Experimental Design and Data Analysis Issues Contribute to Inconsistent Results of C-Bouton Changes in Amyotrophic Lateral Sclerosis

Dukkipati, Saihari S.; Chihi, Aouatef; Wang, Yiwen; Elbasiouny, Sherif M.

doi:10.1523/eneuro.0281-16.2016

Cited by 23 publications

(23 citation statements)

References 38 publications

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“…The pre‐processing and 3D analysis of motoneurons was blinded to minimize bias, as described in our previous work (Dukkipati et al . ), and thresholds were approximated by eye. At least two spinal cord slices per animal were analysed from three to five animals in every experimental and control group.…”

Section: Methodsmentioning

confidence: 99%

“…For measured 3D analysis of motoneurons, images were loaded into ImagePro Premier 3D software (Media Cybernetics, Rockville, MD, USA), and motoneuron somas were reconstructed using the isosurface tool. The pre-processing and 3D analysis of motoneurons was blinded to minimize bias, as described in our previous work (Dukkipati et al 2017), and thresholds were approximated by eye. At least two spinal cord slices per animal were analysed from three to five animals in every experimental and control group.…”

Section: Confocal Microscopy and Morphometric Analysismentioning

confidence: 99%

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The vulnerability of spinal motoneurons and soma size plasticity in a mouse model of amyotrophic lateral sclerosis

Dukkipati

Garrett

Elbasiouny

2018

The Journal of Physiology

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α-Motoneuron soma size is correlated with the cell's excitability and function, and has been posited as a plastic property that changes during cellular maturation, injury and disease. This study examined whether α-motoneuron somas change in size over disease progression in the G93A mouse model of amyotrophic lateral sclerosis (ALS), a disease characterized by progressive motoneuron death. We used 2D- and 3D-morphometric analysis of motoneuron size and measures of cell density at four key disease stages: neonatal (P10 - with earliest known disease changes); young adult (P30 - presymptomatic with early motoneuron death); symptom onset (P90 - with death of 70-80% of motoneurons); and end-stage (P120+ - with full paralysis of hindlimbs). We additionally examined differences in lumbar vs. sacral vs. cervical motoneurons; in motoneurons from male vs. female mice; and in fast vs. slow motoneurons. We present the first evidence of plastic changes in the soma size of spinal α-motoneurons occurring throughout different stages of ALS with profound effects on motoneuron excitability. Somatic changes are time dependent and are characterized by early-stage enlargement (P10 and P30); no change around symptom onset; and shrinkage at end-stage. A key finding in the study indicates that disease-vulnerable motoneurons exhibit increased soma sizes (P10 and P30). This pattern was confirmed across spinal cord regions, genders and motoneuron types. This extends the theory of motoneuron size-based vulnerability in ALS: not only are larger motoneurons more vulnerable to death in ALS, but are also enlarged further in the disease. Such information is valuable for identifying ALS pathogenesis mechanisms.

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Section: Methodsmentioning

confidence: 99%

Section: Confocal Microscopy and Morphometric Analysismentioning

confidence: 99%

The vulnerability of spinal motoneurons and soma size plasticity in a mouse model of amyotrophic lateral sclerosis

Dukkipati

Garrett

Elbasiouny

2018

The Journal of Physiology

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“…Cleaved caspase-3 activity in ChAT-immunoreactive neurones around the central canal (lamina X) is of particular interest, given that this population of cells includes those giving rise to the C-boutons observed on alpha motoneurones (Zagoraiou et al, 2009). A loss of these cells has been shown in G93A mice (Milan et al, 2015), and changes in C-boutons frequency or size have also been observed (Herron and Miles, 2012;Milan et al, 2015;Pullen and Athanasiou, 2009;Saxena et al, 2013) although the results have been inconsistent, which may be due to experimental design (Dukkipati et al, 2017).…”

Section: Does Increased Excitability Contribute To Excitotoxic Cell Dmentioning

confidence: 99%

Increased axon initial segment length results in increased Na⁺currents in spinal motoneurones at symptom onset in the G127X SOD1 mouse model of Amyotrophic Lateral Sclerosis

Jörgensen

Jensen

Dimintiyanova

et al. 2020

Preprint

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Amyotrophic lateral sclerosis is a neurodegenerative disease preferentially affecting motoneurones. Transgenic mouse models have been used to investigate the role of abnormal motoneurone excitability in this disease. Whilst an increased excitability has repeatedly been demonstrated in vitro in neonatal and embryonic preparations from SOD1 mouse models, the results from the only studies to record in vivo from spinal motoneurones in adult SOD1 models have produced conflicting findings. Deficits in repetitive firing have been reported in G93A SOD1 mice but not in presymptomatic G127X SOD1 mice despite shorter motoneurone axon initial segments (AISs) in these mice.These discrepancies may be due to the earlier disease onset and prolonged disease progression in G93A SOD1 mice with recordings potentially performed at a later sub-clinical stage of the disease in this mouse. To test this, and to explore how the evolution of excitability changes with symptom onset we performed in vivo intracellular recording and AIS labelling in G127X SOD1 mice immediately after symptom onset. No reductions in repetitive firing were observed showing that this is not a common feature across all ALS models. Immunohistochemistry for the Na+ channel Nav1.6 showed that motoneurone AISs increase in length in G127X SOD1 mice at symptom onset. Consistent with this, the rate of rise of AIS components of antidromic action potentials were significantly faster confirming that this increase in length represents an increase in AIS Na+ channels occurring at symptom onset in this model.HighightsIn vivo electrophysiological recordings were made in symptomatic G127X SOD1 mice.There were no deficits in repetitive firing in motoneurones in G127X mice.Increased persistent inward currents were still present in the symptomatic mice.Results suggest increases in Na+ currents at axon initial segments (AISs).Immunohistochemistry showed that motoneurone AISs were longer and thinner.

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“…Conflicting data have been presented on whether the number of C-boutons increased or decreased with disease progression in this mouse model (Casas et al, 2013) (Milan et al, 2015) (Lasiene et al, 2016). Dukkipati and colleagues noticed the apparent discrepancies between previous reports of bouton size and count in ALS and performed a reanalysis of the data, which revealed that changes in C-bouton size and density in pre-end stage SOD1 G93A mice are not reproducible (Dukkipati et al, 2017). In support of the apparent difficulties in quantifying morphological changes at the motor neuron-muscle synapse, Tremblay and colleagues find that, in the SOD1 G37R mouse model, NMJ morphological deficits vary with age and muscle location (Tremblay et al, 2017).…”

Section: Aberrant Neuronal Morphology and Synapse Formationmentioning

confidence: 99%

Synaptic dysfunction and altered excitability in C9ORF72 ALS/FTD

Starr

Sattler

2018

Brain Research

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Amyotrophic lateral sclerosis (ALS) is characterized by a progressive degeneration of upper and lower motor neurons, resulting in fatal paralysis due to denervation of the muscle. Due to genetic, pathological and symptomatic overlap, ALS is now considered a spectrum disease together with frontotemporal dementia (FTD), the second most common cause of dementia in individuals under the age of 65. Interestingly, in both diseases, there is a large prevalence of RNA binding proteins (RBPs) that are mutated and considered disease-causing, or whose dysfunction contribute to disease pathogenesis. The most common shared genetic mutation in ALS/FTD is a hexanucleuotide repeat expansion within intron 1 of C9ORF72 (C9). Three potentially overlapping, putative toxic mechanisms have been proposed: loss of function due to haploinsufficient expression of the C9ORF72 mRNA, gain of function of the repeat RNA aggregates, or RNA foci, and repeat-associated non-ATG-initiated translation (RAN) of the repeat RNA into toxic dipeptide repeats (DPRs). Regardless of the causative mechanism, disease symptoms are ultimately caused by a failure of neurotransmission in three regions: the brain, the spinal cord, and the neuromuscular junction. Here, we review C9 ALS/FTD-associated synaptic dysfunction and aberrant neuronal excitability in these three key regions, focusing on changes in morphology and synapse formation, excitability, and excitotoxicity in patients, animal models, and in vitro models. We compare these deficits to those seen in other forms of ALS and FTD in search of shared pathways, and discuss the potential targeting of synaptic dysfunctions for therapeutic intervention in ALS and FTD patients.

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Experimental Design and Data Analysis Issues Contribute to Inconsistent Results of C-Bouton Changes in Amyotrophic Lateral Sclerosis

Abstract: Visual Abstract

Cited by 23 publications

References 38 publications

The vulnerability of spinal motoneurons and soma size plasticity in a mouse model of amyotrophic lateral sclerosis

The vulnerability of spinal motoneurons and soma size plasticity in a mouse model of amyotrophic lateral sclerosis

Increased axon initial segment length results in increased Na⁺currents in spinal motoneurones at symptom onset in the G127X SOD1 mouse model of Amyotrophic Lateral Sclerosis

Synaptic dysfunction and altered excitability in C9ORF72 ALS/FTD

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Experimental Design and Data Analysis Issues Contribute to Inconsistent Results of C-Bouton Changes in Amyotrophic Lateral Sclerosis

Abstract: Visual Abstract

Cited by 23 publications

References 38 publications

The vulnerability of spinal motoneurons and soma size plasticity in a mouse model of amyotrophic lateral sclerosis

The vulnerability of spinal motoneurons and soma size plasticity in a mouse model of amyotrophic lateral sclerosis

Increased axon initial segment length results in increased Na+currents in spinal motoneurones at symptom onset in the G127X SOD1 mouse model of Amyotrophic Lateral Sclerosis

Synaptic dysfunction and altered excitability in C9ORF72 ALS/FTD

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Increased axon initial segment length results in increased Na⁺currents in spinal motoneurones at symptom onset in the G127X SOD1 mouse model of Amyotrophic Lateral Sclerosis