Research Models

APP E693Δ-Tg (Osaka)

Synonyms: APP(OSK)-Tg, APP Osaka mutation transgenic, APPOSK-Tg mice, APPOSK mice

Species: Mouse
Genes: APP
Mutations: APP E693del (Osaka)
Modification: APP: Transgenic
Disease Relevance: Alzheimer's Disease
Strain Name: N/A
Genetic Background: B6C3F1, back-crossed to C57Bl/6
Availability: Available through Hiroshi Mori and Takami Tomiyama

Summary

This transgenic mouse expresses human APP with the E693Δ mutation, a deletion mutation associated with early onset Alzheimer’s disease in several Japanese individuals. This mutation, also called the Osaka mutation, involves the in-frame deletion of a codon in exon 17, resulting in a missing glutamate at position 693 in APP, and at position 22 in resulting Aβ peptides.

The E693Δ mouse model is notable for accumulating Aβ within neurons of the hippocampus and cortex. This intraneuronal Aβ is thought to exist largely in oligomeric form, as demonstrated by immunohistochemistry with an oligomer-specific antibody and fractionation of the cortex followed by immunoprecipitation and western blot (Tomiyama et al., 2010). Despite the enhanced oligomerization of E693Δ Aβ peptides, these mice do not develop extracellular amyloid deposits, even at advanced ages, consistent with in vitro reports of minimal fibril formation of Aβ peptides with the Osaka mutation (Tomiyama et al., 2008). Despite the lack of extracellular plaque pathology, E693Δ mice develop age-associated memory deficits, synaptic deficits, neuronal loss, and tau hyperphosphorylation (Tomiyama et al., 2010). The E693Δ mouse is considered a useful model for investigating Aβ oligomer-related pathologies and for piloting oligomer-targeted therapies.

According to the initial report, three lines of APP E693Δ transgenics were generated. Line 1 is the best-characterized of the three and is the focus of this description. All three lines express low levels of the transgene, with line 1 expressing the highest levels, roughly equivalent to endogenous murine APP, and about 1/10 the transgene expression seen in the Tg2576 mouse. Unless otherwise noted, the data described on this page refer to heterozygous animals. It is not known if homozygous mice are viable or if disease-related phenotypes would be more severe or accelerated in the homozygous state (personal communication, Takami Tomiyama).

Although this model develops hyperphosphorylated tau, it does not develop overt tangle pathology. However, when crossed with the Tau264 model, which expresses low levels of human tau, the double transgenics develop neurofibrillary tangles by 18 months of age. In addition, the presence of human tau in the double transgenic accelerates the pathologies observed in the APP E693Δ single transgenic, including Aβ oligomer accumulation, synapse loss, neuronal loss, and memory impairment (Umeda et al., 2014).

Modification Details

This transgenic model expresses low levels of human APP (isoform 695) carrying the Osaka mutation and driven by the mouse prion promoter.

Availability

For information regarding the availability of this model, contact Hiroshi Mori or Takami Tomiyama.

Phenotype Characterization

When visualized, these models will distributed over a 18 month timeline demarcated at the following intervals: 1mo, 3mo, 6mo, 9mo, 12mo, 15mo, 18mo+.

Absent

  • Plaques
  • Tangles

No Data

Plaques

Extracelluar amyloid plaques are not observed out to 24 months; however, Aβ accumulates within neurons of the hippocampus and cerebral cortex starting around eight months of age.

Tangles

Overt tangle pathology is not observed out to 24 months of age, but abnormal tau phosphorylation is observed starting around eight months of age.

Neuronal Loss

Neuronal loss, as measured by NeuN staining, was observed in the CA3 region of the hippocampus at 24 months of age. Neuronal loss was not detected in the cerebral cortex at this time.

Gliosis

At 12 months of age, microgliosis is seen in transgenic mice, as measured by the presence of Iba-1 staining in the hippocampus and cortex. Astrocytosis, as measured by GFAP-reactivity, increased starting around 18 months of age in these regions.

Synaptic Loss

Starting around eight months of age, transgenic mice exhibit a decrease in synaptic density in the CA3 region of the hippocampus as measured by synaptophysin staining.

Changes in LTP/LTD

By eight months of age, transgenic mice exhibit reduced short term plasticity as measured by paired-pulse facilitation in addition to reduced LTP as elicited by high frequency stimulation to the perforant pathway.

Cognitive Impairment

By 8 months of age, transgenic mice exhibit memory impairment in the Morris water maze compared to mice expressing equivalent levels of wild-type human APP.

COMMENTS / QUESTIONS

  1. My overall feeling about this paper is that it is great that this group has generated a mouse model bearing the human mutation observed in the Japanese kindred. This will open the door to further studies to better understand how this mutation works and what causes the disease in these families. To my knowledge, it is unclear whether these patients show any intraneuronal Aβ staining in the brain and/or have any extracellular Aβ deposition, as I could not find a report of pathology in the literature. One patient had low PIB binding, but that only means that they did not have a lot of fibrillar amyloid at the time of imaging (although, it should be noted that they did have some). PIB does not pick up diffuse Aβ deposition (or at least not well), so it may be possible that these patients have diffuse plaque deposition.

    This mouse model is interesting and deserves further study. It is important to note that in the absence of extracellular plaque deposition, these mice undergo behavioral deficits, synaptic loss, gliosis, hyperphosphorylation of tau, and finally, neuronal loss (at two years of age). Something is going on. This paper provides evidence for a provocative, new role for APP and intracellular fragments (whether they are truly Aβ oligomers or APP β-CTFs) and will be of great interest to the AD community.

    View all comments by Cynthia Lemere
  2. The critique about Aβ oligomers in our paper is certainly an important issue since Aβ oligomers were clearly declared as the possible cause of Alzheimer disease (Selkoe, 2002). The biochemical nature of Aβ oligomers was not discussed thoroughly in our paper (Tomiyama et al., 2010) due to the limited space and to our focus on the new model mice as described in the Journal of Neuroscience news page (see “This Week in The Journal” in the journal website).

    First of all, I have to address the currently confusing nomenclature. Aβ oligomers are referred to in several ways, i.e., Aβ dimer, Aβ trimer, low-n Aβ oligomer, and ADDLs (Lambert et al., 1998), while Aβ*56 (Lesne et al., 2006) and other high-molecular-weight oligomers are claimed. I would like to discuss here all the species of Aβ oligomers published before. In addition to these Aβ oligomer species, there are other nomenclatures dedicated to non-fibrillar Aβ assemblies, such as protofibrils, annulus, or other forms (see the review by Roychaudhuri et al., 2009) that are hard to compare to one another due to the lack of biochemical characterization and mobilities on molecular weight gels. Some of the Aβ oligomers from our model mice (Tomiyama et al., ibid.) are certainly somewhat similar to those observed previously (Walsh et al., 2002). Such low-n Aβ oligomers have been confirmed worldwide, and reproduced in several laboratories with conventional Western blot analysis, although Aβ oligomer bands with the higher Mr than trimer were usually rather faint in the blot. When we used patient CSF, or synthetic peptides with or without the deletion mutation (E693Δ), we observed more clearly Aβ oligomers with higher Mr (Tomiyama et al., 2008). Despite the different names for Aβ oligomers, it is quite likely that one Aβ oligomer actually represents all the Aβ assembly species with different names, and the discrepancy of the apparent Mr comes from the diversities of the preparations and/or detection methods used in different laboratories.

    Therefore, I undoubtedly believe that our mice also contain ADDLs (Gong et al., 2003), probably Aβ*56 or other higher-molecular-weight oligomers, although the latter Aβ species seemed to be less evident with our detection methods. This must be true because we used not only β001 but also NU-1, the monoclonal antibody that specifically recognizes ADDLs, to identify Aβ oligomers (Lambert et al., 1998). This view is further supported by our previous observation (Nishitsuji et al., 2009).

    The prominent Aβ monomer was certainly observed in our blot, not in the soluble TBS-buffer fraction nor in the Triton-buffer fraction, but in the insoluble SDS-buffer fraction and highly insoluble formic-acid (FA) fraction after the fractionation by four-step ultracentrifugation. It is, I think, noteworthy that abnormal accumulation of Aβ monomer seen in the blot was observed in these cellular compartments. We do not know at this moment whether the Aβ monomer was tightly associated with Aβ oligomers or produced in the course of the experimental preparation derived from Aβ oligomers. Further studies are needed to fully characterize both extracellular and intracellular Aβ oligomers. It is, nevertheless, a critical issue that our model animal provides evidence for increased Aβ oligomers to induce Alzheimer disease (AD)-related changes such as memory disturbance, synaptic dysfunction, neuronal death, abnormal phosphorylation of tau, glial reaction, and the decreased synaptic marker, and that these pathologies are successfully reproduced in an aging-dependent manner in the absence of amyloid plaques. In short, our mice would be a crystal AD model. We are still aware of any formation of neurofibrillary tangles yet in this model. That may need more longevity or the co-occurrence of human tau. In this particular sense, our animals could be improved to get a perfect model to completely mimic human AD.

    Finally, the present view of Aβ oligomers is obviously significant for the future diagnostic and therapeutic research on Alzheimer disease. For this purpose, pathologically active Aβ oligomers must be prepared in a reproducible and stable fashion from synthetic Aβ peptides, body fluids, and/or brain tissues to help us beat this dire disease.

    References:

    . Alzheimer's disease is a synaptic failure. Science. 2002 Oct 25;298(5594):789-91. PubMed.

    . Diffusible, nonfibrillar ligands derived from Abeta1-42 are potent central nervous system neurotoxins. Proc Natl Acad Sci U S A. 1998 May 26;95(11):6448-53. PubMed.

    . A specific amyloid-beta protein assembly in the brain impairs memory. Nature. 2006 Mar 16;440(7082):352-7. PubMed.

    . Amyloid beta-protein assembly and Alzheimer disease. J Biol Chem. 2009 Feb 20;284(8):4749-53. PubMed.

    . Naturally secreted oligomers of amyloid beta protein potently inhibit hippocampal long-term potentiation in vivo. Nature. 2002 Apr 4;416(6880):535-9. PubMed.

    . A new amyloid beta variant favoring oligomerization in Alzheimer's-type dementia. Ann Neurol. 2008 Mar;63(3):377-87. PubMed.

    . Alzheimer's disease-affected brain: presence of oligomeric A beta ligands (ADDLs) suggests a molecular basis for reversible memory loss. Proc Natl Acad Sci U S A. 2003 Sep 2;100(18):10417-22. PubMed.

    . Diffusible, nonfibrillar ligands derived from Abeta1-42 are potent central nervous system neurotoxins. Proc Natl Acad Sci U S A. 1998 May 26;95(11):6448-53. PubMed.

    . The E693Delta mutation in amyloid precursor protein increases intracellular accumulation of amyloid beta oligomers and causes endoplasmic reticulum stress-induced apoptosis in cultured cells. Am J Pathol. 2009 Mar;174(3):957-69. PubMed.

    View all comments by Hiroshi Mori

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References

Antibody Citations

  1. β-Amyloid oligomers (NU-1)

Research Models Citations

  1. Tg2576

Paper Citations

  1. . A mouse model of amyloid beta oligomers: their contribution to synaptic alteration, abnormal tau phosphorylation, glial activation, and neuronal loss in vivo. J Neurosci. 2010 Apr 7;30(14):4845-56. PubMed.
  2. . A new amyloid beta variant favoring oligomerization in Alzheimer's-type dementia. Ann Neurol. 2008 Mar;63(3):377-87. PubMed.
  3. . Neurofibrillary tangle formation by introducing wild-type human tau into APP transgenic mice. Acta Neuropathol. 2014 May;127(5):685-98. Epub 2014 Feb 15 PubMed.

Other Citations

  1. Hiroshi Mori

Further Reading

Papers

  1. . Intraneuronal amyloid β oligomers cause cell death via endoplasmic reticulum stress, endosomal/lysosomal leakage, and mitochondrial dysfunction in vivo. J Neurosci Res. 2011 Jul;89(7):1031-42. PubMed.
  2. . Hypercholesterolemia accelerates intraneuronal accumulation of Aβ oligomers resulting in memory impairment in Alzheimer's disease model mice. Life Sci. 2012 Jan 17; PubMed.