Citations

Lewy body dementia (LBD) is an often misdiagnosed and mistreated neurodegenerative disorder clinically characterized by the emergence of neuropsychiatric symptoms followed by motor impairment. LBD falls within an undefined range between Alzheimer’s disease (AD) and Parkinson’s disease (PD) due to the potential pathogenic synergistic effects of tau, beta-amyloid (Aβ), and alpha-synuclein (αsyn). A lack of reliable and relevant animal models hinders the elucidation of the molecular characteristics and phenotypic consequences of these interactions. Here, the goal was to evaluate whether the viral-mediated overexpression of αsyn in adult hTau and APP/PS1 mice or the overexpression of tau in Line 61 hThy1-αsyn mice resulted in pathology and behavior resembling LBD. The transgenes were injected intravenously via the tail vein using AAV-PHP.eB in 3-month-old hThy1-αsyn, hTau, or APP/PS1 mice that were then aged to 6-, 9-, and 12-months-old for subsequent phenotypic and histological characterization. Although we achieved the widespread expression of αsyn in hTau and tau in hThy1-αsyn mice, no αsyn pathology in hTau mice and only mild tau pathology in hThy1-αsyn mice was observed. Additionally, cognitive, motor, and limbic behavior phenotypes were not affected by overexpression of the transgenes. Furthermore, our APP/PS1 mice experienced premature deaths starting at 3 months post-injection (MPI), therefore precluding further analyses at later time points. An evaluation of the remaining 3-MPI indicated no αsyn pathology or cognitive and motor behavioral changes. Taken together, we conclude that the overexpression of αsyn in hTau and APP/PS1 mice and tau in hThy1-αsyn mice does not recapitulate the behavioral and neuropathological phenotypes observed in LBD.

Abstract Neuropathological assessment at autopsy is the gold standard for diagnosing neurodegenerative disorders. We aimed to develop a pipeline for diagnosing Alzheimer's disease and other tauopathies, including corticobasal degeneration, globular glial tauopathy, Pick’s disease, and progressive supranuclear palsy. We used deep learning (DL)-based approach called clustering-constrained-attention multiple instance learning (CLAM) on whole slide images (WSIs) of tau immunohistochemistry in three brain regions from 120 patients. We also augmented gradient-weighted class activation mapping (Grad-CAM) to the model for visualizing cellular-level evidence in the model’s decisions. The model using the sections of cingulate and superior frontal gyri achieved the highest area under the curve (0.970±0.037) and diagnostic accuracy (0.873±0.087). Grad-CAM showed the highest attention in known pathognomonic tau lesions for each disease (e.g., Pick bodies for Pick’s disease). Our findings supported the feasibility of the DL-based approach for the classification task on WSIs, which encouraged further investigation, especially focusing on clinicopathological correlation studies.

Abstract Neuropathological assessment at autopsy is the gold standard for diagnosing neurodegenerative disorders. We aimed to develop a pipeline for diagnosing Alzheimer's disease and other tauopathies, including corticobasal degeneration, globular glial tauopathy, Pick’s disease, and progressive supranuclear palsy. We used deep learning (DL)-based approach called clustering-constrained-attention multiple instance learning (CLAM) on whole slide images (WSIs) of tau immunohistochemistry in three brain regions from 120 patients. We also augmented gradient-weighted class activation mapping (Grad-CAM) to the model for visualizing cellular-level evidence in the model’s decisions. The model using the sections of cingulate and superior frontal gyri achieved the highest area under the curve (0.970±0.037) and diagnostic accuracy (0.873±0.087). Grad-CAM showed the highest attention in known pathognomonic tau lesions for each disease (e.g., Pick bodies for Pick’s disease). Our findings supported the feasibility of the DL-based approach for the classification task on WSIs, which encouraged further investigation, especially focusing on clinicopathological correlation studies.

Frontotemporal dementia and amyotrophic lateral sclerosis (FTD-ALS) are associated with both a repeat expansion in the C9orf72 gene and mutations in the TANK-binding kinase 1 ( TBK1 ) gene. We found that TBK1 is phosphorylated in response to C9orf72 poly(Gly-Ala) [poly(GA)] aggregation and sequestered into inclusions, which leads to a loss of TBK1 activity and contributes to neurodegeneration. When we reduced TBK1 activity using a TBK1-R228H (Arg 228 →His) mutation in mice, poly(GA)-induced phenotypes were exacerbated. These phenotypes included an increase in TAR DNA binding protein 43 (TDP-43) pathology and the accumulation of defective endosomes in poly(GA)-positive neurons. Inhibiting the endosomal pathway induced TDP-43 aggregation, which highlights the importance of this pathway and TBK1 activity in pathogenesis. This interplay between C9orf72 , TBK1 , and TDP-43 connects three different facets of FTD-ALS into one coherent pathway.

Abstract Introduction Alzheimer's disease (AD) biomarkers are increasingly more reliable in predicting neuropathology. To facilitate interpretation of phosphorylated tau sites as an early fluid biomarker, we sought to characterize which neurofibrillary tangle maturity levels (pretangle, intermediary 1, mature tangle, intermediary 2, and ghost tangle) are recognized. Methods We queried the Florida Autopsied Multi‐Ethnic (FLAME) cohort for cases ranging from Braak stages I through VI, excluding non‐AD neuropathologies and tauopathies. Thioflavin‐S staining was compared to immunohistochemical measures of phosphorylated threonine (pT) 181, pT205, pT217, and pT231 in two hippocampal subsectors across n = 24 cases. Results Each phosphorylated tau site immunohistochemically labeled early neurofibrillary tangle maturity levels compared to advanced levels recognized by thioflavin‐S. Hippocampal burden generally increased with each Braak stage. Discussion These results provide neurobiologic evidence that these phosphorylated tau fluid biomarker sites are present during early neurofibrillary tangle maturity levels and may explain why these fluid biomarker measures are observed before symptom onset. Highlights Immunohistochemical evaluation of four phosphorylated tau fluid biomarker sites. Earlier neurofibrillary tangle maturity levels recognized by phosphorylated tau in proline‐rich region. Advanced tangle pathology is elevated in the subiculum compared to the cornu ammonis 1 of the hippocampus. Novel semi‐quantitative frequency to calculate tangle maturity frequency.

G 4 C 2 repeat–derived poly(GR) plays a key role in mediating TDP-43 mislocalization and aggregation in vitro and in vivo.

Abstract Genetic variants that define two distinct haplotypes at the TMEM106B locus have been implicated in multiple neurodegenerative diseases and in healthy brain ageing. In frontotemporal dementia (FTD), the high expressing TMEM106B risk haplotype was shown to increase susceptibility for FTD with TDP-43 inclusions (FTD-TDP) and to modify disease penetrance in progranulin mutation carriers (FTD-GRN). To elucidate the biological function of TMEM106B and determine whether lowering TMEM106B may be a viable therapeutic strategy, we performed brain transcriptomic analyses in 8-month-old animals from our recently developed Tmem106b−/− mouse model. We included 10 Tmem106b+/+ (wild-type), 10 Tmem106b+/− and 10 Tmem106−/− mice. The most differentially expressed genes (153 downregulated and 60 upregulated) were identified between Tmem106b−/− and wild-type animals, with an enrichment for genes implicated in myelination-related cellular processes including axon ensheathment and oligodendrocyte differentiation. Co-expression analysis also revealed that the most downregulated group of correlated genes was enriched for myelination-related processes. We further detected a significant loss of OLIG2-positive cells in the corpus callosum of Tmem106b−/− mice, which was present already in young animals (21 days) and persisted until old age (23 months), without worsening. Quantitative polymerase chain reaction revealed a reduction of differentiated but not undifferentiated oligodendrocytes cellular markers. While no obvious changes in myelin were observed at the ultrastructure levels in unchallenged animals, treatment with cuprizone revealed that Tmem106b−/− mice are more susceptible to cuprizone-induced demyelination and have a reduced capacity to remyelinate, a finding which we were able to replicate in a newly generated Tmem106b CRISPR/cas9 knock-out mouse model. Finally, using a TMEM106B HeLa knock-out cell line and primary cultured oligodendrocytes, we determined that loss of TMEM106B leads to abnormalities in the distribution of lysosomes and PLP1. Together these findings reveal an important function for TMEM106B in myelination with possible consequences for therapeutic strategies aimed at lowering TMEM106B levels.