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We describe in vivo follow-up PET imaging and postmortem findings from an autosomal dominant Alzheimer’s disease (ADAD) PSEN1 E280A carrier who was also homozygous for the APOE3 Christchurch (APOE3ch) variant and was protected against Alzheimer’s symptoms for almost three decades beyond the expected age of onset. We identified a distinct anatomical pattern of tau pathology with atypical accumulation in vivo and unusual postmortem regional distribution characterized by sparing in the frontal cortex and severe pathology in the occipital cortex. The frontal cortex and the hippocampus, less affected than the occipital cortex by tau pathology, contained Related Orphan Receptor B (RORB) positive neurons, homeostatic astrocytes and higher APOE expression. The occipital cortex, the only cortical region showing cerebral amyloid angiopathy (CAA), exhibited a distinctive chronic inflammatory microglial profile and lower APOE expression. Thus, the Christchurch variant may impact the distribution of tau pathology, modulate age at onset, severity, progression, and clinical presentation of ADAD, suggesting possible therapeutic strategies.

We studied small vessel disease (SVD) pathology in Familial Alzheimer's disease (FAD) subjects carrying the presenilin 1 (PSEN1) p.Glu280Ala mutation in comparison to those with sporadic Alzheimer's disease (SAD) as a positive control for Alzheimer's pathology and Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) bearing different NOTCH3 mutations, as positive controls for SVD pathology. Upon magnetic resonance imaging (MRI) in life, some FAD showed mild white matter hyperintensities and no further radiologic evidence of SVD. In post‐mortem studies, total SVD pathology in cortical areas and basal ganglia was similar in PSEN1 FAD and CADASIL subjects, except for the feature of arteriosclerosis which was higher in CADASIL subjects than in PSEN1 FAD subjects. Further only a few SAD subjects showed a similar degree of SVD pathology as observed in CADASIL. Furthermore, we found significantly enlarged perivascular spaces in vessels devoid of cerebral amyloid angiopathy in FAD compared with SAD and CADASIL subjects. As expected, there was greater fibrinogen‐positive perivascular reactivity in CADASIL but similar reactivity in PSEN1 FAD and SAD groups. Fibrinogen immunoreactivity correlated with onset age in the PSEN1 FAD cases, suggesting increased vascular permeability may contribute to cognitive decline. Additionally, we found reduced perivascular expression of PDGFRβ AQP4 in microvessels with enlarged PVS in PSEN1 FAD cases. We demonstrate that there is Aβ‐independent SVD pathology in PSEN1 FAD, that was marginally lower than that in CADASIL subjects although not evident by MRI. These observations suggest presence of covert SVD even in PSEN1, contributing to disease progression. As is the case in SAD, these consequences may be preventable by early recognition and actively controlling vascular disease risk, even in familial forms of dementia.

Pathological hallmarks of Alzheimer’s disease (AD) include deposition and accumulation of amyloid- β (Aβ), neurofibrillary tangle formation and neuronal loss. Pathogenesis of the presymptomatic disease stages remains elusive, although studies suggest that early structural and functional alterations likely occur at neuronal dendritic spines. Presymptomatic alterations may also affect different CNS cell types. However, specific contributions of these cell types as cause or consequence of pathology are difficult to study in vivo. There is a shortage of relatively simple, well-defined and validated in vitro models that allow a straightforward interpretation of results and recapitulate aspects of pathophysiology. For instance, dissecting AD-related processes (e.g. neurotoxicity versus synaptotoxicity) may be difficult with common cell-based systems such as neuronal cell lines or primary neurons. To investigate and characterize the impact of reactive astrocytes on neuronal morphology in the context of AD-related cues, we modified an in vitro co-culture assay of primary mouse neurons and primary mouse astrocytes, based on the so-called Banker „sandwich„ co-culture assay. Here we provide a simple and modular assay with fully differentiated primary mouse neurons to study paracrine interactions between neurons and astrocytes in the co-culture setting. Readouts were obtained from both cell types in our assay. Astrocyte feeders were pre-exposed to neuroinflammatory conditions by means of Aβ42, Aβ40, or LPS. Non-cell-autonomous toxic effects of reactive astrocytes on neurons were assessed using Sholl analysis to evaluate dendritic complexity, whereas synaptic puncta served as a readout of synaptotoxicity. Here we show that astrocytes actively contribute to the phenotype of primary neurons in an AD-specific context, emphasizing the role of different cell types in AD pathology. The cytokine expression pattern were significantly altered in treated astrocytes. Of note, the impact of reactive astrocytes on neurons was highly dependent of defined cell ratios. Our co-culture system is modular, of low-cost, and allows to probe aspects of neurodegeneration and neuroinflammation between two major CNS cell types, neurons and astrocytes, under well-defined experimental conditions. Our easy-to-follow protocol including work-flow figures may provide a methodological outline to study interactions of astrocytes and neurons also in the context of other diseases in the future.

We characterized the world’s second case with ascertained extreme resilience to autosomal dominant Alzheimer’s disease (ADAD). Side-by-side comparisons of this male case and the previously reported female case with ADAD homozygote for the APOE3 Christchurch ( APOECh ) variant allowed us to discern common features. The male remained cognitively intact until 67 years of age despite carrying a PSEN1 -E280A mutation. Like the APOECh carrier, he had extremely elevated amyloid plaque burden and limited entorhinal Tau tangle burden. He did not carry the APOECh variant but was heterozygous for a rare variant in RELN (H3447R, termed COLBOS after the Colombia–Boston biomarker research study), a ligand that like apolipoprotein E binds to the VLDLr and APOEr2 receptors. RELN-COLBOS is a gain-of-function variant showing stronger ability to activate its canonical protein target Dab1 and reduce human Tau phosphorylation in a knockin mouse. A genetic variant in a case protected from ADAD suggests a role for RELN signaling in resilience to dementia. Case report of an individual heterozygous for a rare RELN-COLBOS variant that confers resilience, via a gain-of-function mechanism, to Alzheimer’s disease.

Studying comorbidities in early onset Alzheimer disease (AD) may provide an advantageous perspective on their pathogenesis because aging factors may be largely inoperative for these subjects. We compared AD comorbidities between early-onset sporadic cases and American and Colombian cases with PSEN1 mutations. AD neuropathological changes (ADNC) were very severe in all groups but more severe in the PSEN1 groups. Lewy body disease and cerebral white matter rarefaction were the most common (up to 60%) of AD comorbidities, followed by arteriolosclerosis (up to 37%), and large-vessel atherosclerosis (up to 20%). Differences between the 3 groups included earlier age of onset in the American PSEN1 cases, shorter disease duration in sporadic cases, and more frequent large-vessel atherosclerosis and cerebral amyloid angiopathy in the Colombian PSEN1 cases. Logistic regression models adjusted for age and sex found the presence of a PSEN1 mutation, an apolipoprotein ε4 allele and TDP-43 pathology to predict an earlier age of onset; Hispanic ethnicity and multiracial subjects were predictive of severe CAA. Comorbidities are common in early onset AD and should be considered when planning clinical trials with such subjects. However, they may be at least partially dependent on ADNC and thus potentially addressable by anti-amyloid or and/anti-tau therapies.

Variants in and (encoding apolipoprotein E and presenilin 1, respectively) alter the risk of Alzheimer's disease. We previously reported a delay of cognitive impairment in a person with autosomal dominant Alzheimer's disease caused by the variant who also had two copies of the apolipoprotein E3 Christchurch variant ( ). Heterozygosity for the variant may influence the age at which the onset of cognitive impairment occurs. We assessed this hypothesis in a population in which the variant is prevalent. We analyzed data from 27 participants with one copy of the variant among 1077 carriers of the variant in a kindred from Antioquia, Colombia, to estimate the age at the onset of cognitive impairment and dementia in this group as compared with persons without the variant. Two participants underwent brain imaging, and autopsy was performed in four participants. Among carriers of who were heterozygous for the variant, the median age at the onset of cognitive impairment was 52 years (95% confidence interval [CI], 51 to 58), in contrast to a matched group of carriers without the variant, among whom the median age at the onset was 47 years (95% CI, 47 to 49). In two participants with the and variants who underwent brain imaging, F-fluorodeoxyglucose positron-emission tomographic (PET) imaging showed relatively preserved metabolic activity in areas typically involved in Alzheimer's disease. In one of these participants, who underwent F-flortaucipir PET imaging, tau findings were limited as compared with persons with in whom cognitive impairment occurred at the typical age in this kindred. Four studies of autopsy material obtained from persons with the and variants showed fewer vascular amyloid pathologic features than were seen in material obtained from persons who had the variant but not the variant. Clinical data supported a delayed onset of cognitive impairment in persons who were heterozygous for the variant in a kindred with a high prevalence of autosomal dominant Alzheimer's disease. (Funded by Good Ventures and others.).

A patient with the PSEN1 E280A mutation and homozygous for APOE3 Christchurch ( APOE3Ch ) displayed extreme resistance to Alzheimer’s disease (AD) cognitive decline and tauopathy, despite having a high amyloid burden. To further investigate the differences in biological processes attributed to APOE3Ch , we generated induced pluripotent stem (iPS) cell-derived cerebral organoids from this resistant case and a non-protected control, using CRISPR/Cas9 gene editing to modulate APOE3Ch expression. In the APOE3Ch cerebral organoids, we observed a protective pattern from early tau phosphorylation. ScRNA sequencing revealed regulation of Cadherin and Wnt signaling pathways by APOE3Ch , with immunostaining indicating elevated β-catenin protein levels. Further in vitro reporter assays unexpectedly demonstrated that ApoE3Ch functions as a Wnt3a signaling enhancer. This work uncovered a neomorphic molecular mechanism of protection of ApoE3 Christchurch, which may serve as the foundation for the future development of protected case-inspired therapeutics targeting AD and tauopathies.

Alzheimer′s disease (AD) is the most common cause of dementia among older adults. APOE3 Christchurch (R136S, APOE3Ch) variant homozygosity was reported in an individual with extreme resistance to autosomal dominant AD due to the PSEN1 E280A mutation. This subject had a delayed clinical age at onset and resistance to tauopathy and neurodegeneration despite extremely high amyloid plaque burden. We established induced pluripotent stem (iPS) cell-derived cerebral organoids from this resistant case and from a non-protected kindred control (with PSEN1 E280A and APOE3/3). We used CRISPR/Cas9 gene editing to successfully remove the APOE3Ch to wild type in iPS cells from the protected case and to introduce the APOE3Ch as homozygote in iPS cells from the non-protected case to examine causality. We found significant reduction of tau phosphorylation (pTau 202/205 and pTau396) in cerebral organoids with the APOE3Ch variant, consistent with the strikingly reduced tau pathology found in the resistant case. We identified Cadherin and Wnt pathways as signaling mechanisms regulated by the APOE3Ch variant through single cell RNA sequencing in cerebral organoids. We also identified elevated β-catenin protein, a regulator of tau phosphorylation, as a candidate mediator of APOE3Ch resistance to tauopathy. Our findings show that APOE3Ch is necessary and sufficient to confer resistance to tauopathy in an experimental ex-vivo model establishing a foundation for the development of novel, protected case-inspired therapeutics for tauopathies, including Alzheimer′s.Competing Interest StatementDrs. Arboleda-Velasquez, Quiroz, and Lopera are listed as inventors on a patent application addressing Christchurch-inspired therapeutics. Dr. Arboleda is a co-founder of EPOCH Biotech, an L.L.C. developing Christchurch-inspired therapeutics. Dr. Quiroz serves as a consultant for Biogen.