Biology subjects

Nascimento, F.

Publications and source records attributed to Nascimento, F..

11 recordsLinked to original sources

bioRxiv2026

Neuronal targeted AAV Micro-Dystrophin restores neurobehavioural co-morbidities, grip strength and motor coordination in mdx52 mouse model of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a X-linked disorder caused by mutations in the DMD gene, which disrupts production of multiple isoforms of dystrophin in multiple organs namely muscle, heart and brain. While progressive muscle disease and cardiomyopathy are the hallmarks of DMD, over 40% of individuals also experience significant neurobehavioral comorbidities, including autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), obsessive compulsive disorder (OCD) and intellectual disability. These deficits are linked to the loss of brain isoforms and approximately 90% of DMD individuals have loss of either Dp427 or both Dp427 and Dp140 in the brain. We studied the mdx52 mouse model, which lacks these isoforms and exhibits severe fear and anxiety-like behaviours, suitable to evaluate the therapeutic efficacy on neuro-comorbidities after delivering a neuronal-targeted adeno-associated virus (AAV) micro-dystrophin ({micro}Dys) therapy. We compared two delivery routes intravenous (IV) and intracerebroventricular (ICV) in neonatal mdx52 male mice to assess impact on an extensive range of neurobehavioural aspects including emotional reactivity, neurocognitive, OCD and motor coordination deficits. While both routes successfully reduced emotional reactivity and anxiety-related behaviours, IV delivery emerged as the superior therapeutic strategy addressing a more comprehensive spectrum of DMD related brain co-morbidities. Critically, significant improvements in cognitive deficits and OCD-like behaviours were achieved only through IV delivery. This was associated with a widespread lower transduction pattern across the brain, including hindbrain and cerebellum, which were less effectively targeted by ICV injection, although forebrain transduction with ICV delivery was higher. Brain {micro}Dys expression successfully restored dystrophin interactors dystroglycan, syntrophin and pre- and post-synaptic functional interactors VGLUT1, gephyrin, GABAAR with both delivery methods. These results demonstrate that while ICV gene therapy results in improved emotional reactivity and anxiety-related behaviour in the mdx52, only the systemic, neuronal-targeted gene therapy efficiently transduced the central nervous system restoring neuronal synaptic functional complexes of both Dp427 and 140 isoforms and simultaneously restored peripheral NMJ dystrophin deficiency. Beyond cognitive restoration, while both routes improved aspects of gait on CatWalk XT, only IV delivery significantly enhanced motor coordination on the Beam walk and, unexpectedly, normalised grip strength. This was specifically linked to the selective expression of {micro}Dys at neuromuscular junctions (NMJs), which corrected post-synaptic electrophysiological dysfunction of mdx52 mice. Our findings establish a significant foundation for incorporating brain-directed strategies into the future therapeutic approaches for DMD, offering a holistic approach to treating DMD as a multisystemic disease.

neuroscience↗

bioRxiv2026

High-frequency common inputs entrain motoneuron subpopulations differently

Spinal motoneuron (MN) pools behave as linear systems that transmit common synaptic input to muscles. However, MNs are biophysically heterogeneous and intrinsically nonlinear. How different MN subpopulations integrate and transmit high-frequency inputs remains poorly understood, partly because conventional analyses treat the MN pool as a single functional system rather than examining subpools with different firing rates. Here, we addressed this gap using a combination of computational simulations and human MN recordings. Simulations of MNs receiving a common synaptic input at varying frequencies showed that MNs firings become phase-locked to input oscillations when the input frequency approximates the neurons firing rate or its harmonics. We refer to this frequency-dependent synchronization as entrainment. Importantly, this subpool-specific effect was masked when MN activity was analysed at the whole-pool level. Because entrained MNs effectively sample the input at their firing instants, we developed a MN-firing locked method that uses individual MN firings as endogenous triggering events for peristimulus frequencygrams across the pool. In simulations, this method revealed entrainment-driven firing rate modulations across MN subpools. We then applied this MN-firing locked method to MNs decomposed from high-density surface electromyography recordings obtained during isometric contractions in healthy individuals. We found that faster-firing MNs exhibited larger transient firing rate increases, time-locked to slower MN activity. Furthermore, these modulations correlated with common input in the alpha and beta bands implicating high frequency common input as the driving source. Together, these findings demonstrate that MN nonlinearities generate heterogeneous, frequency-dependent dynamics that remain hidden in conventional pool-level analyses.

neuroscience↗

bioRxiv2026

In vivo motor unit decoding and in vitro cellular characterisation of spinal circuits for urination in adult mice

Urinary dysfunction affects billions of individuals worldwide; however, the fundamental cellular and circuit properties that govern perineal motor control remain largely unknown, serving as a functional "black box". Here, we describe several methods that, when used in concert, characterise cellular, synaptic, and motor unit properties underlying the control of urination in adult mice. High-density electromyography combined with real-time cystometry were used to study external urethral sphincter (EUS) motor units, which follow a hierarchical ("onion skin") recruitment pattern during bladder filling. The transition to the voiding phase is marked by inhibition, followed by synchronised bursts. Furthermore, through concurrent recordings of ischiocavernosus (IC) muscles, the relationship between IC and EUS motor units could be studied to look for shared common inputs that could shed light on circuitry. Whole-cell patch-clamp recordings from retrogradely identified neurons revealed a fundamental biophysical divergence: urinary parasympathetic preganglionic neurons (PPGN) are significantly smaller and more excitable than somatic EUS and IC motoneurons and lack the recurrent excitatory and inhibitory circuits present in both EUS and IC motor pools. Finally, using a novel pressure-clamp preparation, we showed that acute tibial nerve stimulation (a widely used treatment for urinary dysfunction) evokes short-latency inhibition of EUS motor units. Collectively, these methods can be used to delineate patterns of motor unit recruitment, local recurrent microcircuit architecture, and distinct biophysical properties of the perineal motor system, providing mechanistic insights into urinary function.

neuroscience↗

bioRxiv2025

Evidence of spinal cord comparator modules for rapid corrections of movements

Successful movement requires continuous adjustments in response to changes in internal and external environments. To do so, neural circuits continuously compare efference copies of motor commands with sensory feedback to respond to sensory prediction errors. Some responses need to be very fast, indicating that they likely occur within spinal cord circuits. Here, we describe spinal cord circuits involving dI3 neurons, showing that they receive multimodal sensory inputs and direct efferent copies from both Renshaw cells and motor neurons. We further show that they form connections to motor pools. Reducing dI3 neuronal activity diminished stumbling responses, as did disrupting Renshaw cell circuits, providing evidence for a comparator role of dI3 neurons for online corrections. Together, our findings reveal a pivotal role for dI3 neurons functioning as comparators of efference copies and external sensory feedback to mediate rapid corrections of ongoing movements.

neuroscience↗

bioRxiv2025

Personalized mapping of inhibitory spinal circuits via neural decoding of high-density electromyography and in silico modelling

Studying human motoneuron activity through electromyography (EMG) can yield insights into the operation of fundamental spinal cord microcircuits. Traditional surface and needle electromyography (EMG) methodologies have limited capacity to shed light on the diversity of motor unit (MU) control strategies that may be unique to each individual. Here, we employed high-density surface EMG (HDsEMG) to sample multiple MUs per subject to investigate the dynamics of inhibitory spinal microcircuits in both upper and lower limb control. We characterised the net inhibition as a function of individual MU firing rates, revealing subject-specific relationships. In silico modelling replicated these experimental characteristics and suggested that properties of the inhibitory currents rather than motoneuron size are responsible for net functional inhibition. Our results show that HDsEMG can highlight distinct control strategies across circuits and motor pools, revealing subject-specific properties of inhibitory spinal microcircuits. TEASERHigh-density surface EMG electrodes can reveal the functional properties of inhibitory spinal circuits

neuroscience↗

bioRxiv2024

Spinal microcircuits go through multiphasic homeostatic compensations in a mouse model of motoneuron degeneration

In many neurological conditions, early-stage neural circuit adaption can preserve relatively normal behaviour. In some diseases, spinal motoneurons progressively degenerate yet movement is initially preserved. We therefore investigated whether these neurons and associated microcircuits adapt in a mouse model of progressive motoneuron degeneration. Using a combination of in vitro and in vivo electrophysiology and super-resolution microscopy, we found that, early in the disease, neurotransmission in a key pre-motor circuit, the recurrent inhibition mediated by Renshaw cells, is reduced by half due to impaired quantal size associated with decreased glycine receptor density. This impairment is specific, and not a widespread feature of spinal inhibitory circuits. Furthermore, it recovers at later stages of disease. Additionally, an increased probability of release from proprioceptive afferents leads to increased monosynaptic excitation of motoneurons. We reveal that in motoneuron degenerative conditions, spinal microcircuits undergo specific multiphasic homeostatic compensations that may contribute to preservation of force output.

neuroscience↗

bioRxiv2023

On the origin of F-wave: involvement of central synaptic mechanisms

Neurophysiological methods are used widely to gain information about motoneuron excitability and axon conduction in neurodegenerative diseases. The F-wave is a common biomarker used to test motoneuron properties in the diagnosis of neurological diseases. Although the origin of the F-wave is a subject of debate, the most widely accepted mechanism posits that the F-wave is generated by the backfiring of motoneurons stimulated antidromically from the periphery. In this study, we developed an ex vivo mouse sciatic nerve-attached spinal cord preparation with sensory axons severed in which stimulation of the whole sciatic nerve or its tibial branch evoked responses with the electrophysiological signatures of F-waves. Manipulations of synaptic transmission by either removal of extracellular calcium or block of post-synaptic glutamate receptors abolished these responses. These results suggest that F-waves are mediated by spinal microcircuits activated by recurrent motor axon collaterals via glutamatergic synapses.

neuroscience↗

bioRxiv2022

Pathophysiology of Dyt1 dystonia is mediated by spinal cord dysfunction

Dystonia, a neurological disorder defined by abnormal postures and disorganised movements, is considered to be a neural circuit disorder with dysfunction arising within and between multiple brain regions. Given that spinal circuits constitute the final pathway for motor control, we sought to determine their contribution to the movement disorder. Focusing on the most common inherited dystonia, DYT1-TOR1A, we confined a conditional knockout of Tor1a to the spinal cord and dorsal root ganglia (DRG) and found that these mice recapitulated the phenotype of the human condition, developing early onset generalised torsional dystonia. Physiologically, these mice bore the hallmark features of dystonia: spontaneous contractions at rest, excessive sustained contractions during voluntary movements including co-contractions of motor antagonists, and altered sensory-motor reflexes. Furthermore, spinal locomotor circuits were impaired. Together, these data challenge current understanding of dystonia, and lead to broader insights into spinal cord function and movement disorder pathophysiology.

neuroscience↗

bioRxiv2022

In vitro longitudinal lumbar spinal cord preparations to study sensory and recurrent motor microcircuits of juvenile mice

In vitro spinal cord preparations have been extensively used to study microcircuits involved in the control of movement. By allowing precise control of experimental conditions coupled with state-of-the-art genetics, imaging and electrophysiological techniques, isolated spinal cords from mice have been an essential tool in detailing the identity, connectivity and function of spinal networks. The majority of the research has arisen from in vitro spinal cords of neonatal mice, which are still undergoing important postnatal maturation. Studies from adults have been attempted in transverse slices, however, these have been quite challenging due to the poor motoneuron accessibility and viability, as well as to the extensive damage to the motoneuron dendritic trees. In this work, we describe two types of coronal spinal cord preparations with either the ventral or the dorsal horn ablated, obtained from mice of different postnatal ages, spanning from pre-weaned to one month old. These semiintact preparations allow recordings of sensory-afferent and motor-efferent responses from lumbar motoneurons using whole cell patch-clamp electrophysiology. We provide details of the slicing procedure and discuss the feasibility of whole-cell recordings. The in vitro dorsal and ventral horn-ablated spinal cord preparations described here are an useful tool to study spinal motor circuits in young mice that have reached the adult stages of locomotor development. New & NoteworthyIn the past 20 years, most of the research into the mammalian spinal circuitry has been limited to in vitro preparations from embryonic and neonatal mice. We describe two in vitro longitudinal lumbar spinal cord preparations from juvenile mice, that allow the study of motoneuron properties and respective afferent or efferent spinal circuits through whole-cell patch-clamp. These preparations will be useful to those interested in the study of microcircuits at mature stages of motor development.

neuroscience↗

bioRxiv2021

Antibody evasion by the Brazilian P.1 strain of SARS-CoV-2

Terminating the SARS-CoV-2 pandemic relies upon pan-global vaccination. Current vaccines elicit neutralizing antibody responses to the virus spike derived from early isolates. However, new strains have emerged with multiple mutations: P.1 from Brazil, B.1.351 from South Africa and B.1.1.7 from the UK (12, 10 and 9 changes in the spike respectively). All have mutations in the ACE2 binding site with P.1 and B.1.351 having a virtually identical triplet: E484K, K417N/T and N501Y, which we show confer similar increased affinity for ACE2. We show that, surprisingly, P.1 is significantly less resistant to naturally acquired or vaccine induced antibody responses than B.1.351 suggesting that changes outside the RBD impact neutralisation. Monoclonal antibody 222 neutralises all three variants despite interacting with two of the ACE2 binding site mutations, we explain this through structural analysis and use the 222 light chain to largely restore neutralization potency to a major class of public antibodies.

microbiology↗

bioRxiv2019

Sensory neuron-derived Nav1.7 contributes to dorsal horn neuron excitability

Expression of the voltage-gated sodium channel Nav1.7 in sensory neurons is required for pain sensation. We examined the role of Nav1.7 in the dorsal horn of the spinal cord using an epitope-tagged knock-in mouse. Immuno-electron microscopy showed the presence of Nav1.7 in dendrites of lamina II neurons, despite the absence of mRNA. Peripheral nervous system-specific Nav1.7 KO mice showed central deficits with lamina II dorsal horn tonic firing neurons more than halved and single spiking neurons more than doubled. Nav1.7 blocker PF05089771 diminished excitability in dorsal horn neurons, but had no effect on Nav1.7 KO mice. These data demonstrate an unsuspected functional role of peripherally generated Nav1.7 in dorsal horn neurons and an expression pattern that would not be predicted by transcriptomic analysis.

neuroscience↗