The shape, structure and connectivity of nerve cells are important aspects of neuronal function. Genetic and epigenetic factors that alter neuronal morphology or synaptic localization of pre- and post-synaptic proteins contribute significantly to neuronal output and may underlie clinical states. To assess the impact of individual genes and disease-causing mutations on neuronal morphology, reliable methods are needed. Unfortunately, manual analysis of immuno-fluorescence images of neurons to quantify neuronal shape and synapse number, size and distribution is labor-intensive, time-consuming and subject to human bias and error. We have developed an automated image analysis routine using steerable filters and deconvolutions to automatically analyze dendrite and synapse characteristics in immuno-fluorescence images. Our approach reports dendrite morphology, synapse size and number but also synaptic vesicle density and synaptic accumulation of proteins as a function of distance from the soma as consistent as expert observers while reducing analysis time considerably. In addition, the routine can be used to detect and quantify a wide range of neuronal organelles and is capable of batch analysis of a large number of images enabling high-throughput analysis.

Although Munc13-1 and Munc13-2 facilitate dense-core vesicle fusion, they are not required for DCV release, in contrast to their essential role in synaptic vesicle exocytosis.

Liprin-α2 is required for the presynaptic recruitment and turnover of RIM1 and CASK, components of the release machinery, and facilitates synaptic output by regulating synaptic vesicle pool size.

While genetic advances have successfully defined part of the complexity in Parkinson’s disease (PD), the clinical characterization of phenotypes remains challenging. Therapeutic trials and cohort studies typically include patients with earlier disease stages and exclude comorbidities, thus ignoring a substantial part of the real-world PD population. To account for these limitations, we implemented the Luxembourg PD study as a comprehensive clinical, molecular and device-based approach including patients with typical PD and atypical parkinsonism, irrespective of their disease stage, age, comorbidities, or linguistic background. To provide a large, longitudinally followed, and deeply phenotyped set of patients and controls for clinical and fundamental research on PD, we implemented an open-source digital platform that can be harmonized with international PD cohort studies. Our interests also reflect Luxembourg-specific areas of PD research, including vision, gait, and cognition. This effort is flanked by comprehensive biosampling efforts assuring high quality and sustained availability of body liquids and tissue biopsies. We provide evidence for the feasibility of such a cohort program with deep phenotyping and high quality biosampling on parkinsonism in an environment with structural specificities and alert the international research community to our willingness to collaborate with other centers. The combination of advanced clinical phenotyping approaches including device-based assessment will create a comprehensive assessment of the disease and its variants, its interaction with comorbidities and its progression. We envision the Luxembourg Parkinson’s study as an important research platform for defining early diagnosis and progression markers that translate into stratified treatment approaches.

No abstract

Positional information, independent of neuronal activity, regulates presynaptic strength, with the strongest presynaptic terminals closest to the soma.

Presynaptic cannabinoid (CB1R) and metabotropic glutamate receptors (mGluR2/3) regulate synaptic strength by inhibiting secretion. Here, we reveal a presynaptic inhibitory pathway activated by extracellular signal-regulated kinase (ERK) that mediates CB1R-and mGluR2/3-induced secretion inhibition. This pathway is triggered by a variety of events, from foot shock-induced stress to intense neuronal activity, and induces phosphorylation of the presynaptic protein Munc18-1. Mimicking constitutive phosphorylation of Munc18-1 results in a drastic decrease in synaptic transmission. ERK-mediated phosphorylation of Munc18-1 ultimately leads to degradation by the ubiquitin-proteasome system. Conversely, preventing ERK-dependent Munc18-1 phosphorylation increases synaptic strength. CB1R-and mGluR2/3-induced synaptic inhibition and depolarization-induced suppression of excitation (DSE) are reduced upon ERK/MEK pathway inhibition and further reduced when ERK-dependent Munc18-1 phosphorylation is blocked. Thus, ERK-dependent Munc18-1 phosphorylation provides a major negative feedback loop to control synaptic strength upon activation of presynaptic receptors and during intense neuronal activity.

It is known that about 5-10% of cancer patients show severe clinical side effects during and after radiotherapy due to enhanced sensitivity to ionizing radiation. Identification of those radiosensitive individuals by a reliable in vitro assay before onset of treatment would have a great impact on successful radiotherapy. We compared the radiosensitivity of the chromosomes 2, 11 and 17 in prostate cancer patients with and without severe side effects after radiotherapy and in age-matched healthy donors. Each cohort consisted of at least 10 donors. Peripheral blood lymphocytes were irradiated ex vivo with 0.5, 1 und 2 Gy ((137)Cs γ rays). We investigated the radiosensitivity of the chromosomes 2, 11 and 17 by scoring of 100 FISH painted metaphases for each dose point and donor group. Statistical analyses were performed by nonparametric tests as Mann-Whitney test and Kruskal-Wallis ANOVA, paired Wilcoxon rank test, χ(2) goodness-of-fit test and Spearman rank-order correlation at a significance level of P < 0.05. Analysis of the overall aberration yield revealed no significant differences between any donor groups. The translocation frequencies of the chromosomes 2, 11 and 17 coincided with their relative size. Thus, none of the chromosomes analyzed were more or less radiosensitive with respect to the genomic translocation frequency. Additionally, neither of the chromosomes showed enhanced or diminished radiosensitivity in one of the donor groups. Furthermore, variance analyses revealed that the distribution pattern of the aberrations per donor did not differ in each donor group even after exposure to 2 Gy. Prostate cancer patients with and without side effects cannot be distinguished from healthy donors based on aberration yield after irradiation with γ rays.