Biology subjects

Giugliano, M.

Publications and source records attributed to Giugliano, M..

8 recordsLinked to original sources

bioRxiv2026

Prion Protein Deficiency Results in Synaptic, Neural Network and Behavioral Alterations

The cellular form of the prion protein (PrPC) is known for its involvement in the pathogenesis of prion diseases. Recent research implicates the physiological isoform of PrP in neuronal development, excitability, and synaptic plasticity, as well as in other biological processes. However, its precise function in the development and function of neurons remains poorly understood. Here, we investigated its role during different developmental stages, both in vitro and in vivo, using different PrP knock-out (KO) mouse lines (Prnp-/-). Prion protein KO neurons cultured on microelectrode arrays (MEAs) displayed altered network dynamics compared to wild type cultures, comprising reduced burst frequency, and abnormal spike patterns, indicative of impaired maturation of the synaptic circuitry. These functional alterations were associated with a reduced expression of key presynaptic and postsynaptic proteins, including elements of the SNARE complex and regulators of excitation-inhibition balance. Similar molecular changes were also confirmed in a second Prnp-/- model, suggesting that PrPC is directly involved in these mechanisms regardless of genetic backgrounds. Alterations in neuronal networks were traceable into adulthood: in vivo recordings in adult Prnp-/- mice revealed increased neuronal responses to visual danger stimuli, which correlated with behaviorally increased fear responses to those stimuli. Together, our findings support a critical role for PrPC in the establishment and maintenance of functional neuronal networks, from early developmental stages in vitro to behaviorally mature relevant circuits in vivo, beyond genomic background. These results indicate that PrPC acts as a key regulator of synaptic development and function both in physiological and pathological conditions.

molecular biology↗

bioRxiv2024

APOE4 impacts cortical neurodevelopment and alters network formation in human brain organoids

Apolipoprotein E4 (APOE4) is the leading genetic risk factor for Alzheimers disease. While most studies examine the role of APOE4 in aging, imaging, and cognitive assessments reveal that APOE4 influences brain structure and function as early as infancy. Here, we examined human-relevant cellular phenotypes across neurodevelopment using induced pluripotent stem cell (iPSC) derived cortical and ganglionic eminence organoids (COs and GEOs). In COs, we showed that APOE4 decreased BRN2+ and SATB2+ cortical neurons, increased astrocytes and outer radial glia, and was associated with increased cell death and dysregulated GABA-related gene expression. In GEOs, APOE4 accelerated maturation of neural progenitors and neurons. Multi-electrode array recordings in assembloids revealed that APOE4 disrupted network formation and altered response to GABA, resulting in heightened excitability and synchronicity. Together, our data provides new insights into how APOE4 may influence cortical neurodevelopmental processes and network formation in the human brain.

neuroscience↗

bioRxiv2024

Dual effects of ARX poly-alanine mutations in human cortical and interneuron development

Infantile spasms, with an incidence of 1.6 to 4.5 per 10,000 live births, are a relentless and devastating childhood epilepsy marked by severe seizures but also leads to lifelong intellectual disability. Alarmingly, up to 5% of males with this condition carry a mutation in the Aristaless-related homeobox (ARX) gene. Our current lack of human-specific models for developmental epilepsy, coupled with discrepancies between animal studies and human data, underscores the gap in knowledge and urgent need for innovative human models, organoids being one of the best available. Here, we used human neural organoid models, cortical organoids (CO) and ganglionic eminences organoids (GEO) which mimic cortical and interneuron development respectively, to study the consequences of PAE mutations, one of the most prevalent mutation in ARX. ARXPAE produces a decrease expression of ARX in GEOs, and an enhancement in interneuron migration. That accelerated migration is cell autonomously driven, and it can be rescued by inhibiting CXCR4. We also found that PAE mutations result in an early increase in radial glia cells and intermediate progenitor cells, followed by a subsequent loss of cortical neurons at later timepoints. Moreover, ARX expression is upregulated in COs derived from patients at 30 DIV and is associated with alterations in the expression of CDKN1C. Furthermore, ARXPAE assembloids had hyperactivity which were evident at early stages of development. With effective treatments for infantile spasms and developmental epilepsies still elusive, delving into the role of ARXPAE mutations in human brain organoids represents a pivotal step toward uncovering groundbreaking therapeutic strategies.

neuroscience↗

bioRxiv2022

Bidirectional modulation of neuronal excitability via ionic actuation of potassium

Potassium K+ is a fundamental actor in the shaping of action potentials, and its concentration in the extracellular microenvironment represents a crucial modulator of neural excitability. Yet, its employment as a neuromodulation modality is still in its infancy. Recent advances in the technology of ionic actuators are enabling the control of ionic concentrations at the spatiotemporal scales of micrometers and milliseconds, thereby holding the promise of making the control of K+ concentration a key enabling technology for the next generation of neural interfaces. In this regard, a theoretical framework to understand the possibilities and limits offered by such technology is pivotal. To this aim, we exploit the Hodgkin-Huxley modeling framework, augmented to account for the perturbation of extracellular K+ concentration. We leverage methods of bifurcation analysis to investigate which regimes of electrical activity arise in the space of the input variables, namely the extent of ionic actuation and the synaptic current. We show that, depending on the type of target neuron, switchings of the class of excitability may occur in such space. These effects could rule out the possibility of eliciting tonic spiking when the extracellular K+ concentration is assumed as a sole control input. Building upon these findings, we show in simulations how to address the problem of neuromodulation via ionic actuation in a principled fashion. In this respect, we account for a bidirectional scenario, namely from the perspective of both inhibiting and stimulating electrical activity. We then provide a first-order motivation for the switchings of neural excitability in terms of the conductances of the K+-selective channels. Finally, we introduce a Pinsky-Rinzel-like model to investigate the effects of performing the ionic actuation locally at the neural membrane. Author summaryNeural interfaces rely on technologies to sense and perturb the electrical activity of neurons. For the latter aim, many strategies have been established to date, each one targeting a different actor involved in the electrophysiology of neurons. Examples include electrical, chemical, and optogenetic techniques. However, the main actors that shape neuronal signals, namely ions such as potassium K+, are still not directly targeted. Recent advances in bioelectronic technologies are enabling the manipulation of ionic concentrations as a viable strategy for neuromodulation, which we refer to as ionic actuation. These findings come mainly from the experimental literature, and the theoretical understanding of how ionic actuation can be used to shape neural activity is still lacking. This paper aims to help fill this gap, adopting the ionic actuation of K+ as a case study. Our results could guide the design and control of novel neural interfaces targeting the ionic composition of cellular fluids. Moreover, they may suggest novel therapies for pathologies related to impairments in the regulation of ionic homeostasis, such as drug-resistant epilepsy.

neuroscience↗

bioRxiv2019

Modulation of coordinated activity across cortical layers by plasticity of inhibitory synapses onto layer 5 pyramidal neurons

In the neocortex, synaptic inhibition shapes all forms of spontaneous and sensory-evoked activity. Importantly, inhibitory transmission is highly plastic, but the functional role of inhibitory synaptic plasticity is unknown. In the mouse barrel cortex, activation of layer 2/3 PNs elicited strong feed-forward perisomatic inhibition (FFI) onto layer 5 PNs. We found that FFI involving PV cells was strongly potentiated by postsynaptic PN burst firing. FFI plasticity modified PN excitation-to-inhibition (E/I) ratio, strongly modulated PN gain and altered information transfer across cortical layers. Moreover, our LTPi-inducing protocol modified the firing of layer 5 PNs and altered the temporal association of PN spikes to {gamma}-oscillations both in vitro and in vivo. All these effects were captured by unbalancing the E/I ratio in a feed-forward inhibition circuit model. Altogether, our results indicate that activity-dependent modulation of perisomatic inhibitory strength effectively influences the participation of single principal cortical neurons to cognitive-relevant network activity.\n\nImpact StatementLong-term potentiation of feed-forward perisomatic inhibition effectively alters the computational properties of single layer 5 pyramidal neurons and their association to network activity.

neuroscience↗

bioRxiv2018

Single-cell and neuronal network alterations in an in vitro model of Fragile X syndrome

The Fragile X mental retardation protein (FMRP) is involved in many cellular processes and it regulates synaptic and network development in neurons. Its absence is known to lead to intellectual disability, with a wide range of co-morbidities including autism. Over the past decades, FMRP research focused on abnormalities both in glutamatergic and GABAergic signalling, and an altered balance between excitation and inhibition has been hypothesised to underlie the clinical consequences of absence of the protein. Using FMRP knockout mice, we studied an in vitro model of cortical microcircuitry and observed that the loss of FMRP largely affected the electrophysiological correlates of network development and maturation but caused less alterations in single-cell phenotypes. Using a mathematical model, we demonstrated that the combination of an increased excitation and reduced inhibition describes best predicts our experimental observations during the ex vivo formation of the network connections.

neuroscience↗

bioRxiv2018

A cellular basis of human intelligence

It is generally assumed that human intelligence relies on efficient processing by neurons in our brain. Behavioral and brain-imaging studies robustly show that higher intelligence associates with faster reaction times and thicker gray matter in temporal and frontal cortical areas. However, no direct evidence exists that links individual neuron activity and structure to human intelligence. Since a large part of cortical grey matter consists of dendrites, these structures likely determine cortical architecture. In addition, dendrites strongly affect functional properties of neurons, including action potential speed. Thereby, dendritic size and action potential firing may constitute variation in cortical thickness, processing speed, and ultimately IQ.\n\nTo investigate this, we took advantage of brain tissue available from neurosurgery and recorded from pyramidal neurons in the medial temporal cortex, an area showing high association between cortical thickness, cortical activity and intelligence. Next, we reconstructed full dendritic structures of recorded neurons and combined these with brain-imaging data and IQ scores from the same subjects. We find that high IQ scores and large temporal cortical thickness associate with larger, more complex dendrites of human pyramidal neurons. We show in silico that larger dendrites enable pyramidal neurons to track activity of synaptic inputs with higher temporal precision, due to fast action potential initiation. Finally, we find that human pyramidal neurons of individuals with higher IQ scores sustain faster action potentials during repeated firing. These findings provide first evidence that human intelligence is associated with neuronal complexity, action potential speed and efficient information transfer in cortical neurons.

neuroscience↗

bioRxiv2018

The Effect of Acute Pharmacological Inhibition of Urokinase Plasminogen Activator and Neuropsin Extracellular Proteases on Neuronal Networks in vitro

Neuronal networks are surrounded by the extracellular matrix (ECM), which functions both as a scaffold and as a regulator of neuronal function. The ECM is in turn dynamically altered through the action of serine proteases, which break down its constituents. This pathway has been implicated in the regulation of synaptic plasticity and of intrinsic excitability. Here, we determined the effects of acutely inhibiting two important regulators of the ECM, Urokinase Plasminogen Activator and Neuropsin, selectively and potently with the inhibitor UAMC-01162. Spontaneous electrophysiological activity was recorded from in vitro primary rat cortical cultures using microelectrode arrays. While inhibition at a low dosage had no significant effect, at elevated concentrations network bursting dynamics and functional connectivity were drastically altered. These results indicate that the serine protease inhibition affects neuronal and synaptic properties, likely through their actions on the ECM. We propose that in the acute phase, a transient increase of excitatory synaptic efficacy is compensated for by a downregulation of single-cell excitability.

neuroscience↗