BackgroundAmyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder of the upper and lower motor neurons, characterized by rapid progressive weakness, muscle atrophy, dysarthria, dysphagia, and dyspnea. Whereas the exact cause of ALS remains uncertain, the wobbler mouse (phenotype WR; genotype wr/wr) equally develops a progressive degeneration of motor neurons in the spinal cord and motor cortex with striking similarities to sporadic human ALS, suggesting the possibility of a common pathway to cell death.MethodsWith the aid of immunohistochemistry, confocal laser scanning microscopy, and transmission electron microscopy techniques, we analyze the proliferation behavior of microglial cells and astrocytes. We also investigate possible motor neuron death in the mouse motor cortex at different stages of the wobbler disease, which so far has not received much attention.ResultsAn abnormal density of Iba-1-positive microglial cells expressing pro-inflammatory tumor necrosis factor (TNF) alpha- and glial fibrillary acidic protein (GFAP)-positive activated astroglial cells was detected in the motor cortex region of the WR mouse 40 days postnatal (d.p.n.). Motor neurons in the same area show caspase 3 activation indicating neurodegenerative processes, which may cause progressive paralysis of the WR mice. It could also cause cell degeneration, such as vacuolization, dilation of the ER, and swollen mitochondria at the same time, and support the assumption that inflammation might be an important contributing factor of motor neuron degeneration. This would appear to be confirmed by the fact that there was no conspicuous increase of microglial cells and astrocytes in the motor cortex of control mice at any time.ConclusionsActivated microglial cells secrete a variety of pro-inflammatory and neurotoxic factors, such as TNF alpha, which could initiate apoptotic processes in the affected wobbler motor neurons, as reflected by caspase 3 activation, and thus, the neuroinflammatory processes might influence or exacerbate the neurodegeneration. Although it remains to be clarified whether the immune response is primary or secondary and how harmful or beneficial it is in the WR motor neuron disease, anti-inflammatory treatment might be considered.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-015-0435-0) contains supplementary material, which is available to authorized users.

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Amyotrophic lateral sclerosis (ALS) is a common neurodegenerative disease that affects motor neurons in the spinal cord and motor cortex. Various mouse models have been used to investigate the progression of the pathology of sporadic and familial ALS. Degeneration in the spinal cord and motor cortex in the Wobbler mouse model of sporadic ALS have been documented, but alterations of the cerebellum during disease progression have not been well characterized. We analyzed neurodegeneration and inflammatory responses in the cerebellar cortex of preclinical (p20), clinical (p40), and late (p60) stages in these mice. We did not identify evidence of neuron cell death, but we observed an inflammatory response detected by IL1B and TNFA expression by quantitative PCR, increased activated microglia and astrocytosis by immunohistochemistry, and ultrastructural abnormalities in the cerebella of Wobbler mice at late stages. These alterations may be caused by protein aggregations and variations in the distribution of cytoskeletal proteins; they might be reflected in the early manifestation of head tremor, which precedes motor deficits in these mice. Thus, we conclude that, in addition to the motor cortex and spinal cord, the cerebellum is affected by neurodegenerative and inflammatory processes in the Wobbler mouse model of ALS.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with three described forms: The abundant, sporadic ALS (sALS) with approximately 90% of cases, the familial ALS (fALS) with 5-10%, and the very rare juvenile ALS (jALS) group, which is statistically less relevant. The wobbler mouse, a model for sALS, has been in the focus of research for many decades. Due to symptoms strongly resembling the human ALS pathology, the α-motor neurons (αMN) have received the most attention. With regard to pathological cellular processes, particularly those of impaired axonal transport, neuronal tissues in general should be examined. Dorsal root ganglia (DRG) cells are equipped with extremely long axons. Thus, we expected them to be an excellent target for analyzing the cellular mechanisms underlying the disease. In this study, an analysis of the distribution of heavy neurofilaments (NfH) in the perikarya and peripheral nerves of dorsal root ganglia cells from wobbler mice was performed. Here, we demonstrate that sensory neurons are also affected in wobbler mice during the progression of the disease, showing signs of degeneration like those described in the αMN. Furthermore, a highly impaired distribution of neurofilaments and a high number of phosphorylated heavy neurofilaments (pNfH) were observed, not only in large light neurons (LLN), but also in the small dark neurons (SDN) of wobbler mouse DRGs. The accumulation of pNfH in DRG as well as the loss of NfH in their axons are promising links to studies promoting high levels of pNfH in the cerebrospinal fluid (CSF) as an early hallmark of ALS in humans. KeywordsDorsal root ganglia, Amyotrophic lateral sclerosis, Wobbler, Neurofilaments, Neurodegeneration IntroductionNeurological diseases, and in particular motor neuron diseases (MND), have a great impact on a patient's quality of life. ALS is a common MND with an incidence of 1-3 cases per 100.000 per year and a prevalence of 3-8 per 100.000, with men being more often affected than women. The average survival is 3 years after the onset of ALS symptoms, typically between the ages of 55 to 60 [1]. Many pathological mechanisms have already been well investigated in animal models with ALS-like phenotypes, however comparison to the human ALS pathology is difficult. A treatment substantially modifying the diseases progression is still lacking. The well-known degeneration of the upper and lower motor neurons are common in the murine models as well as in humans. This