Impaired burrowing is the most prominent behavioral deficit of aging htau mice

htau mice are deficient of murine tau but express all six human tau isoforms, leading to gradual tau misprocessing and aggregation in brain areas relevant to Alzheimer's disease. Whilst histopathological changes in htau mice have been researched in the past, we focused here on functional consequences of human tau accumulation. htau mice and their background controls - murine tau knock-out (mtau-/-) and C57Bl/6J mice - underwent a comprehensive trial battery to investigate species-specific behaviour, locomotor activity, emotional responses, exploratory traits, spatial and recognition memory as well as acquisition, retention and extinction of contextual fear at two-, four-, six-, nine- and twelve-months-of-age. In htau mice, tau pathology was already present at two-months-of-age, whereas deficits in food burrowing and spatial working memory were first noted at four-months-of-age. At later stages the presence of human tau on a murine tau knockout background appeared to guard cognitive performance; as mtau-/- but not htau mice differed from C57Bl/6J mice in the food burrowing, spontaneous alternation and object discrimination tasks. Aging mtau-/- mice also exhibited increased body mass and locomotor activity. This data highlights that reduced food burrowing performance was the most robust aspect of the htau phenotype with ageing. htau and mtau-/-deficits in food burrowing pointed at the necessity of intact tau systems for daily life activities. Whilst some htau and mtau-/- deficits overlap, age differences between the two genotypes may reflect distinct functional effects and compared to C57Bl/6J mice, the htau phenotype appeared stronger than the mtau-/- phenotype at young ages but milder with ageing

A novel role for the immunophilin FKBP52 in motor coordination

FKBP52 is a ubiquitously distributed immunophilin that has been associated with wideranging functions in cell signalling as well as hormonal and stress responses. Amongst other pathways, it acts via complex-formation with corticosteroid receptors and has consequently been associated with stress- and age-related neurodegenerative disorders including Alzheimer’s and Parkinson’s diseases. Reduced levels of FKBP52 have been linked to tau dysfunction and amyloid beta toxicity in AD. However, FKBP52’s role in cognition and neurodegenerative disorder-like phenotypes remained to be elucidated. The present study aimed therefore at investigating the cognitive and behavioural effects of reduced FKBP52 levels of genetically modified mice during ageing. Female and male FKBP52+/+, FKBP52+/- and FKBP52-/- mice were compared at two-, ten-, twelve-, fifteenand eighteen-months-of-age in a series of behavioural tests covering specie-specific behaviour, motor activity and coordination, fear-, spatial and recognition memory as well as curiosity and emotionality. Whilst cognitively unimpaired, FKBP52+/- mice performed worse on an accelerating rotating rod than FKBP52+/+ littermates across all age-groups suggesting that FKBP52 is involved in processes controlling motor coordination. This deficit did not exacerbate with age but did worsen with repeated testing; pointing towards a role for FKBP52 in learning of tasks requiring motor coordination abilities. This study contributes to the knowledge base of FKBP52’s implication in neurodegenerative diseases by demonstrating that FKBP52 by itself does not directly affect cognition and may therefore rather play an indirect, modulatory role in the functional pathology of AD, whereas it directly affects motor coordination, an early sign of neurodegenerative damages to the brain

NAD-biosynthetic enzyme NMNAT1 reduces early behavioral impairment in the htau mouse model of tauopathy

NAD metabolism and the NAD biosynthetic enzymes nicotinamide nucleotide adenylyltransferases (NMNATs) are thought to play a key neuroprotective role in tauopathies, including Alzheimer’s disease. Here, we investigated whether modulating the expression of the NMNAT nuclear isoform NMNAT1, which is important for neuronal maintenance, influences the development of behavioral and neuropathological abnormalities in htau mice, which express non-mutant human tau isoforms and represent a model of tauopathy relevant to Alzheimer’s disease. Prior to the development of cognitive symptoms, htau mice exhibit tau hyperphosphorylation associated with a selective deficit in food burrowing, a behavior reminiscent to activities of daily living which are impaired early in Alzheimer’s disease. We crossed htau mice with Nmnat1 transgenic and knockout mice and tested the resulting offspring until the age of 6 months. We show that overexpression of NMNAT1 ameliorates the early deficit in food burrowing characteristic of htau mice. At 6 months of age, htau mice did not show neurodegenerative changes in both the cortex and hippocampus, and these were not induced by downregulating NMNAT1 levels. Modulating NMNAT1 levels produced a corresponding effect on NMNAT enzymatic activity but did not alter NAD levels in htau mice. Although changes in local NAD levels and subsequent modulation of NAD-dependent enzymes cannot be ruled out, this suggests that the effects seen on behavior may be due to changes in tau phosphorylation. Our results suggest that increasing NMNAT1 levels can slow the progression of symptoms and neuropathological features of tauopathy, but the underlying mechanisms remain to be established

CDK12 inhibition reduces abnormalities in cells from patients with myotonic dystrophy and in a mouse model

Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Myotonic dystrophy type 1 (DM1) is an RNA-based disease with no current treatment. It is caused by a transcribed CTG repeat expansion within the 3' untranslated region of the dystrophia myotonica protein kinase (DMPK) gene. Mutant repeat expansion transcripts remain in the nuclei of patients' cells, forming distinct microscopically detectable foci that contribute substantially to the pathophysiology of the condition. Here, we report small-molecule inhibitors that remove nuclear foci and have beneficial effects in the HSALR mouse model, reducing transgene expression, leading to improvements in myotonia, splicing, and centralized nuclei. Using chemoproteomics in combination with cell-based assays, we identify cyclin-dependent kinase 12 (CDK12) as a druggable target for this condition. CDK12 is a protein elevated in DM1 cell lines and patient muscle biopsies, and our results showed that its inhibition led to reduced expression of repeat expansion RNA. Some of the inhibitors identified in this study are currently the subject of clinical trials for other indications and provide valuable starting points for a drug development program in DM1