Biology subjects

Arendt, T.

Publications and source records attributed to Arendt, T..

5 recordsLinked to original sources

bioRxiv2022

Tau and α-synuclein shape microtubule organization and microtubule-dependent transport in neuronal dendrites

Tau and -synuclein are major players in neurodegenerative diseases, but their physiological role, particularly in dendrites, is poorly understood. Here we show that, surprisingly, lack of tau protein induces the development of a more elaborate dendritic arbor of hippocampal pyramidal cells in organotypic tissue. Using high-speed volumetric lattice light-sheet microscopy and single particle tracking, we found a more directional KIF1A-mediated transport in dendrites of Tau KO cells. Increased transport processivity correlated with longer and straighter dendritic microtubules as revealed by three-dimensional super-resolution microscopy of cultured hippocampal neurons. Unbiased mass spectrometric analysis of tissue showed highly increased expression of -synuclein in Tau KO hippocampi. Overexpression of -synuclein mimicked the transport characteristics observed in Tau KO cells. Our data indicate that tau and -synuclein shape microtubule-dependent transport in neuronal dendrites, thereby promoting dendritic arborization during maturation. Furthermore, the data demonstrate that transport efficiency and length and straightness of microtubules are correlated.

neuroscience↗

bioRxiv2022

Somatic copy number variant load in neurons of healthy controls and Alzheimer's disease patients

BackgroundThe possible role of somatic copy number variations (CNVs) in Alzheimers disease (AD) aetiology has been controversial. Although cytogenetic studies suggested increased CNV loads in AD brains, a recent single-cell whole-genome sequencing (scWGS) experiment, studying frontal cortex brain samples, found no such evidence. Here we readdressed this issue using lowcoverage scWGS on pyramidal neurons dissected using laser capture microdissection (LCM) across five brain regions: entorhinal cortex, temporal cortex, hippocampal CA1, hippocampal CA3, and the cerebellum. ResultsAmong reliably detected somatic CNVs identified in 1301 cells obtained from the brains of 13 AD patients and 7 healthy controls, deletions were more frequent compared to duplications. Interestingly, we observed slightly higher frequencies of CNV events in cells from AD compared to similar numbers of cells from controls (4.1% vs. 1.4%, or 0.9% vs. 0.7%, using different filtering approaches), although the differences were not statistically significant. We also observed that LCM-isolated cells show higher within-cell read depth variation compared to cells isolated with fluorescence activated cell sorting (FACS), which we argue may have both biological and technical causes. Furthermore, we found that LCM-isolated neurons in AD harbour slightly more read depth variability than neurons of controls, which might be related to the reported hyperploid profiles of some AD-affected neurons. We also propose a principal component analysis-based denoising approach that significantly reduces within-cell read depth variation in scWGS data. ConclusionsWe find slightly higher somatic CNV frequencies in the brains of AD patients, and higher sequencing coverage variability, although the effects measured do not reach statistical significance. The results call for improved experimental protocols to determine the possible role of CNVs in AD pathogenesis.

bioinformatics↗

bioRxiv2020

Molecular Mechanism of Nuclear Tau Accumulation and its Role in Protein Synthesis.

Several neurodegenerative diseases present Tau accumulation as the main pathological marker. Tau post-translational modifications such as phosphorylation and acetylation are increased in neurodegenerative patients. Here, we show that Tau hyper-acetylation at residue 174 increases its own nuclear presence and is the result of DNA damage signaling or the lack of SIRT6, both causative of neurodegeneration. Tau-K174ac is deacetylated in the nucleus by SIRT6. However, lack of SIRT6 or chronic DNA damage result in nuclear Tau-K174ac accumulation. Once there, it induces global changes in gene expression affecting protein translation, synthesis and energy production. Tau-K174Q expressing cells showed changes in the nucleolus increasing their intensity and number, as well as in rRNA synthesis leading to an increase in protein translation and ATP reduction. Concomitantly, AD patients showed increased Nucleolin and a decrease in SIRT6 levels. AD patients present increased levels of nuclear Tau, particularly Tau-K174ac. Our results suggest that increased Tau-K174ac in AD patients is the result of DNA damage signaling and SIRT6 depletion. We propose that Tau-K174ac toxicity is due to its increased stability, nuclear accumulation and nucleolar dysfunction.

molecular biology↗

bioRxiv2020

Measuring the iron content of dopaminergic neurons in substantia nigra with MRI relaxometry

In Parkinsons disease, the depletion of iron-rich dopaminergic neurons in substantia nigras nigrosome 1 precedes first motor symptoms by two decades. Monitoring this neuronal depletion at an early disease stage is needed for diagnosis and treatment monitoring. Magnetic resonance imaging (MRI) is particularly suitable for this task due to its sensitivity to tissue iron. However, the mechanisms of MRI contrast in substantia nigra are not well understood, hindering the development of specific biomarkers. We showed that the dominant contribution to the effective transverse MRI relaxation rate [Formula] in nigrosome 1 originates from iron accumulated in the neuromelanin of dopaminergic neurons. We linked [Formula] quantitatively to the product of cell density and local iron concentration in dopaminergic neurons, combining quantitative 3D iron histology, biophysical modeling, and quantitative MRI on post mortem brain tissue. This knowledge opens an avenue for monitoring neuronal iron and density in vivo and may be applied to detect early neurodegeneration in Parkinsons disease.

neuroscience↗

bioRxiv2017

Alzheimer related genes show accelerated evolution

Alzheimer's disease (AD) is a neurodegenerative disorder of unknown cause with complex genetic and environmental traits. Here, we show that gene structures of loci, that show AD-associated changes in their expression, evolve faster than the genome at large. This phylogenetic trait of AD suggests a critical pathogenetic role of recent adaptive evolution of human brain and might have far reaching consequences with respect to the appropriateness of model systems and the development of disease-modifying strategies.

evolutionary biology↗