Analysis of Human Tau in Cerebrospinal Fluid

Abstract

Alzheimer's disease (AD) is the most common form of dementia. Neuropathologically, it is characterized by two major hallmarks: neurofibrillary tangles (NFT) formed from hyperphosphorylated versions of the tau-protein, and neuritic plaques (NP) containing mostly beta-amyloid peptides (A beta) that are formed from the amyloid precursor protein (APP) by enzymatic cleavage. Despite much progress in recent years, the causes of sporadic (i.e., nonfamiliar) AD are still unclear and its valid diagnosis still relies on autopsy. Clinically used biomarkers present in cerebrospinal fluid (CSF), that is, unphosphorylated or phosphorylated tau and A beta-peptides of different lengths, lack the necessary specificity and sensitivity. Here, we describe a novel strategy to characterize tau versions present in CSF with respect to their molecular mass and isoelectric point. Aliquots of 1 mL CSF (i.e., 700 to 1300 pg tau) from nondemented persons and histopathologically confirmed AD cases were depleted for six dominant proteins, separated by two-dimensional gel electrophoresis, and then electro-transferred onto PVDF-membranes. Tau was detected with monoclonal antibody (mAb) HT7 conjugated with horseradish peroxidase (HRP). In this way, a complex tau pattern was identified in CSF that was very similar to the tau preparations from autopsy brain samples. The presented strategy enables the analysis of the phosphorylation and processing status of tau in CSF samples from healthy people and patients diagnosed with different neurological disorders. This more-detailed information on circulating tau versions and their clearance rates may facilitate the development of new diagnostic tools.

Ectosomes: A New Mechanism for Non-Exosomal Secretion of Tau Protein

“…Similar truncated species are found in cell culture media obtained from cellular models or CSF-Tau from transgenic mice models [15], [52], in addition to human CSF [18], [50], [53]. However, full-length forms of secreted Tau are also found in cell culture media [13], [14], murine ISF [47] and human CSF [53]. By only evaluating the vesicular forms, we reconciled both previous observations, i.e., the presence of full-length secreted Tau in physiological conditions and truncated species in cases of overexpression.…”

“…Truncated forms of intracellular Tau, which lack the C-terminus, are detected in cell models [18], [48], [49] and tangles from autopsy-confirmed AD brains [48], [50], [51]. Similar truncated species are found in cell culture media obtained from cellular models or CSF-Tau from transgenic mice models [15], [52], in addition to human CSF [18], [50], [53]. However, full-length forms of secreted Tau are also found in cell culture media [13], [14], murine ISF [47] and human CSF [53].…”

Immunological memory to hyperphosphorylated tau in asymptomatic individuals

“…Given the range of anti-tau specificities found in the current study, such antibody assays should be able to measure the response against as many different tau epitopes as possible. Various studies have described the use of the presence of tau fragments in CSF [24, 31, 34, 53] and plasma [27, 30] as marker for the diagnosis of AD. Recent studies by Meredith et al [44] and Barthélemy et al [6] show that some fragments are significantly more abundant than others and that discrimination of AD from control is dependent on the subset of tau species measured [44].…”

Divergent CSF alterations in two common tauopathies: Alzheimer's disease and progressive supranuclear palsy

“…15 , 30 , 31 Therefore we used novel CSF tau ELISAs designed to measure tau fragments containing N-terminal and mid-domain sequences. The absolute concentrations of tau fragments measured in the novel ELISAs were higher than those measured with AlzBio3.…”