Citations

AbstractBackgroundAlzheimer’s Disease (AD) presents complex molecular heterogeneity, influenced by a variety of factors including heterogeneous phenotypic, genetic, and neuropathologic presentations. Regulation of gene expression mechanisms is a primary interest of investigations aiming to uncover the underlying disease mechanisms and progression.MethodWe generated bulk RNA‐sequencing in prefrontal cortex from 565 AD brain samples (non‐Hispanic Whites, n = 399; Hispanics, n = 113; African American, n = 12) across six U.S. brain banks, and conducted differential gene expression and enrichment analyses. We sought to identify cross‐ancestry and ancestry‐specific differentially expressed genes (DEG) and pathways across Braak stages, adjusting for sex, age at death, and RNA quality metrics. We validated our findings using the Religious Orders Study/Memory and Aging Project study (ROS/MAP, n = 1,095). Lastly, we validated top DEG using publically‐available human single‐nucleus RNA sequencing (snRNAseq) data.ResultAD‐known genes VGF (LFC = ‐0.661, padj = 3.78) and ADAMTS2 (padj = 1.21) were consistently differentially expressed across statistical models, ethnic groups, and replicated in ROS/MAP (Figure 1). Genes from the heat shock protein (HSP) family, e.g. HSPB7 (padj = 3.78), were the top DEG, also replicated in ROS/MAP. Ethnic‐stratified analyses prioritized TNFSF14 and SPOCD1 as top DEG in Hispanic samples. Gene set enrichment analysis highlighted several significantly pathways, including “TYROBP causal network in microglia” (WP3945; padj = 1.68) and “Alzheimer Disease” (WP5124; padj = 4.24). snRNAseq validated several DEG, including VGF downregulated in neurons (padj = 1.1).ConclusionTo our knowledge, this is the largest diverse transcriptome study for AD in post‐mortem tissue. We identified perturbated genes and pathways resulting in cross‐ethnic and ethnic‐specific findings, ultimately highlighting the importance of diversity in AD investigations.

AbstractBackgroundWe recently developed a novel tau‐PET summary measure THETA, capturing regional heterogeneity and identifying tau status, using ground truth visual assessments from a large single‐center cross‐sectional dataset and validated on independent cohorts [1, 2]. In this study, we aimed to evaluate the performance of THETA on longitudinal and histopathology data.MethodWe included longitudinal tau‐PET ([18F]flortaucipir) data from 696 Mayo Clinic Study of Aging (MCSA) and ADRC participants, with histopathology in n = 90. Fig. 1 shows the model that uses regional standard uptake value ratios (SUVR) and a target of binary class of tau positivity for prediction of THETA. This model was applied to predict tau status on each followup scan. Slopes of the meta‐ROIs’ tau SUVRs and THETA were evaluated by diagnostic group and as a function of baseline amyloid SUVR in discordant CU participants (where meta‐ROI and visual assessments did not match at baseline) and in incident‐THETA+ CU participants (whose THETA moved from below to above 1 over serial tau‐PET scans). We evaluated tau measurements as a function of Braak stages for neurofibrillary tangles.ResultLongitudinal plots of meta‐ROIs for diagnostic groups were very similar, but the expanded range of THETA based on visual positivity prediction clearly identified tau positive or tau‐negative scans. In discordant‐CU (n = 97) and incident‐THETA+ CU participants (n = 14 all amyloid positive at follow‐up but only 65% at baseline), the relationship between baseline amyloid and rate of tau increase was stronger for THETA than temporal meta‐ROI (Fig. 2). Separation between baseline and follow‐up was greater for THETA (t‐statistics = 90) compared to temporal meta‐ROI (t‐statistics = 20) (p<0.01) in the incident‐THETA+ CU participants. THETA showed a slightly stronger association with Braak stage than meta‐ROIs (rho = 0.87 vs. ≤0.83, p<0.05), with better separation of clinical diagnoses (Fig. 3).ConclusionTHETA remained clearly negative or positive in MCI and AD, providing consistent information on underlying etiology of impairment at both baseline and follow‐up. Although binary in its construction, THETA both provided separation of values based on tau status and its change correlated with baseline amyloid burden especially in discordant‐CU where tau deposition is not in typical meta‐ROIs. Further work is needed to confirm if THETA captures early tau changes.

AbstractBackgroundAlthough the rate of Alzheimer’s disease (AD) in African‐ancestry (AA) Americans is higher than that of persons from European‐ancestry (EA) populations, AA participants have been underrepresented in AD neuropathological studies.MethodUtilizing the AD Research Centers (ADRC) infrastructure, we obtained AA donor pre‐frontal cortex (PFC) tissue from brain repositories of 12 ADRC and generated bulk RNA sequencing (RNA‐seq) data for 179 samples that met QC and inclusion criteria. Previously generated PFC RNAseq data were obtained for 28 additional AA donors from the Columbia University ADRC. Differential gene expression was evaluated among 125 donors with a neuropathological diagnosis of AD (NIA‐Reagan intermediate or high likelihood) and 82 neuropathologically confirmed controls using regression models including covariates for age at death, sex, cell‐type frequencies, and RNA integrity number (RIN) calculated with Limma. FDR‐corrected p‐values (padj) were calculated to control for the 33,611 genes examined.ResultA total of 482 genes surpassed the multiple‐testing threshold. The most significant, ADAMTS2 (p = 2.96 × 10‐8, padj = 0.001), showed increased expression in AD cases (see Table/Figure). We note that ADAMTS2 was differentially expressed in a prior EA study of neuropathologically confirmed AD cases and controls (Panitch et al. Molecular Psychiatry 2021). Additionally, a recent analysis of cognitive resilience in EA neuropathological AD cases identified a strong association with ADAMTS2 (See Li et al. AAIC2024 abstract). Of the differentially expressed genes observed in the Panitch et al. EA study, 385 (35%) were nominally significant,65 (5.8%) were corrected significant, and most (89%) of these genes had the same effect direction in the AA cohort. Some of the observed associations appear to be AA specific (e.g., EFR3B, IRS4, and CA12; see Table). Additionally, we found nominally significant (p<0.05) associations with expression of APOE (Log2 fold change [L2FC = ‐0.20, p = 0.012) and several other established AD genes including SORL1 (L2FC = ‐0.10, p = 0.014) and IGF1R(L2FC = 0.11, p = 0.0013).ConclusionThis largest‐ever (to our knowledge) gene expression study of AD in postmortem brain tissue from AA donors implicates many more genes as having a role in AD in this population than previously identified in genome‐wide association studies and provides insight into trans‐ancestry differences risk for AD.

AbstractBackgroundTau aggregation is the major cause of several neurodegenerative tauopathies. Tau interaction with other proteins affects the formation of tau aggregates with seeding activity but less is known about its effects on tau‐seed properties. Our previous study revealed that Bassoon (BSN), a presynaptic protein, interacts with tau‐seed, exacerbating its toxicity in vivo. Bsndownregulation reduced tau spreading and overall pathology. Intriguingly, a parallel study associated missense mutations in BSN with tau aggregation in patients, prompting an investigation into the influence of genetic mutations in BSN on tau pathology for potential therapeutic insights.MethodWe generated a knock‐in mouse model (BSNKI) harboring the disease‐associated p.Pro3866Ala mutation in endogenous Bsn. Cognitive and motor abilities were assessed in aged heterozygous and homozygous BSNKI mice, followed by analyses of BSN and tau patterns, gliosis, and gene expression changes in their brains. Additionally, we validated our findings in a human BSN mutation carrier.ResultAt 10 months, BSNKI mice displayed motor impairments on the rotarod, and grip strength assays compared to WT mice. Their brains displayed somatic BSN and pathological tau accumulation, with the gene expression changes indicating alterations in microglia activation, protein degradation pathways, complement activation, and synapse pruning. We also observed an accumulation of pathological tau at the synapses and synapse engulfment by microglia. Histopathological analyses revealed robust microglia activation and co‐deposition of proteasomal subunits with BSN. The human BSN mutation carrier displayed inclusions of BSN and tau pathology similar to observations in the BSNKI model.ConclusionOur BSNKI mouse model, reflecting a disease‐associated BSN mutation, revealed motor impairments and pathological tau and BSN deposits, mirroring observations in BSN mutation carriers. Notably, BSN seems to play a dual role, promoting tau aggregation and sequestering protein degradation molecules, leading to tau and protein accumulation at the soma and synapse, triggering microgliosis and neuroinflammation. These findings propose BSN as a promising therapeutic target for tauopathies, underscoring the need for further exploration to elucidate underlying mechanisms and therapeutic implications.

AbstractBackgroundPosttranslational modifications of tau occurs throughout disease progression in Alzheimer’s disease (AD) and non‐AD tauopathies. Phosphorylation of tau (p‐tau) in the proline‐rich region is a common target of immunohistochemical and fluid biomarker evaluation. P‐tau217 has emerged as a highly accurate fluid biomarker in AD, however elevated levels are not observed in non‐AD tauopathies.MethodA neuropathologic overview of tau lesions immunopositive for phosphorylation at threonine 217 (pT217) in AD and non‐AD tauopathies will be provided in a didactic format with an emphasis on disease spectrum. The relevant biomarker literature with neuropathologic validation will be highlighted.ResultImmunohistochemical evaluation of pT217 in AD demonstrates immunostaining in pretangles and mature tangles, but rarely observed in ghost tangles. Neuritic pathology in AD with pT217 immunopositivity include both neuropil threads and dystrophic neurites that cluster in neuritic plaques. Lesions in non‐AD tauopathies are also immunopositive for pT217, as exampled by immunolabelling of argyrophilic grains and tufted astrocytes. Digital pathology measures of pT217 and amyloid‐β will be compared with plasma p‐tau217 levels to contextualize the relationship. Additionally, the relationship between neurotransmitter hub vulnerability will be explored to consider upstream factors that may influence soluble tau release into plasma.ConclusionNeuropathologic insights discussed through visual and quantitative comparison of insoluble phospho‐tau accumulation and soluble levels of p‐tau217 may provide neurobiologic insights into the intersection between amyloid‐β and tau in the human brain.

AbstractBackgroundAlzheimer’s disease (AD) is neuropathologically characterized by amyloid‐β (Aβ) plaques and tau neurofibrillary tangles often quantified by Thal phase and Braak stage, respectively. Aβ also frequently deposits in the cerebrovasculature with severity categorized by a cerebral amyloid angiopathy (CAA) score. These and related measures often show high variability within AD suggesting distinct underlying mechanisms. We hypothesize that, within the AD brain, neuropathology and levels of core AD‐related proteins are influenced by variations in DNA methylation (DNAm). To test this, we performed epigenome‐wide association studies (EWAS) using DNAm measures from the temporal cortex (TCX) and cerebellum (CER) with AD‐related neuropathologic measures (Braak, Thal, CAA) and brain biochemical levels of five proteins (apoE, Aβ40, Aβ42, tau, p‐tau).MethodsDNAm from neuropathologically‐confirmed AD cases was measured by reduced representation bisulfite sequencing (RRBS) from 471 TCX samples, 200 of which also had CER RRBS. TCX levels of five AD‐related proteins from three tissue fractions (buffer‐, detergent‐, and in‐soluble) were measured previously by ELISA (Liu 2020). CpG methylation (CpGm) was binned by a 15‐state chromatin model (Kundaje 2015) and averaged into CpGm clusters (rCpGm). rCpGms were tested for association with each AD endophenotype and expression levels of nearby genes through multi‐variable linear regression. Replication of significant rCpGms was performed in two independent datasets with AD‐related endophenotypes (Shireby 2022, De Jager 2014).ResultsOur innovative binning method demonstrated biologically relevant CpGm patterns. We found epigenome‐wide significant associations primarily with tau‐related endophenotypes including 93 that had significant and concordant associations in the replication datasets. These rCpGms also significantly associated with expression of nearby genes showing enrichment in oligodendrocyte marker genes including those related to myelination. In vitro validation of tau effects on oligodendrocyte gene expression through DNAm is ongoing.ConclusionsAlthough all endophenotypes tested are core to AD pathophysiology, our results suggest each has a distinct epigenetic architecture underlying their variability in the AD brain. In particular, we found evidence of DNAm variability associating with brain oligodendrocyte gene expression and TCX tau levels. By discovering AD brain endophenotype‐specific DNAm changes, we can identify core components of complex mechanisms revealing important biological insights into AD pathophysiology.

AbstractBackgroundAutosomal dominant progranulin (GRN) mutations are a common genetic cause of frontotemporal lobar degeneration. Though clinical trials for GRN‐related therapies are underway, there is an unmet need for biomarkers that can predict symptom onset and track disease progression. We previously showed that presymptomatic GRN carriers exhibit thalamocortical hyperconnectivity that increases with age when they are presumably closer to symptom onset. However, whether hyperconnectivity arises concomitantly with markers of neurodegeneration remains unclear.MethodUtilizing T1 and task‐free functional magnetic resonance imaging (tf‐fMRI) from 49 presymptomatic and 26 symptomatic GRN mutation carriers, we determined the relationships between functional connectivity as measured by voxel‐wise whole brain degree and GRN‐relevant markers of disease progression, which included plasma neurofilament light chain (NfL) concentrations, CSF complement C1q and C3b protein levels, grey matter atrophy, and OCD symptom severity.ResultNfL concentrations were associated with frontotemporoparietal and thalamic hyperconnectivity in presymptomatic GRN carriers and extensive regions of atrophy in symptomatic carriers. Complement levels were associated with regions of hyperconnectivity, but not gray matter, in symptomatic carriers. Presymptomatic carriers with thalamic hyperconnectivity tended to have lower grey matter volume in bilateral insula and left lateral parietal cortex, which are among regions that deteriorate in GRN‐FTD. OCD symptom severity was associated with hypoconnectivity across all GRN carriers.ConclusionIn presymptomatic carriers, the co‐occurrence of hyperconnectivity, high NfL, and low gray matter suggests that tf‐fMRI hyperconnectivity may portend the onset of the neurodegenerative phase. These findings point toward hyperconnectivity as an indicator of approaching symptomatic onset.

AbstractBackgroundNeuropathologic inclusions formed by hyperphosphorylated protein tau in the brain are a hallmark of Alzheimer’s disease and other human neurodegenerative disorders commonly referred to as tauopathies. Tau lesions differ in their disease‐specific morphological presentations, affected cell type, subcellular compartments and tau isoforms present in the inclusions. In addition, tau filaments isolated from different tauopathies have distinct fibrillar structures that potentially underlie the morphological diversity of tau lesions. The factors that govern the formation of disease‐specific tau lesions and distinct patterns of neurodegeneration and clinical presentations are unknown. To address this gap of knowledge, we performed profiling of proteomes associated with phospho‐tau aggregates in 4 major tauopathies.MethodWe utilized the in‐house developed Probe‐dependent Proximity Profiling (ProPPr) method combined with data‐independent acquisition mass spectrometry to profile phospho‐tau associate proteomes in formalin‐fixed paraffin‐embedded (FFPE) frontal cortex tissue sections from the Mayo Clinic Florida Brain Bank. Selected candidates were validated by fluorescent co‐immunostaining of patient brains with corresponding antibodies.ResultIn situ proximity proteomic profiling revealed over 1300 protein associated with phospho‐tau pathology, including 229 proteins that were identified in all tauopathies. The most significantly enriched GO terms in this protein set common to all the tauopathies were related to chaperone activity, guanyl nucleotide binding, cadherin binding, cytoskeleton, and ion transporter activity, highlighting biological processes and pathways affected by tau aggregation regardless of the type of tau lesion. In addition, we identified 32 proteins with significantly different association with phospho‐tau between tauopathies. Immunostaining of post‐mortem patient frontal cortices confirmed some of the findings from proteomics and revealed differences in abundance and localization patterns of several tau‐associated proteins between tauopathies, uncovering a potential of using these proteins as biomarkers for antemortem diagnosis.ConclusionTau lesions in different tauopathies have differences in their associated proteomes that can be assessed by the ProPPr assay.

AbstractBackgroundLimbic‐predominant age‐related TDP‐43 encephalopathy (LATE) is a neuropathologically‐defined disease, and it is frequently comorbid with Alzheimer’s disease neuropathological change (ADNC). However, the neurological syndrome associated with LATE neuropathological change (LATE‐NC) is not defined. We propose a set of clinical criteria for a limbic‐predominant amnestic neurodegenerative syndrome (LANS) that is highly associated with LATE‐NC. These criteria assess degree of certainty (highest, high, moderate, low) based on features that are measurable in vivo, including older age at evaluation, a mild clinical syndrome, impaired semantic knowledge, disproportionate hippocampal atrophy, limbic hypometabolism, absence of neocortical degeneration patterns and low likelihood of neocortical tau. We operationalized these criteria using two large datasets with clinical and pathologic outcomes.MethodWe screened autopsied patients from Mayo Clinic and ADNI cohorts and applied the LANS criteria to those with an antemortem predominant amnestic syndrome (Mayo, n = 165; ADNI, n = 53). We compared frequencies of neuropathological diagnoses across LANS likelihoods, compared longitudinal CDR‐SB trajectories across LANS likelihoods, and stratified ADNC/LATE‐NC patients according to their LANS likelihood and compared their longitudinal CDR‐SB trajectories to those with ADNC or LATE‐NC.ResultADNC, ADNC/LATE‐NC and LATE‐NC accounted for 35%, 37% and 4% of cases in the Mayo cohort, respectively, and 30%, 22%, and 9% of cases in the ADNI cohort, respectively (Fig. 1). ADNC cases had the lowest LANS likelihoods, LATE‐NC patients had the highest likelihoods, and ADNC/LATE‐NC patients had intermediate likelihoods. Patients with high LANS likelihoods had a milder and slower clinical course and more severe temporo‐limbic degeneration compared to those with low likelihoods (Fig. 2). ADNC/LATE‐NC patients with higher likelihoods had more temporo‐limbic degeneration and a slower rate of cognitive decline, and those with lower likelihoods had more lateral temporo‐parietal degeneration and a faster rate of cognitive decline (Fig. 3).ConclusionThe implementation of LANS criteria has implications for disambiguating the different driving etiologies of progressive amnestic presentations in older age to guide prognosis, treatment, and clinical trial design and enrollment. The development of in vivo biomarkers specific to TDP‐43 pathology are needed to further refine molecular associations between LANS and LATE‐NC and precise antemortem diagnoses of LATE.

ImportanceRetrieval strategies for children, adolescents, and young adults with relapsed classic Hodgkin lymphoma (cHL) aim to maintain efficacy while minimizing long-term toxic effects. Children, adolescents, and young adults with low-risk, relapsed cHL may benefit from replacing high-dose chemotherapy and autologous stem cell transplant with less intensive involved-site radiotherapy (ISRT).ObjectiveTo evaluate a risk-stratified, response-adapted, transplant-free approach for treatment of children, adolescents, and young adults with low-risk relapsed cHL with nivolumab plus brentuximab vedotin (BV) followed by BV plus bendamustine for patients with suboptimal response and ISRT (30.0 to 30.6 Gy).Design, Setting, and ParticipantsCheckMate 744 (R1 cohort) was a phase 2, nonrandomized, single-arm study enrolling children, adolescents, and young adults aged 5 to 30 years with low-risk cHL between September 25, 2017, and December 16, 2020, across the US, Canada, and Europe. Data were analyzed from September 2017 to November 2022.ExposuresPatients received 4 cycles of nivolumab plus BV induction; patients with complete metabolic response (CMR) received an additional 2 cycles of nivolumab plus BV while patients with suboptimal response received 2 cycles of BV plus bendamustine intensification. Patients with CMR after induction or intensification received ISRT consolidation.Main Outcomes and MeasuresPrespecified coprimary end points were CMR rate (Lugano 2014 classification) any time before ISRT and 3-year event-free survival (EFS) rate, per blinded independent central review (BICR).ResultsOf 28 included patients treated in the low-risk cohort, 18 (64%) were female, and the median (range) age was 17 (6-27) years. At a median (range) follow-up of 31.9 (2.2-55.3) months, CMR per BICR any time before ISRT was 93% (26 of 28; 90% CI, 79.2-98.7; objective response rate [ORR], 100%), and 23 of 28 (82%) achieved CMR per BICR after 4 cycles of nivolumab plus BV (ORR, 96.4%). Kaplan-Meier estimates of EFS and progression-free survival rates at 3 years were 87% (3 of 18; 90% CI, 69.5-94.7) and 95% (1 of 18; 90% CI, 76.7-99.0), respectively. During induction, 22 patients (79%) had treatment-related adverse events, including 7 with grade 3 or 4 adverse events, 2 with anemia, 1 with neutropenia, and 6 with immune-mediated adverse events. Serious adverse events leading to discontinuation occurred in 2 patients.Conclusions and RelevanceThis nonrandomized clinical trial found that for children, adolescents, and young adults with low-risk, relapsed cHL, a transplant-free, risk-adapted, response-based approach with nivolumab plus BV and ISRT offered high CMR rates and high 3-year EFS rate, with a safety profile consistent with that of each agent used.Trial RegistrationClinicalTrials.gov Identifier: NCT02927769