzzeo R ，Tan J ，Arendash GW ，Bradshaw PC ... -  《-》