TREM2 expression in the brain and biological fluids in prion diseases.

Triggering receptor expressed on myeloid cells 2 (TREM2) is an innate immune cell surface receptor that regulates microglial function and is involved in the pathophysiology of several neurodegenerative diseases. Its soluble form (sTREM2) results from shedding of the TREM2 ectodomain. The role of TREM2 in prion diseases, a group of rapidly progressive dementias remains to be elucidated. In the present study, we analysed the expression of TREM2 and its main sheddase ADAM10 in the brain of sporadic Creutzfeldt-Jakob disease (sCJD) patients and evaluated the role of CSF and plasma sTREM2 as a potential diagnostic marker of prion disease. Our data indicate that, compared to controls, TREM2 is increased in sCJD patient brains at the mRNA and protein levels in a regional and subtype dependent fashion, and expressed in a subpopulation of microglia. In contrast, ADAM10 is increased at the protein, but not the mRNA level, with a restricted neuronal expression. Elevated CSF sTREM2 is found in sCJD, genetic CJD with mutations E200K and V210I in the prion protein gene (PRNP), and iatrogenic CJD, as compared to healthy controls (HC) (AUC = 0.78-0.90) and neurological controls (AUC = 0.73-0.85), while CSF sTREM2 is unchanged in fatal familial insomnia. sTREM2 in the CSF of cases with Alzheimer's disease, and multiple sclerosis was not significantly altered in our series. CSF sTREM2 concentrations in sCJD are PRNP codon 129 and subtype-related, correlate with CSF 14-3-3 positivity, total-tau and YKL-40, and increase with disease progression. In plasma, sTREM2 is increased in sCJD compared with HC (AUC = 0.80), displaying positive correlations with plasma total-tau, neurofilament light, and YKL-40. We conclude that comparative study of TREM2 in brain and biological fluids of prion diseases reveals TREM2 to be altered in human prion diseases with a potential value in target engagement, patient stratification, and disease monitoring.

Seeding variability of different alpha synuclein strains in synucleinopathies.

OBJECTIVES: Currently, the exact reasons why different α-synucleinopathies exhibit variable pathologies and phenotypes are still unknown. A potential explanation may be the existence of distinctive α-synuclein conformers or strains. Here, we intend to analyze the seeding activity of dementia with Lewy bodies (DLB) and Parkinson's disease (PD) brain-derived α-synuclein seeds by real-time quaking-induced conversion (RT-QuIC) and to investigate the structure and morphology of the α-synuclein aggregates generated by RT-QuIC. METHODS: A misfolded α-synuclein-enriched brain fraction from frontal cortex and substantia nigra pars compacta tissue, isolated by several filtration and centrifugation steps, was subjected to α-synuclein/RT-QuIC analysis. Our study included neuropathologically well-characterized cases with DLB, PD, and controls (Ctrl). Biochemical and morphological analyses of RT-QuIC products were conducted by western blot, dot blot analysis, Raman spectroscopy, atomic force microscopy, and transmission electron microscopy. RESULTS: Independently from the brain region, we observed different seeding kinetics of α-synuclein in the RT-QuIC in patients with DLB compared to PD and Ctrl. Biochemical characterization of the RT-QuIC product indicated the generation of a proteinase K-resistant and fibrillary α-synuclein species in DLB-seeded reactions, whereas PD and control seeds failed in the conversion of wild-type α-synuclein substrate. INTERPRETATION: Structural variances of α-synuclein seeding kinetics and products in DLB and PD indicated, for the first time, the existence of different α-synuclein strains in these groups. Therefore, our study contributes to a better understanding of the clinical heterogeneity among α-synucleinopathies, offers an opportunity for a specific diagnosis, and opens new avenues for the future development of strain-specific therapies. Ann Neurol 2019;85:691-703.

Quantification of CSF biomarkers using an electrochemiluminescence-based detection system in the differential diagnosis of AD and sCJD.

The identification of reliable diagnostic tools for the differential diagnosis between sporadic Creutzfeldt-Jakob Disease (sCJD) and Alzheimer's disease (AD) remains impeded by the existing clinical, neuropathological and molecular overlap between both diseases. The development of new tools for the quantitative measurement of biomarkers is gaining experimental momentum due to recent advances in high-throughput screening analysis and with the optimization of assays for their quantification in biological fluids, including cerebrospinal fluid (CSF). Electrochemiluminescence (ECL)-based immunoassays have demonstrated to achieve clinical quality performance in a variety of sample types due to its high sensitivity and dynamic range. Here, we quantified the CSF levels of Tau-protein, ß-amyloid 1-42 (Aß42) and α-synuclein, as important biomarkers in CSF used in the differential diagnosis of neurodegenerative disorders in 12 AD, 12 sCJD and 12 control cases by singleplex ECL-based technology. Its performance has been compared to classical enzyme-linked immunosorbent assays (ELISA) to confront their clinical accuracy. ECL-based technology validates previous data obtained with ELISA and presents a higher performance in the discrimination of three analysed groups as determined by increased area under the curve (AUC) values for the three biomarkers. Importantly, α-synuclein levels detected by ECL allow an excellent discrimination between sCJD cases and AD and control cases, unveiling a new clinical approach for the differential diagnosis of sCJD.

Searching for new genetic risk factors for neuropsychiatric disorders in expression databases.

Genetic variations might contribute to differences in protein activities and gene expression levels observed in complex genetic traits, like neuropsychiatric disease. This finding motivated the development of original approaches using expression studies to guide the finding of new genetic variations. We extended this approach to new genes selected from microarrays studies of brain samples of patients with Alzheimer's disease, major depressive disorder, bipolar affective disorder, and sporadic Creutzfeldt-Jakob disease. The CLCbio Workbench Combined version 3.6.2 was initially used to build expression sites tags (ESTs) and mRNA files retrieved, respectively, from the Goldenpath (UCSC) and NCBI databases and latter to perform multiple batches of Smith-Waterman alignments. The total of 438 ESTs sequences were selected after proper stringent parameters were applied to the first set of mismatches. The annotation revealed various classes of variations, most of them deletions ranging from 1 to 10 pb. These deletions were present in coding regions, 5' and 3' UTR regions. Deletions are often associated to major genetic syndromes with dysmorphic features; however, recent studies show that common microdeletions might be highly associated with common neuropsychiatric disorders.