Altered sleep and EEG power in the P301S Tau transgenic mouse model

OBJECTIVE: Sleep disturbances are prevalent in human tauopathies yet despite the importance of sleep, little is known about its relationship with tau pathology. Here, we investigate this interaction by analyzing sleep and tau pathology throughout tauopathy disease progression in P301S human tau transgenic mice. METHODS: P301S and wild‐type mice were analyzed by electroencephalography (EEG)/electromyography at 3, 6, 9, and 11 months of age for sleep/wake time, EEG power, and homeostatic response. Cortical volume and tau pathology was also assessed by anti‐phospho‐tau AT8 staining. RESULTS: P301S tau mice had significantly decreased rapid eye movement (REM) sleep at 9 months of age and decreased REM and non‐REM (NREM) sleep as well as increased wakefulness at 11 months. Sleep loss was characterized by fewer wake, REM, and NREM bouts, increased wake bout duration, and decreased sleep bout duration. Decreased REM and NREM sleep was associated with increased brainstem tau pathology in the sublaterodorsal area and parafacial zone, respectively. P301S mice also showed increased EEG power at 6 and 9 months of age and decreased power at 11 months. Decreased EEG power was associated with decreased cortical volume. Despite sleep disturbances, P301S mice maintained homeostatic response to sleep deprivation. INTERPRETATION: Our results indicate that tau pathology is associated with sleep disturbances that worsen with age and these changes may be related to tau pathology in brainstem sleep regulating regions as well as neurodegeneration. Tau‐induced sleep changes could affect disease progression and be a marker for therapeutic efficacy in this and other tauopathy models

Neuronal activity regulates extracellular tau in vivo

Tau is primarily a cytoplasmic protein that stabilizes microtubules. However, it is also found in the extracellular space of the brain at appreciable concentrations. Although its presence there may be relevant to the intercellular spread of tau pathology, the cellular mechanisms regulating tau release into the extracellular space are not well understood. To test this in the context of neuronal networks in vivo, we used in vivo microdialysis. Increasing neuronal activity rapidly increased the steady-state levels of extracellular tau in vivo. Importantly, presynaptic glutamate release is sufficient to drive tau release. Although tau release occurred within hours in response to neuronal activity, the elimination rate of tau from the extracellular compartment and the brain is slow (half-life of ∼11 d). The in vivo results provide one mechanism underlying neuronal tau release and may link trans-synaptic spread of tau pathology with synaptic activity itself

Endothelial ether lipids link the vasculature to blood pressure, behavior, and neurodegeneration

Vascular disease contributes to neurodegeneration, which is associated with decreased blood pressure in older humans. Plasmalogens, ether phospholipids produced by peroxisomes, are decreased in Alzheimer's disease, Parkinson's disease, and other neurodegenerative disorders. However, the mechanistic links between ether phospholipids, blood pressure, and neurodegeneration are not fully understood. Here, we show that endothelium-derived ether phospholipids affect blood pressure, behavior, and neurodegeneration in mice. In young adult mice, inducible endothelial-specific disruption of PexRAP, a peroxisomal enzyme required for ether lipid synthesis, unexpectedly decreased circulating plasmalogens. PexRAP endothelial knockout (PEKO) mice responded normally to hindlimb ischemia but had lower blood pressure and increased plasma renin activity. In PEKO as compared with control mice, tyrosine hydroxylase was decreased in the locus coeruleus, which maintains blood pressure and arousal. PEKO mice moved less, slept more, and had impaired attention to and recall of environmental events as well as mild spatial memory deficits. In PEKO hippocampus, gliosis was increased, and a plasmalogen associated with memory was decreased. Despite lower blood pressure, PEKO mice had generally normal homotopic functional connectivity by optical neuroimaging of the cerebral cortex. Decreased glycogen synthase kinase-3 phosphorylation, a marker of neurodegeneration, was detected in PEKO cerebral cortex. In a co-culture system, PexRAP knockdown in brain endothelial cells decreased glycogen synthase kinase-3 phosphorylation in co-cultured astrocytes that was rescued by incubation with the ether lipid alkylglycerol. Taken together, our findings suggest that endothelium-derived ether lipids mediate several biological processes and may also confer neuroprotection in mice

Sleep in Alzheimer's Disease–Beyond Amyloid

Sleep disorders are prevalent in Alzheimer's disease (AD) and a major cause of institutionalization. Like AD pathology, sleep abnormalities can appear years before cognitive decline and may be predictive of dementia. A bidirectional relationship between sleep and amyloid β (Aβ) has been well established with disturbed sleep and increased wakefulness leading to increased Aβ production and decreased Aβ clearance; whereas Aβ deposition is associated with increased wakefulness and sleep disturbances. Aβ fluctuates with the sleep-wake cycle and is higher during wakefulness and lower during sleep. This fluctuation is lost with Aβ deposition, likely due to its sequestration into amyloid plaques. As such, Aβ is believed to play a significant role in the development of sleep disturbances in the preclinical and clinical phases of AD. In addition to Aβ, the influence of tau AD pathology is likely important to the sleep disturbances observed in AD. Abnormal tau is the earliest observable AD-like pathology in the brain with abnormal tau phosphorylation in many sleep regulating regions such as the locus coeruleus, dorsal raphe, tuberomammillary nucleus, parabrachial nucleus, and basal forebrain prior to the appearance of amyloid or cortical tau pathology. Furthermore, human tau mouse models exhibit AD-like sleep disturbances and sleep changes are common in other tauopathies including frontotemporal dementia and progressive supranuclear palsy. Together these observations suggest that tau pathology can induce sleep disturbances and may play a large role in the sleep disruption seen in AD. To elucidate the relationship between sleep and AD it will be necessary to not only understand the role of amyloid but also tau and how these two pathologies, together with comorbid pathology such as alpha-synuclein, interact and affect sleep regulation in the brain. Keywords: Alzheimer's disease, Sleep, Amyloid, Tau, Alpha-synuclei

Mapt deletion fails to rescue premature lethality in two models of sodium channel epilepsy

Deletion of Mapt, encoding the microtubuleâ binding protein Tau, prevents disease in multiple genetic models of hyperexcitability. To investigate whether the effect of Tau depletion is generalizable across multiple sodium channel geneâ linked models of epilepsy, we examined the Scn1bâ /â mouse model of Dravet syndrome, and the Scn8aN1768D/+ model of Early Infantile Epileptic Encephalopathy. Both models display severe seizures and early mortality. We found no prolongation of survival between Scn1bâ /â ,Mapt+/+, Scn1bâ /â ,Mapt+/â , or Scn1bâ /â ,Maptâ /â mice or between Scn8aN1768D/+,Mapt+/+, Scn8aN1768D/+,Mapt+/â , or Scn8aN1768D/+,Maptâ /â mice. Thus, the effect of Mapt deletion on mortality in epileptic encephalopathy models is gene specific and provides further mechanistic insight.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145566/1/acn3599.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145566/2/acn3599_am.pd

Smaug/SAMD4A Restores Translational Activity of CUGBP1 and Suppresses CUG-Induced Myopathy

<div><p>We report the identification and characterization of a previously unknown suppressor of myopathy caused by expansion of CUG repeats, the mutation that triggers Myotonic Dystrophy Type 1 (DM1). We screened a collection of genes encoding RNA–binding proteins as candidates to modify DM1 pathogenesis using a well established <i>Drosophila</i> model of the disease. The screen revealed <i>smaug</i> as a powerful modulator of CUG-induced toxicity. Increasing <i>smaug</i> levels prevents muscle wasting and restores muscle function, while reducing its function exacerbates CUG-induced phenotypes. Using human myoblasts, we show physical interactions between human Smaug (SMAUG1/SMAD4A) and CUGBP1. Increased levels of SMAUG1 correct the abnormally high nuclear accumulation of CUGBP1 in myoblasts from DM1 patients. In addition, augmenting SMAUG1 levels leads to a reduction of inactive CUGBP1-eIF2α translational complexes and to a correction of translation of MRG15, a downstream target of CUGBP1. Therefore, Smaug suppresses CUG-mediated muscle wasting at least in part via restoration of translational activity of CUGBP1.</p></div

SMAUG1 and CUGBP1 co-localize and physically interact in DM1 myoblasts.

<p>A. Immunofluorescense and in situ images of DM1 myoblasts transfected with GFP. In control DM1 myoblasts transfected with GFP (green) CUGBP1 is predominantly in the nucleus (red); CUG foci are detected in the nuclei with a Cy3-labelled 5′-CAG-3′ LNA probe (CAG probe, white). B–C. Immunofluorescense and in situ images of DM1 myoblasts transfected with SMAUG1-ECFP. SMAUG1 is detected in the cytoplasm (SMAUG1-ECFP, green). Note that nuclear CUGBP1 signal (α-CUGBP1, red) is clearly diminished in DM1 myoblasts transfected with SMAUG1 (B, arrowhead). Longer exposure of CUGBP1 signal shows cytoplasmic CUGBP1 (C) and its co-localization with SMAUG1 in granules (arrows). D. Bar graph representing the intensity of CUGBP1 nuclear signal in DM1 myoblasts transfected with GFP (DM1-GFP, green bar), versus DM1 myoblasts transfected with SMAUG1 (DM1-SMAUG1, blue bar). Data was analyzed with ANOVA followed by Student's t test, p<0.0001. Black dots represent individual observations, red lines are the standard error of the mean. E. Western blot revealing co-immunoprecipitation between CUGBP1 and human SMAUG1 in extracts from SMAUG1-V5-transfected normal and DM1 human myoblasts. Pull down was carried out using anti-CUGBP1 antibody. SMAUG1 was visualized with anti-V5-HRP antibody. White lines in A–C delineate the nuclei. Scale bar: A–C: 10 µm.</p

SMAUG1 reduces inactive CUGBP1/pS51-eIF2α translational complexes and recuperates normal levels of MRG15 protein in DM1 myoblasts and fibroblasts.

<p>A–B. Protein levels of total CUGBP1 and eIF2α in control and DM1 myoblasts (A) and fibroblasts (B) were detected by Western blotting of cytoplasmic fractions (Western). β-actin serves as a loading control. CUGBP1 levels are compared in untransfected and SMAUG1-transfected normal and DM1 myoblasts. Quantification is based in two experiments in myoblasts and two experiments in fibroblasts. Material immunoprecipitated with CUGBP1 antibodies was probed with antibody to specific inactive pS51-eIF2α (CUGBP1-IP). Note that inactive pS51-eIF2α is not detected after <i>SMAUG1</i> transfection. IgGs, heavy chains of immunoglobulins detected on the same filter. IP was repeated three times in myoblasts and three times in fibroblasts (see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003445#pgen.1003445.s007" target="_blank">Figure S7</a>). C. SMAUG1 recuperates normal levels of MRG15 protein in DM1 myoblasts and fibroblasts. Nuclear proteins of normal and DM1 myoblasts were examined by Western blotting with antibodies to MRG15. The filter was re-probed with antibodies to β-actin. The level of MRG15 in SMAUG1-transfected myoblasts are shown compared to untransfected normal and DM1 myoblasts from two experiments. Quantifications were performed using ImageJ Gel Analyzer software.</p

SMAUG1 expression reduces nuclear accumulation of CUGBP1, and both proteins co-localize in cytoplasmic granules.

<p>Immunofluorescense and in situ images of COSM6 cells. A. Expanded CUG repeat-transfected COSM6 cells show accumulation of the transcripts in nuclear foci (detected with a Cy3-labelled 5′-CAG-3′ LNA probe, white), and increased nuclear CUGBP1 signal (arrowhead) (α-CUGBP1, red). B. COSM6 cells co-transfected with CUGs and SMAUG1-ECFP show cytoplasmic signal of SMAUG1 (SMAUG1-ECFP, green) and CUG nuclear foci (CAG probe, white). These cells have decreased CUGBP1 nuclear signal (arrowhead) (α-CUGBP1, red); in addition, CUGBP1 co-localizes with SMAUG1 in cytoplasmic granules (arrow). C. Untransfected (arrowhead) and GFP-transfected (arrow) cells show similar nuclear CUGBP signal (α-CUGBP1, red). White lines in A–B delineate the nuclei. Scale bar: A–C: 10 µm.</p