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Lebœuf M, Vargas-Abonce SE, Pezé-Hedsieck E, Dupont E, Jimenez-Alonso L, Moya KL, Prochiantz A. ENGRAILED-1 transcription factor has a paracrine neurotrophic activity on adult spinal α-motoneurons. EMBO Rep 2023; 24:e56525. [PMID: 37534581 PMCID: PMC10398658 DOI: 10.15252/embr.202256525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 05/30/2023] [Accepted: 06/01/2023] [Indexed: 08/04/2023] Open
Abstract
Several homeoprotein transcription factors transfer between cells and regulate gene expression, protein translation, and chromatin organization in recipient cells. ENGRAILED-1 is one such homeoprotein expressed in spinal V1 interneurons that synapse on α-motoneurons. Neutralizing extracellular ENGRAILED-1 by expressing a secreted single-chain antibody blocks its capture by spinal motoneurons resulting in α-motoneuron loss and limb weakness. A similar but stronger phenotype is observed in the Engrailed-1 heterozygote mouse, confirming that ENGRAILED-1 exerts a paracrine neurotrophic activity on spinal cord α-motoneurons. Intrathecal injection of ENGRAILED-1 leads to its specific internalization by spinal motoneurons and has long-lasting protective effects against neurodegeneration and weakness. Midbrain dopaminergic neurons express Engrailed-1 and, similarly to spinal cord α-motoneurons, degenerate in the heterozygote. We identify genes expressed in spinal cord motoneurons whose expression changes in mouse Engrailed-1 heterozygote midbrain neurons. Among these, p62/SQSTM1 shows increased expression during aging in spinal cord motoneurons in the Engrailed-1 heterozygote and upon extracellular ENGRAILED-1 neutralization. We conclude that ENGRAILED-1 might regulate motoneuron aging and has non-cell-autonomous neurotrophic activity.
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Affiliation(s)
- Mélanie Lebœuf
- Center for Interdisciplinary Research in Biology, Collège de France, CNRS, INSERM, Université PSL, Paris, France
- BrainEver SAS, Paris, France
| | - Stephanie E Vargas-Abonce
- Center for Interdisciplinary Research in Biology, Collège de France, CNRS, INSERM, Université PSL, Paris, France
- BrainEver SAS, Paris, France
| | - Eugénie Pezé-Hedsieck
- Center for Interdisciplinary Research in Biology, Collège de France, CNRS, INSERM, Université PSL, Paris, France
| | - Edmond Dupont
- Center for Interdisciplinary Research in Biology, Collège de France, CNRS, INSERM, Université PSL, Paris, France
| | | | - Kenneth L Moya
- Center for Interdisciplinary Research in Biology, Collège de France, CNRS, INSERM, Université PSL, Paris, France
| | - Alain Prochiantz
- Center for Interdisciplinary Research in Biology, Collège de France, CNRS, INSERM, Université PSL, Paris, France
- BrainEver SAS, Paris, France
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2
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Vucic S, Pavey N, Haidar M, Turner BJ, Kiernan MC. Cortical hyperexcitability: Diagnostic and pathogenic biomarker of ALS. Neurosci Lett 2021; 759:136039. [PMID: 34118310 DOI: 10.1016/j.neulet.2021.136039] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 03/04/2021] [Accepted: 06/01/2021] [Indexed: 02/06/2023]
Abstract
Cortical hyperexcitability is an early and intrinsic feature of both sporadic and familial forms of amyotrophic lateral sclerosis (ALS).. Importantly, cortical hyperexcitability appears to be associated with motor neuron degeneration, possibly via an anterograde glutamate-mediated excitotoxic process, thereby forming a pathogenic basis for ALS. The presence of cortical hyperexcitability in ALS patients may be readily determined by transcranial magnetic stimulation (TMS), a neurophysiological tool that provides a non-invasive and painless method for assessing cortical function. Utilising the threshold tracking TMS technique, cortical hyperexcitability has been established as a robust diagnostic biomarker that distinguished ALS from mimicking disorders at early stages of the disease process. The present review discusses the pathophysiological and diagnostic utility of cortical hyperexcitability in ALS.
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Affiliation(s)
- Steve Vucic
- Western Clinical School, University of Sydney, Sydney, Australia.
| | - Nathan Pavey
- Western Clinical School, University of Sydney, Sydney, Australia
| | - Mouna Haidar
- Florey Institute of Neuroscieace and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Bradley J Turner
- Florey Institute of Neuroscieace and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, Australia
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3
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Revill AL, Chu NY, Ma L, LeBlancq MJ, Dickson CT, Funk GD. Postnatal development of persistent inward currents in rat XII motoneurons and their modulation by serotonin, muscarine and noradrenaline. J Physiol 2019; 597:3183-3201. [PMID: 31038198 DOI: 10.1113/jp277572] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 04/23/2019] [Indexed: 01/04/2023] Open
Abstract
KEY POINTS Persistent inward currents (PICs) in spinal motoneurons are long-lasting, voltage-dependent currents that increase excitability; they are dramatically potentiated by serotonin, muscarine, and noradrenaline (norepinephrine). Loss of these modulators (and the PIC) during sleep is hypothesized as a major contributor to REM sleep atonia. Reduced excitability of XII motoneurons that drive airway muscles and maintain airway patency is causally implicated in obstructive sleep apnoea (OSA), but whether XII motoneurons possess a modulator-sensitive PIC that could be a factor in the reduced airway tone of sleep is unknown. Whole-cell recordings from rat XII motoneurons in brain slices indicate that PIC amplitude increases ∼50% between 1 and 23 days of age, when potentiation of the PIC by 5HT2 , muscarinic, or α1 noradrenergic agonists peaks at <50%, manyfold lower than the potentiation observed in spinal motoneurons. α1 noradrenergic receptor activation produced changes in XII motoneuron firing behaviour consistent with PIC involvement, but indicators of strong PIC activation were never observed; in vivo experiments are needed to determine the role of the modulator-sensitive PIC in sleep-dependent reductions in airway tone. ABSTRACT Hypoglossal (XII) motoneurons play a key role in maintaining airway patency; reductions in their excitability during sleep through inhibition and disfacilitation, i.e. loss of excitatory modulation, is implicated in obstructive sleep apnoea. In spinal motoneurons, 5HT2 , muscarinic and α1 noradrenergic modulatory systems potentiate persistent inward currents (PICs) severalfold, dramatically increasing excitability. If the PICs in XII and spinal motoneurons are equally sensitive to modulation, loss of the PIC secondary to reduced modulatory tone during sleep could contribute to airway atonia. Modulatory systems also change developmentally. We therefore characterized developmental changes in magnitude of the XII motoneuron PIC and its sensitivity to modulation by comparing, in neonatal (P1-4) and juvenile (P14-23) rat brainstem slices, the PIC elicited by slow voltage ramps in the absence and presence of agonists for 5HT2 , muscarinic, and α1 noradrenergic receptors. XII motoneuron PIC amplitude increased developmentally (from -195 ± 12 to -304 ± 19 pA). In neonatal XII motoneurons, the PIC was only potentiated by α1 receptor activation (5 ± 4%). In contrast, all modulators potentiated the juvenile XII motoneurons PIC (5HT2 , 5 ± 5%; muscarine, 22 ± 11%; α1 , 18 ± 5%). These data suggest that the influence of the PIC and its modulation on XII motoneuron excitability will increase with postnatal development. Notably, the modulator-induced potentiation of the PIC in XII motoneurons was dramatically smaller than the 2- to 6-fold potentiation reported for spinal motoneurons. In vivo measurements are required to determine if the modulator-sensitive, XII motoneuron PIC is an important factor in sleep-state dependent reductions in airway tone.
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Affiliation(s)
- Ann L Revill
- Department of Physiology, University of Alberta, Edmonton, AB, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Women and Children's Health Research Institute, University of Alberta, Edmonton, AB, Canada
| | - Nathan Y Chu
- Department of Physiology, University of Alberta, Edmonton, AB, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Women and Children's Health Research Institute, University of Alberta, Edmonton, AB, Canada
| | - Li Ma
- Department of Physiology, University of Alberta, Edmonton, AB, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | | | - Clayton T Dickson
- Department of Physiology, University of Alberta, Edmonton, AB, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Women and Children's Health Research Institute, University of Alberta, Edmonton, AB, Canada.,Department of Psychology, University of Alberta, Edmonton, AB, Canada
| | - Gregory D Funk
- Department of Physiology, University of Alberta, Edmonton, AB, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Women and Children's Health Research Institute, University of Alberta, Edmonton, AB, Canada
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4
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Quinlan KA, Kajtaz E, Ciolino JD, Imhoff-Manuel RD, Tresch MC, Heckman CJ, Tysseling VM. Chronic electromyograms in treadmill running SOD1 mice reveal early changes in muscle activation. J Physiol 2017; 595:5387-5400. [PMID: 28543166 DOI: 10.1113/jp274170] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 05/12/2017] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS The present study demonstrates that electromyograms (EMGs) obtained during locomotor activity in mice were effective for identification of early physiological markers of amyotrophic lateral sclerosis (ALS). These measures could be used to evaluate therapeutic intervention strategies in animal models of ALS. Several parameters of locomotor activity were shifted early in the disease time course in SOD1G93A mice, especially when the treadmill was inclined, including intermuscular phase, burst skew and amplitude of the locomotor bursts. The results of the present study indicate that early compensatory changes may be taking place within the neural network controlling locomotor activity, including spinal interneurons. Locomotor EMGs could have potential use as a clinical diagnostic tool. ABSTRACT To improve our understanding of early disease mechanisms and to identify reliable biomarkers of amyotrophic lateral sclerosis (ALS), a progressive neurodegenerative disease, we measured electromyogram (EMG) activity in hind limb muscles of SOD1G93A mice. By contrast to clinical diagnostic measures using EMGs, which are performed on quiescent patients, we monitored activity during treadmill running aiming to detect presymptomatic changes in motor patterning. Chronic EMG electrodes were implanted into vastus lateralis, biceps femoris posterior, lateral gastrocnemius and tibialis anterior in mice from postnatal day 55 to 100 and the results obtained were assessed using linear mixed models. We evaluated differences in parameters related to EMG amplitude (peak and area) and timing (phase and skew, a measure of burst shape) when animals ran on level and inclined treadmills. There were significant changes in both the timing of activity and the amplitude of EMG bursts in SOD1G93A mice. Significant differences between wild-type and SOD1G93A mice were mainly observed when animals locomoted on inclined treadmills. All muscles had significant effects of mutation that were independent of age. These novel results indicate (i) locomotor EMG activity might be an early measure of disease onset; (ii) alterations in locomotor patterning may reflect changes in neuronal drive and compensation at the network level including altered activity of spinal interneurons; and (iii) the increased power output necessary on an inclined treadmill was important in revealing altered activity in SOD1G93A mice.
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Affiliation(s)
- Katharina A Quinlan
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Elma Kajtaz
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Jody D Ciolino
- Department of Preventative Medicine, Northwestern University, Chicago, IL, USA
| | - Rebecca D Imhoff-Manuel
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Matthew C Tresch
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,McCormick Biomedical Engineering Department, Northwestern University, Evanston, IL, USA.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Charles J Heckman
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Vicki M Tysseling
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
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5
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Park SB, Kiernan MC, Vucic S. Axonal Excitability in Amyotrophic Lateral Sclerosis : Axonal Excitability in ALS. Neurotherapeutics 2017; 14:78-90. [PMID: 27878516 PMCID: PMC5233634 DOI: 10.1007/s13311-016-0492-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Axonal excitability testing provides in vivo assessment of axonal ion channel function and membrane potential. Excitability techniques have provided insights into the pathophysiological mechanisms underlying the development of neurodegeneration and clinical features of amyotrophic lateral sclerosis (ALS) and related neuromuscular disorders. Specifically, abnormalities of Na+ and K+ conductances contribute to development of membrane hyperexcitability in ALS, thereby leading to symptom generation of muscle cramps and fasciculations, in addition to promoting a neurodegenerative cascade via Ca2+-mediated processes. Modulation of axonal ion channel function in ALS has resulted in significant symptomatic improvement that has been accompanied by stabilization of axonal excitability parameters. Separately, axonal ion channel dysfunction evolves with disease progression and correlates with survival, thereby serving as a potential therapeutic biomarker in ALS. The present review provides an overview of axonal excitability techniques and the physiological mechanisms underlying membrane excitability, with a focus on the role of axonal ion channel dysfunction in motor neuron disease and related neuromuscular diseases.
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Affiliation(s)
- Susanna B Park
- Brain and Mind Centre, University of Sydney, Sydney, Australia
| | | | - Steve Vucic
- Westmead Clinical School, University of Sydney, Sydney, Australia.
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6
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Geevasinga N, Menon P, Özdinler PH, Kiernan MC, Vucic S. Pathophysiological and diagnostic implications of cortical dysfunction in ALS. Nat Rev Neurol 2016; 12:651-661. [DOI: 10.1038/nrneurol.2016.140] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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7
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Faunes M, Oñate-Ponce A, Fernández-Collemann S, Henny P. Excitatory and inhibitory innervation of the mouse orofacial motor nuclei: A stereological study. J Comp Neurol 2015. [DOI: 10.1002/cne.23862] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Macarena Faunes
- Laboratorio de Neuroanatomía, Departamento de Anatomía Normal, Escuela de Medicina; Pontificia Universidad Católica de Chile; Santiago Chile
- Centro Interdisciplinario de Neurociencias; Pontificia Universidad Católica de Chile; Santiago Chile
- Sensory and Motor Systems Group, Department of Anatomy with Radiology, Faculty of Medical and Health Sciences; University of Auckland; Private Bag 92019, Grafton 1023 Auckland New Zealand
| | - Alejandro Oñate-Ponce
- Laboratorio de Neuroanatomía, Departamento de Anatomía Normal, Escuela de Medicina; Pontificia Universidad Católica de Chile; Santiago Chile
- Centro Interdisciplinario de Neurociencias; Pontificia Universidad Católica de Chile; Santiago Chile
| | - Sara Fernández-Collemann
- Laboratorio de Neuroanatomía, Departamento de Anatomía Normal, Escuela de Medicina; Pontificia Universidad Católica de Chile; Santiago Chile
- Centro Interdisciplinario de Neurociencias; Pontificia Universidad Católica de Chile; Santiago Chile
| | - Pablo Henny
- Laboratorio de Neuroanatomía, Departamento de Anatomía Normal, Escuela de Medicina; Pontificia Universidad Católica de Chile; Santiago Chile
- Centro Interdisciplinario de Neurociencias; Pontificia Universidad Católica de Chile; Santiago Chile
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8
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Alves CJ, Maximino JR, Chadi G. Dysregulated expression of death, stress and mitochondrion related genes in the sciatic nerve of presymptomatic SOD1(G93A) mouse model of Amyotrophic Lateral Sclerosis. Front Cell Neurosci 2015; 9:332. [PMID: 26339226 PMCID: PMC4555015 DOI: 10.3389/fncel.2015.00332] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 08/10/2015] [Indexed: 12/11/2022] Open
Abstract
Schwann cells are the main source of paracrine support to motor neurons. Oxidative stress and mitochondrial dysfunction have been correlated to motor neuron death in Amyotrophic Lateral Sclerosis (ALS). Despite the involvement of Schwann cells in early neuromuscular disruption in ALS, detailed molecular events of a dying-back triggering are unknown. Sciatic nerves of presymptomatic (60-day-old) SOD1(G93A) mice were submitted to a high-density oligonucleotide microarray analysis. DAVID demonstrated the deregulated genes related to death, stress and mitochondrion, which allowed the identification of Cell cycle, ErbB signaling, Tryptophan metabolism and Rig-I-like receptor signaling as the most representative KEGG pathways. The protein-protein interaction networks based upon deregulated genes have identified the top hubs (TRAF2, H2AFX, E2F1, FOXO3, MSH2, NGFR, TGFBR1) and bottlenecks (TRAF2, E2F1, CDKN1B, TWIST1, FOXO3). Schwann cells were enriched from the sciatic nerve of presymptomatic mice using flow cytometry cell sorting. qPCR showed the up regulated (Ngfr, Cdnkn1b, E2f1, Traf2 and Erbb3, H2afx, Cdkn1a, Hspa1, Prdx, Mapk10) and down-regulated (Foxo3, Mtor) genes in the enriched Schwann cells. In conclusion, molecular analyses in the presymptomatic sciatic nerve demonstrated the involvement of death, oxidative stress, and mitochondrial pathways in the Schwann cell non-autonomous mechanisms in the early stages of ALS.
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Affiliation(s)
- Chrystian J Alves
- Department of Neurology, Neuroregeneration Center, University of São Paulo School of Medicine São Paulo, Brazil
| | - Jessica R Maximino
- Department of Neurology, Neuroregeneration Center, University of São Paulo School of Medicine São Paulo, Brazil
| | - Gerson Chadi
- Department of Neurology, Neuroregeneration Center, University of São Paulo School of Medicine São Paulo, Brazil
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9
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Quinlan KA, Lamano JB, Samuels J, Heckman CJ. Comparison of dendritic calcium transients in juvenile wild type and SOD1(G93A) mouse lumbar motoneurons. Front Cell Neurosci 2015; 9:139. [PMID: 25914627 PMCID: PMC4392694 DOI: 10.3389/fncel.2015.00139] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 03/23/2015] [Indexed: 12/14/2022] Open
Abstract
Previous studies of spinal motoneurons in the SOD1 mouse model of amyotrophic lateral sclerosis have shown alterations long before disease onset, including increased dendritic branching, increased persistent Na+ and Ca2+ currents, and impaired axonal transport. In this study dendritic Ca2+ entry was investigated using two photon excitation fluorescence microscopy and whole-cell patch-clamp of juvenile (P4-11) motoneurons. Neurons were filled with both Ca2+ Green-1 and Texas Red dextrans, and line scans performed throughout. Steps were taken to account for different sources of variability, including (1) dye filling and laser penetration, (2) dendritic anatomy, and (3) the time elapsed from the start of recording. First, Ca2+ Green-1 fluorescence was normalized by Texas Red; next, neurons were reconstructed so anatomy could be evaluated; finally, time was recorded. Customized software detected the largest Ca2+ transients (area under the curve) from each line scan and matched it with parameters above. Overall, larger dendritic diameter and shorter path distance from the soma were significant predictors of larger transients, while time was not significant up to 2 h (data thereafter was dropped). However, Ca2+ transients showed additional variability. Controlling for previous factors, significant variation was found between Ca2+ signals from different processes of the same neuron in 3/7 neurons. This could reflect differential expression of Ca2+ channels, local neuromodulation or other variations. Finally, Ca2+ transients in SOD1G93A motoneurons were significantly smaller than in non-transgenic motoneurons. In conclusion, motoneuron processes show highly variable Ca2+ transients, but these transients are smaller overall in SOD1G93A motoneurons.
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Affiliation(s)
- Katharina A Quinlan
- Department of Physiology, Feinberg School of Medicine, Northwestern University Chicago, IL, USA
| | - Jonathan B Lamano
- Department of Physiology, Feinberg School of Medicine, Northwestern University Chicago, IL, USA
| | - Julienne Samuels
- Department of Physiology, Feinberg School of Medicine, Northwestern University Chicago, IL, USA
| | - C J Heckman
- Department of Physiology, Feinberg School of Medicine, Northwestern University Chicago, IL, USA ; Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University Chicago, IL, USA ; Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University Chicago, IL, USA
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10
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Abstract
While task‐dependent changes in motor cortical outputs have been previously reported, the issue of whether such changes are specific for complex hand tasks remains unresolved. The aim of the present study was to determine whether cortical inhibitory tone and cortical output were greater during precision grip and power grip. Motor cortex excitability was undertaken by using the transcranial magnetic stimulation threshold tracking technique in 15 healthy subjects. The motor‐evoked potential (MEP) responses were recorded over the abductor pollicis brevis (APB), with the hand in the following positions: (1) rest, (2) precision grip and (3) power grip. The MEP amplitude (MEP amplitude REST 23.6 ± 3.3%; MEP amplitude PRECISIONGRIP 35.2 ± 5.6%; MEP amplitude POWERGRIP 19.6 ± 3.4%, F = 2.4, P < 0.001) and stimulus‐response gradient (SLOPEREST 0.06 ± 0.01; SLOPEPRCISIONGRIP 0.15 ± 0.04; SLOPE POWERGRIP 0.07 ± 0.01, P < 0.05) were significantly increased during precision grip. Short interval intracortical inhibition (SICI) was significantly reduced during the precision grip (SICI REST 15.0 ± 2.3%; SICI PRECISIONGRIP 9.7 ± 1.5%, SICI POWERGRIP 15.9 ± 2.7%, F = 2.6, P < 0.05). The present study suggests that changes in motor cortex excitability are specific for precision grip, with functional coupling of descending corticospinal pathways controlling thumb and finger movements potentially forming the basis of these cortical changes. This manuscript establishes that specific cortical mechanisms underlie the maintenance of the precision grip. The mechanisms appear distinct to the processes maintaining the power grip.
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Affiliation(s)
- Nimeshan Geevasinga
- Sydney Medical School Westmead, University of Sydney, Sydney, NSW, Australia
| | - Parvathi Menon
- Sydney Medical School Westmead, University of Sydney, Sydney, NSW, Australia
| | - Matthew C Kiernan
- The Brain and Mind Research Institute, University of Sydney, Sydney, NSW, Australia
| | - Steve Vucic
- Sydney Medical School Westmead, University of Sydney, Sydney, NSW, Australia
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11
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Eisen A, Kiernan M, Mitsumoto H, Swash M. Amyotrophic lateral sclerosis: a long preclinical period? J Neurol Neurosurg Psychiatry 2014; 85:1232-8. [PMID: 24648037 DOI: 10.1136/jnnp-2013-307135] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The onset of amyotrophic lateral sclerosis (ALS) is conventionally considered as commencing with the recognition of clinical symptoms. We propose that, in common with other neurodegenerations, the pathogenic mechanisms culminating in ALS phenotypes begin much earlier in life. Animal models of genetically determined ALS exhibit pathological abnormalities long predating clinical deficits. The overt clinical ALS phenotype may develop when safety margins are exceeded subsequent to years of mitochondrial dysfunction, neuroinflammation or an imbalanced environment of excitation and inhibition in the neuropil. Somatic mutations, the epigenome and external environmental influences may interact to trigger a metabolic cascade that in the adult eventually exceeds functional threshold. A long preclinical and subsequent presymptomatic period pose a challenge for recognition, since it offers an opportunity for protective and perhaps even preventive therapeutic intervention to rescue dysfunctional neurons. We suggest, by analogy with other neurodegenerations and from SOD1 ALS mouse studies, that vulnerability might be induced in the perinatal period.
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Affiliation(s)
- Andrew Eisen
- Division of Neurology, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Hiroshi Mitsumoto
- Wesley J. Howe Professor of Neurology at CUMC, Eleanor and Lou Gehrig MDA/ALS Research Center, The Neurological Institute of New York, Columbia University Medical Center, New York, USA
| | - Michael Swash
- Queen Mary University of London, UK Institute of Neuroscience, University of Lisbon, Portugal
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12
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Shoenfeld L, Westenbroek RE, Fisher E, Quinlan KA, Tysseling VM, Powers RK, Heckman CJ, Binder MD. Soma size and Cav1.3 channel expression in vulnerable and resistant motoneuron populations of the SOD1G93A mouse model of ALS. Physiol Rep 2014; 2:2/8/e12113. [PMID: 25107988 PMCID: PMC4246589 DOI: 10.14814/phy2.12113] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Although the loss of motoneurons is an undisputed feature of amyotrophic lateral sclerosis (ALS) in man and in its animal models (SOD1 mutant mice), how the disease affects the size and excitability of motoneurons prior to their degeneration is not well understood. This study was designed to test the hypothesis that motoneurons in mutant SOD1G93A mice exhibit an enlargement of soma size (i.e., cross‐sectional area) and an increase in Cav1.3 channel expression at postnatal day 30, well before the manifestation of physiological symptoms that typically occur at p90 (Chiu et al. 1995). We made measurements of spinal and hypoglossal motoneurons vulnerable to degeneration, as well as motoneurons in the oculomotor nucleus that are resistant to degeneration. Overall, we found that the somata of motoneurons in male SOD1G93A mutants were larger than those in wild‐type transgenic males. When females were included in the two groups, significance was lost. Expression levels of the Cav1.3 channels were not differentiated by genotype, sex, or any interaction of the two. These results raise the intriguing possibility of an interaction between male sex steroid hormones and the SOD1 mutation in the etiopathogenesis of ALS. This study was designed to test the hypothesis that motoneurons in mutant SOD1G93A mice exhibit an enlargement of soma size (i.e., cross‐sectional area) and an increase in Cav1.3 channel expression at postnatal day 30, well before the manifestation of physiological symptoms that typically occur at p90 (Chiu et al. 1995). We made measurements of spinal and hypoglossal motoneurons vulnerable to degeneration, as well as motoneurons in the oculomotor nucleus that are resistant to degeneration. Overall, we found that the somata of motoneurons in male SOD1G93A mutants were larger than those in wild‐type transgenic males. When females were included in the two groups, significance was lost. These results raise the intriguing possibility of an interaction between male sex steroid hormones and the SOD1 mutation in the etiopathogenesis of ALS.
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Affiliation(s)
- Liza Shoenfeld
- Graduate Program in Neurobiology & Behavior, University of Washington, Seattle, Washington, USA
| | - Ruth E Westenbroek
- Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Erika Fisher
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, Washington, USA
| | - Katharina A Quinlan
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Vicki M Tysseling
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA Department of Physical Therapy and Human Movement Sciences, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Randall K Powers
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, Washington, USA
| | - Charles J Heckman
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA Department of Physical Therapy and Human Movement Sciences, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Marc D Binder
- Graduate Program in Neurobiology & Behavior, University of Washington, Seattle, Washington, USA Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, Washington, USA
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13
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Menon P, Kiernan MC, Vucic S. Cortical excitability differences in hand muscles follow a split-hand pattern in healthy controls. Muscle Nerve 2014; 49:836-44. [DOI: 10.1002/mus.24072] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 08/26/2013] [Accepted: 09/03/2013] [Indexed: 12/13/2022]
Affiliation(s)
- Parvathi Menon
- Department of Neurology; Westmead Hospital; Cnr Hawkesbury and Darcy Road Westmead NSW 2145
| | - Matthew C. Kiernan
- Neuroscience Research Australia; Randwick NSW Australia
- Prince of Wales Clinical School; University of New South Wales; Sydney Australia
| | - Steve Vucic
- Department of Neurology; Westmead Hospital; Cnr Hawkesbury and Darcy Road Westmead NSW 2145
- Neuroscience Research Australia; Randwick NSW Australia
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14
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Akay T. Long-term measurement of muscle denervation and locomotor behavior in individual wild-type and ALS model mice. J Neurophysiol 2014; 111:694-703. [DOI: 10.1152/jn.00507.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The increasing number of mouse models of human degenerative and injury-related diseases that affect motor behavior raises the importance of in vivo methodologies allowing measurement of physiological and behavioral changes over an extended period of time in individual animals. A method that provides long-term measurements of muscle denervation and its behavioral consequences in individual mice for several months is presented in this article. The method is applied to mSod1G93A mice, which model human amyotrophic lateral sclerosis (ALS). The denervation process of gastrocnemius and soleus muscles in mSod1G93A mice is demonstrated for up to 3 mo. The data suggest that as muscle denervation progresses, massive behavioral compensation occurs within the spinal cord that allows animals to walk almost normally until late ages. Only around the age of 84 days is the first sign of abnormal movement during walking behavior detected as an abnormal tibialis anterior activity profile that is manifested in subtle but abnormal swing movement during walking. Additionally, this method can be used with other mouse models of human diseases, such as spinal cord injury, intracerebral hemorrhage, Parkinson's diseases, and spinal muscular atrophy.
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Affiliation(s)
- Turgay Akay
- Department of Neurological Surgery, Center for Motor Neuron Biology and Disease, Columbia University Medical Center, New York, New York
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15
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Linne ML, Jalonen TO. Astrocyte-neuron interactions: from experimental research-based models to translational medicine. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 123:191-217. [PMID: 24560146 DOI: 10.1016/b978-0-12-397897-4.00005-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In this chapter, we review the principal astrocyte functions and the interactions between neurons and astrocytes. We then address how the experimentally observed functions have been verified in computational models and review recent experimental literature on astrocyte-neuron interactions. Benefits of computational neuroscience work are highlighted through selected studies with neurons and astrocytes by analyzing the existing models qualitatively and assessing the relevance of these models to experimental data. Common strategies to mathematical modeling and computer simulation in neuroscience are summarized for the nontechnical reader. The astrocyte-neuron interactions are then further illustrated by examples of some neurological and neurodegenerative diseases, where the miscommunication between glia and neurons is found to be increasingly important.
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Affiliation(s)
- Marja-Leena Linne
- Computational Neuroscience Group, Department of Signal Processing, Tampere University of Technology, Tampere, Finland
| | - Tuula O Jalonen
- Department of Physiology and Neuroscience, St. George's University, School of Medicine, Grenada, West Indies
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16
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Hebron M, Chen W, Miessau MJ, Lonskaya I, Moussa CEH. Parkin reverses TDP-43-induced cell death and failure of amino acid homeostasis. J Neurochem 2013; 129:350-61. [PMID: 24298989 DOI: 10.1111/jnc.12630] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 11/27/2013] [Accepted: 11/27/2013] [Indexed: 12/13/2022]
Abstract
The E3 ubiquitin ligase Parkin plays a central role in the pathogenesis of many neurodegenerative diseases. Parkin promotes specific ubiquitination and affects the localization of transactivation response DNA-binding protein 43 (TDP-43), which controls the translation of thousands of mRNAs. Here we tested the effects of lentiviral Parkin and TDP-43 expression on amino acid metabolism in the rat motor cortex using high frequency ¹³C NMR spectroscopy. TDP-43 expression increased glutamate levels, decreased the levels of other amino acids, including glutamine, aspartate, leucine and isoleucine, and impaired mitochondrial tricarboxylic acid cycle. TDP-43 induced lactate accumulation and altered the balance between excitatory (glutamate) and inhibitory (GABA) neurotransmitters. Parkin restored amino acid levels, neurotransmitter balance and tricarboxylic acid cycle metabolism, rescuing neurons from TDP-43-induced apoptotic death. Furthermore, TDP-43 expression led to an increase in 4E-BP levels, perhaps altering translational control and deregulating amino acid synthesis; while Parkin reversed the effects of TDP-43 on the 4E-BP signaling pathway. Taken together, these data suggest that Parkin may affect TDP-43 localization and mitigate its effects on 4E-BP signaling and loss of amino acid homeostasis.
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Affiliation(s)
- Michaeline Hebron
- Department of Neuroscience, Georgetown University Medical Center, Washington, District of Columbia, USA
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17
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Armstrong GAB, Drapeau P. Loss and gain of FUS function impair neuromuscular synaptic transmission in a genetic model of ALS. Hum Mol Genet 2013; 22:4282-92. [PMID: 23771027 DOI: 10.1093/hmg/ddt278] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) presents clinically in adulthood and is characterized by the loss of motoneurons in the spinal cord and cerebral cortex. Animal models of the disease suggest that significant neuronal abnormalities exist during preclinical stages of the disease. Mutations in the gene fused in sarcoma (FUS) are associated with ALS and cause impairment in motor function in animal models. However, the mechanism of neuromuscular dysfunction underlying pathophysiological deficits causing impairment in locomotor function resulting from mutant FUS expression is unknown. To characterize the cellular pathophysiological defect, we expressed the wild-type human gene (wtFUS) or the ALS-associated mutation R521H (mutFUS) gene in zebrafish larvae and characterized their motor (swimming) activity and function of their neuromuscular junctions (NMJs). Additionally, we tested knockdown of zebrafish fus with an antisense morpholino oligonucleotide (fus AMO). Expression of either mutFUS or knockdown of fus resulted in impaired motor activity and reduced NMJ synaptic fidelity with reduced quantal transmission. Primary motoneurons expressing mutFUS were found to be more excitable. These impairments in neuronal function could be partially restored in fus AMO larvae also expressing wtFUS (fus AMO+wtFUS) but not mutFUS (fus AMO+mutFUS). These results show that both a loss and gain of FUS function result in defective presynaptic function at the NMJ.
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Affiliation(s)
- Gary A B Armstrong
- Department of Pathology and Cell Biology and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, QC, Canada H3C 3J7
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18
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Loss of calretinin- and parvalbumin-immunoreactive axons in anterolateral columns beyond the corticospinal tracts of amyotrophic lateral sclerosis spinal cords. J Neurol Sci 2013; 331:61-6. [PMID: 23764361 DOI: 10.1016/j.jns.2013.05.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 05/03/2013] [Accepted: 05/10/2013] [Indexed: 12/13/2022]
Abstract
In amyotrophic lateral sclerosis (ALS) spinal cords, diffuse myelin pallor (dMP) in the anterolateral columns (ALCs) beyond the corticospinal tracts has been frequently observed; however, its origin still remains to be elucidated. To address this issue, we focused on calretinin (CR) and parvalbumin (PV), since these buffer calcium-binding proteins (CaBP) are predominantly expressed in axons in the ALCs of neurologically normal human spinal white matter. Immunohistochemical methods revealed that numbers of both CR-immunoreactive (ir) and PV-ir axons were significantly lower in ALS patients' spinal cords with dMP compared to those in controls. In ALS patients' spinal cords without dMP, there were also significant reductions in the number of these CaBP-ir axons compared to controls. In contrast, the number of CR-ir neurons in the spinal gray matter did not differ significantly among ALS patients and controls. These findings suggest that a loss of CaBP-ir axons may precede the development of dMP in ALS patients' spinal cords, and the dying back mechanism would underlie this phenomenon.
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19
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Fuchs A, Kutterer S, Mühling T, Duda J, Schütz B, Liss B, Keller BU, Roeper J. Selective mitochondrial Ca2+ uptake deficit in disease endstage vulnerable motoneurons of the SOD1G93A mouse model of amyotrophic lateral sclerosis. J Physiol 2013; 591:2723-45. [PMID: 23401612 PMCID: PMC3678052 DOI: 10.1113/jphysiol.2012.247981] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 02/04/2013] [Indexed: 12/13/2022] Open
Abstract
Amyotrophic lateral sclerosis is a progressive neurodegenerative disease that targets some somatic motoneuron populations, while others, e.g. those of the oculomotor system, are spared. The pathophysiological basis of this pattern of differential vulnerability, which is preserved in a transgenic mouse model of amyotrophic lateral sclerosis (SOD1(G93A)), and the mechanism of neurodegeneration in general are unknown. Hyperexcitability and calcium dysregulation have been proposed by others on the basis of data from juvenile mice that are, however, asymptomatic. No studies have been done with symptomatic mice following disease progression to the disease endstage. Here, we developed a new brainstem slice preparation for whole-cell patch-clamp recordings and single cell fura-2 calcium imaging to study motoneurons in adult wild-type and SOD1(G93A) mice up to disease endstage. We analysed disease-stage-dependent electrophysiological properties and intracellular Ca(2+) handling of vulnerable hypoglossal motoneurons in comparison to resistant oculomotor neurons. Thereby, we identified a transient hyperexcitability in presymptomatic but not in endstage vulnerable motoneurons. Additionally, we revealed a remodelling of intracellular Ca(2+) clearance within vulnerable but not resistant motoneurons at disease endstage characterised by a reduction of uniporter-dependent mitochondrial Ca(2+) uptake and enhanced Ca(2+) extrusion across the plasma membrane. Our study challenged the notion that hyperexcitability is a direct cause of neurodegeneration in SOD1(G93A) mice, but molecularly identified a Ca(2+) clearance deficit in motoneurons and an adaptive Ca(2+) handling strategy that might be targeted by future therapeutic strategies.
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Affiliation(s)
- Andrea Fuchs
- Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, Retzius Väg 8, 17177 Stockholm, Sweden.
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20
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Calcium channel agonists protect against neuromuscular dysfunction in a genetic model of TDP-43 mutation in ALS. J Neurosci 2013; 33:1741-52. [PMID: 23345247 DOI: 10.1523/jneurosci.4003-12.2013] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
TAR DNA binding protein (TDP-43, encoded by the TARDBP gene) has recently been shown to be associated with amyotrophic lateral sclerosis (ALS), but the early pathophysiological deficits causing impairment in motor function are unknown. Here we expressed the wild-type human gene (wtTARDBP) or the ALS mutation G348C (mutTARDBP) in zebrafish larvae and characterized their motor (swimming) activity and the structure and function of their neuromuscular junctions (NMJs). Of these groups only mutTARDBP larvae showed impaired swimming and increased motoneuron vulnerability with reduced synaptic fidelity, reduced quantal transmission, and more orphaned presynaptic and postsynaptic structures at the NMJ. Remarkably, all behavioral and cellular features were stabilized by chronic treatment with either of the L-type calcium channel agonists FPL 64176 or Bay K 8644. These results indicate that expression of mutTARDBP results in defective NMJs and that calcium channel agonists could be novel therapeutics for ALS.
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21
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Wootz H, Fitzsimons-Kantamneni E, Larhammar M, Rotterman TM, Enjin A, Patra K, André E, Van Zundert B, Kullander K, Alvarez FJ. Alterations in the motor neuron-renshaw cell circuit in the Sod1(G93A) mouse model. J Comp Neurol 2013; 521:1449-69. [PMID: 23172249 DOI: 10.1002/cne.23266] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 09/14/2012] [Accepted: 11/06/2012] [Indexed: 12/12/2022]
Abstract
Motor neurons become hyperexcitable during progression of amyotrophic lateral sclerosis (ALS). This abnormal firing behavior has been explained by changes in their membrane properties, but more recently it has been suggested that changes in premotor circuits may also contribute to this abnormal activity. The specific circuits that may be altered during development of ALS have not been investigated. Here we examined the Renshaw cell recurrent circuit that exerts inhibitory feedback control on motor neuron firing. Using two markers for Renshaw cells (calbindin and cholinergic nicotinic receptor subunit alpha2 [Chrna2]), two general markers for motor neurons (NeuN and vesicular acethylcholine transporter [VAChT]), and two markers for fast motor neurons (Chondrolectin and calcitonin-related polypeptide alpha [Calca]), we analyzed the survival and connectivity of these cells during disease progression in the Sod1(G93A) mouse model. Most calbindin-immunoreactive (IR) Renshaw cells survive to end stage but downregulate postsynaptic Chrna2 in presymptomatic animals. In motor neurons, some markers are downregulated early (NeuN, VAChT, Chondrolectin) and others at end stage (Calca). Early downregulation of presynaptic VAChT and Chrna2 was correlated with disconnection from Renshaw cells as well as major structural abnormalities of motor axon synapses inside the spinal cord. Renshaw cell synapses on motor neurons underwent more complex changes, including transitional sprouting preferentially over remaining NeuN-IR motor neurons. We conclude that the loss of presynaptic motor axon input on Renshaw cells occurs at early stages of ALS and disconnects the recurrent inhibitory circuit, presumably resulting in diminished control of motor neuron firing. J. Comp. Neurol. 521:1449-1469, 2013. © 2012 Wiley Periodicals, Inc.
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Affiliation(s)
- Hanna Wootz
- Department of Neuroscience, Uppsala University, 75124 Uppsala, Sweden
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22
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van Zundert B, Izaurieta P, Fritz E, Alvarez FJ. Early pathogenesis in the adult-onset neurodegenerative disease amyotrophic lateral sclerosis. J Cell Biochem 2013; 113:3301-12. [PMID: 22740507 DOI: 10.1002/jcb.24234] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating paralytic disorder caused by dysfunction and degeneration of motor neurons starting in adulthood. Most of our knowledge about the pathophysiological mechanisms of ALS comes from transgenic mice models that emulate a subgroup of familial ALS cases (FALS), with mutations in the gene encoding superoxide dismutase (SOD1). In the more than 15 years since these mice were generated, a large number of abnormal cellular mechanisms underlying motor neuron degeneration have been identified, but to date this effort has led to few improvements in therapy, and no cure. Here, we consider that this surfeit of mechanisms is best interpreted by current insights that suggest a very early initiation of pathology in motor neurons, followed by a diversity of secondary cascades and compensatory mechanisms that mask symptoms for decades, until trauma and/or aging overloads their protective function. This view thus posits that adult-onset ALS is the consequence of processes initiated during early development. In fact, motor neurons in neonatal mutant SOD mice display important alterations in their intrinsic electrical properties, synaptic inputs and morphology that are accompanied by subtle behavioral abnormalities. We consider evidence that human mutant SOD1 protein in neonatal hSOD1(G93A) mice instigates motor neuron degeneration by increasing persistent sodium currents and excitability, in turn altering synaptic circuits that control excessive motor neuron firing and leads to excitotoxicity. We also discuss how therapies that are aimed at suppressing abnormal neuronal activity might effectively mitigate or prevent the onset of irreversible neuronal damage in adulthood. J. Cell. Biochem. 113: 3301-3312, 2012. © 2012 Wiley Periodicals, Inc.
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Affiliation(s)
- Brigitte van Zundert
- Faculty of Biological Sciences and Faculty of Medicine, Center for Biomedical Research, Universidad Andres Bello, Avenida Republica 217, Santiago, Chile.
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