Pathogenic tau recruits wild-type tau into brain inclusions and induces gut degeneration in transgenic SPAM mice

Abstract

Pathological tau inclusions are neuropathologic hallmarks of many neurodegenerative diseases. We generated and characterized a transgenic mouse model expressing pathogenic human tau with S320F and P301S aggregating mutations (SPAM) at transgene levels below endogenous mouse tau protein levels. This mouse model develops a predictable temporal progression of tau pathology in the brain with biochemical and ultrastructural properties akin to authentic tau inclusions. Surprisingly, pathogenic human tau extensively recruited endogenous mouse tau into insoluble aggregates. Despite the early onset and rapid progressive nature of tau pathology, major neuroinflammatory and transcriptional changes were only detectable at later time points. Moreover, tau SPAM mice are the first model to develop loss of enteric neurons due to tau accumulation resulting in a lethal phenotype. With moderate transgene expression, rapidly progressing tau pathology, and a highly predictable lethal phenotype, the tau SPAM model reveals new associations of tau neurotoxicity in the brain and intestinal tract.

Novel Conformation-Dependent Tau Antibodies Are Modulated by Adjacent Phosphorylation Sites

“…Furthermore, despite not containing phospho-mimetics at these sites, pro-aggregant P301L/S320F tau showed enhanced signal compared to WT 0N/4R. This increase could be due to the P301L/S320F mutations promoting conformation changes within tau or indirectly due to robust aggregation that also results in tau hyperphosphorylation, which can occur in HEK293T cells [ 24 , 25 ]. The signal ratio of 4E(210–217) tau/WT tau is 36.1 for 5E2 and 34.5 for 2F12, the signal ratio of 12E tau/WT tau is 30.7 for 5E2 and 39.9 for 2F12, while the signal ratio of P301L/S320F tau to WT tau is 13.4 for 5E2 and 25 for 2F12.…”

“…Immunohistochemistry (IHC) was performed using mouse brain tissue from tau KO [ 26 ], non-transgenic (nTg), and pathogenic P301S/S320F 0N/4R tau (SPAM) transgenic mice [ 25 ]. Notably, SPAM mice developed neuropathology throughout the cerebral cortex and hippocampus.…”

“…For IHC, brains were fixed in 70% ethanol/150 mM solution, embedded in paraffin, and sectioned at 5 µm. For biochemical analysis, brain tissue from SPAM (S320F/P301S 0N/4R tau) transgenic [ 25 ], non-transgenic (nTg), and tau-null mice [ 26 ] brain tissue was isolated and frozen. For Western blotting, mouse tissue was sonicated in 4% SDS/50mM Tris, pH7.5 and heated for 10 min at 95 °C.…”

“…For IHC, brains were fixed in 70% ethanol/150 mM solution, embedded in paraffin, and sectioned at 5 µm. For biochemical analysis, brain tissue from SPAM (S320F/P301S 0N/4R tau) transgenic [25], non-transgenic (nTg), and tau-null mice [26] brain tissue was isolated and frozen. For Western blotting, mouse tissue was sonicated in 4% SDS/50mM Tris, pH7.5 and heated for 10 min at 95 • C. Following determination of protein concentrations with the BCA assay with BSA as a standard, 5× sample buffer was added to a final 1× concentration (10 mM Tris, pH 6.8, 1 mM EDTA, 40 mM DTT, 0.005% bromophenol blue, 0.0025% pyronin yellow, 1% SDS, 10% sucrose) and samples were heated for 10 min at 95 • C, and stored at −80 • C until further use.…”

Gut-brain connections in neurodegenerative disease: immunotherapeutic targeting of Bin1 in inflammatory bowel disease and Alzheimer’s disease

“…The gut microbiome has a major impact on ENS structure and function, including to orchestrate bowel movement ( Carabotti et al, 2015 ; Rao and Gershon, 2016 ), acting as a “second brain” that shares many features with the CNS ( Derkinderen et al, 2021 ). Indeed, ENS dysfunction associated with neuronal loss has been directly linked to aging and dementia ( Xia et al, 2022 ). Constipation is an early sign of AD and Parkinson’s disease ( Camacho et al, 2021 ; Nakase et al, 2022 ) and regular use of laxatives is associated with a higher risk of dementia ( Yang et al, 2023 ).…”