1. AD Transgenic Models

Transgenic models involve genetic modification of existing genes or alteration of the location of target genes on normal chromosomes. To understand the pathogenesis of AD, various transgenic mouse models have been developed to accelerate the accumulation of Aβ and Tau tangles. These include different strains such as APP23, TgCRND8, APPPS1, etc.

● Case

Using pronuclear microinjection, two separate transgenic constructs encoding human APP_Swe and Ttau^P301L (4R/0N) were co-injected into single-cell embryos from homozygous PS1_M146V knock-in mice. Embryos carrying the APP and Tau genes were transferred into recipient mice, and subsequent offspring were genotyped to identify 3×Tg-AD mice. Western blot analysis revealed elevated levels of APP and Tau proteins in the brains of these transgenic mice.

Figure 1. Construction and Identification of the 3×Tg-AD Mouse Model

Reference：

Oddo S, Caccamo A, Shepherd JD, et al. Triple-transgenic model of Alzheimer’s disease with plaques and tangles: intracellular Abeta and synaptic dysfunction. Neuron. 2003 Jul 31;39(3):409-21.

2. AAV-Induced AD Model (Developed by Genevoyager)

We develop AD models by expressing AAV-mediated genes via different administration routes.

● Case 1

An AAV-AD model was generated by expressing Tau or APP protein in the hippocampal region of mice via stereotactic injection of AAV. After 12 weeks, analysis of the mouse brain revealed significant expression of APP.SLA in pyramidal neurons of the CA region and cortex. Antibody 6E10 showed extensive accumulation of APP metabolites within the neurons. Western blot analysis demonstrated that the relative levels of APP.SLA or Tau^P301L in hippocampal extracts were approximately twice as high as endogenous mouse APP or Tau^P301L, respectively. Six months after intracerebral injection of AAV-APP.SLA, amyloid plaques appeared, along with phosphorylated Tau in dystrophic axons surrounding the plaques.

Figure 2. Construction and Identification of AD model through stereotactic injection of AAV

Reference：

Jaworski T, Dewachter I, Lechat B, et al. AAV-tau mediates pyramidal neurodegeneration by cell-cycle re-entry without neurofibrillary tangle formation in wild-type mice. PLoS One. 2009 Oct 1;4(10):e7280.

● Case 2

Six months after stereotactic injection of AAV-Tau^P301L in mice, behavioral (exploration, anxiety, learning, and memory) and neuropathological assessments were performed. The results showed that in the Open-Field Assay (OFA), AAV1-Tau^P301L mice exhibited hyperactivity and a reduced tendency to explore the central area of the open field,  indicative  of increased anxiety; in the Elevated Plus Maze (EPM) experiment, AAV1-Tau^P301L mice exhibited abnormal exploratory and disinhibitory behaviors; in the contextual fear conditioning experiment, these mice also exhibited deficits, demonstrating significant  impairments in memory associated with contextual or auditory cues.

Figure 3. Behavioral and neuropathological analysis of the AD mouse model

Reference：

Cook C, Kang SS, Carlomagno Y, et al. Tau deposition drives neuropathological, inflammatory and behavioral abnormalities independently of neuronal loss in a novel mouse model. Hum Mol Genet. 2015 Nov 1;24(21):6198-212.

Using AAV vectors, we canefficiently generate largequantitiesof AD animal models in a shorttime-frame,mitigating the drawbacksassociated with transgenic animal models,such as extended acquisitionperiods, limitedavailability, andhigh costs. AAV vectorsenables specific expression in different brain nuclei, playing a crucial role in studying theneuralcircuit mechanisms underlying clinical symptoms of AD.Moreover, by adjusting the viral dosage, we can induce phenotypes of neurodegenerative lesions ranging from mild to severein animals.