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Single-cell transcriptomics has revealed specific glial activation states associated with the pathogenesis of neurodegenerative diseases, such as Alzheimer’s and Parkinson’s disease. While these findings may eventually lead to new therapeutic opportunities, little is known about how these glial responses are reflected by biomarker changes in bodily fluids. Such knowledge, however, appears crucial for patient stratification, as well as monitoring disease progression and treatment responses in clinical trials. Here, we took advantage of well-described mouse models of β-amyloidosis and α-synucleinopathy to explore cerebrospinal fluid (CSF) proteome changes related to their respective proteopathic lesions. Nontargeted liquid chromatography-mass spectrometry revealed that the majority of proteins that undergo age-related changes in CSF of either mouse model were linked to microglia and astrocytes. Specifically, we identified a panel of more than 20 glial-derived proteins that were increased in CSF of aged β-amyloid precursor protein- and α-synuclein-transgenic mice and largely overlap with previously described disease-associated glial genes identified by single-cell transcriptomics. Our results also show that enhanced shedding is responsible for the increase of several of the identified glial CSF proteins as exemplified for TREM2. Notably, the vast majority of these proteins can also be quantified in human CSF and reveal changes in Alzheimer’s disease cohorts. The finding that cellular transcriptome changes translate into corresponding changes of CSF proteins is of clinical relevance, supporting efforts to identify fluid biomarkers that reflect the various functional states of glial responses in cerebral proteopathies, such as Alzheimer’s and Parkinson’s disease.

Hydrocephalus, characterized by cerebral ventricular dilatation, is routinely attributed to primary defects in cerebrospinal fluid (CSF) homeostasis. This fosters CSF shunting as the leading reason for brain surgery in children despite considerable disease heterogeneity. In this study, by integrating human brain transcriptomics with whole-exome sequencing of 483 patients with congenital hydrocephalus (CH), we found convergence of CH risk genes in embryonic neuroepithelial stem cells. Of all CH risk genes, TRIM71/lin-41 harbors the most de novo mutations and is most specifically expressed in neuroepithelial cells. Mice harboring neuroepithelial cell-specific Trim71 deletion or CH-specific Trim71 mutation exhibit prenatal hydrocephalus. CH mutations disrupt TRIM71 binding to its RNA targets, causing premature neuroepithelial cell differentiation and reduced neurogenesis. Cortical hypoplasia leads to a hypercompliant cortex and secondary ventricular enlargement without primary defects in CSF circulation. These data highlight the importance of precisely regulated neuroepithelial cell fate for normal brain-CSF biomechanics and support a clinically relevant neuroprogenitor-based paradigm of CH.

β-glucocerebrosidase (GBA)-associated mutations are a significant risk factor for Parkinson’s disease (PD) that aggravate the disease pathology by upregulating the deposition of α-Synuclein (α-Syn). The resultant clinical profile varies for PD patients without GBA mutations. The current study aimed to identify the proteomic targets involved in the pathogenic pathways leading to the differential clinical presentation of GBA-associated PD. CSF samples (n = 32) were obtained from PD patients with GBA mutations (n = 22), PD patients without GBA mutations (n = 7), and healthy controls that were carriers of GBA mutations (n = 3). All samples were subjected to in-gel tryptic digestion followed by the construction of the spectral library and quantitative SWATH-based analysis. CSF α-Syn levels were reduced in both PDIdiopathic and PDGBA cases. Our SWATH-based mass spectrometric analysis detected 363 proteins involved in immune response, stress response, and cell signaling in various groups. Intergroup analysis showed that 52 proteins were significantly up- or downregulated in various groups. Of these 52 targets, 20 proteins were significantly altered in PDGBA cases only while 2 showed different levels in PDIdiopathic patients. Our results show that the levels of several pathologically relevant proteins, including Contactin-1, Selenium-binding protein 1, Adhesion G Protein-Coupled Receptor, and Apolipoprotein E are significantly different among the sporadic and genetic variants of PD and hint at aggravated synaptic damage, oxidative stress, neuronal loss, and aggregation of α-Syn in PDGBA cases.

Introduction Although the link between autoimmune thyroiditis and mental illnesses is well established, the precise underlying pathophysiology and the influence of anti-thyroid antibodies on diagnostic findings require further research. Patients and Methods A total of 530 patients with schizophreniform and affective syndromes were screened for anti-thyroid antibodies against thyroid peroxidase (TPO), thyroglobulin (TG), and thyroid-stimulating hormone receptor (TSH-R). The patient group analyzed here is a patient subgroup of a previously published cohort (Endres et al., 2020, Translational Psychiatry). The anti-thyroid antibody positive (N = 91) and negative (N = 439) patients were compared in terms of various clinical parameters, routine cerebrospinal fluid (CSF) findings, and the number of positive anti-neuronal antibodies in serum and/or CSF, as well as electroencephalography (EEG), magnetic resonance imaging (MRI), and [18 F]fluorodeoxyglucose positron emission tomography (FDG-PET) findings. Results Anti-TPO antibodies were increased in 17%, anti-TG antibodies in 15%, and anti-TSH-R antibodies in 2% of all patients. In CSF, higher protein concentrations (p = 0.018) and albumin quotients (p = 0.008) were found in the anti-thyroid antibody positive patient group. Also, there were more patients with elevated age-corrected albumin quotients in this group (p = 0.031). FDG-PET hypometabolism was significantly more frequent and the number of positive anti-neuronal intracellular antibodies was significantly higher in patients with anti-thyroid antibodies (p = 0.048, N = 29 and p = 0.032, N = 497 respectively). In addition, there was a trend for higher white blood cell (WBC) counts in all patients with anti-thyroid antibodies (p = 0.090). In the patient subgroup with anti-TPO antibodies this difference was statistically significant (p = 0.027). No relevant differences were found in the other CSF routine parameters, the number of anti-neuronal antibodies against cell surface antigens in serum and/or CSF, EEG and MRI findings. Discussion The present study provides evidence of impaired blood CSF barrier (BCSFB) function in patients with anti-TPO and anti-TG antibodies. An influence of anti-TG antibodies on BCSFB structures has been shown in previous laboratory studies, which reported that the antibodies bind to vascular smooth muscle cells. Due to BCSFB breakdown anti-thyroid antibodies might lead to increased autoimmune susceptibility. The alterations in the FDG-PET, WBC count, and anti-neuronal antibody findings against intracellular structures indicate that it could be useful to extend diagnostic investigations in patients with anti-thyroid antibodies. Further studies should investigate whether anti-thyroid antibodies can also act as “drivers of disease”.

Background YKL-40 (also known as Chitinase 3-like 1) is a glycoprotein produced by inflammatory, cancer and stem cells. Its physiological role is not completely understood but YKL-40 is elevated in the brain and cerebrospinal fluid (CSF) in several neurological and neurodegenerative diseases associated with inflammatory processes. Yet the precise characterization of YKL-40 in dementia cases is missing. Methods In the present study, we comparatively analysed YKL-40 levels in the brain and CSF samples from neurodegenerative dementias of different aetiologies characterized by the presence of cortical pathology and disease-specific neuroinflammatory signatures. Results YKL-40 was normally expressed in fibrillar astrocytes in the white matter. Additionally YKL-40 was highly and widely expressed in reactive protoplasmic cortical and perivascular astrocytes, and fibrillar astrocytes in sporadic Creutzfeldt-Jakob disease (sCJD). Elevated YKL-40 levels were also detected in Alzheimer’s disease (AD) but not in dementia with Lewy bodies (DLB). In AD, YKL-40-positive astrocytes were commonly found in clusters, often around β-amyloid plaques, and surrounding vessels with β-amyloid angiopathy; they were also distributed randomly in the cerebral cortex and white matter. YKL-40 overexpression appeared as a pre-clinical event as demonstrated in experimental models of prion diseases and AD pathology. CSF YKL-40 levels were measured in a cohort of 288 individuals, including neurological controls (NC) and patients diagnosed with different types of dementia. Compared to NC, increased YKL-40 levels were detected in sCJD (p 0.05, AUC = 0.71) or in DLB/Parkinson’s disease dementia (PDD) (p > 0.05, AUC = 0.70). Further, two independent patient cohorts were used to validate the increased CSF YKL-40 levels in sCJD. Additionally, increased YKL-40 levels were found in genetic prion diseases associated with the PRNP-D178N (Fatal Familial Insomnia) and PRNP-E200K mutations. Conclusions Our results unequivocally demonstrate that in neurodegenerative dementias, YKL-40 is a disease-specific marker of neuroinflammation showing its highest levels in prion diseases. Therefore, YKL-40 quantification might have a potential for application in the evaluation of therapeutic intervention in dementias with a neuroinflammatory component.

Stuendl et al. show that CSF exosomes of patients with Parkinson’s disease or dementia with Lewy bodies contain α-synuclein and induce α-synuclein aggregation in a reporter cell line. Thus, exosomes may support inter-neuronal transmission of α-synuclein pathology. CSF exosomal α-synuclein may serve as a biomarker in α-synuclein-related neurodegeneration., Extracellular α-synuclein has been proposed as a crucial mechanism for induction of pathological aggregate formation in previously healthy cells. In vitro, extracellular α-synuclein is partially associated with exosomal vesicles. Recently, we have provided evidence that exosomal α-synuclein is present in the central nervous system in vivo. We hypothesized that exosomal α-synuclein species from patients with α-synuclein related neurodegeneration serve as carriers for interneuronal disease transmission. We isolated exosomes from cerebrospinal fluid from patients with Parkinson’s disease, dementia with Lewy bodies, progressive supranuclear palsy as a non-α-synuclein related disorder that clinically overlaps with Parkinson’s disease, and neurological controls. Cerebrospinal fluid exosome numbers, α-synuclein protein content of cerebrospinal fluid exosomes and their potential to induce oligomerization of α-synuclein were analysed. The quantification of cerebrospinal fluid exosomal α-synuclein showed distinct differences between patients with Parkinson’s disease and dementia with Lewy bodies. In addition, exosomal α-synuclein levels correlated with the severity of cognitive impairment in cross-sectional samples from patients with dementia with Lewy bodies. Importantly, cerebrospinal fluid exosomes derived from Parkinson’s disease and dementia with Lewy bodies induce oligomerization of α-synuclein in a reporter cell line in a dose-dependent manner. Our data suggest that cerebrospinal fluid exosomes from patients with Parkinson’s disease and dementia with Lewy bodies contain a pathogenic species of α-synuclein, which could initiate oligomerization of soluble α-synuclein in target cells and confer disease pathology.

The purpose of this study is to characterize the spectrum of cerebrospinal fluid (CSF) findings in patients with posterior reversible encephalopathy syndrome (PRES)and determine its associations with severity of edema. In this retrospective cross-sectional study electronic medical reports were screened for patients with PRES. Clinical and laboratory data closest to onset of clinical symptoms were collected. Neuroimaging reports from all patients were categorized according to the presence of vasogenic edema,cytotoxic edema and contrast enhancement. From Jan 1999to Feb 2015, 87 patients with PRES and CSF findings were included. Mean total protein levels were 793 ± 929 mg/l. Median cell counts were 2/μl (IQR 1-4). Eight patients had cell counts[6/μl with a maximum of 41/μl. In 31 patients with extended CSF analysis, mean CSF/serum albuminquotient (QAlb) was 10.1 (IQR 6-17.3). An elevated QAlb (age-adjusted) was found in 74 % of these 31 patients. PRES patients with severe edema had higher mean total protein levels in CSF (mean difference = 407 mg/l; 95 %CI 187-628). Significant correlations were found for edema severity with levels of CSF protein (r = 0.48, p

Phosphospecific enrichment techniques and mass spectrometry (MS) are essential tools for comprehending the cellular phosphoproteome. Here, we report a fast and simple approach for low sequence-bias phosphoserine (pS) peptide capture and enrichment that is compatible with low biological or clinical sample input. The approach exploits molecularly imprinted polymers (MIPs, “plastic antibodies”) featuring tight neutral binding sites for pS or pY that are capable of cross-reacting with phosphopeptides of protein proteolytic digests. The versatility of the resulting method was demonstrated with small samples of whole-cell lysate from human embryonic kidney (HEK) 293T cells, human neuroblastoma SH-SY5Y cells, mouse brain or human cerebrospinal fluid (CSF). Following pre-fractionation of trypsinized proteins by strong cation exchange (SCX) chromatography, pS-MIP enrichment led to the identification of 924 phosphopeptides in the HEK 293T whole-cell lysate, exceeding the number identified by TiO2-based enrichment (230). Moreover, the phosphopeptides were extracted with low sequence bias and showed no evidence for the characteristic preference of TiO2 for acidic amino acids (aspartic and glutamic acid). Applying the method to human CSF led to the discovery of 47 phosphopeptides belonging to 24 proteins and revealed three previously unknown phosphorylation sites.

Eating behavior, body weight regulation, peripheral glucose metabolism, and cognitive function depend on adequate insulin action in the brain, and recent studies in humans suggested that impaired insulin action in the brain emerges upon fat intake, obesity, and genetic variants. As insulin enters into the brain in a receptor-mediated fashion, we hypothesized that whole-body insulin sensitivity might affect the transport of insulin into the brain and contribute to the aversive effect of insulin resistance in the central nervous system. In this study, we aimed to determine the ratio of insulin in the cerebrospinal fluid and serum to whole-body insulin sensitivity. Healthy human subjects participated in an oral glucose tolerance test to determine whole-body insulin sensitivity and underwent lumbar puncture. Blood and CSF concentrations of insulin were significantly correlated. The CSF/serum ratio for insulin was significantly associated with whole body insulin sensitivity with reduced insulin transported into the CSF in insulin-resistant subjects. Together, our data suggest that transport of insulin into the CSF relates to peripheral insulin sensitivity and impairs insulin action in the brain. This underlines the need for sensitizing measures in insulin-resistant subjects.

Multidimensional single-cell analyses of T cells have fueled the debate about whether there is extensive plasticity or ‘mixed’ priming of helper T cell subsets in vivo. Here, we developed an experimental framework to probe the idea that the site of priming in the systemic immune compartment is a determinant of helper T cell–induced immunopathology in remote organs. By site-specific in vivo labeling of antigen-specific T cells in inguinal (i) or gut draining mesenteric (m) lymph nodes, we show that i-T cells and m-T cells isolated from the inflamed central nervous system (CNS) in a model of multiple sclerosis (MS) are distinct. i-T cells were Cxcr6+, and m-T cells expressed P2rx7. Notably, m-T cells infiltrated white matter, while i-T cells were also recruited to gray matter. Therefore, we propose that the definition of helper T cell subsets by their site of priming may guide an advanced understanding of helper T cell biology in health and disease. Korn and colleagues demonstrate that the site of T cell priming (gut versus skin draining lymph nodes) dictates their effector phenotypes and homing to distal sites of immunopathology.