Biology subjects

Mainardi, M.

Publications and source records attributed to Mainardi, M..

5 recordsLinked to original sources

bioRxiv2026

The PSD-95 interactome of hippocampal synapses potentiated in response to an in vivo learning task

Changes in the molecular composition of synapses underlie the functional changes in synaptic strength after learning. These phenomena have been studied either via imaging of individual candidate proteins, or via the global analysis of the synaptic proteome, lumping together all synapses, regardless of their activation or potentiation status. As a step towards the characterization of the proteome of synapses that have undergone potentiation following a learning paradigm, we have designed SynActive-PSD95-FLAG, a genetically encoded probe consisting of a FLAG-tagged PSD-95 endowed with activity-dependent local translation and expression enrichment at potentiating dendritic spines. SynActive-PSD95-FLAG was expressed via Adeno Associated Viral vectors (AAVs) in the hippocampus of mice which were exposed to contextual fear conditioning. Then, PSD95-FLAG immunoprecipitation from hippocampal extracts, followed by mass spectrometry, was used to characterize the changes in the PSD-95 interactome caused by in vivo synaptic potentiation. This revealed extensive rearrangements in the stoichiometry between PSD-95 and its direct and indirect interactors, highlighting proteins involved in peptide translation, including ribosomal components, and vesicle trafficking. Our results, obtained with a selectively expressed proteomic handle, provide new insight into the molecular substrates of hippocampal learning and a novel tool to study the proteome of potentiated synapses.

neuroscience↗

bioRxiv2025

Distinct spatial distribution of potentiated dendritic spines in encoding- and recall-activated hippocampal neurons

Experimental advancements in neuroscience have identified cellular engrams -- ensembles of neurons whose activation is necessary and sufficient for memory retrieval. Synaptic plasticity, including long-term potentiation, is key to memory encoding and recall, but the relationship between learning-induced dendritic spine potentiation and neuron-wide activation remains unclear. Here, we employ a post-synaptic translation-dependent potentiation reporter (SA-PSD{Delta}Venus) and a neuronal activation reporter (ESARE-dTurquoise) to determine their spatiotemporal correlation in the mouse hippocampal CA1 following contextual fear conditioning (CFC). Potentiated spines were enriched in activated neurons, with distribution varying across CA1 layers at different phases of memory: potentiated spines were more frequent in activated neurons in stratum oriens and stratum lacunosum moleculare after CFC (encoding), while recall-activated neurons showed a larger number of potentiated spines in the stratum radiatum. These findings demonstrate that the relative weight and spatial distribution of potentiated synaptic inputs to hippocampal CA1 pyramidal neurons changes between the encoding and retrieval phases of memory.

neuroscience↗

bioRxiv2022

Low forces push the maturation of neural precursors into neurons

Mechanical stimulation modulates neural development and neuronal activity. In a previous study, we proposed magnetic "nano-pulling" as a tool to generate active forces. By loading neural cells with magnetic nanoparticles (MNPs), a precise force vector is remotely generated through static magnetic fields. In the present study, human neural stem cells (NSCs) were subjected to a standard differentiation protocol, in the presence or absence of nano-pulling. Under mechanical stimulation, we found an increase in the length of the neural processes which showed an enrichment in microtubules, endoplasmic reticulum, and mitochondria. A stimulation lasting up to 52 days induced a strong remodelling at the level of synapse density and a re-organization of the neuronal network, halving the time required for the maturation of neural precursors into neurons. We then injected the MNP-loaded NSCs into mouse spinal cord slices, demonstrating that nano-pulling stimulates the elongation of the NPC processes and modulates their orientation even in an ex vivo model system. To the best of our knowledge, this is the first evidence showing that active mechanical stimuli can guide the outgrowth of NSCs transplanted into the spinal cord tissue. Our findings suggest that MNPs play an important role in neuronal maturation which could be applied in regenerative medicine.

neuroscience↗

bioRxiv2018

Nuclear Tau modulates VGluT1 expression: a new function for Tau

Summary\n\nTau displacement from microtubules is the first step in the onset of tauopathies, and is followed by toxic protein aggregation. However, other non-canonical functions of Tau might have a role in these pathologies. Here, we demonstrate that a small amount of Tau localizes in the nuclear compartment and accumulates in both the soluble and DNA-bound fractions. We show that nuclear Tau regulates the expression of VGluT1, a disease-relevant gene directly involved in glutamatergic synaptic transmission. Impeding Tau/tubulin interaction in the cytosol favours its nuclear translocation and increases VGluT1 expression. Remarkably, the P301L mutation impairs this mechanism leading to a loss of function. Altogether, our results provide the demonstration of a direct physiological role of Tau on gene expression. Alterations of this mechanism may be at the basis of the onset of neurodegeneration.

molecular biology↗

bioRxiv2018

A congenital pain insensitivity mutation in the nerve growth factor gene uncouples nociception from affective pain in heterozygous humans and mice

Pain is an unpleasant but necessary sensory experience, which facilitates adaptive behaviours, such as fear. Despite recent advances, the question of how the pain experience influences learning of the fear response is still debated1,2. Genetic disorders rendering patients congenitally unable to feel pain have been described, and are usually explained by defects in peripheral nociceptors3-5. It is not known how growing up without pain affects central emotional and motivational responses to aversive stimuli. The rare autosomal recessive Hereditary Sensory and Autonomic Neuropathy type V (HSAN V) is caused by a mutation in the nerve growth factor (NGF) gene (R100W). HSAN V homozygous patients display a congenital indifference to painful events, with deficits in peripheral nociceptors but without overt cognitive impairment6. In contrast, heterozygous carriers do not present with pain-related deficits and have been identified only through pedigree and genetic screening7,8. We exploited this clinically silent population to dissociate nociceptive from affective features of pain. To address this we investigated both heterozygous knock-in mice bearing the R100W mutation (NGFR100W/m mice) and a cohort of HSAN V heterozygous human carriers. Surprisingly, we found that NGFR100W/m mice, despite normal responses to a noxious conditioning stimulus, show a deficit in learned fear while their social and innate fear responses are normal. The lack of pain-related fear response was linked to a reduced activation of anterior cingulate and motor cortices and of striatum, but not in primary somatosensory cortex. Likewise, human heterozygous R100W carriers, despite perceiving noxious stimuli and reporting subjective pain thresholds, show increased reaction latencies in response to painful stimulation, alongside a decreased subjective urgency to react. Functional magnetic resonance imaging (fMRI) revealed, comparably to the mouse data, an altered processing of painful stimuli in rostral anterior cingulate, medial premotor cortical regions and striatum. These findings from both human and mouse HSAN V carriers uncover behavioural and motivational consequences of a mild genetic pain insensitivity on the establishment of pain-dependent affective responses and memories.

neuroscience↗