Nicolas Barthélemy

Washington University in St. Louis | WUSTL , Wash U · Department of Neurology

Cerebrospinal fluid (CSF) amyloid-β peptide (Aβ)42/Aβ40 and the concentration of tau phosphorylated at site 181 (p-tau181) are well-established biomarkers of Alzheimer’s disease (AD). The present study used mass spectrometry to measure concentrations of nine phosphorylated and five nonphosphorylated tau species and phosphorylation occupancies (perc...

Objective: In Alzheimer's disease, hyperphosphorylated tau is associated with formation of insoluble paired helical filaments that aggregate as neurofibrillary tau tangles and are associated with neuronal loss and cognitive symptoms. Dual orexin receptor antagonists decrease soluble amyloid-β levels and amyloid plaques in mouse models over-express...

Objective: Identifying cerebrospinal fluid measures of the microtubule binding region of tau (MTBR-tau) species that reflect tau aggregation could provide fluid biomarkers that track Alzheimer disease related neurofibrillary tau pathological changes. We examined CSF MTBR-tau species in dominantly inherited Alzheimer disease (DIAD) mutation carrier...

Introduction: Sleep deprivation increases cerebrospinal fluid (CSF) amyloid beta (Aβ) and tau levels; however, sleep's effect on Aβ and tau in plasma is unknown. Methods: In a cross-over design, CSF Aβ and tau concentrations were measured in five cognitively normal individuals who had blood and CSF collected every 2 hours for 36 hours during sle...

Neurofilament light chain, a putative measure of neuronal damage, is measurable in blood and CSF and is predictive of cognitive function in individuals with Alzheimer’s disease. There has been limited prior work linking neurofilament light and functional connectivity, and no prior work has investigated neurofilament light associations with function...

Associations 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...

Hyperphosphorylated tau isoforms (p‐tau) in cerebrospinal fluid (CSF) and plasma represent promising measures to monitor Alzheimer disease (AD) pathological changes. Brain amyloid deposition precedes tau aggregation and associated clinical decline by two decades. Several CSF and plasma p‐tau isoforms have been described as potential surrogates for...

In autosomal dominant AD (ADAD), elevated cerebrospinal fluid (CSF) soluble phosphorylated tau (pT181) increases shortly after amyloid positron emission tomography. Recent advancements have identified additional phosphorylated tau sites, such as phosphorylated tau 217 and 205 (pT217 and pT205), which are associated with amyloid deposition and neuro...

Brain tau aggregation is a pathological hallmark of Alzheimer’s disease (AD) and the tau microtubule binding region (MTBR) is the core of AD tau tangles. Recently, we identified the enrichment of some specific MTBR species in sporadic AD brain tangles. Corresponding soluble MTBR species in the CSF increased together with clinical progression and ta...

Despite recent advances in fluid biomarker research in Alzheimer’s disease (AD), there are no fluid biomarkers or imaging tracers with utility for diagnosis and/or theragnosis available for other tauopathies. Using immunoprecipitation and mass spectrometry, we show that 4 repeat (4R) isoform-specific tau species from microtubule-binding region (MTB...

Macrophages are important players in the maintenance of tissue homeostasis1. Perivascular and leptomeningeal macrophages reside near the central nervous system (CNS) parenchyma2, and their role in CNS physiology has not been sufficiently well studied. Given their continuous interaction with the cerebrospinal fluid (CSF) and strategic positioning, w...

CSF Aβ42/Aβ40 and tau phosphorylated at site 181 (p-tau181) are well-established biomarkers of Alzheimer disease (AD). This study used mass spectrometry to measure concentrations of 9 phosphorylated and 5 non-phosphorylated species, and phosphorylation occupancies (phosphorylated/non-phosphorylated [%]) at 10 sites. In 750 individuals with a median...

Plasma phospho-tau (p-tau) species have emerged as the most promising blood-based biomarkers of Alzheimer's disease. Here, we performed a head-to-head comparison of p-tau181, p-tau217 and p-tau231 measured using 10 assays to detect abnormal brain amyloid-β status and predict future progression to Alzheimer's dementia. The study included 135 patient...

Tau is a microtubule-binding protein expressed in neurons, and the equal ratios between 4-repeat (4R) and 3-repeat (3R) isoforms are maintained in normal adult brain function. Dysregulation of 3R:4R ratio causes tauopathy, and human neurons that recapitulate tau isoforms in health and disease will provide a platform for elucidating pathogenic proce...

Background Therapeutic modulation of TREM2-dependent microglial function might provide an additional strategy to slow the progression of Alzheimer's disease. Although studies in animal models suggest that TREM2 is protective against Alzheimer's pathology, its effect on tau pathology and its potential beneficial role in people with Alzheimer's disea...

Background Hyperphosphorylation of tau leads to conformational changes that destabilize microtubules and hinder axonal transport in Alzheimer's disease (AD). However, it remains unknown whether white matter (WM) decline due to AD is associated with specific Tau phosphorylation site(s). Methods In autosomal dominant AD (ADAD) mutation carriers (MC)...

IMPORTANCE: Allelic variation in the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism moderates increases in cerebrospinal fluid (CSF) levels of tau and phosphorylated tau 181 (p-tau181), measured using immunoassay, and cognitive decline in presymptomatic dominantly inherited Alzheimer disease (DIAD). Advances in mass spectrometry sho...

Neurofilament light is a well-established marker of both acute and chronic neuronal damage and is increased in multiple neurodegenerative diseases. However, the protein is not well characterized in brain tissue or body fluids, and it is unknown what neurofilament light species are detected by commercial assays and whether additional species exist....

Importance: Allelic variation in the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism moderates increases in cerebrospinal fluid (CSF) levels of tau and phosphorylated tau 181 (p-tau181), measured using immunoassay, and cognitive decline in presymptomatic dominantly inherited Alzheimer disease (DIAD). Advances in mass spectrometry sh...

Tau hyperphosphorylation at Threonine 217 (pT217) in cerebrospinal fluid (CSF) has recently been linked to early amyloidosis and could serve as a highly sensitive biomarker for Alzheimer disease (AD). However, it remains unclear whether pT217 could be modified in other tauopathies. Using immunoprecipitation and mass spectrometry, we compared CSF T2...

Recent advances in the development of novel Alzheimer’s disease (AD) measures of amyloid, tau, and neurodegeneration in cerebrospinal fluid (CSF) and blood have enabled a better understanding of the links between amyloid‐beta (Aβ), tau species and neurodegeneration in the brain, CSF, and blood. The discoveries of novel tau species in CSF and blood,...

Recent analyses of tau phosphorylation in cerebrospinal fluid (CSF) from dominantly inherited Alzheimer disease (DIAD) patients have pinpointed early modification of phosphorylated tau (p‐tau) at 217 (pT217) occurring simultaneously with emergence of amyloid plaques. This has opened new perspective in diagnosing AD pathology at preclinical stages u...

Accumulations of tau aggregates and amyloid plaques in brain are hallmarks of Alzheimer’s disease (AD). Recent studies in characterizing tau species, especially phosphorylated tau‐181 (p‐tau181) and p‐tau217 in AD brain and biofluids suggested that these species start increasing at preclinical stage, correlate with amyloid plaques, and improve the...

Background: Understanding patterns of association between CSF phosphorylated tau (p-tau) species and clinical disease severity will aid Alzheimer's disease (AD) diagnosis and treatment. Objective: To evaluate changes in tau phosphorylation ratios to brain imaging (amyloid PET, [18F]GTP1 PET, and MRI) and cognition across clinical stages of AD in...

Brain atrophy occurs in aging even in the absence of dementia, but it is unclear to what extent this is due to undetected preclinical Alzheimer disease. Here we examine a cross-sectional cohort (ages 18-88) free from confounding influence of preclinical Alzheimer disease, as determined by amyloid PET scans and three years of clinical evaluation pos...

Objective Tau hyperphosphorylation at threonine 217 (pT217) in cerebrospinal fluid (CSF) has recently been linked to early amyloidosis and could serve as a highly sensitive biomarker for Alzheimer’s disease (AD). However, it remains unclear whether other tauopathies induce pT217 modifications. To determine if pT217 modification is specific to AD, C...

Tau is a microtubule associated protein in the brain that aggregates in Alzheimer’s disease to form pathological tangles and neurites. Insoluble tau aggregates composed of the microtubule binding region (MTBR) of tau are highly associated with the cognitive and clinical symptoms of Alzheimer’s disease. In contrast, levels of soluble forms of tau, s...

Brain tau aggregates are, together with amyloid plaques, hallmarks of Alzheimer Disease (AD). Structural characterization of tau aggregates in AD, Pick’s disease and Chronic Traumatic Encephalopathy demonstrate distinct folds leading to tau aggregation. However, initiation and propagation mechanisms involved are still unknown. One hypothesis includ...

Understanding tau kinetics in the human central nervous system is critical for evaluating the effects of tau‐targeted therapies and designing clinical trials against tau in Alzheimer disease (AD) and other primary tauopathies. We hypothesized that tau production or clearance is altered in tauopathies and measured tau kinetics in AD and in a small s...

Recent advances in understanding the links between amyloid‐beta (Aβ) and specific tau isoforms in brain, cerebrospinal fluid (CSF), and blood indicate that a cascade of events of Alzheimer’s disease (AD) pathophysiology begin with detection of altered CSF and blood Aβ 42/40 ratio, followed by increases in amyloid plaques by Positron Emission Tomogr...

Tau deposition in brain is a pathological hallmark of some neurodegenerative disorders including Alzheimer’s disease (AD). Braak staging of post‐mortem tissue suggests pathological tau spreads through the brain via synaptically connected pathways, and specific tau isoforms containing the microtubule binding region (MTBR) are thought to be essential...

Abstract Alzheimer’s disease (AD) neuropathologic change is characterized by amyloid plaques and neurofibrillary tangles (NFTs) that consist of aggregated amyloid beta (Abeta) and hyperphosphorylated tau proteins (p-tau), respectively. Although the global relationship between Abeta and p-tau has been studied for decades, it is still unclear whether...

Highly sensitive and specific plasma biomarkers for Alzheimer's disease (AD) have the potential to improve diagnostic accuracy in the clinic and facilitate research studies including enrollment in prevention and treatment trials. We recently reported CSF tau hyperphosphorylation, especially on T217, is an accurate predictor of β-amyloidosis at asym...

Interest in neurofilaments has risen sharply in recent years with recognition of their potential as biomarkers of brain injury or neurodegeneration in CSF and blood. This is in the context of a growing appreciation for the complexity of the neurobiology of neurofilaments, new recognition of specialized roles for neurofilaments in synapses and a dev...

Background: Cerebrospinal fluid biomarker profiles characterized by decreased amyloid-beta peptide levels and increased total and phosphorylated tau levels at threonine 181 (pT181) are currently used to discriminate between Alzheimer's disease and other neurodegenerative diseases. However, these changes are not entirely specific to Alzheimer's dis...

Measurement of phosphorylated tau protein in blood plasma allows Alzheimer’s disease to be distinguished from other neurological diseases and may assist in disease detection during the prodromal stage.

Development of tau-based therapies for Alzheimer’s disease requires an understanding of the timing of disease-related changes in tau. We quantified the phosphorylation state at multiple sites of the tau protein in cerebrospinal fluid markers across four decades of disease progression in dominantly inherited Alzheimer’s disease. We identified a patt...

Tau hyperphosphorylation is an early step in tau‐mediated neurodegeneration and is associated with intracellular aggregation of tau as neurofibrillary tangles, neuronal and synaptic loss, and eventual cognitive dysfunction in Alzheimer's disease. Sleep loss increases the cerebrospinal fluid concentration of amyloid‐β and tau. Using mass spectrometr...

Alzheimer disease (AD) is one of several neurodegenerative diseases characterized by dysregulation, misfolding and accumulation of specific proteins in the CNS. The stable isotope labelling kinetics (SILK) technique is based on generating amino acids labelled with naturally occurring stable (that is, nonradioactive) isotopes of carbon and/or nitrog...

Tau protein aggregation into neurofibrillary tangles in the central nervous system contributes to the etiology of certain neurodegenerative disorders, including Alzheimer’s disease (AD). Though the mechanism of tau destabilization is not fully understood yet, tau protein has been found to be hyperphosphorylated in tau aggregates. To investigate thi...

Figure S3. Correlation between all hSOD1 peptides measured. Linear regression analysis comparing peptides shows strong correlations exist between all peptide measurements. All P values < 0.0001 for each analysis.

Figure S5. No changes in peripheral hSOD1 after 1000 ug hSOD1 ASO intracerebroventricular injection. A. hSOD1 protein levels relative to N15‐labeled recombinant standard by LC‐MS in plasma. No changes in plasma hSOD1 protein levels were observed (Student's T‐test). B. 13C6‐Leu labeled hSOD1 in plasma by LC‐MS. No changes in plasma 13C6‐Leu labeled...

Figure S2. Correlation between all hTau peptides measured. Linear regression analysis comparing peptides shows strong correlations exist between all three peptide measurements. All p values < 0.0001 for each analysis.

Figure S4. Characterizing 13C6‐Leucine incorporation into hTau protein in hTauWT transgenic mice. hTau mice were acclimated to leucine‐free chow for 7 days, and labeled with 5 mg/ml 13C6‐leucine for 7 days. Mice were euthanized at 6 (n = 2), 10 (n = 3), 14 (n = 3), and 17 (n = 2) days post‐end of label. Because of the high label incorporation (near...

Table S2. Transition ions used for hSOD1 tandem LC‐MS/MS. GLHGFHVHE peptide measurements were used as representative data in figures.

Figure S1. No differences in 13C6‐Leucine oral labeling between treatment groups in all experiments performed. Plasma 13C6‐Leucine values were analyzed in all samples analyzed and compared between groups. A. hTau ICV ASO plasma 13C6‐Leucine at Day 23 post surgery, as seen in Figure 2. No differences were observed (Student's T‐test, P = 0.4496). B....

Table S1. Primers and probes used for genotyping and qPCR analysis of hTau (MAPT), hSOD1 (SOD1) and mouse GAPDH (GAPDH) DNA.

Figure S6. No protein concentration pharmacodynamics observed in CSF after 1000 ug hSOD1 ASO intracerebroventricular injection at 50 days post treatment. A. hSOD1 mRNA levels in the CNS by qPCR. hSOD1 mRNA levels are significantly lowered in spinal cord and frontal cortex by ~70% and 50%, respectively, after ASO treatment relative to inactive ASO c...

Table S3. Transition ions used for hTau tandem LC‐MS/MS. TPSLPTPPTR peptide measurements were used as representative data in figures.

Objectives Clinical trials for progressive neurodegenerative disorders such as Alzheimer's Disease and Amyotrophic Lateral Sclerosis have been hindered due to the absence of effective pharmacodynamics markers to assay target engagement. We tested whether measurements of new protein production would be a viable pharmacodynamics tool for RNA‐targeted...

We developed stable isotope labeling and mass spectrometry approaches to measure the kinetics of multiple isoforms and fragments of tau in the human central nervous system (CNS) and in human induced pluripotent stem cell (iPSC)-derived neurons. Newly synthesized tau is truncated and released from human neurons in 3 days. Although most tau proteins...

Introduction Modification of CSF tau phosphorylation in AD remains controversial since total-tau and phospho-tau levels measured by immunoassays are highly correlated. Methods Stoichiometry of phosphorylation of CSF tau was monitored on five sites by mass spectrometry. We compared 50 participants with AD at mild to moderate stages, others tauopath...

Microtubule-associated Tau proteins are major actors in neurological disorders, the so-called tauopathies. In some of them, and specifically in Alzheimer's disease (AD), hyperphosphorylated forms of Tau aggregate into neurofibrillary tangles. Following and understanding the complexity of Tau's molecular profile with its multiple isoforms and post-t...

Tau protein plays a major role in neurodegenerative disorders, appears to be a central biomarker of neuronal injury in cerebrospinal fluid (CSF) and is a promising target for Alzheimer's disease immunotherapies. To quantify tau at high sensitivity and gain insights into its naturally occurring structural variations in human CSF, we coupled absolute...

Tau protein concentration in cerebrospinal fluid (CSF) is currently used as a sensitive and specific biomarker for Alzheimer's disease. Its detection currently relies on ELISA but the perspective of using mass spectrometry (MS) to detect its different proteoforms represents an interesting alternative. This is however an analytical challenge because...

Tau protein concentration in cerebrospinal fluid (CSF) is currently quantified by performing ELISA tests, however mass spectrometry represents a valuable alternative. Obviously, the quantification of Tau in CSF is an analytical challenge because of 1) the existence of 6 different isoforms, 2) its low concentration, 3) the low volume of precious sam...

Abstract Alzheimer's disease (AD) is the most common form of dementia in humans, and a major public health concern with 35 million of patients worldwide. Cerebrospinal fluid (CSF) biomarkers being early diagnostic indicators of AD, it is essential to use the most efficient analytical methods to detect and quantify them accurately. These biomarkers,...

Background: Detection of biomarkers in the CSF has proven to be useful to follow and understand the metabolism of molecular actors of Alzheimer's disease (AD), as well as, for diagnosis purposes. Immunodetection is mostly used to detect and quantify these biomarkers but this approach has sometime a poor specify and a limited detection range of the...

Human hair is principally composed of hair keratins and keratin-associated proteins (KAPs) that form a complex network giving the hair its rigidity and mechanical properties. However, during their growth, hairs are subject to various treatments that can induce irreversible damage. For a better understanding of the human hair protein structures, pro...