Non-motor Neurons Research Articles

Chemotherapy-induced peripheral neuropathy models constructed from human induced pluripotent stem cells and directly converted cells: a systematic review.

Developments in human cellular reprogramming now allow for the generation of human neurons for in vitro disease modelling. This technique has since been used for chemotherapy-induced peripheral neuropathy (CIPN) research, resulting in the description of numerous CIPN models constructed from human neurons. This systematic review provides a critical analysis of available models and their methodological considerations (ie, used cell type and source, CIPN induction strategy, and validation method) for prospective researchers aiming to incorporate human in vitro models of CIPN in their research. The search strategy was developed with assistance from a clinical librarian and conducted in MEDLINE (PubMed) and Embase (Ovid) on September 26, 2023. Twenty-six peer-reviewed experimental studies presenting original data about human reprogrammed nonmotor neuron cell culture systems and relevant market available chemotherapeutics drugs were included. Virtually, all recent reports modeled CIPN using nociceptive dorsal root ganglion neurons. Drugs known to cause the highest incidence of CIPN were most used. Furthermore, treatment effects were almost exclusively validated by the acute effects of chemotherapeutics on neurite dynamics and cytotoxicity parameters, enabling the extrapolation of the half-maximal inhibitory concentration for the 4 most used chemotherapeutics. Overall, substantial heterogeneity was observed in the way studies applied chemotherapy and reported their findings. We therefore propose 6 suggestions to improve the clinical relevance and appropriateness of human cellular reprogramming-derived CIPN models.

Motor neuron involvement threatens survival in spinocerebellar ataxia type 1.

Motor neuron involvement threatens survival in spinocerebellar ataxia type 1.

Compartment specific mitochondrial dysfunction in Drosophila knock-in model of ALS reversed by altered gene expression of OXPHOS subunits and pro-fission factor Drp1

Amyotrophic Lateral Sclerosis (ALS) is a fatal multisystem neurodegenerative disease, characterized by a loss in motor function. ALS is genetically diverse, with mutations in genes ranging from those regulating RNA metabolism, like TAR DNA-binding protein (TDP-43) and Fused in sarcoma (FUS), to those that act to maintain cellular redox homeostasis, like superoxide dismutase 1 (SOD1). Although varied in genetic origin, pathogenic and clinical commonalities are clearly evident between cases of ALS. Defects in mitochondria is one such common pathology, thought to occur prior to, rather than as a consequence of symptom onset, making these organelles a promising therapeutic target for ALS, as well as other neurodegenerative diseases. Depending on the homeostatic needs of neurons throughout life, mitochondria are normally shuttled to different subcellular compartments to regulate metabolite and energy production, lipid metabolism, and buffer calcium. While originally considered a motor neuron disease due to the dramatic loss in motor function accompanied by motor neuron cell death in ALS patients, many studies have now implicated non-motor neurons and glial cells alike. Defects in non-motor neuron cell types often preceed motor neuron death suggesting their dysfunction may initiate and/or facilitate the decline in motor neuron health. Here, we investigate mitochondria in a Drosophila Sod1 knock-in model of ALS. In depth, in vivo, examination reveals mitochondrial dysfunction evident prior to onset of motor neuron degeneration. Genetically encoded redox biosensors identify a general disruption in the electron transport chain (ETC). Compartment specific abnormalities in mitochondrial morphology is observed in diseased sensory neurons, accompanied by no apparent defects in the axonal transport machinery, but instead an increase in mitophagy in synaptic regions. The decrease in networked mitochondria at the synapse is reversed upon downregulation of the pro-fission factor Drp1. Furthermore, altered expression of specific OXPHOS subunits reverses ALS-associated defects in mitochondrial morphology and function.

Unexpected postmortem diagnoses in cases of clinically diagnosed amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a motor neuron disease that is clinically and pathologically characterized by impairment of the upper and lower motor neurons. The clinical diagnosis of ALS is not always straightforward because of the lack of specific biomarkers and clinical heterogeneity. This review presents the clinical and pathological findings of four autopsied cases that had been diagnosed with ALS before death. These cases had demonstrated definite and progressive motor neuron signs and symptoms, whereas postmortem assessment revealed miscellaneous disorders, including fungal infection, paraneoplastic syndrome, and amyloidosis. Importantly, nonmotor neuron signs and symptoms, including seizures, extra-pyramidal signs, ocular movement disorders, sensory disturbance, and dysautonomia, had also been documented during the disease course of the cases in the present study. The ALS-unlike symptoms were indicative of the "true" diagnosis in each case when those symptoms were isolated from motor neuron signs/symptoms.

Development of the human hypoglossal nucleus from mid-gestation to the perinatal period: A morphological study

IntroductionThe human hypoglossal nucleus (nXII) was morphologically examined from mid-gestation to the perinatal period. Materials/methodsSerial brain sections from 6 preterm and 4 perinatal infants aged 21–43 postmenstrual weeks (PW) were stained with the Klüver–Barrera method. Following microscopic observation, morphometric parameters (volume, neuronal number, and neuronal profile area [PA]) were analysed. ResultsTwo types of neurons, motor and non-motor neurons, were observed at 21 PW. The motor neurons were distributed into clusters, which were not completely separated. The non-motor neurons were dispersed among the motor neurons. Myelination of the hypoglossal nerve roots was noted at 21 PW, when degenerated neurons were sporadically encountered. To a lesser extent, they were seen until 35 PW. The nXII volume increased exponentially with age. Conversely, the neuronal numerical density decreased exponentially, while the total number remained relatively stable. The neuronal PA increased gradually, with a greater rate of increase measured in the caudal part. ConclusionsIn the human nXII, motor and non-motor neurons are distinguishable from mid-gestation. Then, while the nXII expands exponentially in volume, the two types of neurons change in number and PA almost in parallel during the second half of gestation. Natural neuronal death may also occur.

Progressive Mitochondrial SOD1G93A Accumulation Causes Severe Structural, Metabolic and Functional Aberrations through OPA1 Down-Regulation in a Mouse Model of Amyotrophic Lateral Sclerosis.

In recent years, the “non-autonomous motor neuron death” hypothesis has become more consolidated behind amyotrophic lateral sclerosis (ALS). It postulates that cells other than motor neurons participate in the pathology. In fact, the involvement of the autonomic nervous system is fundamental since patients die of sudden death when they become unable to compensate for cardiorespiratory arrest. Mitochondria are thought to play a fundamental role in the physiopathology of ALS, as they are compromised in multiple ALS models in different cell types, and it also occurs in other neurodegenerative diseases. Our study aimed to uncover mitochondrial alterations in the sympathoadrenal system of a mouse model of ALS, from a structural, bioenergetic and functional perspective during disease instauration. We studied the adrenal chromaffin cell from mutant SOD1G93A mouse at pre-symptomatic and symptomatic stages. The mitochondrial accumulation of the mutated SOD1G93A protein and the down-regulation of optic atrophy protein-1 (OPA1) provoke mitochondrial ultrastructure alterations prior to the onset of clinical symptoms. These changes affect mitochondrial fusion dynamics, triggering mitochondrial maturation impairment and cristae swelling, with increased size of cristae junctions. The functional consequences are a loss of mitochondrial membrane potential and changes in the bioenergetics profile, with reduced maximal respiration and spare respiratory capacity of mitochondria, as well as enhanced production of reactive oxygen species. This study identifies mitochondrial dynamics regulator OPA1 as an interesting therapeutic target in ALS. Additionally, our findings in the adrenal medulla gland from presymptomatic stages highlight the relevance of sympathetic impairment in this disease. Specifically, we show new SOD1G93A toxicity pathways affecting cellular energy metabolism in non-motor neurons, which offer a possible link between cell specific metabolic phenotype and the progression of ALS.

A specific biomarker for amyotrophic lateral sclerosis: Quantitative susceptibility mapping

ObjectiveAccurate and timely diagnosis of amyotrophic lateral sclerosis (ALS) is a diagnostic challenge given the lack of specific diagnostic and imaging biomarkers as well as the significant clinic overlap with mimic syndromes. We hypothesize that MR quantitative susceptibility mapping (QSM) can help differentiate ALS from mimic diagnoses. MethodsIn a blinded retrospective study of MRIs with QSM from 2015 to 2018, we compared motor cortex susceptibility along the hand and face homunculi in ALS patients and patients with similar clinical presentations. Inclusion required a confirmed ALS or a mimic diagnosis. Comparative groups included age-matched patients with MRIs performed for non-motor neuron symptoms that were reported as normal or demonstrated leukoaraiosis. Quantitative susceptibility values were compared with ANOVA and Tukey-Kramer (post-hoc). ROC analysis and Youden's index were used to identify optimal cutoff values. ResultsFifty ALS, 35 mimic, and 70 non-motor neuron symptom patients (35 normal, 35 leukoaraiosis) were included. Hand and face homunculus mean susceptibility values were significantly higher in the ALS group compared to the mimic (p=0.001, p=0.004), leukoaraiosis (p<0.001, p=0.003), and normal (p<0.001, p<0.001) groups. ROC curve analysis comparing ALS to mimics resulted in an area under the curve of 0.71 and 0.67 for the hand and face homunculus measurements, respectively. In differentiating ALS from mimics, Youden's index showed 100% specificity and 36% sensitivity for hand homunculus measurements. ConclusionsQSM has diagnostic potential in the assessment of suspected ALS patients, demonstrating very high specificity in differentiating ALS from mimic diagnoses.

L-Citrulline Level and Transporter Activity Are Altered in Experimental Models of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease caused by the death of the neurons regulating the voluntary muscles which leads to the progressive paralysis. We investigated the difference of transport function of L-citrulline in ALS disease model (NSC-34/hSOD1G93A, MT) and a control model (NSC-34/hSOD1wt, WT). The [14C]L-citrulline uptake was significantly reduced in MT cells as compared with that of control. The Michaelis-Menten constant (Km) for MT cells was 0.67 ± 0.05mM, whereas it was 1.48 ± 0.21mM for control. On the other hand, the Vmax values for MT and control were 10.9 ± 0.8nmol/mg protein/min and 18.3 ± 2.9nmol/mg protein/min, respectively. The Km and Vmax values showed the high affinity and low capacity for MT as compared with control. Moreover, the uptake of [14C]L-citrulline was significantly inhibited by 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) and harmaline which is the inhibitor of the large neutral amino acid transporter1 (LAT1) in NSC-34 cell lines. Furthermore, [14C]L-citrulline uptakes took place in Na+-independent manner. It was also inhibited by the neutral amino acids such as citrulline and phenylalanine. Likewise, L-dopa, gabapentin, and riluzole significantly inhibited the [14C]L-citrulline uptake. It shows the competitive inhibition for L-dopa in ALS cell lines. On the other hand, [14C]L-citrulline uptake in the presence of riluzole showed competitive inhibition in WT cells, whereas it was uncompetitive for MT cells. The small interfering RNA experiments showed that LAT1 is involved in the [14C]L-citrulline uptake in NSC-34 cell lines. On the other hand, in the examination of the alteration in the expression level of LAT1, it was significantly lower in MT cells as compared with that of control. Similarly, in the spinal cord of ALS, transgenic mice revealed a slight but significant decrease in LAT1 immunoreactivity in motor neurons of ALS mice compared with control. However, the LAT1 immunoreactivity in non-motor neurons and in astrocytes was relatively increased in the spinal cord gray matter of ALS mice. The experimental evidences of our results suggest that the change of transport activity of [14C]L-citrulline may be partially responsible for the pathological alteration in ALS.

Circuit Dysfunction in SOD1-ALS Model First Detected in Sensory Feedback Prior to Motor Neuron Degeneration Is Alleviated by BMP Signaling.

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease for which the origin and underlying cellular defects are not fully understood. Although motor neuron degeneration is the signature feature of ALS, it is not clear whether motor neurons or other cells of the motor circuit are the site of disease initiation. To better understand the contribution of multiple cell types in ALS, we made use of a Drosophila Sod1G85R knock-in model, in which all cells harbor the disease allele. End-stage dSod1G85R animals of both sexes exhibit severe motor deficits with clear degeneration of motor neurons. Interestingly, earlier in dSod1G85R larvae, motor function is also compromised, but their motor neurons exhibit only subtle morphological and electrophysiological changes that are unlikely to cause the observed decrease in locomotion. We analyzed the intact motor circuit and identified a defect in sensory feedback that likely accounts for the altered motor activity of dSod1G85R We found cell-autonomous activation of bone morphogenetic protein signaling in proprioceptor sensory neurons which are critical for the relay of the contractile status of muscles back to the central nerve cord, completely rescues early-stage motor defects and partially rescue late-stage motor function to extend lifespan. Identification of a defect in sensory feedback as a potential initiating event in ALS motor dysfunction, coupled with the ability of modified proprioceptors to alleviate such motor deficits, underscores the critical role that nonmotor neurons play in disease progression and highlights their potential as a site to identify early-stage ALS biomarkers and for therapeutic intervention.SIGNIFICANCE STATEMENT At diagnosis, many cellular processes are already disrupted in the amyotrophic lateral sclerosis (ALS) patient. Identifying the initiating cellular events is critical for achieving an earlier diagnosis to slow or prevent disease progression. Our findings indicate that neurons relaying sensory information underlie early stage motor deficits in a Drosophila knock-in model of ALS that best replicates gene dosage in familial ALS (fALS). Importantly, studies on intact motor circuits revealed defects in sensory feedback before evidence of motor neuron degeneration. These findings strengthen our understanding of how neural circuit dysfunctions lead to neurodegeneration and, coupled with our demonstration that the activation of bone morphogenetic protein signaling in proprioceptors alleviates both early and late motor dysfunction, underscores the importance of considering nonmotor neurons as therapeutic targets.

Modeling hallmark pathology using motor neurons derived from the family and sporadic amyotrophic lateral sclerosis patient-specific iPS cells

BackgroundAmyotrophic lateral sclerosis (ALS) represents a devastating, progressive, heterogeneous, and the most common motor neuron (MN) disease. To date, no cure has been available for the condition. Studies with transgenic mice have yielded significant results that help us understand the underlying mechanisms of ALS. Nonetheless, none of more than 30 large clinical trials over the past 20 years proved successful, which led some researchers to challenge the validity of the preclinical models.MethodsHuman-induced pluripotent cells (iPSCs) were established by introducing Sendai virus into fibroblast cells. We established TDP-43 HES by inserting CAG-TDP43 (G298S) cassette or the CAG-EGFP cassette into PPP1R12C-locus of human embryonic stem cells (ESC, H9) by TALEN-mediated homologous recombination. iPSCs or HESC were differentiated to motor neurons and non-motor neuron as control. Relevant biomarkers were detected in different differentiated stages. TDP-43 aggregates, neurofilament, and mitochondria analyses were performed.ResultsIn this study, using iPSCs-derived human MN from an ALS patient with a TDP43 G298S mutation and two sporadic ALS patients, we showed that both sporadic and familial ALS were characterized by TDP-43 aggregates in the surviving MN. Significantly higher neurofilament (NF) inclusion was also found in ALS MN compared with wild-type (WT) GM15 controls (P < 0.05). The neurite mitochondria density was significantly lower in ALS MN than that in the control MNs. Transgenesis of TDP-43 G298S into AAVS locus in human embryonic stem cells reproduced phenotype of patient-derived G289S MN. By challenging MNs with a proteasome inhibitor, we found that MNs were more vulnerable to MG132, with some accompanying phenotype changes, such as TDP43 translocation, NF inclusion, mitochondria distribution impairment, and activation of caspase3.ConclusionsOur results suggested that changes in TDP43 protein, NF inclusion, and distribution impairment of mitochondria are common early pathology both in familial and sporadic ALS. These findings will help us gain insight into the pathogenesis of the condition and screen relevant drugs for the disease.

A Stem Cell-Based Screening Platform Identifies Compounds that Desensitize Motor Neurons to Endoplasmic Reticulum Stress.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease selectively targeting motor neurons in the brain and spinal cord. The reasons for differential motor neuron susceptibility remain elusive. We developed a stem cell-based motor neuron assay to study cell-autonomous mechanisms causing motor neuron degeneration, with implications for ALS. A small-molecule screen identified cyclopiazonic acid (CPA) as a stressor to which stem cell-derived motor neurons were more sensitive than interneurons. CPA induced endoplasmic reticulum stress and the unfolded protein response. Furthermore, CPA resulted in an accelerated degeneration of motor neurons expressing human superoxide dismutase 1 (hSOD1) carrying the ALS-causing G93A mutation, compared to motor neurons expressing wild-type hSOD1. A secondary screen identified compounds that alleviated CPA-mediated motor neuron degeneration: three kinase inhibitors and tauroursodeoxycholic acid (TUDCA), a bile acid derivative. The neuroprotective effects of these compounds were validated in human stem cell-derived motor neurons carrying a mutated SOD1 allele (hSOD1A4V). Moreover, we found that the administration of TUDCA in an hSOD1G93A mouse model of ALS reduced muscle denervation. Jointly, these results provide insights into the mechanisms contributing to the preferential susceptibility of ALS motor neurons, and they demonstrate the utility of stem cell-derived motor neurons for the discovery of new neuroprotective compounds.

Abolishment of Spontaneous Flight Turns in Visually Responsive Drosophila

Animals react rapidly to external stimuli, such as an approaching predator, but in other circumstances, they seem to act spontaneously, without any obvious external trigger. How do the neural processes mediating the execution of reflexive and spontaneous actions differ? We studied this question in tethered, flying Drosophila. We found that silencing a large but genetically defined set of non-motor neurons virtually eliminates spontaneous flight turns while preserving the tethered flies' ability to perform two types of visually evoked turns, demonstrating that, at least in flies, these two modes of action are almost completely dissociable.

RETRACTED ARTICLE: Neuromodulation of internal emergent representations for sequential tasks

Serotonin and dopamine transmitters are synthesized in the lower brain but are transmitted widely to many areas of the brain for diffused use. Emergent representations are critical for understanding their effects. In prior work Zheng et al. (in: Proceedings of 2013 international joint conference on neural networks (IJCNN2013), pp 1404–1411, Dallas, Texas, USA, August 4–9, 2013), their effects on internal, non-motor neurons were studied for only pattern recognition tasks. In this paper, we study their effects on sequential tasks—robot navigation under different settings. They are sequential tasks because the outcome of behavior depends on not only the current behavior as in pattern recognition but also the previous behaviors and environment (e.g., previous navigational trajectories). Analytically, we show that the serotonin and dopamine systems affect the performance of sequential tasks in a compound way. Experimentally, we show that the effect on the learning rate of internal feature neurons (in the Y area) allows the agent to approach a friend and avoid an enemy faster as compounding effects of sequential states in static and dynamic environment. Further, we test the effect of punishment and reward schedule with the same initial locations. These simulation experiments all indicate that the reinforcement learning via the serotonin and dopamine systems is beneficial for developing desirable behaviors in this set of sequential tasks—staying statistically close to its friend and away from its enemy. As far as we know, this is the first work that investigates the effects of reinforcer (via serotonin and dopamine) on internal neurons (Y neurons) for sequential tasks using emergent representations.

Sensory neuropathy in progressive motor neuronopathy (pmn) mice is associated with defects in microtubule polymerization and axonal transport.

Motor neuron diseases such as amyotrophic lateral sclerosis (ALS) are now recognized as multi-system disorders also involving various non-motor neuronal cell types. The precise extent and mechanistic basis of non-motor neuron damage in human ALS and ALS animal models remain however unclear. To address this, we here studied progressive motor neuronopathy (pmn) mice carrying a missense loss-of-function mutation in tubulin binding cofactor E (TBCE). These mice manifest a particularly aggressive form of motor axon dying back and display a microtubule loss, similar to that induced by human ALS-linked TUBA4A mutations. Using whole nerve confocal imaging of pmn × thy1.2-YFP16 fluorescent reporter mice and electron microscopy, we demonstrate axonal discontinuities, bead-like spheroids and ovoids in pmn suralis nerves indicating prominent sensory neuropathy. The axonal alterations qualitatively resemble those in phrenic motor nerves but do not culminate in the loss of myelinated fibers. We further show that the pmn mutation decreases the level of TBCE, impedes microtubule polymerization in dorsal root ganglion (DRG) neurons and causes progressive loss of microtubules in large and small caliber suralis axons. Live imaging of axonal transport using GFP-tagged tetanus toxin C-fragment (GFP-TTC) demonstrates defects in microtubule-based transport in pmn DRG neurons, providing a potential explanation for the axonal alterations in sensory nerves. This study unravels sensory neuropathy as a pathological feature of mouse pmn, and discusses the potential contribution of cytoskeletal defects to sensory neuropathy in human motor neuron disease.

No Change in Executive Performance in ALS Patients: A Longitudinal Neuropsychological Study

Background/Aims: A substantial proportion of amyotrophic lateral sclerosis (ALS) patients develop cognitive impairments. Longitudinal investigations of cognition in ALS have shown mixed results. While some authors report that cognitive performance remains stable as the disease progresses, others have found evidence for deterioration in various domains. Our objective was to investigate cognitive performance in ALS longitudinally, using the example of executive functions. Methods: 93 ALS patients and 73 age-, sex- and education-matched healthy controls underwent up to four neuropsychological evaluations, separated by 3- to 6-month intervals. We examined whether performance declined longitudinally on seven tests assessing various sub-components of executive functioning. Furthermore, we assigned an executive-performance-based ‘cognitive status' to each participant for every evaluation, examining whether cognitive deterioration (if present) was modulated by their baseline cognitive status and whether cognitive status changed over time. Results: Regardless of their cognitive status at baseline, ALS patients showed no significant decline in the sub-components of executive functioning. Conclusion: Our findings imply that the executive deficits which develop in some ALS patients emerge before motor symptoms and remain stable after an initial decline. The discrepancy between this trajectory and the progressive decline in motor functions may result from a differential vulnerability of motor and non-motor prefrontal neurons to the pathomechanism of ALS.

Bunina bodies in motor and non‐motor neurons revisited: A pathological study of anALSpatient after long‐term survival on a respirator

Bunina bodies (BBs) are small eosinophilic neuronal cytoplasmic inclusions (NCIs) found in the remaining lower motor neurons (LMNs) of patients with sporadic amyotrophic lateral sclerosis (SALS), being a specific feature of the cellular pathology. We examined a case of SALS, unassociated with TDP-43 or C9ORF72 mutation, of 12 years duration in a 75-year-old man, who had received artificial respiratory support for 9 years, and showed widespread multisystem degeneration with TDP-43 pathology. Interestingly, in this patient, many NCIs reminiscent of BBs were observed in the oculomotor nucleus, medullary reticular formation and cerebellar dentate nucleus. As BBs in the cerebellar dentate nucleus have not been previously described, we performed ultrastructural and immunohistochemical studies of these NCIs to gain further insight into the nature of BBs. In each region, the ultrastructural features of these NCIs were shown to be identical to those of BBs previously described in LMNs. These three regions and the relatively well preserved sacral anterior horns (S1 and S2) and facial motor nucleus were immunostained with antibodies against cystatin C (CC) and TDP-43. Importantly, it was revealed that BBs exhibiting immunoreactivity for CC were a feature of LMNs, but not of non-motor neurons, and that in the cerebellar dentate nucleus, the ratio of neurons with BBs and TDP-43 inclusions/neurons with BBs was significantly lower than in other regions. These findings suggest that the occurrence of BBs with CC immunoreactivity is intrinsically associated with the particular cellular properties of LMNs, and that the mechanism responsible for the formation of BBs is distinct from that for TDP-43 inclusions.

Postural leg tremor in X-linked spinal and bulbar muscular atrophy

X-linked spinal and bulbar muscular atrophy (SBMA) is an adult-onset neuromuscular disorder caused by a CAG repeat expansion in the androgen receptor gene. Postural hand tremor is well known as a non-motor neuron sign, but to our knowledge postural leg tremor has not been reported. We studied the occurrence and physiological features of postural leg tremor in 12 male patients (38–64years old) with genetically proven SBMA. Three patients had postural leg tremor with a frequency of 4–7Hz. In these patients, sensory nerve action potential (SNAP) was not detected in the lower limbs. There were significant differences between the patients with postural leg tremor and those without postural leg tremor in both the SNAP of the sural nerve and the length of the CAG repeat. Phenotypical differences between shorter CAG repeats, which indicate a sensory-dominant phenotype, and longer CAG repeats, which indicate a motor-dominant phenotype, have been previously reported. In the present study, 60% of patients with shorter CAG repeats (<47) showed leg tremor and none of the patients with longer CAG repeats (⩾47) did. Postural leg tremor could be a clinical feature that predicts shorter CAG repeats of the androgen receptor gene.

Overexpression of human mutated G93A SOD1 changes dynamics of the ER mitochondria calcium cycle specifically in mouse embryonic motor neurons

Motor neurons vulnerable to the rapidly progressive deadly neurodegenerative disease amyotrophic lateral sclerosis (ALS) inherently express low amounts of calcium binding proteins (CaBP), likely to allow physiological motor neuron firing frequency modulation. At the same time motor neurons are susceptible to AMPA receptor mediated excitotoxicity and internal calcium deregulation which is not fully understood. We analysed ER mitochondria calcium cycle (ERMCC) dynamics with subsecond resolution in G93A hSOD1 overexpressing motor neurons as a model of ALS using fluorescent calcium imaging. When comparing vulnerable motor neurons and non-motor neurons from G93A hSOD1 mice and their non-transgenic littermates, we found a decelerated cytosolic calcium clearance in the presence of G93A hSOD1. While both non-transgenic as well as G93A hSOD1 motor neurons displayed large mitochondrial calcium uptake by the mitochondrial uniporter (mUP), the mitochondrial calcium extrusion system was altered in the presence of G93A hSOD1. In addition, ER calcium uptake by the sarco-/endoplasmic reticulum ATPase (SERCA) was increased in G93A hSOD1 motor neurons. In survival assays, blocking the mitochondrial sodium calcium exchanger (mNCE) by CGP37157 as well as inhibiting SERCA by cyclopiazonic acid showed protective effects against kainate induced excitotoxicity. Thus, our study shows for the first time that the functional consequence of G93A hSOD1 overexpression in intact motor neurons is indeed a disturbance of the ER mitochondria calcium cycle, and identified two promising targets for therapeutic intervention in the pathology of ALS.

Treadmill training stimulates brain-derived neurotrophic factor mRNA expression in motor neurons of the lumbar spinal cord in spinally transected rats

Brain-derived neurotrophic factor (BDNF) induces plasticity within the lumbar spinal circuits thereby improving locomotor recovery in spinal cord-injured animals. We examined whether lumbar spinal cord motor neurons and other ventral horn cells of spinally transected (ST) rats were stimulated to produce BDNF mRNA in response to treadmill training. Rats received complete spinal cord transections as neonates (n=20) and one month later, received four weeks of either a low (100 steps/training session; n=10) or high (1000 steps/training session; n=10) amount of robotic-assisted treadmill training. Using combined non-radioactive in situ hybridization and immunohistochemical techniques, we found BDNF mRNA expression in heat shock protein 27-labeled motor neurons and in non-motor neuron cells was greater after 1000 steps/training session compared to the 100 steps/training session and was similar to BDNF mRNA labeling in untrained Intact rats. In addition, there were significantly more motor neurons that contained BDNF mRNA labeling within processes in the ST rats that received the higher amount of treadmill training. These findings suggested that motor neurons and other ventral horn cells in ST rats synthesized BDNF in response to treadmill training. The findings support a mechanism by which postsynaptic release of BDNF from motor neurons contributed to synaptic plasticity.

Coadministration of bicuculline and NMDA induces paraplegia in the rat

Motor neurons (MNs) of an adult rat are normally insensitive to the neurotoxic action of NMDA. Meanwhile, the experiments in non-motor neurons showed that sensitivity to NMDA can be increased by bicuculline, an antagonist at GABAA receptors. The aim of the present work was to examine whether bicuculline would produce such an effect in the adult MNs. In adult Wistar rats, intrathecal injection of bicuculline and NMDA individually failed to affect motor activity of the extremities. In contrast, bicuculline–NMDA combination dose-dependently impaired hindlimb functions. At the 9th day after injections of the combination, a paraplegia with persistent bilateral spastic extension developed in all animals. Light microscopic assessment showed that the development of the motor deficit is associated with pathological changes in spinal motor neurons (swelling, accumulation of the Nissl substance near nucleus, hyperchromatosis, shrinkage, and chromatolysis), mainly in the lumbar ventral horns. Additionally, distinct abnormalities were observed in the white matter of the lumbar cords. The bicuculline–NMDA combination induced a loss of spinal cord MNs while sparing the dorsal horn neurons. The effects of the combination were reversed by muscimol, a GABAA agonist. Thus, an inhibition of GABAAergic processes can induce NMDA sensitivity in adult MNs. The present data may provide new insights into the mechanism of motor disorders in amyotrophic lateral sclerosis and other states wherein the combination of glutamatergic overstimulation and GABAAergic understimulation takes place.