Biology subjects

Allodi, I.

Publications and source records attributed to Allodi, I..

8 recordsLinked to original sources

bioRxiv2025

Predicting therapeutic windows for synaptic intervention in ALS

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive breakdown of neural circuits which leads to motoneuron death. Earlier work from our lab showed that dysregulation of inhibitory V1 interneurons precedes the degeneration of excitatory V2a interneurons and motoneurons and that stabilizing V1-motoneuron connections improved motor function and saved motoneurons in the SOD1G93A ALS mouse model. However, the optimal timing for this intervention remains unclear. To address this, we developed a spiking neural network model of spinal locomotor circuits to simulate healthy and ALS-like conditions. By modeling changes in network connectivity and synaptic dynamics, we predict that V1 dysregulation induces hyperexcitation in motoneurons which is preferentially observed in flexor motoneurons leading to the disruption of flexor-extensor coordination, and potentially contributing to selective vulnerability of flexor motoneurons. Stabilizing V1 synapses preserved motor output even after motoneuron loss, suggesting that therapeutic benefit is possible into symptomatic stages. However, model predictions also highlighted that after sustained synaptic loss and the development of slower synaptic dynamics within the network, synaptic stabilization leads to maladaptive extensor-biased activity, suggesting that excitatory/inhibitory balance impacts treatment effectiveness. Finally, the model indicated that V1 stabilization could lead to rescue of the V2a excitatory interneurons, a finding that we were able to confirm experimentally in the SOD1G93A ALS mouse model. By exploring different scenarios of synaptic loss and cell dysregulation during synaptic stabilization, our models provide a framework for predicting candidate time windows for spinal circuit interventions, which may guide future preclinical investigations.

neuroscience↗

bioRxiv2024

The neurovascular coupling response of the aged brain is brain-state dependent.

Brain aging lead to reduced cerebral blood flow and cognitive decline, but how normal aging affects neurovascular coupling (NVC) in the awake brain is unclear. Here, we investigated NVC in relation to calcium changes in vascular mural cells (VMCs) in awake adult and aged mice. We show that NVC responses are reduced and prolonged in the aged brain and that this is more pronounced at the capillary level than in arterioles. However, the overall NVC response, measured as the time integral of vasodilation, is the same in two age groups. In adult, but not in aged mice, the NVC response correlated with Ca2+ signaling in VMCs, while the overall Ca2+ kinetics were slower in aged than in adult mice. In particular, the rate of Ca2+ transport, and the Ca2+ sensitivity of VMCs were reduced in aged mice, explaining the reduced and prolonged vasodilation. Spontaneous locomotion was less frequent and reduced in aged mice as compared to young adult mice, and this was reflected in the slow but prolonged NVC and vascular Ca2+ responses. Taken together, our data characterize the NVC in the aged awake brain as slow but prolonged, and underscoring the importance of brain state in understanding age-related mechanisms.

neuroscience↗

bioRxiv2023

Spinal inhibitory neurons degenerate before motor neurons and excitatory neurons in a mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is characterized by the progressive loss of somatic motor neurons. Major focus has been directed to motor neuron intrinsic properties as a cause for degeneration while less attention has been given to the contribution of spinal interneurons. In the present work, we applied multiplexing detection of transcripts and machine learning-based image analysis to investigate the fate of multiple spinal interneuron populations during ALS progression in the SOD1G93A mouse model. The analysis showed that spinal inhibitory interneurons are affected early in disease, before motor neurons death, and are characterized by a slow progressive degeneration, while excitatory interneurons are affected later with a steep progression. Moreover, we report differential vulnerability within inhibitory and excitatory subpopulations, with interneurons directly projecting onto motor neurons being preferentially affected. Our study reveals a strong interneuron involvement in ALS development with interneuron specific degeneration. This points to differential involvement of diverse spinal neuronal circuits that eventually may be determining for motor neuron degeneration. TeaserA new approach to study the motor neuron disorder Amyotrophic Lateral Sclerosis shows the early and differential dysregulation of spinal interneurons.

neuroscience↗

bioRxiv2022

Stabilization of V1 interneuron-motor neuron connectivity ameliorates motor phenotype in a mouse model of ALS

Loss of connectivity between spinal V1 inhibitory inter-neurons and motor neurons is found early in disease in the SOD1G93A ALS mice. Such changes in premotor inputs can contribute to homeostatic imbalance of vulnerable motor neurons. Here, we show, for the first time, that stabilization of V1 synapses by overexpression of the Extended Synap-totagmin 1 presynaptic organizer increases motor neuron survival and ameliorates motor phenotypes, demonstrating that interneurons can be a potential target to attenuate ALS symptoms.

neuroscience↗

bioRxiv2020

Locomotor deficits in ALS mice are paralleled by loss of V1-interneuron-connections onto fast motor neurons

ALS is characterized by progressive inability to execute movements. Motor neurons innervating fast-twitch muscle fibers exhibit preferential degeneration. The reason for differential vulnerability of fast motor neurons, and its consequence on motor output is not known. Here, we show that fast motor neurons receive more inhibitory synaptic inputs than slow motor neurons, and loss of inhibitory synapses onto fast motor neurons precedes disease progression in the SOD1G93A mouse model of ALS. Loss of inhibitory synapses on fast motor neurons is accounted for by a loss of synapses from inhibitory V1 spinal interneurons. Deficits in V1-motor neuron connectivity appear prior to motor neuron death and are paralleled by development of specific SOD1G93A locomotor deficits. These distinct SOD1G93A locomotor deficits are phenocopied by silencing of inhibitory V1 spinal interneurons in wild-type mice. Silencing inhibitory V1 spinal interneurons does not exacerbate SOD1G93A locomotor deficits, suggesting phenotypic pathway interaction. Our study identifies a potential cell non-autonomous source of motor neuronal vulnerability in ALS, and links ALS-induced changes in locomotor phenotypes to inhibitory V1 interneurons.

neuroscience↗

bioRxiv2020

Spinal motoneurones are intrinsically more responsive in the adult G93A SOD1 mouse model of Amyotrophic Lateral Sclerosis

In vitro studies from transgenic Amyotrophic Lateral Sclerosis models have suggested an increased excitability of spinal motoneurones. However, in vivo intracellular recordings from adult ALS mice models have produced conflicting findings. Previous publications using barbiturate anaesthetised G93A SOD1 mice suggested that some motoneurones are hypo-excitable, defined by deficits in repetitive firing. Our own previous recordings in G127X SOD1 mice using different anaesthesia, however, showed no repetitive firing deficits, and increased persistent inward currents at symptom onset. These discrepancies may be due to differences between models, symptomatic stage, anaesthesia or technical differences. To investigate this, we repeated our original experiments, but in adult male G93A mice at both presymptomatic and symptomatic stages, under barbiturate anaesthesia. In vivo intracellular recordings from antidromically identified spinal motoneurones revealed no significant differences in the ability to fire repetitively in the G93A SOD1 mice. Motoneurones in G93A SOD1 mice fired significantly more spontaneous action potentials. Rheobase was significantly lower and the input resistance and input-output gain were significantly higher in both presymptomatic and symptomatic G93A SOD1 mice. This was despite a significant increase in the duration of the post-spike after-hyperpolarisation (AHP) in both presymptomatic and symptomatic G93A SOD1 mice. Finally, evidence of increased activation of persistent inward currents was seen in both presymptomatic and symptomatic G93A SOD1 mice. Our results do not confirm previous reports of hypo-excitability of spinal motoneurones in the G93A SOD1 mouse and demonstrate that the motoneurones do in fact show an increased response to inputs. Key Point SummaryO_LIAlthough in vitro recordings using neonatal preparations from mouse models of Amyotrophic Lateral Sclerosis (ALS) suggest increased motoneurone excitability, in vivo recordings in adult ALS mouse models have been conflicting. C_LIO_LIIn adult G93A SOD1 models, spinal motoneurones have previously been shown to have deficits in repetitive firing, in contrast to the G127X SOD1 mouse model. C_LIO_LIOur in vivo intracellular recordings in barbiturate-anaesthetised adult male G93A SOD1 mice reveal no deficits in repetitive firing either prior to or after symptom onset. C_LIO_LIWe show that deficits in repetitive firing ability can be a consequence of experimental protocol and should not be used alone to classify otherwise normal motoneurones as hypo-excitable. C_LIO_LIMotoneurones in the G93A SOD1 mice showed an increased response to inputs, with lower rheobase, higher input-output gains and increased activation of persistent inward currents. C_LI

neuroscience↗

bioRxiv2018

Modeling motor neuron resilience in ALS using stem cells

Oculomotor neurons, which regulate eye movement, are resilient to degeneration in the lethal motor neuron disease amyotrophic lateral sclerosis (ALS). It would be highly advantageous if motor neuron resilience could be modeled in vitro. Towards this goal, we generated a high proportion of oculomotor neurons from mouse embryonic stem cells through temporal overexpression of Phox2a in neuronal progenitors. We demonstrate, using immunocytochemistry and RNA sequencing, that in vitro generated neurons are bona fide oculomotor neurons based on their similarity to their in vivo counterpart in rodent and man. We also show that in vitro generated oculomotor neurons display a robust activation of survival-promoting Akt signaling and are more resilient to the ALS-like toxicity of kainic acid than spinal motor neurons. Thus, we can generate bona fide oculomotor neurons in vitro which display a resilience similar to that seen in vivo.

neuroscience↗

bioRxiv2018

LCM-seq reveals unique transcriptional adaption mechanisms of resistant neurons in spinal muscular atrophy

Somatic motor neurons are selectively vulnerable in spinal muscular atrophy (SMA), a lethal disease caused by a deficiency of the ubiquitously expressed survival of motor neuron (SMN) protein. However, some brainstem motor neuron groups, including oculomotor and trochlear (ocular), which innervate the muscles around the eyes, are for unknown reasons spared. Here, using laser capture microdissection coupled with RNA sequencing (LCM-seq), we investigate the transcriptional dynamics in discrete neuronal populations in health and SMA to reveal mechanisms of vulnerability and resistance. Using gene correlation network analysis, we reveal a p53-mediated stress response that is intrinsic to all somatic motor neurons independent of their vulnerability, but absent in resistant red nucleus and visceral motor neurons. However, our temporal and spatial differential expression analysis across neuron types clearly demonstrates that the majority of SMA-induced modulations are cell-type specific. Notably, using gene ontology and protein-network analyses we show that ocular motor neurons present unique disease-adaptation mechanisms that could explain their resilience. In particular, ocular motor neurons up-regulate; i) Syt1, Syt5 and Cplx2, which modulate neurotransmitter release; ii) the motor neuron survival factors Chl1 and Lif, iii) Aldh4, that can protect cells from oxidative stress and iv) the caspase inhibitor Pak4. In conclusion, our in-depth longitudinal analysis of gene expression changes in SMA reveal novel cell-type specific changes that present compelling targets for future gene therapy studies aimed towards preserving vulnerable motor neurons.

neuroscience↗