Biology subjects

Restivo, L.

Publications and source records attributed to Restivo, L..

4 recordsLinked to original sources

bioRxiv2023

Local translation is required for sustained circuit integrity in impaired Wallerian degeneration

After injury, the severed axon separated from the soma activates programmed axon degeneration, an evolutionarily conserved pathway to initiate its degeneration within a day. Conversely, severed projections deficient in programmed axon degeneration remain morphologically preserved with functional synapses for weeks to months after injury. How this synaptic function is sustained remains currently unknown. Here, we demonstrate that dNmnat-mediated over-expression attenuates programmed axon degeneration in distinct neuronal populations. Severed projections remain morphologically preserved for weeks after injury. When evoked, they elicit a postsynaptic behavior which is a readout for preserved synaptic function. We used ribosomal pulldown to isolate translatomes from these projections. Transcriptional profiling revealed several enriched biological classes. Identified candidates were validated in a screen using a novel system to automatically quantify evoked antennal grooming behavior as a proxy for preserved synaptic function. We used RNAi-mediated knockdown to identify mTOR as a mediator of local protein synthesis, and specifically candidates involved in protein ubiquitination and calcium homeostasis, required for preserved synaptic function. Our dataset uncovered several uncharacterized genes linked to human diseases. It may therefore offer insights into novel avenues for therapeutic treatments.

neuroscience↗

bioRxiv2022

Autophagy in parvalbumin interneurons is required for inhibitory transmission and memory via regulation of synaptic proteostasis

With the emerging role of the autophagic machinery in healthy brain development and aging, there is a pressing need to better characterize its functions in different neuronal populations, providing cellular insight into autophagy-related brain diseases. Here, we generated and characterized mice with conditional ablation of atg5 in GABAergic neurons expressing parvalbumin (PV-atg5KO), mostly comprising fast-spiking interneurons, as well as Purkinje cells in the cerebellum. Using light-sheet microscopy to image PV neurons throughout the brain, we reveal that autophagy is required for the sustenance of Purkinje cells but not of PV-interneurons. Yet, proteomic analysis showed that autophagy deficiency in cortical and hippocampal PV-interneurons alters the proteostasis of key synaptic proteins, as well as the surface expression of glutamate receptor subunits. Consistently, hippocampal autophagy-deficient PV-interneurons exhibit reduced inhibitory neurotransmission and PV-atg5KO mice display excitation-inhibition imbalance in the hippocampus and memory deficits. Our findings demonstrate a neuronal type-specific vulnerability to autophagy deficiency, while also identifying PV-interneurons as cellular substrates where autophagy is required for memory.

neuroscience↗

bioRxiv2022

Using the glial mitochondrial machinery to prevent multilevel dysfunctions observed in a mouse model of Alzheimer s disease

Alzheimers disease (AD) is becoming increasingly prevalent worldwide. It represents one of the greatest medical challenge as no pharmacologic treatments are available to prevent disease progression. Astrocytes play crucial functions within neuronal circuits by providing metabolic and functional support, regulating interstitial solute composition, and modulating synaptic transmission. In addition to these physiological functions, growing evidence points to an essential role of astrocytes in neurodegenerative diseases like AD. Early stage AD is associated with hypometabolism and oxidative stress. Contrary to neurons that are vulnerable to oxydative stress, astrocytes are particularly resistant to mitochondrial dysfunction and are therefore more resilient cells. In our study, we leveraged astrocytic mitochondrial uncoupling and examined neuronal function in the 3xTg AD mouse model. We overexpressed the mitochondrial uncoupling protein 4 (UCP4), which has been shown to improve neuronal survival in vitro. We found that this treatment efficiently prevented alterations of hippocampal metabolite levels observed in AD mice, along with hippocampal atrophy and reduction of basal dendrite arborization of subicular neurons. This approach also averted aberrant neuronal excitability observed in AD subicular neurons and preserved episodic-like memory in AD mice assessed in a spatial recognition task. These findings show that targeting astrocytes and their mitochondria is an effective strategy to prevent the decline of neurons facing AD-related stress at the early stages of the disease.

neuroscience↗

bioRxiv2019

Heterogeneous habenular neuronal ensembles during selection of defensive behaviors

Optimal selection of threat-driven defensive behaviors is paramount to an animals survival. The lateral habenula (LHb) is a key neuronal hub coordinating behavioral responses to aversive stimuli. Yet, how individual LHb neurons represent defensive behaviors in response to threats remains unknown. Here we show that, in mice, a visual threat promotes distinct defensive behaviors, namely runaway (escape) and action-locking (immobile-like). Fiber photometry of bulk LHb neuronal activity in behaving animals revealed an increase and decrease of calcium signal time-locked with runaway and action-locking, respectively. Imaging single-cell calcium dynamics across distinct threat-driven behaviors identified independently active LHb neuronal clusters. These clusters participate during specific time epochs of defensive behaviors. Decoding analysis of this neuronal activity unveiled that some LHb clusters either predict the upcoming selection of the defensive action or represent the selected action. Thus, heterogeneous neuronal clusters in LHb predict or reflect the selection of distinct threat-driven defensive behaviors.

neuroscience↗