Martin Regensburger

Adult Hippocampal Neurogenesis in Parkinson's Disease: Impact on Neuronal Survival and Plasticity

In Parkinsons disease (PD) and other synucleinopathies, chronic neurodegeneration occurs within different areas of the central nervous system leading to progressive motor and nonmotor symptoms. The symptomatic treatment options that are currently available do not slow or halt disease progression. This highlights the need of a better understanding of disease mechanisms and disease models. The generation of newborn neurons in the adult hippocampus and in the subventricular zone/olfactory bulb system is affected by many different regulators and possibly involved in memory processing, depression, and olfaction, symptoms which commonly occur in PD. The pathology of the adult neurogenic niches in human PD patients is still mostly elusive, but different preclinical models have shown profound alterations of adult neurogenesis. Alterations in stem cell proliferation, differentiation, and survival as well as neurite outgrowth and spine formation have been related to different aspects in PD pathogenesis. Therefore, neurogenesis in the adult brain provides an ideal model to study disease mechanisms and compounds. In addition, adult newborn neurons have been proposed as a source of endogenous repair. Herein, we review current knowledge about the adult neurogenic niches in PD and highlight areas of future research.

The Ca2+ Sensor Protein Swiprosin-1/EFhd2 Is Present in Neurites and Involved in Kinesin-Mediated Transport in Neurons

Swiprosin-1/EFhd2 (EFhd2) is a cytoskeletal Ca2+ sensor protein strongly expressed in the brain. It has been shown to interact with mutant tau, which can promote neurodegeneration, but nothing is known about the physiological function of EFhd2 in the nervous system. To elucidate this question, we analyzed EFhd2−/−/lacZ reporter mice and showed that lacZ was strongly expressed in the cortex, the dentate gyrus, the CA1 and CA2 regions of the hippocampus, the thalamus, and the olfactory bulb. Immunohistochemistry and western blotting confirmed this pattern and revealed expression of EFhd2 during neuronal maturation. In cortical neurons, EFhd2 was detected in neurites marked by MAP2 and co-localized with pre- and post-synaptic markers. Approximately one third of EFhd2 associated with a biochemically isolated synaptosome preparation. There, EFhd2 was mostly confined to the cytosolic and plasma membrane fractions. Both synaptic endocytosis and exocytosis in primary hippocampal EFhd2−/− neurons were unaltered but transport of synaptophysin-GFP containing vesicles was enhanced in EFhd2−/− primary hippocampal neurons, and notably, EFhd2 inhibited kinesin mediated microtubule gliding. Therefore, we found that EFhd2 is a neuronal protein that interferes with kinesin-mediated transport.

Propofol-related urine discoloration in a patient with fatal atypical intracerebral hemorrhage treated with hypothermia

IntroductionMild therapeutic hypothermia is an increasingly recognised treatment option to reduce perihemorrhagic edema in severe intracerebral hemorrhage.Case descriptionWe report the case of a 77-year old woman with atypical intracerebral hemorrhage that was treated with mild hypothermia in addition to osmotic therapy. The patient’s urine subsequently showed a green discoloration. Urine discoloration was completely reversible upon discontinuation of propofol.Discussion and evaluationPropofol-related urine discoloration may have been provoked by hypothermia. Due to the benign nature of this side effect, propofol should be stopped and gastrointestinal function should be supported.ConclusionMore studies are needed to show a causal role of hypothermia and related decreased enzymatic function.

The Temporal Expression Pattern of Alpha-Synuclein Modulates Olfactory Neurogenesis in Transgenic Mice

Background Adult neurogenesis mirrors the brain´s endogenous capacity to generate new neurons throughout life. In the subventricular zone/ olfactory bulb system adult neurogenesis is linked to physiological olfactory function and has been shown to be impaired in murine models of neuronal alpha-Synuclein overexpression. We analyzed the degree and temporo-spatial dynamics of adult olfactory bulb neurogenesis in transgenic mice expressing human wild-type alpha-Synuclein (WTS) under the murine Thy1 (mThy1) promoter, a model known to have a particularly high tg expression associated with impaired olfaction. Results Survival of newly generated neurons (NeuN-positive) in the olfactory bulb was unchanged in mThy1 transgenic animals. Due to decreased dopaminergic differentiation a reduction in new dopaminergic neurons within the olfactory bulb glomerular layer was present. This is in contrast to our previously published data on transgenic animals that express WTS under the control of the human platelet-derived growth factor β (PDGF) promoter, that display a widespread decrease in survival of newly generated neurons in regions of adult neurogenesis, resulting in a much more pronounced neurogenesis deficit. Temporal and quantitative expression analysis using immunofluorescence co-localization analysis and Western blots revealed that in comparison to PDGF transgenic animals, in mThy1 transgenic animals WTS is expressed from later stages of neuronal maturation only but at significantly higher levels both in the olfactory bulb and cortex. Conclusions The dissociation between higher absolute expression levels of alpha-Synuclein but less severe impact on adult olfactory neurogenesis in mThy1 transgenic mice highlights the importance of temporal expression characteristics of alpha-Synuclein on the maturation of newborn neurons.

Detection radius of EMG for fasciculations: Empiric study combining ultrasonography and electromyography

OBJECTIVE The aims of this study were to investigate the detection radius and sensitivity of EMG for fasciculations. METHODS Muscle ultrasonography was performed simultaneously to EMG recordings in patients with fasciculations in the context of amyotrophic lateral sclerosis. Ultrasonography and EMG parameters were analyzed for selected fasciculations. RESULTS A total of 381 fasciculations were detected by ultrasonography in 18 muscles of 10 patients. Out of these, 125 (33%) were EMG-negative. In contrast, none of the fasciculations detected by EMG were ultrasonography-negative. EMG detection probability decreased significantly with increasing distance from the center of the fasciculation. EMG detection rate was 98% when the EMG needle was located within the fasciculation and 50% at 7.75 mm distance from the fasciculation center. In addition, EMG detection depended significantly on cross-sectional area of the fasciculation and presence of neurogenic changes. CONCLUSIONS For detecting the same fasciculations, EMG is less sensitive than ultrasonography. EMG detection probability decreases sharply at a distance comparable to motor unit size. SIGNIFICANCE These results extend previous knowledge about superior sensitivity of ultrasonography for fasciculations. Moreover, our novel bimodal detection method provides first in vivo data about the EMG detection radius for fasciculations in a clinical setting.

Towards a multi-sensor system for the diagnosis of neurological disorders

The occurrence of fasciculations is an indication for several neurological disorders. However, due to the low amplitude and irregular occurrence, these involuntary muscle movements are hard to quantify. Currently used techniques have to be applied manually from a trained specialist and lack the possibility of a remote measurement of fasciculations. Therefore, we introduce a new approach which is able to remotely measure fasciculations with high temporal resolution. Moreover, we compare the sensitivity of our technique with established methods and give an outlook how our technology can be expanded to a multi-sensor system for the automated diagnosis of neurological disorders.

Need for high-resolution Genetic Analysis in iPSC: Results and Lessons from the ForIPS Consortium

Genetic integrity of induced pluripotent stem cells (iPSCs) is essential for their validity as disease models and for potential therapeutic use. We describe the comprehensive analysis in the ForIPS consortium: an iPSC collection from donors with neurological diseases and healthy controls. Characterization included pluripotency confirmation, fingerprinting, conventional and molecular karyotyping in all lines. In the majority, somatic copy number variants (CNVs) were identified. A subset with available matched donor DNA was selected for comparative exome sequencing. We identified single nucleotide variants (SNVs) at different allelic frequencies in each clone with high variability in mutational load. Low frequencies of variants in parental fibroblasts highlight the importance of germline samples. Somatic variant number was independent from reprogramming, cell type and passage. Comparison with disease genes and prediction scores suggest biological relevance for some variants. We show that high-throughput sequencing has value beyond SNV detection and the requirement to individually evaluate each clone.

Impact of Swiprosin-1/Efhd2 on Adult Hippocampal Neurogenesis

Summary Swiprosin-1/Efhd2 (Efhd2) is highly expressed in the CNS during development and in the adult. EFHD2 is regulated by Ca2+ binding, stabilizes F-actin, and promotes neurite extension. Previous studies indicated a dysregulation of EFHD2 in human Alzheimers disease brains. We hypothesized a detrimental effect of genetic ablation of Efhd2 on hippocampal integrity and specifically investigated adult hippocampal neurogenesis. Efhd2 was expressed throughout adult neuronal development and in mature neurons. We observed a severe reduction of the survival of adult newborn neurons in Efhd2 knockouts, starting at the early neuroblast stage. Spine formation and dendrite growth of newborn neurons were compromised in full Efhd2 knockouts, but not upon cell-autonomous Efhd2 deletion. Together with our finding of severe hippocampal tauopathy in Efhd2 knockout mice, these data connect Efhd2 to impaired synaptic plasticity as present in Alzheimers disease and identify a role of Efhd2 in neuronal survival and synaptic integration in the adult hippocampus.

Monozygotic twins with a new compound heterozygous SPG11 mutation and different disease expression

BACKGROUND A pair of monozygotic 22-year-old twins with complicated hereditary spastic paraplegia caused by a novel SPG11 mutation is described. METHODS Genetic testing and thorough clinical examination, magnetic resonance imaging (MRI) and MR-spectroscopy were performed. RESULTS The twins were compound heterozygous for a known frameshift as well as a novel splice site mutation in the SPG11 gene. Clinically the patients showed a similar spectrum of symptoms but different disease presentation. MRI studies including morphometry and regional microstructural analysis by diffusion tensor imaging (DTI) of the corpus callosum (CC) by 3T MRI revealed marked thinning and corresponding increases of radial diffusivity (RD) and apparent diffusion coefficient (ADC) and reduction of the fractional anisotropy (FA) as compared to controls in all CC sections, particularly in the anterior callosal body. There was marked mainly supratentorial white matter reduction and to a lesser extent grey matter reduction in both patients. Involvement of the cortico-spinal tracts was reflected by FA and RD alterations. The more strongly affected patient showed a higher degree of callosal microstructural damage and cervical cord atrophy. CONCLUSIONS This study shows a similar symptom spectrum, but distinct clinical and imaging findings in monozygotic twins suffering from SPG 11, suggesting individual downstream genetic effects and/or non-genetic modifiers.

P 157 Detection radius of EMG for fasciculations: combined ultrasonographic-electromyographic analysis

Background Fasciculations are caused by spontaneous discharges of single motor units. In electromyography (EMG), they are characterized by single motor unit action potentials. Muscle ultrasonography is increasingly applied as a non-invasive screening tool for the examination of fasciculations. In the context of motor neuron disease, the sensitivity of muscle ultrasonography to detect fasciculations was superior to EMG. Limited detection radius of concentric needle EMG may explain this discrepancy, but a direct EMG-ultrasonography-correlation of single fasciculations has not been reported so far. In the current study, we aimed to define an “EMG detection radius” of fasciculations by simultaneous recording of EMG and muscle ultrasonography. Methods Parallel to concentric needle EMG, we recorded in-plane high-resolution videos of muscle ultrasonography showing the needle tip within the transverse section of the muscle. A total of 200 fasciculations were acquired during 50 recordings of 10 patients with motor neuron disease. Amplitude and duration of EMG fasciculation potentials were subsequently correlated to the corresponding ultrasonographic muscle displacement and the distance from the EMG needle tip. Results The onset of ultrasonographic muscle displacement was concurrent to its EMG fasciculation potential whereas the plateau phase and the backward movement occurred when the EMG had already returned to baseline. About 40% of fasciculations observed on ultrasonography were not detected in EMG and this included fasciculations located close to the needle tip. The amplitude of EMG-positive fasciculations was negatively correlated to their distance from the needle tip. However, the correlation differed significantly between different patients and between different muscles. Discussion Analysis of fasciculations on simultaneous EMG and ultrasonography recordings improves the understanding of the “EMG-detection radius” of fasciculations. A relevant portion of ultrasonographic fasciculations was not detected on EMG which may in part explain the superior sensitivity of ultrasonography. Different localization of neuromuscular endplates and of myofibrils along the longitudinal axis of the analyzed muscles might explain the occurrence of “EMG-negative” fasciculations. Alternatively, muscle remodeling or changes of axon terminals due to neurodegeneration may alter the sensitivity of EMG. Further studies are needed to classify fasciculations of other entities with this method.