Supranuclear Research Articles

Sentence completion in progressive supranuclear palsy following transcranial direct current stimulation

Progressive supranuclear palsy (PSP) is an atypical Parkinsonian disorder which results in deterioration of motor and cognitive skills, including language disorders such as impaired word retrieval. While there is evidence of successful use of tDCS to improve word fluency in PSP, little is known about the effectiveness of brain stimulation for word retrieval in sentence context. Therefore, we investigated whether tDCS reduces sentence completion time in PSP patients. In this sham-controlled, triple-blinded crossover study, anodal tDCS (atDCS) was applied over the left Broca’s area at 2 mA for 20 min (n = 23). In contrast to patients with multiple system atrophy (MSA), also an atypical Parkinsonian disorder, and healthy elderlies, sentence completion improved in PSP patients when tDCS was applied. The improvement in word fluency reported in previous studies using other electrode positions was not replicated. By using atDCS of the left Broca’s area, we were able to demonstrate a difference between the two movement disorders. The obtained insight could be helpful to improve language therapy of these disorders.

Physiotherapy case reports on three people with progressive supranuclear palsy.

Progressive supranuclear palsy (PSP) is a neurodegenerative brain disease that affects patient's functionality and quality of life. Physiotherapy should be recommended at the time of diagnosis to slow the progression of disability and enhance the quality of life of these patients. Here, we describe three cases of patients with PSP, outlining their motor and non-motor symptoms and examining their clinical progression with physiotherapy intervention. During the initial intervention years, a reduction in the number of falls was achieved, along with improvements in gait and balance. Exercise and physiotherapy appear to be beneficial for patients with PSP by enhancing their functionality and quality of life. Controlling or reducing the number of falls should be the primary goal of any intervention for patients with PSP.

Disease-Associated Mutations in Tau Encode for Changes in Aggregate Structure Conformation.

The accumulation of tau fibrils is associated with neurodegenerative diseases, which are collectively termed tauopathies. Cryo-EM studies have shown that the packed fibril core of tau adopts distinct structures in different tauopathies, such as Alzheimer's disease, corticobasal degeneration, and progressive supranuclear palsy. A subset of tauopathies are linked to missense mutations in the tau protein, but it is not clear whether these mutations impact the structure of tau fibrils. To answer this question, we developed a high-throughput protein purification platform and purified a panel of 37 tau variants using the full-length 0N4R splice isoform. Each of these variants was used to create fibrils in vitro, and their relative structures were studied using a high-throughput protease sensitivity platform. We find that a subset of the disease-associated mutations form fibrils that resemble wild-type tau, while others are strikingly different. The impact of mutations on tau structure was not clearly associated with either the location of the mutation or the relative kinetics of fibril assembly, suggesting that tau mutations alter the packed core structures through a complex molecular mechanism. Together, these studies show that single-point mutations can impact the assembly of tau into fibrils, providing insight into its association with pathology and disease.

The tauopathy‐associated PERK variant, PERK‐B, induces maladaptive translation and reveals novel pathogenic mechanisms of PSP

AbstractBackgroundA major challenge in the field is identification of molecular mechanisms driving pathological tau accumulation in tauopathies such as progressive supranuclear palsy (PSP). The largest GWAS for PSP identified a protein kinase endoplasmic reticulum kinase haplotype B (PERK‐B) hypomorph as a risk factor for the disease. This variant is less effective at reducing translation as its counterpart, PERK haplotype A (PERK‐A) and promotes the accumulation of pathological hyperphosphorylated tau species. However, the functional differences between PERK‐A and ‐B remain unknown, and this is partly due to the need for chemical induction of ER stress with compounds that provoke pleiotropic effects.MethodTo address these gaps in knowledge and overcome technical issues, we developed novel molecular tools and models to study PERK function. Using CRISPR/Cas9, we generated PERK‐KO HEK cells, transfected them with newly designed PERK plasmids, ER stress sensors, and markers of cap‐dependent translation. We also measured changes in tau accumulation and insolubility because of PERK‐B. In addition, we performed transcriptomic and puromycin proteomics to specifically identify the transcriptome and the nascent proteome resulting from PERK‐B expression.ResultWe established that expression of both PERK variants equally induced ER stress and reduced cap‐dependent translation. In addition, the PERK‐A and ‐B transcriptomes were virtually identical. However, while PERK activity was protective, PERK‐B less effectively cleared tau, leading to accumulation of insoluble pathological hyperphosphorylated tau. SUnSET proteomics revealed four proteins that were only present in the PERK‐B translatome. Given that these proteins had not been previously associated with PSP, we measured their levels in human brains and identified that at least one of them was significantly increased in PSP cases.ConclusionOur data suggest that the PERK‐B variant promotes accumulation of specific proteins associated with PSP. The new link between these proteins and PSP may reveal novel pathogenic mechanisms and could uncover new and effective therapeutic targets. Efforts to establish the role of these proteins in PSP is underway.

Discriminative power of multi‐PET tracer approach targeting reactive astrogliosis, tau pathology, and dopaminergic impairment in 4R primary tauopathies

AbstractBackgroundThe 4R tauopathies corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) are described as dementias with parkinsonian syndrome. Even if they are proven to represent clinically different entities, their complex neuropathology and common hallmarks often make the differential clinical diagnosis of CBD and PSP challenging. The highly entangled astrocytic and tau pathologies observed in these diseases are however displaying unique disparities which might unravel specific neuropathological profiles for each disease. The multi‐PET tracer approach applied in the present study in postmortem brain tissue might provide new mechanistic insights. We recently demonstrated that the second‐generation tau PET tracer, 3H‐PI2620 had a discriminative potential in CBD, PSP, and Alzheimer’s disease (AD) brains (Malarte et al. Mol. Psychiatry. 2022). To further understand the interaction between tau spatial distribution and its potential effects on astrocytic reactivity, we conducted a comparative multi‐tracer investigation in CBD, PSP, AD, and control brains using novel tau and astrocytic tracers. To gain a deeper insight into the relationship between tau, astrogliosis, and concomitant motor impairments, we also studied the interaction with the dopaminergic system.MethodWe performed autoradiography studies on large frozen hemispherical brain tissue of CBD, PSP, AD, and control cases using the tau PET tracer 3H‐PI2620, in comparison to astrocytic tracers (3H‐BU99008 and 3H‐Deprenyl) and dopaminergic tracers (3H‐Raclopride and 3H‐FE‐PE2I). We also analyzed the regional distribution of these tracers in small adjacent frozen brain sections of pathologically specific brain regions (globus pallidus, putamen, caudate, frontal cortex, medulla oblongata). We also performed saturation studies with 3H‐BU99008 and 3H‐Deprenyl on CBD and PSP brain homogenatesResultOur preliminary results are promising and suggest high astrogliosis measured by 3H‐BU99008 and 3H‐Deprenyl in large frozen autoradiography in CBD and PSP brains, and with different binding intensities in different brain regions comparable with regional 3H‐PI2620 binding. 3H‐BU99008 and 3H‐Deprenyl both highlighted two binding sites in the putamen of CBD cases, but only one site in PSP.ConclusionOngoing multi‐PET tracer studies targeting different pathological hallmarks of CBD and PSP tauopathies will improve differentiation and provide new knowledge regarding the spatial distribution of tau and its correlation with astrogliosis and the dopaminergic system in primary tauopathies.

Discriminative power of multi‐PET tracer approach targeting reactive astrogliosis, tau pathology, and dopaminergic impairment in 4R primary tauopathies

AbstractBackgroundThe 4R tauopathies corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) are described as dementias with parkinsonian syndrome. Even if they are proven to represent clinically different entities, their complex neuropathology and common hallmarks often make the differential clinical diagnosis of CBD and PSP challenging. The highly entangled astrocytic and tau pathologies observed in these diseases are however displaying unique disparities which might unravel specific neuropathological profiles for each disease. The multi‐PET tracer approach applied in the present study in postmortem brain tissue might provide new mechanistic insights. We recently demonstrated that the second‐generation tau PET tracer, 3H‐PI2620 had a discriminative potential in CBD, PSP, and Alzheimer’s disease (AD) brains (Malarte et al. Mol. Psychiatry. 2022). To further understand the interaction between tau spatial distribution and its potential effects on astrocytic reactivity, we conducted a comparative multi‐tracer investigation in CBD, PSP, AD, and control brains using novel tau and astrocytic tracers. To gain a deeper insight into the relationship between tau, astrogliosis, and concomitant motor impairments, we also studied the interaction with the dopaminergic system.MethodWe performed autoradiography studies on large frozen hemispherical brain tissue of CBD, PSP, AD, and control cases using the tau PET tracer 3H‐PI2620, in comparison to astrocytic tracers (3H‐BU99008 and 3H‐Deprenyl) and dopaminergic tracers (3H‐Raclopride and 3H‐FE‐PE2I). We also analyzed the regional distribution of these tracers in small adjacent frozen brain sections of pathologically specific brain regions (globus pallidus, putamen, caudate, frontal cortex, medulla oblongata). We also performed saturation studies with 3H‐BU99008 and 3H‐Deprenyl on CBD and PSP brain homogenatesResultOur preliminary results are promising and suggest high astrogliosis measured by 3H‐BU99008 and 3H‐Deprenyl in large frozen autoradiography in CBD and PSP brains, and with different binding intensities in different brain regions comparable with regional 3H‐PI2620 binding. 3H‐BU99008 and 3H‐Deprenyl both highlighted two binding sites in the putamen of CBD cases, but only one site in PSP.ConclusionOngoing multi‐PET tracer studies targeting different pathological hallmarks of CBD and PSP tauopathies will improve differentiation and provide new knowledge regarding the spatial distribution of tau and its correlation with astrogliosis and the dopaminergic system in primary tauopathies.

Biochemical Evidence for a Pathological Variant of Progressive Supranuclear Palsy

AbstractBackgroundTau proteins aggregate into spatially and morphologically distinct lesions in primary and secondary tauopathies. These signature lesions result from deposition of tau proteins that are distinctly modified via missense mutation and/or post‐translational modification for each disease strain. Identifying the unique tau protein abnormalities that lead to specific neurodegenerative diseases is beneficial in their early diagnosis and treatment. This is especially true for Progressive Supranuclear Palsy a primary tauopathy with clinical symptoms mirroring Parkinsonian syndromes and frontotemporal dementias.MethodBiochemical analysis of tau aggregates from patients with a pathological diagnosis of Progressive Supranuclear Palsy (n = 60) demonstrate that the tau protein modifications observed in this disease result from tau that is specifically modified and thereby forms the basis of the distinct disease strains observed. Here data collected using the sarkosyl‐insoluble tau fractions from tissue samples of pathologically diagnosed patients with Progressive Supranuclear Palsy without comorbidities allows for the direct observation of the modifications. Most interesting is the variability of the tau proteins that actually accumulate for this disease opening up the possibility that tau strains may exist within any given tauopathy even as the clinical manifestations appear similar. This indicates that early and specific identification and detection of these strains is critical for the development of therapies for these diseases.ResultExtraction and examination of sarkosyl‐insoluble tau proteins from deceased patients pathologically diagnosed with Progressive Supranuclear Palsy indicate that multiple tau strains exist within this primary tauopathy. Western blotting of these extracts from patient tissues demonstrates a unique banding pattern of insoluble tau in a subset of the cases that exhibit extreme hyperphosphorylation as indicated by additional high molecular weight tau banding. These patients also had an earlier age of onset and age of death indicating a more aggressive disease strain. Additional data is presented comparing the structure and seeding capability of this insoluble tau and the distribution and burden of insoluble tau in these Progressive Supranuclear Palsy patients compared to those with typical onset and insoluble tau signature.ConclusionMultiple pathological tau strains exist in Progressive Supranuclear Palsy.

Study of TMEM106B expression levels under neurodegenerative conditions

AbstractBackgroundTMEM106B is a transmembrane protein involved in dendrite morphogenesis and lysosome trafficking. TMEM106B was identified as a susceptibility gene for frontotemporal lobar degeneration with TDP‐43 inclusions (FTLD‐TDP). Brain tissue from patients with FTLD‐TDP showed increased mRNA levels of TMEM106B compared to normal controls (Van Deerlin et al, Nat Genet 2010). Our goal is to study TMEM106B expression levels in other neurodegenerative conditions such as progressive supranuclear palsy (PSP), Alzheimer’s disease (AD) and a well‐established mouse model of entorhinal cortex lesions (ECL).MethodUnilateral electrolytic lesions to the entorhinal cortex were conducted on two‐to‐three months old male C57BL/6j mice by stereotaxic surgery. For sham‐operated animals, the electrode was lowered only 1 mm without current and sacrifices were performed on the same day. All other lesioned mice were sacrificed 2, 7, 14, 21 or 40 days post‐lesion (DPL). Total RNA was extracted from frozen ipsilateral and contralateral hippocampi and expression profiles were measured with the Affymetrix Mouse ClariomTM D Assay. The Mayo Clinic Brain Bank collected RNA samples from temporal cortex and measured gene expression levels using next‐generation RNA sequencing (RNAseq). Results are available for 274 subjects with the following conditions: PSP, N = 84; AD, N = 82; pathological aging (PA), N = 30; and cognitively unimpaired (CU), N = 78.ResultIn the ECL mouse model, ipsilateral Tmem106b expression levels were significantly reduced during the deafferentation phase (DPL2: p = 0.046) and reached maximum levels during the reinnervation phase (DPL14: p = 0.030 and DPL21: p = 0.019), compared to sham‐operated animals. In human temporal cortices, TMEM106B expression increased progressively from CU (10.76±0.62), to PSP (11.25±0.43), PA (12.13±1.27) and finally AD (13.10±0.44) (mean CPM ±SEM). TMEM106B mRNA levels were significantly higher in AD compared to CU (p = 0.002) and PSP (p = 0.003).ConclusionElevated levels of TMEM106B in FTLD‐TDP, AD and during the reinnervation phase of the ECL mouse model suggest an active response to tissue damage that is consistent with compensatory synaptic and terminal remodeling, independently from tau‐mediated pathology. This hypothesis is consistent with TMEM106B levels found in PSP, which is characterized by abundant neurofibrillary tangles that differ in both distribution and composition from those associated with AD.

DNA Damage as an Early Marker of Senescence in Tauopathies

AbstractBackgroundHyperphosphorylated tau accumulation in neurons and astrocytes is a pathological hallmark of a class of neurodegenerative disorders known as “tauopathies”, such as progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), Alzheimer’s disease (AD) and chronic traumatic encephalopathy (CTE). Previous research investigating the toxic effects of astrocytic tau pathology identified the DNA damage marker p16 in astrocytes from post‐mortem human cases of AD and FTD. DNA damage is one of many markers of cellular senescence, a state in which cells undergo irreversible cell cycle arrest. Senescence initiation can also be identified via the expression of phosphorylated histone H2AX (gamma‐H2AX) and cyclin‐dependent kinase inhibitor p21. Senescence in astrocytes leads to reduced functional support for neurons. While recognized, the role of senescent astrocytes in tauopathies is not well understood. Here, we sought to determine how expression of other DNA damage markers, such as gamma‐H2AX and p21, and the DAMP protein HMGB1 varies across different tauopathies.MethodImmunohistochemistry (IHC) was performed on postmortem human frontal cortex tissue of CTE (n = 3), AD (N = 3), PSP (n = 3), CBD (n = 3), Healthy (n = 1) and glioblastoma (GBM) (n = 1) cases with antibodies against markers of early senescence gamma H2A.x (yH2A.x) and p21, late senescence, p16, and a senescence‐associated secretory phenotype, HMGB1. Positively stained nuclei were quantified. Immunofluorescence (IF) was employed on postmortem cases using either glial fibrillary acidic protein (GFAP) or Neurofilament H (NF‐H) antibodies with yH2A.x, p16, p21 and HMGB1 markers in order to qualitatively and quantitatively measure the prevalence of senescent astrocytes and neurons in tauopathies.ResultImmunohistochemistry revealed yH2Ax expression was observed in AD, PSP, and CBD cases. Immunofluorescence experiments employing yH2AX co‐stained with astrocytic and neuronal markers revealed expression in AD, PSP and CBD cases. Minimal expression of yH2Ax was revealed in the CTE and healthy control cases. Results from p21 stains were inconclusive. Preliminary evidence reveals HMGB1 expression in CBD and PSP cases utilizing IF techniques, and p16 expression in cells employing IHC.ConclusionOverall, results indicate that DNA damage may be broadly associated with astrocytes in tauopathies. Utilizing alternative approaches to recognize and evaluate astrocyte senescence in post‐mortem human tissue will provide further insight into these findings.

α‐Synuclein in Blood CNS‐originating Extracellular Vesicles For Parkinsonian Disorders: Systematic Review and Meta‐analysis

AbstractBackgroundParkinsonian disorders, including Parkinson’s disease (PD), multiple system atrophy (MSA), dementia with Lewy bodies (DLB), progressive supranuclear palsy (PSP), and corticobasal syndrome (CBS), present shared early motor symptoms but differing cellular and regional pathophysiology. Accurate premortem diagnosis remains challenging. Extracellular vesicles (EVs) contain cell‐state‐specific biomolecules and can cross the blood‐brain barrier to the peripheral circulation, providing a unique central nervous system (CNS) insight. Measuring biomarkers in blood CNS‐originating EVs have become a promising avenue for minimally invasive diagnostics. This study evaluated the potential the levels of blood‐isolated neuronal and oligodendroglial EVs (nEVs and oEVs) α‐synuclein (α‐syn) proteoforms in parkinsonian disorders.MethodWe searched PUBMED, EMBASE, google scholar and recent reviews of the literature to include studies that have measured mean ± SD of α‐syn in putative nEVs and oEVs in patients with PD and at least one other parkinsonian disorder or healthy controls (HCs). Thirteen studies were included in the final meta‐analysis and demographic and clinical variables were collected for meta‐regressions. We quantified the effect size (SMD) using an inverse‐variance random‐effects model. QUADAS‐2 was used to assess risk of bias. Begg’s rank correlation and Egger’s regression tests were used to assess publication bias.ResultThe studies included 1,565 patients with PD, 206 with MSA, 21 with DLB, 172 with PSP, 152 with CBS and 967 HCs. Findings suggest that a combination of nEVs and oEVs α‐syn concentrations are higher in patients with PD vs. HCs (k = 14, SMD = 0.21; 95% CI 0.01, 0.42 p = 0.021), while nEVs α‐syn is lower in patients with PSP and CBS vs. PD (k = 6, SMD = ‐1.04; p = 0.0017) or HCs (k = 4, SMD = ‐0.41, p < 0.001). Additionally, α‐syn levels in oEVs didn’t effectively differ among PD, MSA, or HCs, contradicting the literature. Meta‐regressions showed demographic/ clinical were not significant predictors of nEVs or oEVs α‐syn concentrations.ConclusionThese findings highlight the need for adopting more rigorous, standardized procedures and independent validations across all laboratories studying biomarkers in CNS‐originating EVs. Additionally, there is a pressing need for improved biomarkers to distinguish among parkinsonian disorders more effectively.

Neuroimmune proteins can differentiate between distinct neurodegenerative diseases

AbstractBackgroundAlthough we have greatly increased our ability to identify the presence of neurodegenerative pathology during life, additional techniques and targets are still needed to increase diagnostic specificity. Recently, it has become evident that the neuroinflammatory response might be tailored towards distinct diseases resulting in disease specific “neuroinflammatory signatures”. Therefore, a detailed comparison of neuroinflammatory molecules present among distinct neurodegenerative diseases could provide novel information of disease specific therapeutic targets or differential biomarkers.MethodTo better examine potential neuroinflammatory signatures, a 71 immune‐related protein multiplex ELISA panel was utilized to analyze anterior cingulate grey matter from 127 individuals neuropathologically diagnosed with Alzheimer’s disease (AD), but chronic traumatic encephalopathy (CTE), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and argyrophilic grain disease (AGD). A partial least square regression analysis was used for unbiased clustering and identifying proteins that were distinctly correlated with each disease correcting for age and gender. Receiver operator characteristic and binary logistic regression analyses were then used to examine the ability of each candidate protein to distinguish diseases. Validation in postmortem cerebrospinal fluid (CSF) from 15 AD and 14 CTE cases was performed to determine if candidate proteins could act as possible biomarkers. Finally, histology was performed using candidate proteins to visualize cell type expression for better understanding of potential mechanistic pathways.ResultFive clusters of neuroimmune proteins were identified and compared to determine if clusters were specific to distinct disease. Each cluster was found to correlate with either CTE, AD, PSP, CBD, or AGD. When examining which proteins were the strongest driver of each cluster, it was observed the most distinctive protein for CTE was CCL21, AD was FLT3L, and PSP was IL13. Individual proteins that were specific to CBD and AGD were not observed. CCL21 was observed to be elevated in CTE CSF compared to AD, further validating the use as possible biomarkers.ConclusionOverall, these results highlight that different neuroinflammatory responses might underlie unique mechanisms in related neurodegenerative pathologies. Additionally, the use of distinct neuroinflammatory signatures could help differentiate between neuropathologies and act as novel biomarker candidate to increase specificity for in‐life diagnoses.

Clinical value of CSF TMEM106B in familial and sporadic frontotemporal lobar degeneration

AbstractBackgroundTMEM106B, a lysosomal trafficking protein, is an important genetic susceptibility risk factor for frontotemporal lobar degeneration (FTLD). In GRN mutation carriers, minor allele homozygosity in the TMEM106B rs1990622 SNP modulates the risk of FTLD. TMEM106B is often the main component of amyloid fibrils in FTLD with TDP43 aggregates. TMEM106B has been quantified in human brain specimens, but its role as a fluid biomarker is unknown. Here, we investigate the clinical value of CSF TMEM106B in FTLD.MethodsCSF TMEM106B was quantified with SOMAmer proteomics (v3.0, SomaLogic®) in an original cohort of C9orf72, GRN and MAPT symptomatic and asymptomatic mutation carriers and family non‐carrier controls, recruited through ALLFTD (n = 182), and a validation cohort of sporadic neuropathology‐confirmed FTLD‐tau and FTLD‐TDP43, clinically‐diagnosed progressive supranuclear palsy – Richardson syndrome (PSP‐RS) and age‐matched controls (n = 96). CSF TMEM106B was correlated with disease severity, measured by the Frontotemporal Lobar Degeneration module global scores (CDR+NACC/FTLD); brain volume, measured with Bayesian linear mixed‐effect modeling, using age, sex and total‐intracranial volume‐corrected permutations with threshold‐free cluster enhancement; and CSF neurofilament light chain (NfL) measured with Simoa. TMEM106B SOMAmer specificity was validated in cell culture overexpression systems and human brain specimens with high TMEM106B burden.ResultsIn both cohorts, there were no differences in CSF TMEM106B by sex, phenotype or neuropathological diagnosis, except for lower levels in PSP‐RS compared to controls (‐0.31 Log2‐fold change, p < 0.001). CSF TMEM106B did not correlate with age. Regardless of disease‐causing mutation, lower CSF TMEM106B was associated with worse disease severity (Figure 1 and 2). CSF TMEM106B was lower in homozygous TMEM106B rs1990622 protective allelein C9orf2 and MAPT, but not in GRN mutation carriers (Figures 3). CSF TMEM106B showed a trend for inverse correlation with NfL in the whole sample (r = ‐0.135, p = 0.052), and correlated positively with left frontal volume in symptomatic FTLD mutation gene carriers (p < 0.05).ConclusionCSF TMEM106B is quantifiable in CSF in vivo. CSF TMEM106B levels are affected by an interaction of disease severity and FTLD and TMEM106B genotypes. Further work is needed to determine its value as a clinical biomarker.

The prioritization of biomarkers in the diagnostic workup of motor tauopathy

AbstractMotor tauopathies represent a spectrum of degenerative, poorly levodopa‐responsive parkinsonisms unified by the pathological accumulation of hyperphosphorylated tau protein fragments in the brain. The principal entities, progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), are rare conditions (<10 per 100,000) and present with non‐amnestic cognitive impairment ‐ mostly involving frontal‐subcortical networks – in around 40% of patients at baseline. Additionally, the phenotypic PSP spectrum expresses with oculomotor dysfunction, falls and bulbar symptoms at varying degrees. On the other hand, CBD tauopathy is the most frequent aetiology underlying the corticobasal syndrome (CBS) that is a multifaceted disorder characterized by a markedly asymmetric Parkinsonism with apraxia and neocortical deficits. Paralleling the clinical symptoms, the distribution of functional and metabolic impairment specifically involves different brain regions in PSP and CBD. Hence, metabolism assessment by FDG‐positron emission tomography (PET) allows for accurate distinction of motor tauopathies from other parkinsonisms or one with another (AUC 0.80 and 0.92‐0.97, respectively). In this context, the European Intersociety Consensus Diagnostic Task Force recommends the use of FDG‐PET as the first‐level diagnostic biomarker to achieve early and accurate differential diagnosis of motor tauopathies. Afterwards, the assessment of CSF biomarkers of Alzheimer’s disease (AD) is advised to identify that minority of cases of CBS underpinned by an AD aetiology (10‐20%). With this sequence of biomarkers, the diagnostic workflow aims to an early identification of motor tauopathies and advocates in‐depth etiological investigation of CBS where access to AD‐specific drugs, when available, should be considered in a non‐negligible proportion of patients.

Cerebellar atrophy in pathological subtypes of Alzheimer’s disease and related dementias

AbstractBackgroundThe cerebellum is differentially affected in various neurodegenerative diseases (Gellersen et al., 2017), but associations of cerebellar atrophy with specific neuropathologies have not been systematically analyzed. We used brain imaging to examine cerebellar grey matter volume with patients with all major pathological subtypes of Alzheimer’s disease and related dementias (ADRD).MethodWe applied voxel‐based morphometry to the earliest structural magnetic resonance imaging scans of autopsy‐proven ADRD cases (n = 309), and age‐, sex‐, and education‐matched healthy controls (n = 80). Seventy‐seven AD cases, 74 cases with mixed Lewy body disease and AD (LBD‐AD), and 158 frontotemporal lobar degeneration (FTLD) cases were included in this study. Patients with FTLD were further classified into FTLD major molecular classes and subtypes: FTLD‐TDP [FTLD‐TDP type A (TDP‐A) (n = 21), FTLD‐TDP type B (TDP‐B) (n = 21), FTLD‐TDP type C (TDP‐C) (n = 26)] and FTLD‐tau [Pick’s disease (n = 25), corticobasal degeneration (CBD) (n = 32), progressive supranuclear palsy (PSP) (n = 33)]. Clinical function was assessed with the Clinical Dementia Rating Scale (CDR) (Morris, 1993; Hughes et al., 1982) at the time of MRI scan, with global score ranging from 0 (normal), 0.5 (very mildly impaired), 1 (mildly impaired), 2 (moderately impaired) to 3 (severely impaired).ResultsCompared with controls, distinct patterns of cerebellar atrophy were observed in all pathological subtypes spanning bilateral hemispheres and vermis (PFWE‐corr<0.05, >100 contiguous voxels). Significant cerebellar grey matter changes were even found in the early stage (CDR ≦ 1) of all subtypes, with the exception of TDP‐B, and in the very early stage (CDR 0‐0.5) of AD, LBD‐AD, TDP‐A and PSP. Degree of cortical atrophy positively predicted degree of cerebellar atrophy in all subtypes.ConclusionThis study is the first to identify distinct early patterns of cerebellar atrophy across pathological subtypes of ADRD, and to show a direct relationship between cerebellar and cortical grey matter volume. These results clarify the cerebellar involvement in ADRD and underscore the potential for cerebellar neuroimaging to be a non‐invasive biomarker for differential diagnosis among pathologies and disease monitoring.

RNA‐seq study on the effect of MAPT rs242557 deletion in HMC3 cells

AbstractBackgroundMicrotubule associated protein tau (MAPT) is associated with neurodegenerative diseases including Frontotemporal dementia (FTD), Progressive supranuclear palsy (PSP), Corticobasal degeneration (CBD), Alzheimer’s disease (AD) and Parkinson’s disease (PD). Multiple GWAS on AD, PD, PSP and CBD have identified strong signal in MAPT intronic region (SNP, rs242557). Being part of FANTOM5 enhancer in eye and brain, we are interested in the effect of this region in HMC3 (human microglial clone 3) cell line.MethodUsing CRISPR‐Cas9 genome editing, a clone was isolated having homozygous 309 bp deletion encompassing rs242557 and its flanking sequences in HMC3. Sanger sequencing confirmed the deletion while whole genome sequencing corroborated the same and also confirmed no off‐target effects. To identify gene transcripts whose expression was altered due to the deletion, paired‐end RNA‐seq was performed using total RNA extracted from rs242557 KO and wild type (WT) clones.ResultThere were 272 up‐ and 861 down‐regulated transcripts (p< = 0.01) between WT and KO cells. Down‐regulated transcripts include AD risk genes ICA1, EPDR1, PTK2B, SORL1, DOC2A, and TSPOAP1, and PD candidate gene, SNCA. Notable among up‐regulated transcripts was AD risk gene, CASS4. Enrichment analyses revealed biological processes and pathways that are related to structural constituents and organization of neurons and synapses. Currently, we are validating the transcript data.ConclusionOur preliminary data suggests that the genomic region encompassing rs242557 might affect multiple AD risk genes.

Deep quantitative proteomics analysis of the brain vasculature in Alzheimer’s disease and related tauopathies.

AbstractBackgroundDysfunction of neurovascular unit represents a major pathological hallmark of Alzheimer’s disease (AD) and age‐related cognitive impairment. Diminished blood flow and blood‐brain barrier breakdown have been linked to the accumulation of amyloid‐b (Ab) peptide in brain parenchyma and cerebral blood vessels. Additionally, cerebrovascular dysfunction has been associated with tau pathology in primary tauopathies, including progressive supranuclear palsy (PSP) where amyloid deposition is not present. Despite the significance of brain vasculature in maintaining the proper neuronal function, the proteomic profiles of cerebrovasculature remain poorly characterized.MethodsHere, for the first time we implemented a tandem mass tag spectrometry (TMT‐MS) approach to thoroughly examine proteomic features of human cerebrovasculature from postmortem brain tissues from AD, PSP, and non‐demented control individuals (N = 20‐24 cases/diagnosis) from the University of Pennsylvania School of Medicine Brain Bank. The human cerebrovasculature was isolated from frontal cortex using density‐mediated separation to purify blood vessels from parenchymal components.ResultsThe quantification of over 9,800 proteins allowed us to generate deep TMT protein co‐expression network consisting of 93 communities of proteins displaying wide biological heterogeneity associated with diverse brain pathologies. Importantly, the comparison of vascular proteome with proteomic data obtained from bulk brain tissues from the same individuals gave us a unique opportunity to interrogate the relationship and preservation between different data sets. We also explored how candidate gene products that confer the risk for AD or PSP map to the discovered protein modules.ConclusionsIn summary, by taking advantage of our network‐driven approach we nominated pathways strongly correlated with AD‐like neuropathological traits and vascular biology that could provide the foundation for our understanding of the mechanisms governing AD‐linked breakdown of BBB, dysregulation of the cerebral blood flow, and pathological accumulation of protein aggregates in human vasculature.

Functional connectivity trajectories in genetic frontotemporal dementia

AbstractBackgroundCharacterizing disease trajectories in frontotemporal lobar degeneration (FTLD) is essential to determine the optimal timing for initiating therapeutic interventions, and there is an urgent need for novel and sensitive disease biomarkers. Intrinsic connectivity network (ICN) mapping using task‐free fMRI is a promising biomarker which reveals early abnormalities even before symptomatic onset (Dopper et al. 2014; Lee et al. 2016). Yet, ICN trajectories from the presymptomatic to symptomatic stages in FTLD mutation carriers remain unclear.MethodIn this cross‐sectional study, we used UCSF and ALLFTD Consortia data to study 129 carriers with variants in MAPT (presymptomatic/prodromal/symptomatic: 34/4/7), C9orf72 (30/9/12) and GRN (22/4/7). Using cross‐sectional data to construct ICN trajectories by genotype, we built separate generalized additive models for each genetic group to estimate non‐linear relationships between standardized connectivity changes and disease age across clinical stages. ICN connectivity was based on seed‐based analyses for networks associated with common clinical syndromes for each genetic group (i.e., salience and default mode [MAPT/C9orf72/GRN], corticobasal syndrome [MAPT/GRN], progressive supranuclear palsy syndrome [MAPT], sensorimotor and medial pulvinar‐related [C9orf72], and non‐fluent variant primary progressive aphasia (nfvPPA) syndrome networks [GRN]). We included 127 healthy controls as a reference to calculate ICN z‐scores for each carrier. Each carrier’s disease age was defined as the difference between the carrier’s chronological age and estimated age of onset based on multimodal measures of structural imaging, fluid biomarker and clinical assessments (Staffaroni et al. 2022).ResultIn MAPT+, presymptomatic carriers showed declining salience network connectivity starting approximately 30 years before estimated onset, which plateaued about 20 years before onset. In C9orf72+, salience network hyperconnectivity emerged about 30 years before onset and declined throughout the presymptomatic and symptomatic stages. For GRN+, connectivity changes as a function of disease age were found within the salience and nfvPPA networks, with connectivity stable until around 10 years before estimated onset, followed by decline starting in the late presymptomatic phase and continuing through the prodromal and symptomatic stages.ConclusionThese findings demonstrate that FTLD genes show distinct ICN trajectories throughout the clinical spectrum. These results help pave the way for determining the optimal timing to initiate therapeutic interventions.

Functional connectivity trajectories in genetic frontotemporal dementia

AbstractBackgroundCharacterizing disease trajectories in frontotemporal lobar degeneration (FTLD) is essential to determine the optimal timing for initiating therapeutic interventions, and there is an urgent need for novel and sensitive disease biomarkers. Intrinsic connectivity network (ICN) mapping using task‐free fMRI is a promising biomarker which reveals early abnormalities even before symptomatic onset (Dopper et al. 2014; Lee et al. 2016). Yet, ICN trajectories from the presymptomatic to symptomatic stages in FTLD mutation carriers remain unclear.MethodIn this cross‐sectional study, we used UCSF and ALLFTD Consortia data to study 129 carriers with variants in MAPT (presymptomatic/prodromal/symptomatic: 34/4/7), C9orf72 (30/9/12) and GRN (22/4/7). Using cross‐sectional data to construct ICN trajectories by genotype, we built separate generalized additive models for each genetic group to estimate non‐linear relationships between standardized connectivity changes and disease age across clinical stages. ICN connectivity was based on seed‐based analyses for networks associated with common clinical syndromes for each genetic group (i.e., salience and default mode [MAPT/C9orf72/GRN], corticobasal syndrome [MAPT/GRN], progressive supranuclear palsy syndrome [MAPT], sensorimotor and medial pulvinar‐related [C9orf72], and non‐fluent variant primary progressive aphasia (nfvPPA) syndrome networks [GRN]). We included 127 healthy controls as a reference to calculate ICN z‐scores for each carrier. Each carrier’s disease age was defined as the difference between the carrier’s chronological age and estimated age of onset based on multimodal measures of structural imaging, fluid biomarker and clinical assessments (Staffaroni et al. 2022).ResultIn MAPT+, presymptomatic carriers showed declining salience network connectivity starting approximately 30 years before estimated onset, which plateaued about 20 years before onset. In C9orf72+, salience network hyperconnectivity emerged about 30 years before onset and declined throughout the presymptomatic and symptomatic stages. For GRN+, connectivity changes as a function of disease age were found within the salience and nfvPPA networks, with connectivity stable until around 10 years before estimated onset, followed by decline starting in the late presymptomatic phase and continuing through the prodromal and symptomatic stages.ConclusionThese findings demonstrate that FTLD genes show distinct ICN trajectories throughout the clinical spectrum. These results help pave the way for determining the optimal timing to initiate therapeutic interventions.

In vivo MRI assessment of locus coeruleus and nucleus basalis of Meynert integrity in frontotemporal degeneration and corticobasal syndrome.

AbstractBackgroundNeuropathological studies have shown alterations in both locus coeruleus (LC) and basal forebrain in frontotemporal degeneration (FTD) and corticobasal syndrome (CBS) particularly in progressive supranuclear palsy (PSP). We aimed to investigate in vivo the LC and nucleus basalis of Meynert (NBM) integrity in patients with FTD and CBS.MethodWe compared the LC signal intensity (LC‐I), which reflects the LC integrity, and the NBM volume on 3T MRI in i) FTD patients (n = 17) ii) CBS patients (n = 8;) iii) prodromal/mild AD (n = 34) and iv) amyloid‐negative controls (n = 15). PiB‐PET and/or AD CSF biomarkers were negative in all FTD and CBS patients, and positive in all AD patients. All subjects underwent a complete neuropsychological assessment and 3T brain MRI performed on the same scan. The four groups were age‐matched. The MMSE score did not differ significantly between the 3 groups of patients.ResultCompared to controls, LC‐I and NBM volume were significantly decreased in FTD (p = 0.05 and 0.00015, respectively) and AD patients (p = 0.0005 and 0.002, respectively). LC‐I and NBM volume were also decreased in CBS in comparison with controls but the difference was not statistically significant. In addition, we found no statistically significant difference in LC‐I and NBM volume between the three groups of patients. We observed no correlation between LC‐I or NBM volume and amyloid load, either when considering the whole group of patients or AD and FTD/CBS patients separately.ConclusionOur results are in line with neuropathological data and suggest that both cholinergic and noradrenergic systems are altered in AD and FTD. Post mortem data have suggested that, in FTD, both structures were more impaired in tau than in TDP‐43 proteinopathy, which cannot be explored in our study. In CBS, our results are less clear‐cut, probably due to the small sample size. Taken together, our data support the pathophysiological model in which both LC and NBM play a critical role not only in AD but also in other diseases and proteinopathies like FTD.

RNAi knockdown of microtubule‐associated protein Tau prevents axonal damage and clears pre‐existing Tau aggregates in P301S transgenic tauopathy model mice

AbstractBackgroundThe hyperphosphorylation and subsequent aggregation of the microtubule‐associated protein Tau (encoded by the MAPT gene) is one of the major histopathological hallmarks of numerous tauopathies, including Alzheimer’s disease and progressive supranuclear palsy. The intracellular accumulation of aggregated Tau is associated with neuronal loss and disease progression in tauopathies. There is a high‐unmet need to identify strategies to target the intracellular accumulation of Tau aggregates with the aim of slowing tauopathy progression.MethodTo model this, we used mice carrying multiple copies of a transgene with a prion promoter driving human MAPT with human tauopathy‐inducing mutation P301S. P301S‐Tau transgenic mice progressively accumulate neuroglial Tau aggregates associated with axonal damage, gliosis, body weight loss, and ambulatory dysfunction.ResultP301S mice treated with a single intracerebroventricular injection of Tau siRNA at eight months of age, had a sustainable decrease in MAPT mRNA and soluble Tau protein for three months following siRNA treatment (reduced ∼83% and ∼59%, respectively). siRNA treatment also prevented the progressive decrease in body weight and abrogated axonal damage, evidenced by decreased neurofilament light (NFL) chain in plasma and cerebrospinal fluid of eleven‐month‐old mice. Importantly, immunohistochemical analysis of misfolded Tau in vivo and HEK293‐4RD‐CFP/YFP Tau aggregate biosensor assay testing in vitro revealed a ∼97% decrease of Tau aggregates in the eleven‐month‐old mice, suggesting there exists a yet‐to‐be identified mechanism of Tau fibril clearance.ConclusionTogether, these results suggest an RNAi therapeutics approach targeting of MAPT mRNA may be sufficient to improve multiple parameters of tauopathy disease progression and a provide a compelling rationale for further development of Tau‐lowering strategies.