Autosomal Dominant Alzheimer's Disease Mutation Research Articles

Cognitive Outcomes in Autosomal-Dominant Alzheimer's Disease: A Comprehensive Review from a Colombian Kindred with the Presenilin-1 E280A Mutation.

The largest identified kindred worldwide with a single mutation causing autosomal-dominant Alzheimer's disease (ADAD) is a family from Antioquia, Colombia, carrying the Presenilin-1 (PSEN1) E280A (Paisa) mutation. The majority of mutation carriers develop dementia, typically commencing in their late 30 s, with a median onset age of 49 years. Cognitive decline is a hallmark feature. This review synthesizes the existing literature on neuropsychological assessments in PSEN1 E280A mutation carriers throughout their lifespan. We provide a comprehensive overview of cognitive outcomes in this unique population. We reviewed and integrated the published research, analyzing studies on neuropsychological assessments in PSEN1 E280A carriers. Our focus was on measures of verbal, semantic, episodic, and spatial memory, and encompassed other cognitive domains such as language, attention, visuospatial memory, and executive functioning. Verbal, semantic, episodic, and spatial memory emerged as the most sensitive indicators of preclinical changes in PSEN1 E280A carriers. Inconsistencies were noted in findings from tests assessing language, attention, visuospatial memory, and executive functioning, suggesting potential limitations in detecting early cognitive changes in PSEN1 mutation carriers. Specific cognitive tasks developed for this population proved effective but underutilized. The review underscores the importance of continued test development tailored to detect early cognitive changes in PSEN1 E280A carriers, potentially enhancing ADAD screening. Furthermore, investigating ADAD mutations in children may identify early changes in AD and enhance our understanding of neuropsychological functioning across the lifespan. This synthesis provides valuable insights for researchers, clinicians, and policymakers engaged in the study and management of ADAD.

α-Synuclein seed amplification assay detects Lewy body co-pathology in autosomal dominant Alzheimer's disease late in the disease course and dependent on Lewy pathology burden.

Amyloid beta and tau pathology are the hallmarks of sporadic Alzheimer's disease (AD) and autosomal dominant AD (ADAD). However, Lewy body pathology (LBP) is found in ≈ 50% of AD and ADAD brains. Using an α-synuclein seed amplification assay (SAA) in cerebrospinal fluid (CSF) from asymptomatic (n=26) and symptomatic (n=27) ADAD mutation carriers, including 12 with known neuropathology, we investigated the timing of occurrence and prevalence of SAA positive reactivity in ADAD in vivo. No asymptomatic participant and only 11% (3/27) of the symptomatic patients tested SAA positive. Neuropathology revealed LBP in 10/12 cases, primarily affecting the amygdala or the olfactory areas. In the latter group, only the individual with diffuse LBP reaching the neocortex showed α-synuclein seeding activity in CSF in vivo. Results suggest that in ADAD LBP occurs later than AD pathology and often as amygdala- or olfactory-predominant LBP, for which CSF α-synuclein SAA has low sensitivity. Cerebrospinal fluid (CSF) real-time quaking-induced conversion (RT-QuIC) detects misfolded α-synuclein in ≈ 10% of symptomatic autosomal dominant Alzheimer's disease (ADAD) patients. CSF RT-QuIC does not detect α-synuclein seeding activity in asymptomatic mutation carriers. Lewy body pathology (LBP) in ADAD mainly occurs as olfactory only or amygdala-predominant variants. LBP develops late in the disease course in ADAD. CSF α-synuclein RT-QuIC has low sensitivity for focal, low-burden LBP.

Autosomal Dominant Alzheimer's Disease Mutations in Human Microglia Are Not Sufficient to Trigger Amyloid Pathology in WT Mice but Might Affect Pathology in 5XFAD Mice.

Several genetic variants that affect microglia function have been identified as risk factors for Alzheimer's Disease (AD), supporting the importance of this cell type in disease progression. However, the effect of autosomal dominant mutations in the amyloid precursor protein (APP) or the presenilin (PSEN1/2) genes has not been addressed in microglia in vivo. We xenotransplanted human microglia derived from non-carriers and carriers of autosomal dominant AD (ADAD)-causing mutations in the brain of hCSF1 WT or 5XFAD mice. We observed that ADAD mutations in microglia are not sufficient to trigger amyloid pathology in WT mice. In 5XFAD mice, we observed a non-statistically significant increase in amyloid plaque volume and number of dystrophic neurites, coupled with a reduction in plaque-associated microglia in the brain of mice xenotransplanted with ADAD human microglia compared to mice xenotransplanted with non-ADAD microglia. In addition, we observed a non-statistically significant impairment in working and contextual memory in 5XFAD mice xenotransplanted with ADAD microglia compared to those xenotransplanted with non-ADAD-carrier microglia. We conclude that, although not sufficient to initiate amyloid pathology in the healthy brain, mutations in APP and PSEN1 in human microglia might cause mild changes in pathological and cognitive outcomes in 5XFAD mice in a manner consistent with increased AD risk.

The MAPP Room Memory Test: Examining Contextual Memory Using a Novel Computerized Test in Cognitively-Unimpaired Individuals with Autosomal Dominant Alzheimer's Disease.

Contextual memory, the ability to remember spatial or temporal features related to an event, is affected in Alzheimer's disease (AD). There is a shortfall of tests that measure contextual memory. To evaluate visuospatial contextual memory, we developed a computerized cognitive test, the MAPP Room Memory Test, which requires participants to identify in which visual scene target items were previously presented. We hypothesized that cognitively-unimpaired carriers of an autosomal dominant AD mutation (Presenilin-1 E280A, n=15) would perform more poorly on this test than non-carrier family members (n=31). Compared to non-carriers, the carriers had significantly worse delayed room recognition. The results indicate that the MAPP Room Memory Test may be sensitive to subtle cognitive changes associated with risk of AD. Future studies with larger samples using the MAPP Room Memory Test and biomarkers are needed to examine whether this test may also be sensitive to the earliest pathological changes in preclinical AD.

Advanced structural brain aging in preclinical autosomal dominant Alzheimer disease

Background“Brain-predicted age” estimates biological age from complex, nonlinear features in neuroimaging scans. The brain age gap (BAG) between predicted and chronological age is elevated in sporadic Alzheimer disease (AD), but is underexplored in autosomal dominant AD (ADAD), in which AD progression is highly predictable with minimal confounding age-related co-pathology.MethodsWe modeled BAG in 257 deeply-phenotyped ADAD mutation-carriers and 179 non-carriers from the Dominantly Inherited Alzheimer Network using minimally-processed structural MRI scans. We then tested whether BAG differed as a function of mutation and cognitive status, or estimated years until symptom onset, and whether it was associated with established markers of amyloid (PiB PET, CSF amyloid-β-42/40), phosphorylated tau (CSF and plasma pTau-181), neurodegeneration (CSF and plasma neurofilament-light-chain [NfL]), and cognition (global neuropsychological composite and CDR-sum of boxes). We compared BAG to other MRI measures, and examined heterogeneity in BAG as a function of ADAD mutation variants, APOE ε4 carrier status, sex, and education.ResultsAdvanced brain aging was observed in mutation-carriers approximately 7 years before expected symptom onset, in line with other established structural indicators of atrophy. BAG was moderately associated with amyloid PET and strongly associated with pTau-181, NfL, and cognition in mutation-carriers. Mutation variants, sex, and years of education contributed to variability in BAG.ConclusionsWe extend prior work using BAG from sporadic AD to ADAD, noting consistent results. BAG associates well with markers of pTau, neurodegeneration, and cognition, but to a lesser extent, amyloid, in ADAD. BAG may capture similar signal to established MRI measures. However, BAG offers unique benefits in simplicity of data processing and interpretation. Thus, results in this unique ADAD cohort with few age-related confounds suggest that brain aging attributable to AD neuropathology can be accurately quantified from minimally-processed MRI.

Taking it to the extreme: The search for determinants of cognitive vulnerability and resilience in children with autosomal dominant Alzheimer’s disease

Abstract:Presenilin-1 (PSEN1) mutations predispose individuals to develop autosomal-dominant Alzheimer's disease (ADAD) in middle adulthood. While the pathogenesis of ADAD may be different from late-onset sporadic AD (e.g., differences in disease etiology, age of disease onset, etc), these conditions share many characteristics, including similar abnormalities in amyloid and tau biomarkers, brain structure and brain activity, and clinical features (Quiroz et al., 2010, Quiroz et al., 2011, Quiroz et al. 2018). Biomarker investigations of families with ADAD have already shed light on the trajectory of some AD-related brain changes, especially prior to the onset of clinical symptoms.We have been studying a Colombian kindred with a genetic form of AD caused by a single genetic mutation in the PSEN1 (E280A), which serves as a unique model for preclinical AD. Because of a well-defined age at clinical onset, and near 100% penetrance, this kindred provides important information about the time course and relationships between physiological mechanisms and cognitive changes, and in so doing, it has yielded new insights about presymptomatic AD that will enhance future prevention trials for AD, including primary prevention trials.The well-characterized clinical trajectory of these PSEN1 E280A mutation carriers allow us to examine brain function in children, more than three decades before the average age of onset of mild cognitive impairment (MCI) and dementia in this cohort (45 years for MCI, 50 years for dementia). This is giving us the unique opportunity to characterize the cognitive and behavioral profiles of children genetically determined to develop dementia in their forties, and is helping us improve our understanding of the impact of ADAD mutations in early life cognitive and brain functioning, as well as its potential impact on learning, academic performance and educational attainment. We previously studied 20 PSEN1 E280A carriers and 20 non-carriers aged 9 to 17 years from the Colombian ADAD cohort and showed that mutation-carrying children were distinguished from non-carriers by plasma biomarker findings consistent with Aß1-42 overproduction, as well as by increased functional connectivity of the posterior cingulate cortex with medial temporal lobe regions (Quiroz et al 2015). More recently, we used the WISC-IV, a measure of general intellectual abilities to examine cognitive abilities in these children. We reported in 265 children with the E280A mutation and 1089 non-carriers that they did not differ on any of the WISC-IV indices. Surprisingly, male carriers performed slightly worse than female carriers on working memory (mean difference = -4.97; P = .001) (Fox-Fuller et al., 2021). Some of our ongoing work includes comprehensive examinations of social, educational and developmental histories along with functional brain networks, as markers of synaptic dysfunction in individuals with ADAD, as this is particularly relevant to understanding the impact of PSEN1 mutations on the developing brain and subsequent neurodegenerative changes seen later in life, without the confounds of aging and age-related comorbidities that often exist in late-onset sporadic AD.Disclosures: Financial: Dr. Quiroz receives a consulting fee from Biogen. Non-Financial: Dr. Quiroz is a Hispanic Neuropsychological Society Member-At-Large and serves as the INS Teleneuropsychology Special Interest Group Chair

Alzheimer risk-increasing TREM2 variant causes aberrant cortical synapse density and promotes network hyperexcitability in mouse models

The R47H variant of triggering receptor expressed on myeloid cells 2 (TREM2) increases the risk of Alzheimer's disease (AD). To investigate potential mechanisms, we analyzed knockin mice expressing human TREM2-R47H from one mutant mouse Trem2 allele. TREM2-R47H mice showed increased seizure activity in response to an acute excitotoxin challenge, compared to wildtype controls or knockin mice expressing the common variant of human TREM2. TREM2-R47H also increased spontaneous thalamocortical epileptiform activity in App knockin mice expressing amyloid precursor proteins bearing autosomal dominant AD mutations and a humanized amyloid-β sequence. In mice with or without such App modifications, TREM2-R47H increased the density of putative synapses in cortical regions without amyloid plaques. TREM2-R47H did not affect synaptic density in hippocampal regions with or without plaques. We conclude that TREM2-R47H increases AD-related network hyperexcitability and that it may do so, at least in part, by causing an imbalance in synaptic densities across brain regions.

Associations of category fluency clustering performance with in vivo brain pathology in autosomal dominant Alzheimer's disease.

Alzheimer's disease (AD) is known to impact semantic access, which is frequently evaluated using the Category Fluency (Animals) test. Recent studies have suggested that in addition to overall category fluency scores (total number of words produced over time), poor clustering could signal AD-related cognitive difficulties. In this study, we examined the association between category fluency clustering performance (i.e., stating words sequentially that are all contained within a subcategory, such as domestic animals) and brain pathology in individuals with autosomal dominant Alzheimer's disease (ADAD). A total of 29 non-demented carriers of the Presenilin1 E280A ADAD mutation and 32 noncarrier family members completed the category fluency test (Animals) and the Mini-Mental State Examination (MMSE). The participants also underwent positron emission tomography (PET) scans to evaluate in vivo amyloid-beta in the neocortex and tau in medial temporal lobe regions. Differences between carriers and noncarriers on cognitive tests were assessed with Mann-Whitney tests; associations between cognitive test performance and brain pathology were assessed with Spearman correlations. Animal fluency scores did not differ between carriers and noncarriers. Carriers, however, showed a stronger association between animal fluency clustering and in vivo AD brain pathology (neocortical amyloid and entorhinal tau) relative to noncarriers. This study indicates that using category fluency clustering, but not total score, is related to AD pathophysiology in the preclinical and early stages of the disease.

Memory for Semantically Related Objects Differentiates Cognitively Unimpaired Autosomal Dominant Mutation Carriers from Non-Carrier Family Members.

Early cognitive changes due to Alzheimer's disease (AD) include difficulties in semantic access and working memory. Using a computerized cognitive test developed by our group, called the Memory for Semantically Related Objects test (MESERO), we evaluated if cognitively unimpaired carriers of an autosomal dominant AD (ADAD) mutation performed worse on this test than non-carrier family members. 35 cognitively unimpaired ADAD mutation carriers and 26 non-carrier family members from a Colombian ADAD cohort took the MESERO on a laptop computer. Cognitively unimpaired ADAD carriers had significantly worse MESERO total scores than non-carrier family members, driven by worse performance in semantically-related object sets; group performances did not differ on semantically unrelated object sets. Findings suggest that MESERO performance may be sensitive to subtle cognitive changes associated with AD. Future MESERO research should examine performances between healthy older adults and people at risk for sporadic AD.

CSF tau phosphorylation at sites 217 and 205 mediate the relationship between PET amyloid and downstream AD markers

AbstractBackgroundAssociations between amyloid and downstream measures of Alzheimer disease (AD) are often lacking. In autosomal dominant AD (ADAD), cerebrospinal fluid (CSF) phosphorylated tau 217 and 181 (pT217 and pT181) increase shortly after amyloid positron emission tomography (PET), followed by tau 205 (pT205), then tau PET. Each site also tracks closely with disease progression and is associated with longitudinal cognitive decline. Collectively these findings lead to the question of which p‐tau sites affect the relationship between amyloid and downstream AD markers (i.e., tau, MRI cortical thickness, Clinical Dementia Rating [CDR] Scale status), and more specifically whether they mediate such associations.MethodCSF tau phosphorylation occupancy on 217, 181 and 205 residues, CSF total tau (t‐tau), amyloid PET, ADAD cortical thickness signature, and CDR status were measured in 150 individuals from the Dominantly Inherited Alzheimer Network (non‐mutation carrier [MC‐]; n=64; and mutation carrier [MC+]; n=86). Three multiple mediation analyses assuming nonlinear relationships were performed with amyloid PET as the predictor variable, CSF p‐tau sites (pT217, pT181, pT205) and t‐tau (when appropriate) as mediators, and either CSF t‐tau, cortical thickness, or CDR status as the outcome variables. For each model, estimated years to symptom onset (EYO), age, sex, and ADAD mutation status were included as covariates. All models were run with 500 iterations to bootstrap confidence intervals.ResultIncreased amyloid PET was associated with elevated CSF pT217, pT181, and pT205 (p’s<0.03). For each model, the effects of amyloid PET on downstream AD markers were jointly mediated by CSF pT217 and pT205. Specifically, elevated CSF pT217 and pT205 were associated with increased CSF t‐tau, decreased cortical thickness, and higher CDR scores (p’s<0.01). CSF t‐tau and pT181 did not mediate these relationships (p’s>0.05).ConclusionElevated pT217 and pT205, but not pT181 or t‐tau, mediate the relationship between amyloid and downstream AD biomarkers in ADAD. AD‐related brain atrophy and clinical status may be dependent on specific tau sites; future mechanistic experiments are needed to fully understand such relationships. These results support the hypothesis that tau phosphorylation at specific sites plays a critical role in the progression and pathogenesis of ADAD, and may be a possible target for future treatments.

Different rates of cognitive decline in autosomal dominant and late-onset Alzheimer disease.

As prevention trials advance with autosomal dominant Alzheimer disease (ADAD) participants, understanding the similarities and differences between ADAD and "sporadic" late-onset AD (LOAD) is critical to determine generalizability of findings between these cohorts. Cognitive trajectories of ADAD mutation carriers (MCs) and autopsy-confirmed LOAD individuals were compared to address this question. Longitudinal rates of change on cognitive measures were compared in ADAD MCs (n=310) and autopsy-confirmed LOAD participants (n=163) before and after symptom onset (estimated/observed). LOAD participants declined more rapidly in the presymptomatic (preclinical) period and performed more poorly at symptom onset than ADAD participants on a cognitive composite. After symptom onset, however, the younger ADAD MCs declined more rapidly. The similar but not identical cognitive trajectories (declining but at different rates) for ADAD and LOAD suggest common AD pathologies but with some differences.

Multi-omics data integration reveals clinically meaningful molecular profiles of Alzheimer disease.

Alzheimer disease (AD) is a complex polygenic disease in which multiple molecular pathways and biological processes are affected in distinct cell-types of the brain. Increasingly, novel machine learning approaches have been applied in other areas of similarly high complexity (e.g., cancer) to integrate different modalities of "-omics" data and provide novel insights. We sought to apply high-throughput "multi-omics" and machine learning approaches to a large assembly of clinically and neuropathologically well-characterized brain samples to identify genes and biological pathways that may lead to new biomarkers and therapies for AD. We analyzed high-throughput transcriptomics, proteomics, metabolomics and lipidomics profiles of postmortem parietal cortex samples from the Knight ADRC (n=328) and the DIAN (n =21) participants including APP, PSEN1 and PSEN2 autosomal dominant AD mutation carriers (ADAD, n=28), sporadic AD (sAD, n=282), presymptomatic AD (preAD, n=14), and controls with minimal neuropathologic changes (n=25). We applied a Bayesian integrative clustering method (iClusterBayes), designed to identify disease subtypes, to cluster sAD samples on the basis of 2,676 transcripts, 1,067 proteins, 350 metabolites, and 277 lipids. Our analyses identified four different molecular signatures among sAD cases (Figure 1A). Cluster 4 was associated with higher Clinical Dementia Rating (CDR; p=2.2 x10-20) scores and shorter life span (p=5.6 x10-3, HR=1.6; Figure 1B). In particular, alpha-synuclein (SNCA) transcriptomic and proteomic levels were differentially expressed between samples in cluster 4 and others representing sAD, ADAD, preAD, and controls (Figure 1C) suggesting a unique role for SNCA in sAD cases with unfavorable outcomes. The lower levels of soluble SNCA protein in AD samples may be associated with insoluble aggregated SNCA (Lewy bodies) reported in 50-60% of sAD. By applying machine learning approaches to sAD samples with high-throughput multi-omic profiles, we identified novel molecular signatures missed by single layer analyses. These signatures are associated with clinical phenotypes and offer new insights into which molecules may wax or wane as cognition declines. The association of SNCA with poor outcomes suggests that concomitant Lewy bodies may be a negative prognostic factor in sAD. Currently, we are extending these analyses to incorporate replication cohorts and to perform downstream pathway and enrichment analyses.

Diffusion Tensor MRI Structural Connectivity and PET Amyloid Burden in Preclinical Autosomal Dominant Alzheimer Disease: The DIAN Cohort.

Background Pathologic evidence of Alzheimer disease (AD) is detectable years before onset of clinical symptoms. Imaging-based identification of structural changes of the brain in people at genetic risk for early-onset AD may provide insights into how genes influence the pathologic cascade that leads to dementia. Purpose To assess structural connectivity differences in cortical networks between cognitively normal autosomal dominant Alzheimer disease (ADAD) mutation carriers versus noncarriers and to determine the cross-sectional relationship of structural connectivity and cortical amyloid burden with estimated years to symptom onset (EYO) of dementia in carriers. Materials and Methods In this exploratory analysis of a prospective trial, all participants enrolled in the Dominantly Inherited Alzheimer Network between January 2009 and July 2014 who had normal cognition at baseline, T1-weighted MRI scans, and diffusion tensor imaging (DTI) were analyzed. Amyloid PET imaging using Pittsburgh compound B was also analyzed for mutation carriers. Areas of the cerebral cortex were parcellated into three cortical networks: the default mode network, frontoparietal control network, and ventral attention network. The structural connectivity of the three networks was calculated from DTI. General linear models were used to examine differences in structural connectivity between mutation carriers and noncarriers and the relationship between structural connectivity, amyloid burden, and EYO in mutation carriers. Correlation network analysis was performed to identify clusters of related clinical and imaging markers. Results There were 30 mutation carriers (mean age ± standard deviation, 34 years ± 10; 17 women) and 38 noncarriers (mean age, 37 years ± 10; 20 women). There was lower structural connectivity in the frontoparietal control network in mutation carriers compared with noncarriers (estimated effect of mutation-positive status, -0.0266; P = .04). Among mutation carriers, there was a correlation between EYO and white matter structural connectivity in the frontoparietal control network (estimated effect of EYO, -0.0015, P = .01). There was no significant relationship between cortical global amyloid burden and EYO among mutation carriers (P > .05). Conclusion White matter structural connectivity was lower in autosomal dominant Alzheimer disease mutation carriers compared with noncarriers and correlated with estimated years to symptom onset. Clinical trial registration no. NCT00869817 © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by McEvoy in this issue.

Neuropsychiatric symptoms in early stage autosomal dominant and sporadic Alzheimer’s disease

AbstractBackgroundNeuropsychiatric symptoms (NPS) in AD, though more prevalent and severe in advanced disease, can occur as early features, with case reports suggesting more robust NPS in autosomal dominant Alzheimer disease (ADAD). The characterization of NPS in person with ADAD and their comparison to late‐onset Alzheimer’s disease (LOAD) enhances our ability to anticipate such symptoms and provides insight into differences in the underlying pathology of the two forms of the disease.MethodInformants of 19 participants with mutations known to cause ADAD (mean age 45.58, 36.8% male) and 115 participants with LOAD (mean age 74.71, 42.6% male) were administered the full Neuropsychiatric Inventory (NPI) to assess the presence, frequency, and severity of 12 NPS, namely delusions, hallucinations, agitation, depression, anxiety, elation, apathy, disinhibition, irritability, aberrant motor behavior, sleep, and eating disorders. All participants had Clinical Dementia Rating (CDR) scores of 0.5. Chi‐square tests were used to compare the prevalence of NPS between ADAD and LOAD patients using both NPI screening and subquestions.ResultADAD and LOAD groups did not significantly differ in terms of MMSE score, CDR Sum of Boxes, gender, or years of education though ADAD subjects were more likely to be of Latinx origin (84% vs. 23%, p<0.001). ADAD and LOAD subjects did not differ on any qualifying questions, except for apathy, which was more common in ADAD mutation carriers (20.9% of LOAD subjects vs. 44.4% of ADAD subjects, p=0.039). Positive responses to subquestions regarding whether the participant was less affectionate and less interested in family were more commonly endorsed in ADAD.ConclusionAlthough apathy was more prevalent in ADAD subjects, the difference was not large and was not maintained when controlling for multiple comparisons. We therefore failed to identify robust differences in NPS between ADAD and LOAD. Our findings are limited by the small sample size of ADAD subjects but suggest that NPS are not markedly different in the early stages of ADAD and LOAD.

Association Between Visual Memory and In Vivo Amyloid and Tau Pathology in Preclinical Autosomal Dominant Alzheimer's Disease.

Visual memory (ViM) declines early in Alzheimer's disease (AD). However, it is unclear whether ViM impairment is evident in the preclinical stage and relates to markers of AD pathology. We examined the relationship between ViM performance and in vivo markers of brain pathology in individuals with autosomal dominant AD (ADAD). Forty-five cognitively unimpaired individuals from a Colombian kindred with the Presenilin 1 (PSEN1) E280A ADAD mutation (19 carriers and 26 noncarriers) completed the Rey-Osterrieth Complex Figure immediate recall test, a measure of ViM. Cortical amyloid burden and regional tau deposition in the entorhinal cortex (EC) and inferior temporal cortex (IT) were measured using 11C-Pittsburgh compound B positron emission tomography (PET) and 11F-flortaucipir PET, respectively. Cognitively unimpaired carriers and noncarriers did not differ on ViM performance. Compared to noncarriers, carriers had higher levels of cortical amyloid and regional tau in both the EC and IT. In cognitively unimpaired carriers, greater cortical amyloid burden, higher levels of regional tau, and greater age were associated with worse ViM performance. Only a moderate correlation between regional tau and ViM performance remained after adjusting for verbal memory scores. None of these correlations were observed in noncarriers. Results suggest that AD pathology and greater age are associated with worse ViM performance in ADAD before the onset of clinical symptoms. Further investigation with larger samples and longitudinal follow-up is needed to examine the utility of ViM measures for identifying individuals at high risk of developing dementia later in life.

Association of education with Aβ burden in preclinical familial and sporadic Alzheimer disease.

To determine whether years of education and the ε4 risk allele at APOE influence β-amyloid (Aβ) pathology similarly in asymptomatic individuals with a family history of sporadic Alzheimer disease (AD) and presymptomatic autosomal dominant AD mutation carriers. We analyzed cross-sectional data from 106 asymptomatic individuals with a parental history of sporadic AD (PREVENT-AD cohort; age 67.28 ± 4.72 years) and 117 presymptomatic autosomal dominant AD mutation carriers (DIAN cohort; age 35.04 ± 9.43 years). All participants underwent structural MRI and Aβ-PET imaging. In each cohort we investigated the influence of years of education, APOE ε4 status, and their interaction on Aβ-PET. Asymptomatic individuals with a parental history of sporadic AD showed increased Aβ burden associated with APOE ε4 carriage and lower level of education, but no interaction between these. Presymptomatic mutation carriers of autosomal dominant AD showed no relation between APOE ε4 and Aβ burden, but increasing level of education was associated with reduced Aβ burden. The association between educational attainment and Aβ burden was similar in the 2 cohorts. While the APOE ε4 allele confers increased tendency toward Aβ accumulation in sporadic AD only, protective environmental factors, like increased education, may promote brain resistance against Aβ pathology in both sporadic and autosomal dominant AD.

Cortical microstructural correlates of astrocytosis in autosomal-dominant Alzheimer disease.

ObjectiveTo study the macrostructural and microstructural MRI correlates of brain astrocytosis, measured with 11C-deuterium-L-deprenyl (11C-DED)–PET, in familial autosomal-dominant Alzheimer disease (ADAD).MethodsThe total sample (n = 31) comprised ADAD mutation carriers (n = 10 presymptomatic, 39.2 ± 10.6 years old; n = 3 symptomatic, 55.5 ± 2.0 years old) and noncarriers (n = 18, 44.0 ± 13.7 years old) belonging to families with mutations in either the presenilin-1 or amyloid precursor protein genes. All participants underwent structural and diffusion MRI and neuropsychological assessment, and 20 participants (6 presymptomatic and 3 symptomatic mutation carriers and 11 noncarriers) also underwent 11C-DED-PET.ResultsVertex-wise interaction analyses revealed a differential relationship between carriers and noncarriers in the association between 11C-DED binding and estimated years to onset (EYO) and between cortical mean diffusivity (MD) and EYO. These differences were due to higher 11C-DED binding in presymptomatic carriers, with lower binding in symptomatic carriers compared to noncarriers, and to lower cortical MD in presymptomatic carriers, with higher MD in symptomatic carriers compared to noncarriers. Using a vertex-wise local correlation approach, 11C-DED binding was negatively correlated with cortical MD and positively correlated with cortical thickness.ConclusionsOur proof-of-concept study is the first to show that microstructural and macrostructural changes can reflect underlying neuroinflammatory mechanisms in early stages of Alzheimer disease (AD). The findings support a role for neuroinflammation in AD pathogenesis, with potential implications for the correct interpretation of neuroimaging biomarkers as surrogate endpoints in clinical trials.

Seizures as an early symptom of autosomal dominant Alzheimer's disease

Our objective was to assess the reported history of seizures in cognitively asymptomatic mutation carriers for autosomal dominant Alzheimer's disease (ADAD) and the predictive value of seizures for mutation carrier status in cognitively asymptomatic first-degree relatives of ADAD patients. Seizure occurrence in the Dominantly Inherited Alzheimer Network observational study was correlated with mutation carrier status in cognitively asymptomatic subjects. Of 276 cognitively asymptomatic individuals, 11 (4%) had experienced seizures, and nine of these carried an ADAD mutation. Thus, in the Dominantly Inherited Alzheimer Network population, seizure frequency in mutation carriers was significantly higher than in noncarriers (p = 0.04), and the positive predictive value of seizures for the presence of a pathogenic mutation was 81.8%. Among cognitively asymptomatic ADAD family members, the occurrence of seizures increases the a priori risk of 50% mutation-positive status to about 80%. This finding suggests that ADAD mutations increase the risk of seizures.

Impairment of memory generalization in preclinical autosomal dominant Alzheimer's disease mutation carriers

Fast, inexpensive, and noninvasive identification of Alzheimer's disease (AD) before clinical symptoms emerge would augment our ability to intervene early in the disease. Individuals with fully penetrant genetic mutations causing autosomal dominant Alzheimer's disease (ADAD) are essentially certain to develop the disease, providing a unique opportunity to examine biomarkers during the preclinical stage. Using a generalization task that has previously shown to be sensitive to medial temporal lobe pathology, we compared preclinical individuals carrying ADAD mutations to noncarrying kin to determine whether generalization (the ability to transfer previous learning to novel but familiar recombinations) is vulnerable early, before overt cognitive decline. As predicted, results revealed that preclinical ADAD mutation carriers made significantly more errors during generalization than noncarrying kin, despite no differences between groups during learning or retention. This impairment correlated with the left hippocampal volume, particularly in mutation carriers. Such identification of generalization deficits in early ADAD may provide an easily implementable and potentially linguistically and culturally neutral way to identify and track cognition in ADAD.

Effect of Alzheimer Familial Chromosomal Mutations on the Amyloid Fibril Interaction with Different PET Tracers: Insight from Molecular Modeling Studies.

Alzheimer's disease (AD) is the most common neurodegenerative disorder. Along with an increasing number of elderly worldwide, it poses a great challenge for the society and health care. Although sporadic AD is the common form of AD, 2-3% of the AD cases are expected to be due to mutations in the β region of the amyloid precursor protein, which is referred to as autosomal dominant AD (ADAD). These mutations may cause changes in the secondary structure of the amyloid β fibrils and may alter the fibrillization rate leading to changes in the disease development and could also affect the binding to tracers used in diagnosis. In particular, from some recent clinical studies using PET tracers for detection of fibrillar amyloids, it is evident that in ADAD patients with Arctic mutation no amyloid plaque binding can be detected with the 11C-Pittsburgh Compound B (11C-PIB). However, for in vitro conditions, significant binding of 3H-PIB has been reported for the amyloid fibrils carrying the Arctic mutation. The aim of the present study is to investigate if there is any mutation specific binding of commonly used amyloid tracers, namely, florbetaben, florbetapir, FPIB, AZD4694, and AZD2184, by means of molecular modeling techniques. Other than Arctic, ADAD mutations, such as the Dutch, Italian, Iowa, and Flemish mutations, are considered in this study. We report that all tracers except florbetapir show reduced binding affinity toward amyloid β fibrils with the Arctic mutation when compared to the native type. Moreover, florbetapir is the only tracer that binds to all mutants with increased affinity when compared to the native fibril. The results obtained from these studies could increase the understanding of the structural changes caused by mutation and concomitant changes in the interaction pattern of the PET tracers with the mutated variants, which in turn can be useful in selecting the appropriate tracers for the purpose of diagnosis as well as for designing new tracers with desirable properties.