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Articles by Jan C. Koch in JoVE
JoVE Clinical and Translational Medicine
السريرية اختبار وإزالة العمود الفقري الحبل في الفأر نموذج لتصلب الأنسجة العضلية الجانبية (ALS)
1Dept. of Neurology, University Medicine Göttingen, 2DFG Research Center for the Molecular Physiology of the Brain (CMPB), Göttingen, Germany
يتم فحص الفأر نموذج لتصلب الأنسجة العضلية الجانبية (ALS) سريريا وسلوكيا. كشرط أساسي لتحليل 1 immunohistological المرافق وصفت إعداد الحبل الشوكي بالتفصيل.
Other articles by Jan C. Koch on PubMed
TGF-beta 1 Enhances Neurite Outgrowth Via Regulation of Proteasome Function and EFABP
Malfunction of the ubiquitin-proteasome system has been implicated as a causal factor in the pathogenesis of aggregation-related disorders, e.g. Parkinson's disease. We show here that Transforming growth factor-beta 1 (TGF-beta), a multifunctional cytokine and trophic factor for dopaminergic (DAergic) neurons modulates proteasome function in primary midbrain neurons. TGF-beta differentially inhibited proteasomal subactivities with a most pronounced time-dependent inhibition of the peptidyl-glutamyl peptide hydrolyzing-like and chymotrypsin-like subactivity. Regulation of proteasomal activity could be specifically quantified in the DAergic subpopulation. Protein blot analysis revealed an accumulation of ubiquitinated proteins after TGF-beta treatment. The identity of these enriched proteins was further analyzed by 2D-gel electrophoresis and mass spectrometry. We found epidermal fatty acid binding protein (EFABP) to be strongly increased and ubiquitinated after TGF-beta treatment and confirmed this finding by co-immunoprecipitation. While application of TGF-beta increased neurite regeneration in a scratch lesion model, downregulation of EFABP by siRNA significantly decreased this effect. We thus postulate that a differential regulation of proteasomal function, as demonstrated for TGF-beta, can result in an enrichment of proteins, such as EFABP, that mediate physiological functions, such as neurite regeneration.
Mechanisms of Acute Axonal Degeneration in the Optic Nerve in Vivo
Axonal degeneration is an initial key step in traumatic and neurodegenerative CNS disorders. We established a unique in vivo epifluorescence imaging paradigm to characterize very early events in axonal degeneration in the rat optic nerve. Single retinal ganglion cell axons were visualized by AAV-mediated expression of dsRed and this allowed the quantification of postlesional acute axonal degeneration (AAD). EM analysis revealed severe structural alterations of the cytoskeleton, cytoplasmatic vacuolization, and the appearance of autophagosomes within the first hours after lesion. Inhibition of autophagy resulted in an attenuation of acute axonal degeneration. Furthermore, a rapid increase of intraaxonal calcium levels following crush lesion could be visualized using a calcium-sensitive dye. Application of calcium channel inhibitors prevented crush-induced calcium increase and markedly attenuated axonal degeneration, whereas application of a calcium ionophore aggravated the degenerative phenotype. We finally demonstrate that increased postlesional autophagy is calcium dependent and thus mechanistically link autophagy and intraaxonal calcium levels. Both processes are proposed to be major targets for the manipulation of axonal degeneration in future therapeutic settings.
Acute Axonal Degeneration in Vivo is Attenuated by Inhibition of Autophagy in a Calcium-dependent Manner
Axonal degeneration is a pathological hallmark of many traumatic and neurodegenerative neurological disorders. Although the underlying mechanisms remain largely unclear, increased autophagy and the influx of extracellular calcium have been implicated in the pathogenesis of axonal degeneration based on in vitro data. Using in vivo imaging of the rat optic nerve after crush lesion we could now show that both mechanisms are linked and play an important role in acute axonal degeneration in vivo. Our data suggest that crush lesion of the optic nerve induces a rapid calcium influx through calcium channels, which results in a secondary induction of autophagy that participates actively in axonal degradation. Therapeutic manipulation of both events could significantly alter the time course of acute axonal degeneration in vivo and may thus represent promising therapeutic targets for the future.
Plasmids Containing NRSE/RE1 Sites Enhance Neurite Outgrowth of Retinal Ganglion Cells Via Sequestration of REST Independent of NRSE DsRNA Expression
Repressor element-1 silencing transcription factor (REST) is a transcriptional repressor of neuron-specific genes that binds to a conserved DNA element, the neuron restrictive silencer element (NRSE/RE1). Interestingly, increased REST activity is found in several neurological diseases like Huntington's disease and cerebral ischemia. Recently, it was shown that NRSE dsRNA, a double-stranded non-coding RNA can bind to REST during a defined period of neuronal differentiation, and thereby changes REST from a transcriptional repressor to an activator of neuron-specific genes. Here, we analyzed the effects of NRSE dsRNA expression in primary retinal ganglion cells. We found that NRSE dsRNA expression vectors significantly enhance neurite outgrowth even when axonal degeneration is induced by neurotrophin deprivation. Transfection of HEK cells with NRSE dsRNA-expressing vectors altered their morphology leading to the formation of thin processes and induced the expression of neurofilament-68. Surprisingly, control vectors containing REST-binding sites, but not expressing NRSE dsRNA, resulted in the same effects, also in the retinal ganglion cell model. Reporter assays and retention of REST in the cytoplasm with a labeled NRSE/RE1-containing plasmid incapable of entering the nucleus suggest that sequestration of REST in the cytoplasm is the reason for the observed effects. No evidence for a biological function of NRSE dsRNA could be found in these models. We conclude that sequestration of REST leads to enhanced neurite outgrowth in retinal ganglion cells and that an increased activity of REST, as it is found in several neurodegenerative diseases, can be effectively modulated by sequestration of REST with plasmids containing NRSE/RE1 sites.
Imaging of Rat Optic Nerve Axons in Vivo
In this protocol, we describe the imaging of single axons in the rat optic nerve in vivo. Axons are labeled through the intravitreal injection of adeno-associated viral vectors (AAVs) expressing a fluorophore (duration of the procedure ∼1 h). Two weeks after intravitreal injection, the optic nerve is surgically exposed (duration ∼1 h) and labeled axons are imaged with an epifluorescence microscope either for up to 8 h or repetitively on the following days. Additionally, intravitreal injection of calcium-sensitive dyes allows for imaging of intra-axonal calcium kinetics. This procedure enables the analysis of the morphological changes of degenerating axons in the optic nerve in different lesion paradigms, such as optic nerve crush, axotomy or pin lesion. Furthermore, the effects of pharmacological manipulations on axonal stability and axonal calcium kinetics in axons of the central nervous system can be studied in vivo.
Axonal Degeneration As a Therapeutic Target in the CNS
Degeneration of the axon is an important step in the pathomechanism of traumatic, inflammatory and degenerative neurological diseases. Increasing evidence suggests that axonal degeneration occurs early in the course of these diseases and therefore represents a promising target for future therapeutic strategies. We review the evidence for axonal destruction from pathological findings and animal models with particular emphasis on neurodegenerative and neurotraumatic disorders. We discuss the basic morphological and temporal modalities of axonal degeneration (acute, chronic and focal axonal degeneration and Wallerian degeneration). Based on the mechanistic concepts, we then delineate in detail the major molecular mechanisms that underlie the degenerative cascade, such as calcium influx, axonal transport, protein aggregation and autophagy. We finally concentrate on putative therapeutic targets based on the mechanistic prerequisites.
