PSEN1 Mutations Research Articles

Atypical presentations of autosomal dominant familial Alzheimer’s disease: insights into genetic, neuropathological and clinical heterogeneity

AbstractBackgroundAutosomal dominant familial Alzheimer’s disease (ADAD), caused by APP, PSEN1 and PSEN2 mutations, is clinically and pathologically similar to sporadic AD, with both typically presenting with memory impairment. However as in sporadic AD, atypical phenotypes and neuropathological heterogeneity occur, including variable vascular Aβ deposition as cerebral amyloid angiopathy (CAA). Investigating relationships between clinical, genetic and neuropathological heterogeneity in ADAD may provide insights into pathophysiological pathways relevant to AD in general.Methods256 symptomatic individuals from ADAD families seen at our Centre were included in a survival analysis, with detailed clinical phenotype data available for 138 (101 PSEN1, 37 APP). 33 of these individuals underwent brain donation (24 PSEN1, 9 APP), all demonstrating end‐stage AD pathology. Frontal and occipital cortex sections were stained immunohistochemically for Aβ and vessel counts used to determine the proportion of cortical and leptomeningeal blood vessels affected by CAA.ResultsAge at onset was, on average, seven years younger for PSEN1 than APP mutations and was influenced by mutation much more than survival was. Atypical (non‐amnestic) cognitive presentations with initial behavioral, language, dyscalculic or dysexecutive symptoms, and atypical clinical features (pyramidal, extrapyramidal and cerebellar signs) were more common in PSEN1 than APP cases, particularly those with post‐codon 200 mutations. Atypical cognitive presentations were associated with longer survival. There was some indication that APOE4 carriers had longer survival and that this effect may be restricted to PSEN1. In the post‐mortem cohort, atypical cognitive presentations occurred in 15%. Additional neurological features comprised myoclonus (45%), seizures (21%), pyramidal signs (21%) and extrapyramidal signs (15%), one individual had cerebellar signs. Increased frontal cortical and leptomeningeal CAA occurred in individuals with pyramidal and extrapyramidal signs, and in PSEN1 post‐codon 200 compared to pre‐codon 200 mutations. Atypical cognitive presentations were associated with increased frontal cortical CAA.ConclusionsPhenotypic heterogeneity in ADAD is influenced by causative gene and mutation type, and atypical clinical presentations are associated with increased CAA. Exploring mechanisms by which certain mutations drive Aβ deposition towards the vasculature, and how these may be impacted by other genetic factors and by therapies targeting Aβ, is an important direction for future research.

Neuronal lipid metabolism genetics and Early‐Onset Alzheimer’s Disease: A systematic review and meta‐analysis of observational studies

AbstractBackgroundEarly Onset Alzheimer’s disease (EOAD) is associated with mutations in APP, PSEN1 and PSEN 2 genes but few studies have assessed its relationship with mutations involved in lipid metabolism and the amyloid cascade. Therefore, this study seeks to determine the association of ABCA7, SORL1 and APOE mutations with EOAD.MethodThe protocol was registered in PROSPERO(CRD42022328366). We included comparative observational studies assessing the association of ABCA7, SORL1 and APOE mutations with the development of EOAD in patients younger than 65 years old. The search strategy was performed in five databases (MEDLINE, Scopus, Web of Science, EMBASE, Opengray) from their inception to May 7th,2022. Abstract and full‐text screening, data extraction and risk of bias (RoB) assessment were performed in duplicates. RoB was assessed with Newcastle‐Ottawa Scale. We performed a random effects meta‐analysis for dichotomous outcomes by using the DerSimoniain Laird method. Effect sizes were reported as odds ratio (OR) with their corresponding 95% confidence intervals (95%CI).ResultA total of 2191 studies were screened and seven studies (n = 8992) were included; one was a retrospective cohort and six were case‐control studies. Three studies had high RoB and four had low RoB. Overall, 60% were female and the mean age ranged from 33.9(SD±17.1) to 57.4(SD±5.6). Three case‐control studies (n = 5098) found a significant association of ABCA7 mutation with EOAD (OR:2.51 95%CI[1.33‐4.73]; tau‐squared = 0.20, I‐squared = 66%). Two case‐control studies (n = 3107) found that SORL1 mutation was not associated with EOAD (OR:3.65 95%CI[0.76‐17.49]; tau‐squared = 1.15, I‐squared = 89%). Two case‐control studies and one cohort study (n = 787) found that APOE4 allelic variant mutation of the APOE gene had significant association with EOAD (OR:13.21; 95%CI[3.81‐45.85]; tau‐squared = 0.90, I‐squared = 75%) and that the APOE2 allelic variant mutation was not associated with EOAD.ConclusionDespite the high heterogeneity in our results and limited number of studies, this study shows that ABCA7 and APOE mutations may be associated with an increased risk of EOAD. Larger high‐quality cohort studies are needed to address this research question.

Longitudinal effects of sex on pathology accumulation, neurodegeneration and cognitive decline in Presenilin‐1 E280A mutation carriers: preliminary findings from the Colombia‐Boston (COLBOS) biomarker study

AbstractBackgroundPrevious work showed that females at risk for autosomal dominant Alzheimer’s disease (AD) due to a single mutation (E280A) in the Presenilin‐1 gene (PSEN1) may have greater cognitive resilience to AD‐pathology and neurodegeneration than males. However, more research is needed to clarify the effect of sex on AD risk and progression. We investigated the effects of sex on rates of amyloid and tau accumulation, neurodegeneration, and memory decline in PSEN1 mutation carriers with and without cognitive impairment, who are genetically determined to develop early‐onset dementia.MethodA total of 66 cognitively unimpaired mutation carriers (mean age of 34.41 +/‐ 4.86 years; 38 females), and 23 cognitively impaired mutation carriers (mean age of 44.91 +/‐ 2.83 years; 17 females) from the Colombia‐Boston Biomarker (COLBOS) study completed baseline cognitive assessments. A subset of 52 participants also completed florbetapir‐ and flortaucipir‐PET, and structural MRI. Cognitive and neuroimaging follow‐up visits were completed at 2‐ (n = 29) and 4‐year (n = 13) intervals. We used linear mixed‐effects models, with random intercepts, to predict rate of change in MMSE scores, CERAD word list delayed recall, cortical amyloid burden, tau in the entorhinal, inferior temporal, and precuneus cortices, and hippocampal volume by sex, controlling for education.ResultOver time, carriers exhibited greater cortical amyloid burden (p<.001), inferior temporal tau (p = .019), precuneus tau (p = .003), lower hippocampal volume (p = .005), and showed a trend towards lower MMSE scores (p = .059) and word list delayed recall (p<.080); entorhinal tau did not significantly increase (p = .137). Female carriers showed a steeper decline in word list delayed recall than male carriers (p = .021). There were no sex differences in the rate of accumulation of mean cortical amyloid or regional tau, hippocampal atrophy, or change in MMSE scores (all ps>.05).ConclusionPreliminary findings of this ongoing study suggest that despite similar rates of pathology accumulation or atrophy between female and male PSEN1 E280A carriers, female mutation carriers may have faster memory decline. Future analyses with additional participants and follow‐up intervals are needed to characterize sex differences in ADAD risk and resilience, as well as inform development of treatments and interventions.

Phonetic‐phonological disturbances of spontaneous speech in autosomal dominant Alzheimer disease due to A431E PSEN1 mutation

AbstractBackgroundConsiderable cognitive research in Alzheimer Disease (AD) has focused on memory as it is often the primary symptom; nevertheless, in A431E PSEN1 mutation carriers in Jalisco, a rapidly language impairment and verbal fluency decrease during the disease is reported (Petersen‐Dumois, et al., 2020) though this deficit is not well‐characterized. The aim of this study was to identify and characterize phonetic‐phonological abnormalities in the spontaneous speech through different stages of A431E PSEN1 mutation‐related AD.MethodEleven symptomatic A431E PSEN1 mutation carriers, with a mean age of 42.54 years (DE = 4.17) participated in the study: five with Mild Cognitive Impairment (MCI), three with Mild Dementia (MiD) and five with Moderate Dementia (MoD). We used three language tasks: trip planning, picture description, and narrative discourse of a risky and happy moment of their lives which were recorded and transcribed. For each participant, we computed the frequency of phonetic‐phonological features: stuttering, unintelligible productions, phonological paraphasias, fillers and pauses (≥2 seconds) and then converted into percentages dividing the number of occurrences of each feature by the number of words used on the speech sample (for pauses, time in seconds). Then, we obtained the percentage mean of each feature per group.ResultWe analyzed a total of 134.65 minutes of speech sample. Regarding verbal fluency, words per minute (means) varied across the groups MCI: 85.55 (SD = 39.34); MiD: 128.56 (SD = 34.14) MoD: 67.80. (SD = 32.71). All phonological features were present, stuttering: MCI: 1.38%; MiD: 3.2%; MoD: 4.05%; unintelligible productions: MCI: .22%; MiD: .64%; MoD: .76%; phonological paraphasias; MCI: 0.002%; MiD: .01% MoD: .01%; fillers: MCI: 2.05%; MiD: .29%; MoD: 2.88%; number of pauses: MCI: .04%; MiD: .05%; MoD: .03%. and pauses average: MCI: 3.42 (SD = .62); MiD: 2.55 (SD = .03) MoD = 3.43. (SD: 1.61).ConclusionWe found that A431E PSEN1 mutation carriers present phonetic‐phonological traits even in the earliest stage (MCI) and for three of them (stuttering, unintelligible productions, and phonological paraphasias) their frequency is greater the more severe the impairment (MoD). Stuttering is their most prominent feature. These disturbances in the spontaneous speech could be a phenotype trait of this ADAD mutation.

Differential spatial transcriptome profile of the hippocampal formation of protected PSEN1 E280A familial Alzheimer’s disease cases

AbstractBackgroundWe have described two cases with ∼ 30 years of delayed disease onset among carriers of PSEN1 mutation E280A, suffering from familial Alzheimer’s disease (FAD). One case was homozygous for the ApoE Christchurch (hApoEch) mutation. This case showed sparse hyperphosphorylated tau (pTau) pathology in several cortical areas. The second case was heterozygous for the RELN‐COLBOS mutation and was globally affected by severe pTau and amyloid beta pathology, with evidence of localized cellular protection in the entorhinal cortex (EC). Here we used digital spatial profiling (DSP) transcriptomics to characterize the hippocampal formation of FAD protected cases and identify possible molecular mechanisms of protection.MethodsIn depth morphological characterization of the EC together with identification of thirteen different regions of interest (ROIs) were performed in Formalin‐fixed paraffinized 3 mm thick slides taken from the hippocampal formation (Fig. 1A) of the RELN‐COLBOS FAD case, the hApoEch FAD case, three FAD cases, and three sporadic Alzheimer’s cases (SAD). Slides were immunostained for NeuN and GFAP for morphological ROIs identification and processed for localized transcriptome analyses using the GeoMX DSP platform from Nanostring. Obtained data was processed for quality control, dimensionality reduction and differential gene expression (DGE) analyses.ResultsDimensionality reduction of transcriptomic data obtained from all ROIs and studied cases showed a distinctive distribution of ROIs belonging to both protected cases (Fig. 1B). Furthermore, DGE was observed in all sampled ROIs. ROIs such as hippocampal white matter or dentate gyri showed a higher number of differentially expressed genes due to a more homogeneous cellular composition of the ROIs (Fig. 1C). Also, EC and dentate gyrus from FAD protected cases showed distinctive molecular signatures compatible with excitatory neuronal pathways (Fig. 1D). Complementary morphological analyses showed increased neuronal density in the supragranular region of the EC in the RELN‐COLBOS FAD protected case, specifically in neuronal layer II.ConclusionOur results suggest that regardless of the protective gene conferring protection to FAD, the EC is one key protected structure with distinctive regional transcriptomic profiles suggesting the preservation of neuronal function in this region and hinting towards a possible therapeutic target in the protection against Alzheimer’s disease.

Characterizing plasma biomarkers of Alzheimer’s Disease in aging marmosets and genetically engineered PSEN1 mutation carriers.

AbstractBackgroundAlzheimer’s Disease (AD) is a progressive disease that presents as a continuum evolution from preclinical AD to mild cognitive impairment and, ultimately, dementia. The phenotypic characterization of AD was unified under a biological construct research framework supported by the National Institutes on Aging and Alzheimer’s Association (NIA‐AA). This framework, referred to as ATN, is based on the presence of biomarkers for amyloid (Aβ, A), pathologic tau (T), and neurodegeneration (N). The present studies aimed to establish normative values of these biomarkers in our colony of outbred marmosets from infancy through aged individuals and compare them to the values from our population of marmosets genetically engineered with early onset familial mutations in the PSEN1 gene.MethodPlasma (EDTA) and fibroblast media from skin biopsies were evaluated using MesoScale Discovery (MSD) Aβ peptide panel 4G8 ELISA and Human Neurofilament L (NfL) per the manufacturer’s protocols for each kit.ResultThere was a significant increase in the plasma Aβ42:40 ratio in PSEN1 mutation carriers relative to age‐ and sex‐matched wild‐type (WT) controls, which was also observed in culture media generated from fibroblasts of the same individuals. Longitudinal analysis of plasma Aβ revealed consistent levels in WT controls across multiple samplings with persistent increases in PSEN1 carriers. An increase in Nfl was observed in aging WT marmosets relative to young subjects.ConclusionWe have optimized the detection of plasma biomarkers for amyloid and NfL in marmosets and established normative values within our colony. Importantly, these results demonstrate the sensitivity and validity of these reagents for tracking plasma Aβ longitudinally across the marmoset lifespan. Other clinically utilized commercially available reagents are in the process of being optimized and validated to enable an analogous marmoset ATN. Pilot studies are ongoing evaluating the potential of pTau plasma biomarkers as part of the longitudinal assessments. The application of the NIA‐AA Research Framework to marmosets will attain a more accurate characterization and understanding of the etiological sequence of events that lead to AD development, in line with the currently used framework in AD patients.

CSF proteomics in autosomal dominant Alzheimer’s disease highlights parallels with sporadic disease

AbstractBackgroundAutosomal dominant Alzheimer’s disease (ADAD) offers a unique opportunity to study pathophysiological changes in a relatively young population with few comorbidities. A comprehensive investigation of proteome changes occurring in ADAD could provide valuable insights into AD‐related biological mechanisms and uncover novel biomarkers and therapeutic targets. Furthermore, ADAD might serve as a model for sporadic AD, but in‐depth proteome comparisons are lacking. We aimed to identify dysregulated CSF proteins in ADAD and determine the degree of overlap with sporadic AD.MethodUsing proximity extension‐based immunoassays (PEA) by Olink, we measured 1472 proteins in CSF of APP or PSEN1 mutation carriers (n = 22) and age‐ and sex‐matched controls (n = 20) from the Amsterdam Dementia Cohort. We compared protein abundance between groups using two‐sided t‐tests and identified enriched biological pathways. Using the same protein panels in paired plasma samples, we investigated correlations between CSF proteins and their plasma counterparts. Finally, we compared our results with recently published PEA data from an international cohort of sporadic AD (n = 230) and non‐AD dementias (n = 301). All analyses were false discovery rate‐corrected.ResultWe detected 66 differentially abundant CSF proteins (65 increased, one decreased) in ADAD compared to controls (q<0.05). The most strongly upregulated proteins (fold change >1.8) were related to immunity (CHIT1, ITGB2, SMOC2), cytoskeletal structure (MAPT, NEFL) and tissue remodeling (TMSB10, MMP‐10). Significant CSF‐plasma correlations were found for the upregulated proteins SMOC2 and LILR1B. 36 of the 66 differentially expressed proteins had been previously measured in the sporadic dementias cohort, 34 of which (94%) were also significantly upregulated in sporadic AD, with a strong correlation between the fold changes of these proteins in both cohorts (rs = 0.730, p<0.001). 29 of these 36 proteins (81%) were also upregulated among non‐AD patients with suspected AD co‐pathology.ConclusionThis CSF proteomics study demonstrates substantial biochemical similarities between ADAD and sporadic AD, suggesting involvement of the same biological processes. Besides known AD‐related proteins, we identified several relatively novel proteins, such as TMSB10, MMP‐10 and SMOC2, which have potential as novel biomarkers. With shared pathophysiological CSF changes, ADAD study findings might be translatable to sporadic AD, which could greatly expedite therapy development.

22 Semantic Processing and its Relation to Brain Pathology in Individuals with Autosomal Dominant Alzheimer's Disease: Preliminary Findings from the Colombia-Boston Biomarker Study

Objective:Semantic processing dysfunction has been shown to be an early indicator of cognitive decline in Alzheimer's disease (AD) and has been linked to early accumulation of AD-pathology. We examined semantic processing and its relation to AD pathology in non-demented individuals from a Colombian kindred with autosomal dominant AD due to the Presenilin1 E280A mutation (PSEN1).Participants and Methods:A total of 13 cognitively unimpaired PSEN1 mutation carriers (mean age: 36.92± 4.94), 7 carriers with mild cognitive impairment (MCI; mean age: 45±2.65), and 17 family non-carriers (mean age: 36±6.38) from the Colombia-Boston (COLBOS) longitudinal biomarker study were included. We used the Bateria IV Woodcock-Munoz verbal analogies and text comprehension subtests to examine semantic processing, the Mini-Mental State Examination (MMSE) to assess global cognition and the CERAD word list delayed recall task to measure verbal memory. Participants also underwent PiB and flortaucipir-PET to measure mean cortical amyloid and regional tau burden (entorhinal cortex and precuneus), respectively. Mann-Whitney U tests and Spearman's Rho correlations compared group differences in semantic processing, and its associations with age and pathological markers. Post-hoc analyses excluded carriers with MCI and controlled for education.Results:Carriers (including cognitively unimpaired and symptomatic individuals) performed significantly worse on the MMSE (carriers: 14.55, non-carriers: 24.24; U=81.00, p=.006), CERAD word list delayed recall (carriers: 13.63, non-carriers: 25.32; U=48.00, p=.001), and text comprehension (carriers: 16.36, non-carriers: 23.81; l/=107.00, p=.042,) than non-carriers, and showed a trend towards worse performance on verbal analogies (carriers: 17.16, non-carriers: 23.68; U=124.50, p=.077). There were no differences in text comprehension or verbal analogies performance between cognitively-unimpaired carriers and non-carriers.Across the whole sample, age was negatively associated with performance on verbal analogies (r=-.341, p=.039), but not text comprehension (r=-.136, p=.428). Among carriers only, better MMSE and CERAD delayed recall performance was associated with higher verbal analogies (r=.561, p=<.001; r=.662, p=<.001, respectively) and text comprehension scores (r=.468, p=.004; r=.480, p=.003, respectively). Greater amyloid burden was associated with worse verbal analogies performance (r=-.432, p=.007) and text comprehension (r=-.430, p=.008). Greater entorhinal cortex (r=-.384, p=.016) and precuneus tau burden (r=-.318, p=.049) was associated with worse performance on verbal analogies, but not text comprehension. These associations did not survive when excluding carriers with MCI or controlling for education.Conclusions:Preliminary results show that non-demented mutation carriers had worse performance in semantic processing than non-carriers and performance was associated with markers of AD pathology. These findings suggest that changes in semantic processing may be early indicators of disease progression in individuals at increased risk for Alzheimer's disease dementia. Future studies with larger samples need to examine the role of education and the longitudinal trajectory of semantic processing dysfunction in AD.

An Alternative View of Familial Alzheimer's Disease Genetics.

Probabilistic and parsimony-based arguments regarding available genetics data are used to propose that Hardy and Higgin's amyloid cascade hypothesis is valid but is commonly interpreted too narrowly to support, incorrectly, the primacy of the amyloid-β peptide (Aβ) in driving Alzheimer's disease pathogenesis. Instead, increased activity of the βCTF (C99) fragment of AβPP is the critical pathogenic determinant altered by mutations in the APP gene. This model is consistent with the regulation of APP mRNA translation via its 5' iron responsive element. Similar arguments support that the pathological effects of familial Alzheimer's disease mutations in the genes PSEN1 and PSEN2 are not exerted directly via changes in AβPP cleavage to produce different ratios of Aβ length. Rather, these mutations likely act through effects on presenilin holoprotein conformation and function, and possibly the formation and stability of multimers of presenilin holoprotein and/or of the γ-secretase complex. All fAD mutations in APP, PSEN1, and PSEN2 likely find unity of pathological mechanism in their actions on endolysosomal acidification and mitochondrial function, with detrimental effects on iron homeostasis and promotion of "pseudo-hypoxia" being of central importance. Aβ production is enhanced and distorted by oxidative stress and accumulates due to decreased lysosomal function. It may act as a disease-associated molecular pattern enhancing oxidative stress-driven neuroinflammation during the cognitive phase of the disease.

Cerebral organoids derived from patients with Alzheimer’s disease with PSEN1/2 mutations have defective tissue patterning and altered development

During the past two decades, induced pluripotent stem cells (iPSCs) have been widely used to study human neural development and disease. Especially in the field of Alzheimer's disease (AD), remarkable effort has been put into investigating molecular mechanisms behind this disease. Then, with the advent of 3D neuronal cultures and cerebral organoids (COs), several studies have demonstrated that this model can adequately mimic familial and sporadic AD. Therefore, we created an AD-CO model using iPSCs derived from patients with familial AD forms and explored early events and the progression of AD pathogenesis. Our study demonstrated that COs derived from three AD-iPSC lines with PSEN1(A246E) or PSEN2(N141I) mutations developed the AD-specific markers invitro, yet they also uncover tissue patterning defects and altered development. These findings are complemented by single-cell sequencing data confirming this observation and uncovering that neurons in AD-COs likely differentiate prematurely.

Promising Prospects for Human Cerebral Organoids to Advance Alzheimer's Disease Research

The causes of the alterations found in the brains of patients with alzheimer's disease (AD) begin before the first signs of memory loss appear, and are still unclear. Adequate research models are essential to understand the mechanisms that cause the onset of these alterations, as well as to advance in the diagnosis, development and testing of treatments for the AD. Animal research models fail to recreate the great diversity and complexity inherent to the human brain, so in vitro systems based on human pluripotent stem cells (hPSCs) present themselves as an important alternative. Differentiation of hPSCs into two-dimensional (2D) cell culture models allows recreation of various brain functional processes and the three-dimensional (3D) cell culture models or human brain organoids (hCOs) recapitulate the cellular diversity and structure of the human brain. hCOs from human induced pluripotent stem cells (hiPSCs) from patients with familial (APP, PSEN1 and PSEN2 mutations) or sporadic AD allow identifying and studying changes due to this pathology. This review presents an overview of the research models used to study the AD, and recapitulates the advantages and discusses the challenges of the hCOs as an innovative and promising technology that will aid in the understanding of AD.

Human Presenilin-1 delivered by AAV9 rescues impaired γ-secretase activity, memory deficits, and neurodegeneration in Psen mutant mice

Mutations in the Presenilin (PSEN1 and PSEN2) genes are the major cause of early-onset familial Alzheimer's disease (FAD). Presenilin (PS) is the catalytic subunit of the γ-secretase complex, which cleaves type I transmembrane proteins, such as Notch and the amyloid precursor protein (APP), and plays an evolutionarily conserved role in the protection of neuronal survival during aging. FAD PSEN1 mutations exhibit impaired γ-secretase activity in cell culture, in vitro, and knockin (KI) mouse brains, and the L435F mutation is the most severe in reducing γ-secretase activity and is located closest to the active site of γ-secretase. Here, we report that introduction of the codon-optimized wild-type human PSEN1 cDNA by adeno-associated virus 9 (AAV9) results in broadly distributed, sustained, low to moderate levels of human PS1 (hPS1) expression and rescues impaired γ-secretase activity in the cerebral cortex of Psen mutant mice either lacking PS or expressing the Psen1 L435F KI allele, as evaluated by endogenous γ-secretase substrates of APP and recombinant γ-secretase products of Notch intracellular domain and Aβ peptides. Furthermore, introduction of hPS1 by AAV9 alleviates impairments of synaptic plasticity and learning and memory in Psen mutant mice. Importantly, AAV9 delivery of hPS1 ameliorates neurodegeneration in the cerebral cortex of aged Psen mutant mice, as shown by the reversal of age-dependent loss of cortical neurons and elevated microgliosis and astrogliosis. These results together show that moderate hPS1 expression by AAV9 is sufficient to rescue impaired γ-secretase activity, synaptic and memory deficits, and neurodegeneration caused by Psen mutations in mouse models.

Developing a Gene Therapy for the Treatment of Autosomal Dominant Alzheimer's Disease.

Autosomal dominant Alzheimer's disease (ADAD) is a rare early-onset form of Alzheimer's disease, caused by dominant mutations in one of three genes: presenilin 1, presenilin 2, and amyloid β precursor protein (APP). Mutations in the presenilin 1 gene (PSEN1) account for the majority of cases, and individuals who inherit a single-mutant PSEN1 allele go on to develop early-onset dementia, ultimately leading to death. The presenilin 1 protein (PS1) is the catalytic subunit of the γ-secretase protease, a tetrameric protease responsible for cleavage of numerous transmembrane proteins, including Notch and the APP. Inclusion of a mutant PS1 subunit in the γ-secretase complex leads to a loss of enzyme function and a preferential reduction of shorter forms of Aβ peptides over longer forms, an established biomarker of ADAD progression in human patients. In this study, we describe the development of a gene therapy vector expressing a wild-type (WT) copy of human PSEN1 to ameliorate the loss of function associated with PSEN1 mutations. We have carried out studies in mouse models using a recombinant AAV9 vector to deliver the PSEN1 gene directly into the central nervous system (CNS) and shown that we can normalize γ-secretase function and slow neurodegeneration in both PSEN1 conditional knockout and PSEN1 mutant knockin models. We have also carried out biodistribution studies in nonhuman primates (NHPs) and demonstrated the ability to achieve broad PS1 protein expression throughout the cortex and the hippocampus, two regions known to be critically involved in ADAD progression. These studies demonstrate preclinical proof of concept that expression of a WT human PSEN1 gene in cells harboring a dominant PSEN1 mutation can correct the γ-secretase dysfunction. In addition, direct administration of the recombinant AAV9 into the NHP brain can achieve broad expression at levels predicted to provide efficacy in the clinic.

The Proteome Profile of Olfactory Ecto-Mesenchymal Stem Cells-Derived from Patients with Familial Alzheimer's Disease Reveals New Insights for AD Study.

Alzheimer's disease (AD), the most common neurodegenerative disease and the first cause of dementia worldwide, has no effective treatment, and its pathological mechanisms are not yet fully understood. We conducted this study to explore the proteomic differences associated with Familial Alzheimer's Disease (FAD) in olfactory ecto-mesenchymal stem cells (MSCs) derived from PSEN1 (A431E) mutation carriers compared with healthy donors paired by age and gender through two label-free liquid chromatography-mass spectrometry approaches. The first analysis compared carrier 1 (patient with symptoms, P1) and its control (healthy donor, C1), and the second compared carrier 2 (patient with pre-symptoms, P2) with its respective control cells (C2) to evaluate whether the protein alterations presented in the symptomatic carrier were also present in the pre-symptom stages. Finally, we analyzed the differentially expressed proteins (DEPs) for biological and functional enrichment. These proteins showed impaired expression in a stage-dependent manner and are involved in energy metabolism, vesicle transport, actin cytoskeleton, cell proliferation, and proteostasis pathways, in line with previous AD reports. Our study is the first to conduct a proteomic analysis of MSCs from the Jalisco FAD patients in two stages of the disease (symptomatic and presymptomatic), showing these cells as a new and excellent in vitro model for future AD studies.

Cholinergic-like neurons and cerebral spheroids bearing the PSEN1 p.Ile416Thr variant mirror Alzheimer's disease neuropathology

Familial Alzheimer’s disease (FAD) is a complex neurodegenerative disorder for which there are no therapeutics to date. Several mutations in presenilin 1 (PSEN 1), which is the catalytic component of γ-secretase complex, are causal of FAD. Recently, the p.Ile416Thr (I416T) PSEN 1 mutation has been reported in large kindred in Colombia. However, cell and molecular information from I416T mutation is scarce. Here, we demonstrate that menstrual stromal cells (MenSCs)-derived planar (2D) PSEN 1 I416T cholinergic-like cells (ChLNS) and (3D) cerebral spheroids (CSs) reproduce the typical neuropathological markers of FAD in 4 post-transdifferentiating or 11 days of transdifferentiating, respectively. The models produce intracellular aggregation of APPβ fragments (at day 4 and 11) and phosphorylated protein TAU at residue Ser202/Thr205 (at day 11) suggesting that iAPPβ fragments precede p-TAU. Mutant ChLNs and CSs displayed DJ-1 Cys106-SO3 (sulfonic acid), failure of mitochondria membrane potential (ΔΨm), and activation of transcription factor c-JUN and p53, expression of pro-apoptotic protein PUMA, and activation of executer protein caspase 3 (CASP3), all markers of cell death by apoptosis. Moreover, we found that both mutant ChLNs and CSs produced high amounts of extracellular eAβ42. The I416T ChLNs and CSs were irresponsive to acetylcholine induced Ca2+ influx compared to WT. The I416T PSEN 1 mutation might work as dominant-negative PSEN1 mutation. These findings might help to understanding the recurring failures of clinical trials of anti-eAβ42, and support the view that FAD is triggered by the accumulation of other intracellular AβPP metabolites, rather than eAβ42.

Familial Alzheimer's disease-associated PSEN1 mutations affect neurodevelopment through increased Notch signaling.

Alzheimer's disease (AD) is the most common neurodegenerative disorder, but its root cause may lie in neurodevelopment. PSEN1 mutations cause the majority of familial AD, potentially by disrupting proper Notch signaling, causing early unnoticed cellular changes that affect later AD progression. While rodent models are useful for modeling later stages of AD, human induced pluripotent stem cell-derived cortical spheroids (hCSs) allow access to studying the human cortex at the cellular level over the course of development. Here, we show that the PSEN1 L435F heterozygous mutation affects hCS development, increasing size, increasing progenitors, and decreasing post-mitotic neurons as a result of increased Notch target gene expression during early hCS development. We also show altered Aβ expression and neuronal activity at later hCS stages. These results contrast previous findings, showing how individual PSEN1 mutations may differentially affect neurodevelopment and may give insight into fAD progression to provide earlier time points for more effective treatments.

Bridging the rodent to human translational gap: Marmosets as model systems for the study of Alzheimer's disease.

Our limited understanding of the mechanisms that trigger the emergence of Alzheimer's disease (AD) has contributed to the lack of interventions that stop, prevent, or fully treat this disease. We believe that the development of a non-human primate model of AD will be an essential step toward overcoming limitations of other model systems and is crucial for investigating primate-specific mechanisms underlying the cellular and molecular root causes of the pathogenesis and progression of AD. A new consortium has been established with funding support from the National Institute on Aging aimed at the generation, characterization, and validation of Marmosets As Research Models of AD (MARMO-AD). This consortium will study gene-edited marmoset models carrying genetic risk for AD and wild-type genetically diverse aging marmosets from birth throughout their lifespan, using non-invasive longitudinal assessments. These include characterizing the genetic, molecular, functional, behavioral, cognitive, and pathological features of aging and AD. The consortium successfully generated viable founders carrying PSEN1 mutations in C410Y and A426P using CRISPR/Cas9 approaches, with germline transmission demonstrated in the C410Y line. Longitudinal characterization of these models, their germline offspring, and normal aging outbred marmosets is ongoing. All data and resources from this consortium will be shared with the greater AD research community. By establishing marmoset models of AD, we will be able to investigate primate-specific cellular and molecular root causes that underlie the pathogenesis and progression of AD, overcome limitations of other model organisms, and support future translational studies to accelerate the pace of bringing therapies to patients.

APOE ε4 allele, along with G206D-PSEN1 mutation, alters mitochondrial networks and their degradation in Alzheimer's disease.

Alzheimer's disease remains the most common neurodegenerative disorder, depicted mainly by memory loss and the presence in the brain of senile plaques and neurofibrillary tangles. This disease is related to several cellular alterations like the loss of synapses, neuronal death, disruption of lipid homeostasis, mitochondrial fragmentation, or raised oxidative stress. Notably, changes in the autophagic pathway have turned out to be a key factor in the early development of the disease. The aim of this research is to determine the impact of the APOE allele ε4 and G206D-PSEN1 on the underlying mechanisms of Alzheimer's disease. Fibroblasts from Alzheimer's patients with APOE 3/4 + G206D-PSEN1 mutation and homozygous APOE ε4 were used to study the effects of APOE polymorphism and PSEN1 mutation on the autophagy pathway, mitochondrial network fragmentation, superoxide anion levels, lysosome clustering, and p62/SQSTM1 levels. We observed that the APOE allele ε4 in homozygosis induces mitochondrial network fragmentation that correlates with an increased colocalization with p62/SQSTM1, probably due to an inefficient autophagy. Moreover, G206D-PSEN1 mutation causes an impairment of the integrity of mitochondrial networks, triggering high superoxide anion levels and thus making APOE 3/4 + PSEN1 fibroblasts more vulnerable to cell death induced by oxidative stress. Of note, PSEN1 mutation induces accumulation and clustering of lysosomes that, along with an increase of global p62/SQSTM1, could compromise lysosomal function and, ultimately, its degradation. The findings suggest that all these modifications could eventually contribute to the neuronal degeneration that underlies the pathogenesis of Alzheimer's disease. Further research in this area may help to develop targeted therapies for the treatment of Alzheimer's disease.

CSF proteomics in autosomal dominant Alzheimer's disease highlights parallels with sporadic disease.

Autosomal dominant Alzheimer's disease (ADAD) offers a unique opportunity to study pathophysiological changes in a relatively young population with few comorbidities. A comprehensive investigation of proteome changes occurring in ADAD could provide valuable insights into AD-related biological mechanisms and uncover novel biomarkers and therapeutic targets. Furthermore, ADAD might serve as a model for sporadic AD, but in-depth proteome comparisons are lacking. We aimed to identify dysregulated CSF proteins in ADAD and determine the degree of overlap with sporadic AD. We measured 1472 proteins in CSF of PSEN1 or APP mutation carriers (n = 22) and age- and sex-matched controls (n = 20) from the Amsterdam Dementia Cohort using proximity extension-based immunoassays (PEA). We compared protein abundance between groups with two-sided t-tests and identified enriched biological pathways. Using the same protein panels in paired plasma samples, we investigated correlations between CSF proteins and their plasma counterparts. Finally, we compared our results with recently published PEA data from an international cohort of sporadic AD (n = 230) and non-AD dementias (n = 301). All statistical analyses were false discovery rate-corrected. We detected 66 differentially abundant CSF proteins (65 increased, 1 decreased) in ADAD compared to controls (q < 0.05). The most strongly upregulated proteins (fold change >1.8) were related to immunity (CHIT1, ITGB2, SMOC2), cytoskeletal structure (MAPT, NEFL) and tissue remodelling (TMSB10, MMP-10). Significant CSF-plasma correlations were found for the upregulated proteins SMOC2 and LILR1B. Of the 66 differentially expressed proteins, 36 had been measured previously in the sporadic dementias cohort, 34 of which (94%) were also significantly upregulated in sporadic AD, with a strong correlation between the fold changes of these proteins in both cohorts (rs = 0.730, P < 0.001). Twenty-nine of the 36 proteins (81%) were also upregulated among non-AD patients with suspected AD co-pathology. This CSF proteomics study demonstrates substantial biochemical similarities between ADAD and sporadic AD, suggesting involvement of the same biological processes. Besides known AD-related proteins, we identified several relatively novel proteins, such as TMSB10, MMP-10 and SMOC2, which have potential as novel biomarkers. With shared pathophysiological CSF changes, ADAD study findings might be translatable to sporadic AD, which could greatly expedite therapy development.

Sex differences in blood biomarkers and cognitive performance in individuals with autosomal dominant Alzheimer's disease.

Plasma tau phosphorylated at threonine 217 (P-tau217) and neurofilament light (NfL) have emerged as markers of Alzheimer's disease (AD) pathology. Few studies have examined the role of sex in plasma biomarkers in sporadic AD, yielding mixed findings, and none in autosomal dominant AD. We examined the effects of sex and age on plasma P-tau217 and NfL, and their association with cognitive performance in a cross-sectional study of 621 Presenilin-1 E280A mutation carriers (PSEN1) and non-carriers. As plasma P-tau217 levels increase, cognitively unimpaired female carriers showed better cognitive performance than cognitively unimpaired male carriers. Yet, as disease progresses, female carriers had a greater plasma NfL increase than male carriers. There were no sex differences in the association between age and plasma biomarkers among non-carriers. Our findings suggest that, among PSEN1 mutation carriers, females had a greater rate of neurodegeneration than males, yet it did not predict cognitive performance. We examined sex differences in plasma P-tau217 and NfL in Presenilin-1 E280A (PSEN1) mutation carriers and non-carriers. Female carriers had a greater plasma NfL increase, but not P-tau217, than male carriers. As plasma P-tau217 levels increase, cognitively unimpaired female carriers showed better cognitive performance than cognitively unimpaired male carriers. The interaction effect of sex by plasma NfL levels did not predict cognition among carriers.