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Elevated levels of neurofilament light chain (NF-L) in CSF and blood are linked to the presymptomatic and symptomatic phase of patients suffering from amyotrophic lateral sclerosis (ALS). However, whether the NF-L level in extracellular liquids like serum or CSF is a marker of destruction or NF-L is secreted actively outside the cell is not known so far. NF-L levels in CSF and blood clearly separate ALS patients and controls [9], serving as a prognostic biomarker for ALS [4]. Also in pre-symptomatic ALS gene mutation carriers NF-L levels are elevated thus allowing prediction for clinical phenoconversion [3, 4]. The picture of NF-L levels in ALS mouse models is less clear. Previous studies report on elevated NF-L plasma levels in SOD1G93Adl and TDP-43 (TAR6/6) mice [6], but the correlation to motor neuron (MN) loss has not been determined. We therefore employed a transgenic TDP-43G298S mouse model to study the interaction of motor neuron pathophysiology, muscle denervation and NF-L levels. TDP-43G298S mutant mice show decreased performance in grip strength and motor activity compared to controls [10]., publishedVersion

TAR DNA binding protein 43 (TDP-43) is closely related to the pathogenesis of amyotrophic lateral sclerosis (ALS) and translocates to stress granules (SGs). The role of SGs as aggregation-promoting “crucibles” for TDP-43, however, is still under debate. We analyzed TDP-43 mobility and localization under different stress and recovery conditions using live cell single-molecule tracking and super-resolution microscopy. Besides reduced mobility within SGs, a stress induced decrease of TDP-43 mobility in the cytoplasm and the nucleus was observed. Stress removal led to a recovery of TDP-43 mobility, which strongly depended on the stress duration. ‘Stimulated-emission depletion microscopy’ (STED) and ‘tracking and localization microscopy’ (TALM) revealed not only TDP-43 substructures within stress granules but also numerous patches of slow TDP-43 species throughout the cytoplasm. This work provides insights into the aggregation of TDP-43 in living cells and provide evidence suggesting that TDP-43 oligomerization and aggregation takes place in the cytoplasm separate from SGs., publishedVersion

Despite extensive effort on studying inflammatory processes in the CNS of Parkinson’s disease (PD) patients, implications of peripheral monocytes are still poorly understood. Here, we set out to obtain a comprehensive picture of circulating myeloid cells in PD patients. We applied a human primary monocyte culture system and flow cytometry-based techniques to determine the state of monocytes from PD patients during disease. We found that the classical monocytes are enriched in the blood of PD patients along with an increase in the monocyte-recruiting chemoattractant protein CCL2. Moreover, we found that monocytes from PD patients display a pathological hyperactivity in response to LPS stimulation that correlates with disease severity. Inflammatory pre-conditioning was also reflected on the transcriptome in PD monocytes using next-generation sequencing. Further, we identified the CD95/CD95L as a key regulator for the PD-associated alteration of circulating monocytes. Pharmacological neutralization of CD95L reverses the dysregulation of monocytic subpopulations in favor of non-classical monocytes. Our results suggest that PD monocytes are in an inflammatory predisposition responding with hyperactivation to a “second hit”. These results provide the first direct evidence that circulating human peripheral blood monocytes are altered in terms of their function and composition in PD patients. This study provides insights into monocyte biology in PD and establishes a basis for future studies on peripheral inflammation. Electronic supplementary material The online version of this article (doi:10.1007/s00401-014-1345-4) contains supplementary material, which is available to authorized users.