mTh1 driven expression of hTDP-43 results in typical ALS/FTLD neuropathological symptoms.

Transgenic mouse models are indispensable tools to mimic human diseases and analyze the effectiveness of related new drugs. For a long time amyotrophic lateral sclerosis (ALS) research depended on only a few mouse models that exhibit a very strong and early phenotype, e.g. SOD1 mice, resulting in a short treatment time window. By now, several models are available that need to be characterized to highlight characteristics of each model. Here we further characterized the mThy1-hTDP-43 transgenic mouse model TAR6/6 that overexpresses wild type human TARDBP, also called TDP-43, under control of the neuronal Thy-1 promoter presented by Wils and colleagues, 2010, by using biochemical, histological and behavioral readouts. Our results show that TAR6/6 mice exhibit a strong TDP-43 expression in the hippocampus, spinal cord, hypothalamus and medulla oblongata. Apart from prominent protein expression in the nucleus, TDP-43 protein was found at lower levels in the cytosol of transgenic mice. Additionally, we detected insoluble TDP-43 in the cortex, motoneuron loss, and increased neuroinflammation in the central nervous system of TAR6/6 animals. Behavioral analyses revealed early motor deficits in the clasping- and wire suspension test as well as decreased anxiety in the elevated plus maze. Further motor tests showed differences at later time points compared to non-transgenic littermates, thus allowing the observation of onset and severity of such deficits. Together, TAR6/6 mice are a valuable tool to test new ALS/FTLD drugs that target TDP-43 expression and insolubility, neuroinflammation, motoneuron loss or other TDP-43 related downstream signaling pathways since these mice exhibit a later pathology as previously used ALS/FTLD mouse models.

Phosphorylation of different tau sites during progression of Alzheimer's disease.

Alzheimer's disease is characterized by accumulation of amyloid plaques and tau aggregates in several cortical brain regions. Tau phosphorylation causes formation of neurofibrillary tangles and neuropil threads. Phosphorylation at tau Ser202/Thr205 is well characterized since labeling of this site is used to assign Braak stage based on occurrence of neurofibrillary tangles. Only little is known about the spatial and temporal phosphorylation profile of other phosphorylated tau (ptau) sites. Here, we investigate total tau and ptau at residues Tyr18, Ser199, Ser202/Thr205, Thr231, Ser262, Ser396, Ser422 as well as amyloid-ß plaques in human brain tissue of AD patients and controls. Allo- and isocortical brain regions were evaluated applying rater-independent automated quantification based on digital image analysis. We found that the level of ptau at several residues, like Ser199, Ser202/Thr205, and Ser422 was similar in healthy controls and Braak stages I to IV but was increased in Braak stage V/VI throughout the entire isocortex and transentorhinal cortex. Quantification of ThioS-stained plaques showed a similar pattern. Only tau phosphorylation at Tyr18 and Thr231 was already significantly increased in the transentorhinal region at Braak stage III/IV and hence showed a progressive increase with increasing Braak stages. Additionally, the increase in phosphorylation relative to controls was highest at Tyr18, Thr231 and Ser199. By contrast, Ser396 tau and Ser262 tau showed only a weak phosphorylation in all analyzed brain regions and only minor progression. Our results suggest that the ptau burden in the isocortex is comparable between all analyzed ptau sites when using a quantitative approach while levels of ptau at Tyr18 or Thr231 in the transentorhinal region are different between all Braak stages. Hence these sites could be crucial in the pathogenesis of AD already at early stages and therefore represent putative novel therapeutic targets.

Decreased Plasma Aß in Hyperlipidemic APPSL Transgenic Mice Is Associated with BBB Dysfunction.

Besides the continued focus on Aß and Tau in Alzheimer's disease (AD), it is increasingly evident that other pathologic characteristics, such as vascular alterations or inflammation, are associated with AD. Whether these changes are an initial cause for the onset of AD or occur as a result of the disease in late stages is still under debate. In the present study, the impact of the high-fat diet (HFD) induced vascular risk factor hyperlipidemia on Aß levels and clearance as well as cerebral vasculature and blood-brain barrier (BBB) integrity was examined in mice. For this purpose, human APP transgenic (APPSL) and wildtype (WT) mice were fed a HFD for 12 weeks. Plasma and tissues were subsequently investigated for Aß distribution and concentrations of several vascular markers. Decreased plasma Aß together with increased levels of insoluble Aß and amyloid plaques in the brains of HFD fed APPSL mice point toward impaired Aß clearance due to HFD. Additionally, HFD induced manifold alterations in the cerebral vasculature and BBB integrity exclusively in human APP overexpressing mice but not in wildtype mice. Therefore, HFD appears to enhance Aß dependent vascular/BBB dysfunction in combination with an increased proportion of cerebral to plasma Aß in APPSL mice.