Aims

Our overall objective for this project is to develop the first sets of Alzheimer’s Disease Related Dementias (ADRD) mouse lines that model the genetics of ADRDs as closely as possible.

Methods

We developed Gene Replacement (GR) technologies that allow us for the first time to routinely replace mouse genes with their full human orthologs up to several hundred kb in size.

Results

We generated a matched set of MAPT-GR lines of mice in which we replaced the full mouse Mapt genomic coding and regulatory region (156,547bp) with the full human MAPT genomic sequence (190,081bp). We confirmed that mice homozygous for MAPT-GR alleles express human tau at endogenous levels, and that all expected splice variants are found in the appropriate tissues and in ratios expected for the fully functional human MAPT gene. This matched set of lines currently consists of two different wt control lines (H1 and H2 haplotypes) and five variant lines that differ from the H1 haplotype control line only at the pathogenic variant sequence. We are working to identify quantifiable endophenotypes that differ significantly between pathogenic MAPT-GR variant lines and the wt control, while expediting the release of these lines without restriction (JAX). Similarly, we have completed the first line of a SNCA-GR set (158kb GR allele) and are working towards developing a C9orf72-GR model set.

Conclusions

These models will serve as experimental systems for probing molecular dysfunctions caused by pathogenic ADRD mutations, identifying quantifiable early-stage endophenotypes directly linked to these mutations, and developing therapeutic interventions for correcting these dysfunctions.

Aims

Alzheimer’s disease (AD) is a debilitating neurodegenerative disorder, with no effective treatment currently available. Although the vast majority of cases are late-onset AD (LOAD), current animal models do not recapitulate LOAD and thus are not ideal for the development of therapeutics. In addition to genetic factors, a western-style diet (e.g. high fat, high sugar, low vitamins) in combination with a sedentary lifestyle can lead to an increased risk for dementia. The MODEL-AD Center is charged with creating, defining, and distributing novel mouse models of LOAD for broad use.

Methods

MODEL-AD has created a mouse strain carrying a humanized ApoE4 knock-in mutation, an App allele with a humanized Aβ1-42 region in the mouse gene and an R47H point mutation of the Trem2 gene (B6.APOEe4/Trem2*R47H/hAβ). Cohorts of mice were aged to 4, 12, 18 and 24 months on standard or Western diet. Transcriptomics, biomarker and cognitive assays as well as immunohistochemistry and in vivo imaging studies were established to characterize these models and the effect of diet.

Results

Analyses of transcriptomic data in combination with behavioral and molecular phenotypes and in vivo imaging has yielded additional insight into genetic and environmental influences on AD endophenotypes and disease mechanisms.

Conclusions

The MODEL-AD consortium has established a new model to study the effects of genetic and environmental factors for LOAD. Furthermore, this model will serve as a backbone strain for the further addition of LOAD risk alleles to more closely align phenotypes in the mouse to outcomes observed in human AD.

Aims

Alzheimer’s disease (AD) is the most common form of progressive neurodegenerative disease and dementia. The endocannabinoid (eCB) system appears to be a novel therapeutic target to treat AD, as it can modulate a range of aspects of AD pathology. The present study has been designed to explore the expression of the eCB system in a 5xFAD transgenic mouse model of AD, taking into consideration the genetic load of the disease: heterozygous (HTZ) versus homozygous (HZ) conditions.

Methods

Experiments were performed on 11-month-old 5xFAD transgenic mice. The Novel Object Recognition (NOR) test was performed to evaluate cognitive functions. Hippocampus samples were obtained to quantify protein expression of eCB system components, neuroinflammation markers, and ß-amyloid (Aß) plaques.

Results

Based on NOR, anxiety-like behaviour and memory were altered in HTZ and HZ 5xFAD mice. HTZ and HZ 5xFAD animals displayed a clear reduction of the expression of CB₁ receptor in hippocampus which is related to memory dysfunction. Importantly, the increased levels of CB₂ receptors in the HZ group positively correlates with the accumulation observed of Aß (total Aß, Aß_1-40 and Aß_1-42), indicating enhanced glial reactivity. Moreover, HZ 5xFAD transgenic mice exhibited increased expression of GPR55 compared to HTZ and non-transgenic mice. Also, HZ group showed an alteration in the eCB production/degradation pathway, favouring the production as a compensatory mechanism.

Conclusions

These results highlight the importance of eCB signalling for the development AD pathogenesis beyond Aß deposition.

Aims

This study aimed to determine whether a gradual and relatively modest accumulation of mutated human tau in the forebrain of a novel transgenic rat model was sufficient to trigger early-stage pathological processes leading to end-stage tau pathology.

Methods

R955-hTau transgenic rats expressing the longest isoform of human tau (2N4R) with the P301S mutation for frontotemporal dementia were used. Transgenic rats were bred and raised to 10, 18-20 and 24-26 months of age and were subject to behavioral testing of cognition. At these time points, examination of tau pathology in the brain was also performed using immunohistochemistry, immunofluorescence and electron microscopy.

Results

R955-hTau rats developed an age-associated accumulation of human tau in the brain resulting in tau hyperphosphorylation and tau pathology at 24-26 months of age. Cognitive deficits in learning and memory were present at late life stages, coinciding with neurodegeneration. Coincidentally with advanced tau pathology we also observed microglial and astrocytic activation as well as myelin abnormalities and vascular alterations.

Conclusions

R955-hTau, a novel transgenic rat model with a gradual pathological accumulation of human P301S tau, represents an attractive model for the identification of novel indicators of early tau pathology. Since extensive neurodegeneration, neuroinflammation, and vascular and myelin alterations are present only at late life stages, this model presents a more sensitive time frame to identify early tau-mediated pathological changes in the brain. As such it should be a suitable model for examining mechanisms involved in tauopathy as well factors exacerbating tau pathology in a species with a greater degree of translation to humans.

Aims

Increasing epidemiological evidence highlighted the correlation between central metabolic dysfunction, such as insulin resistance, and Alzheimer’s disease (AD). In the present study, we aimed to investigate the systemic metabolic phenotype in a mutated hAPP overexpressing mouse model of AD (APP23+/-) with a specific focus on the systemic insulin functionality.

Methods

Age-matched APP23^+/- and C57BL/6 J mice at 4 (n=7-11) and 12 months (n=11-21) were tested for memory and spatial learning by a Morris Water Maze (MWM) test. In addition, animals were metabolically tested with an intraperitoneal glucose and insulin tolerance test (GTT, ITT). Circulating insulin levels were determined in blood serum. Data are represented as mean ± SEM.

Results

MWM data revealed cognitive decline in APP23^+/- at 12 months of age, as total path lengths increased compared to C57BL/6 animals (AUC= 129 ± 8 vs. 172 ± 2 m; p=0.0003). Peripheral glucose homeostasis remained unchanged. At 4 months of age, APP23^+/- mice presented with peripheral insulin resistance compared to control littermates (AUC= 984 ± 272 vs. 2007 ± 238 mg*min/dL; p=0.007), which stabilized at 12 months of age. Serum insulin levels were similar between genotypes at 4 months (0.6 ± 0.1 and 0.4 ± 0.1 ng/mL, respectively), but were significantly elevated in APP23^+/- mice (1.9 ± 0.9 vs. 1.1 ± 0.1 ng/mL; p=0.002) at 12 months of age.

Conclusions

These results suggest that peripheral insulin resistance could be a potential metabolic biomarker in the pre-symptomatic phase of AD.

Aims

Increasing evidence support that metabolic dysregulation plays a key role in Alzheimer’s disease (AD) etiology. Previous research demonstrated male AβPP/PS1 mice have an impaired metabolic profile compared to age-matched C57BL/6J littermate controls. We hypothesized that chronically altering the environmental temperature (eT) could improve their metabolic profile thereby ameliorating cognitive deficits.

Methods

Starting at 6 months of age (mild amyloid pathology and cognitive impairment) male AβPP/PS1 mice were housed at either 23°C (standard), or 30°C (thermoneutral) eT for 6 months. Following 6 months of chronic eT treatment (12 months of age), mice were assayed for insulin sensitivity, glucose tolerance, and cognitive performance using the Morris water maze (MWM) behavioral paradigm. Post mortem analysis of circulating plasma levels elucidated changes in markers associated with successful aging.

Results

AβPP/PS1 mice housed in thermoneutral eT had reduced body weight compared to standard eT. Male AβPP/PS1 in thermoneutral eT had improved glucose tolerance as well as cognitive performance in the MWM. Plasma levels of insulin-like growth factor 1, leptin, and receptor for advanced glycation endproducts were reduced in AβPP/PS1 mice housed at thermoneutral eT.

Conclusions

A thermoneutral eT may provide a nonpharmacological strategy to improve metabolism and cognitive performance during the early stages of AD. Ongoing studies will elucidate changes in peripheral and cerebral markers of inflammation as well as soluble / insoluble amyloid accumulation.

This work was supported by: NIH R01AG057767 and R01AG061937.

Aims

Emerging human genetics and preclinical research revealed that microglia are likely contributing to AD pathophysiology. Microglia are responding to various pathogenic drivers of AD but the mechanisms by which microglia become dysfunctional and contribute to disease remain unclear. Here, we aimed to characterize amyloid-β related pathology and microglial responses in a novel APP knock-in mouse model. In particular, we sought to determine if pathogenic fibrillar form of Aβ causes transcriptomic and lipid dysregulation in microglia as a result of phagocytic uptake and to which extent this dysregulation perturbs immunometabolism.

Methods

We developed and characterized a new APP knock-in (KI) mouse model that circumvent limitations of transgenesis and applied multi-omics approaches in combination with cell population enrichment techniques to deeply characterize cellular perturbations of microglia in this mouse model.

Results

We validated the novel APP-KI mouse model by showing a dramatic increase of Aβ42/40 ratio in the brain, CSF and plasma at various ages, and demonstrated that it was associated with a progressive accumulation of amyloid plaques and an increase of markers of neuroinflammation and neurodegeneration. We then describe profound transcriptomic and lipidomic perturbations in brain-sorted microglia and reveal that some of those changes were exacerbated or unique in microglia showing evidence of Aβ accumulation.

Conclusions

Our in-depth analysis of this novel APP KI mouse model confirms emergence of disease-relevant biology and progressive accumulation of pathological hallmarks of AD. Additionally, we reveal profound immunometabolic perturbations in microglia supporting the notion that profound cellular alterations may lead to lysosomal dysfunction in highly phagocytic microglia.