Biology subjects

Marino, V.

Publications and source records attributed to Marino, V..

6 recordsLinked to original sources

bioRxiv2026

Residual cortical responses and network reorganization in inherited retinal degeneration: electrophysiological evidence

Retinitis pigmentosa (RP) progressively deprives the retina of input, but whether the responsiveness of the visual cortex declines in parallel, remains preserved, or increases through compensatory gain remains unclear. Indeed, a weaker visually evoked response cannot, on its own, distinguish these possibilities, since it is equally compatible with a passively degraded input and with an actively recalibrated cortex. We combined spatially resolved steady-state visual evoked potentials (SSVEPs), which index stimulus-driven activity, with transcranial magnetic stimulation combined with electroencephalography (TMS-EEG), which probes cortical reactivity independently of vision, in patients with RP and in healthy controls. Nine patients (PTs) with RP (five women, age range 28 to 69 years) and nineteen sex-, age-, and handedness-matched healthy controls (thirteen women, mean age 42.6 years) were tested. They underwent SSVEP recordings to stimuli presented at three eccentricities (central, intermediate, peripheral) and single-pulse TMS-EEG over the left and right occipital cortex and, as a non-visual control site, the dominant motor cortex. We quantified SSVEP amplitude and phase at 12 Hz, early TMS-evoked potentials, oscillatory power, inter-trial phase synchrony, and functional connectivity and graph-theoretical network measures derived from the weighted phase lag index. SSVEP amplitude followed the expected central-to-peripheral gradient: PTs were comparable to healthy controls at the center, reduced but still above their own resting baseline at intermediate eccentricity, and no longer distinguishable from baseline in the periphery; phase differed from controls in a quarter of the central and half of the intermediate sectors. Occipital stimulation elicited a larger early negative deflection after left-hemisphere stimulation in PTs compared to controls, a stronger beta-band event-related spectral perturbation after stimulation of either hemisphere, and stronger, more efficiently distributed post-stimulus connectivity, despite comparable pre-stimulus connectivity, resting motor threshold, and most early evoked components. The pattern was site- and hemisphere-specific: left occipital stimulation produced widespread, mainly contralateral effects; right occipital stimulation a more circumscribed ipsilateral one, and motor cortex stimulation showed altered alpha-band activity without the bilateral occipital beta effect. Together, these results show that progressive retinal deafferentation in RP does not produce a parallel decline in cortical responsiveness. Visually driven activity weakens with eccentricity, while direct cortical perturbation reveals preserved and, at selected sites, enhanced reactivity. This dissociation is consistent with a homeostatic increase in cortical gain rather than a uniform loss of cortical function, and indicates that the deafferented cortex retains, and in places strengthens, its capacity to respond as retinal input deteriorates.

neuroscience↗

bioRxiv2026

A knock-in model of severe GUCA1A cone-rod dystrophy reveals retinal network dysfunction beyond phototransduction

Autosomal dominant cone-rod dystrophy caused by GUCA1A mutations is generally viewed as a disorder of phototransduction, yet the mechanisms linking photoreceptor dysfunction to progressive vision loss remain unclear. Here, using a knock-in mouse carrying the severe GCAP1 p.(E111V) variant, we show that retinal network dysfunction precedes structural degeneration. Mutant mice exhibited delayed rod photoresponses, increased light sensitivity, selective visuospatial deficits, and progressive impairment of visually evoked responses in the superior colliculus and visual cortex, demonstrating propagation of functional deficits beyond photoreceptors. Transcriptomic and ultrastructural analyses revealed early synaptic, mitochondrial and inflammatory alterations despite largely preserved retinal architecture. Acute ex vivo delivery of recombinant wild-type GCAP1 partially restored mutant rod photoresponse kinetics, indicating that these early functional deficits remain biochemically modifiable. These findings redefine severe GUCA1A-associated disease as a progressive disorder of retinal network function, identifying an early therapeutic window before structural degeneration. One-Sentence SummaryVisual function breaks down long before photoreceptors are lost, opening an early window for intervention.

neuroscience↗

bioRxiv2024

Supramolecular complexes of GCAP1: towards the development of effective biologics for inherited retinal dystrophies

Guanylate Cyclase Activating Protein 1 (GCAP1) is a neuronal Ca2+-sensor protein expressed in photoreceptors where it regulates the enzymatic activity of retinal Guanylate Cyclase 1 (GC1) in a Ca2+-dependent manner. Recently, over 20 missense mutations in GUCA1A (encoding for GCAP1) have been associated with inherited autosomal dominant retinal diseases, namely cone dystrophy (COD) and cone-rod dystrophy (CORD). Since GCAP1 is known to be a functional dimer, COD/CORD patients present a heterogeneous pool of GCAP1 assemblies constituted by wild-type and mutated homodimers and heterodimers. Here, we present an integrated in silico and biochemical investigation on the effects of the E111V substitution, associated with a severe form of CORD, on GCAP1 homo- and hetero-dimerization. Despite inducing a constitutive activation of GC1 due to impaired Ca2+-binding in the high-affinity EF-hand 3 motif, the E111V substitution did not affect either the homo- or the hetero dimerization process as clearly highlighted by aSEC and molecular docking experiments. Indeed, both variants exhibited micromolar monomer-dimer equilibrium constants in the presence of both Mg2+ and Ca2++, indicating that at physiological cellular concentrations both variants are predominantly monomers under Ca2+-loaded and, to a lesser extent, Mg2+-loaded conditions. Molecular docking and dynamics simulations confirmed chromatographic results highlighting slight alterations in free energy of binding involving the pathogenic E111V variant in the Ca2+-bound state and increased mobility over time affecting the Ca2+-coordinating EF3 motif. In addition, to evaluate possible therapeutic approaches, the regulation of the catalytic activity of GC1 by WT and E111V-GCAP1 was studied in the presence of retinal degeneration protein 3 (RD3), an -helical protein that strongly inhibits GC1, and a RD3-derived peptide (RD3ppt) which encompasses a region of RD3 that is essential for its inhibitory activity. GC1 activity assays in the presence of RD3ppt suggest that the enzymatic activity is partially inhibited by the peptide at low micromolar concentrations when GCAP1 variants are present. The incomplete shut down of GC1 by RD3 could be explained by the interaction occurring between RD3 and GCAP1, known to form a complex with GC1 in the endoplasmic reticulum. This fundamental interaction was here investigated spectroscopically and in silico, unveiling major structural rearrangements upon complex formation. Interestingly, the full RD3 protein was able to better modulate GC1 activity and restore the abnormal cGMP production induced by the pathogenic E111V-GCAP1 variant to a physiological level.

biochemistry↗

bioRxiv2023

Structural analysis and genetic code expansion reveal the functional impact of NR2F1 mutations associated with BBSOA-Syndrome

Deciphering the structural effects of variants is essential for understanding the pathophysiological mechanisms of genetic diseases. Using a neurodevelopmental disorder called Bosch-Boonstra-Schaaf Optic Atrophy Syndrome (BBSOAS) as a genetic disease model, we applied a combined Genetic Code Expansion (GCE) and structural bioinformatics strategy to assess the pathogenic impact of several human NR2F1 variants. Nonsense mutations in the ligand binding domain (LBD) resulted in truncated proteins, while missense variants significantly affected the folding of NR2F1 monomers as well as its supramolecular complexes. The GCE-enabled covalent and site-specific capture of transient supramolecular interactions in living cells revealed the variable quaternary conformations of NR2F1 variants and pinpointed the disrupted interplay with dimeric partners and the newly identified cofactor, CRABP2, while the computational analyses of the NR2F1 structure delineated the molecular basis of the impact of the variants on the isolated and complexed structures. The revealed consequence of the pathogenic mutations on the conformation, supramolecular interplay, and alterations in the cell cycle, viability, and subcellular localization of the different variants reflect the heterogeneous disease spectrum and establish the foundation for further understanding the complexity of BBSOAS.

biochemistry↗

bioRxiv2022

Recombinant protein delivery enables modulation of the phototransduction cascade in mouse retina

Retinal dystrophies of genetic origin are often associated with mutations in the genes involved in the phototransduction cascade in photoreceptors, a paradigmatic signaling pathway mediated by G protein-coupled receptors. Photoreceptor viability is strictly dependent on the levels of the second messengers cGMP and Ca2+. Here we explored the possibility of modulating the phototransduction cascade in mouse rods using direct or liposome-mediated administration of a recombinant protein crucial for regulating the interplay of the second messengers in photoreceptor outer segments. The effects of administration of the free and liposome-encapsulated human guanylate cyclase-activating protein (GCAP1) were compared in biological systems of increasing complexity (in cyto, ex vivo, and in vivo). Analysis of protein biodistribution and direct measurement of functional alteration in rod photoresponses show that the exogenous GCAP1 protein is fully incorporated into the mouse retina and photoreceptor outer segments. Furthermore, only in the presence of a point mutation associated with cone-rod dystrophy in humans p.(E111V), protein delivery induces a disease-like electrophysiological phenotype, consistent with constitutive activation of the retinal guanylate cyclase. Our study demonstrates that both direct and liposome-mediated protein delivery are powerful tools for targeting signaling cascades in neuronal cells, which could be particularly important for the treatment of autosomal dominant genetic diseases.

neuroscience↗

bioRxiv2021

Divergent epigenetic profiles from two differentially impacted wild populationsof estuarine cordgrass (Sporobolus alterniflorus)

The effects of urbanization on watershed ecosystems present critical challenges to modern survival. Organisms in urbanized areas experience high rates of evolutionary change, but genetic adaptation alone cannot mitigate the rapid and severe effects of urbanization on biodiversity. Highly resilient, foundation species are key to maintaining an ecosystems integrity in the face of urban stressors. However, the rapid collapse and disappearance of watershed ecosystems calls into question the extent to which we can rely on such species for their services. Our research investigates the molecular mechanisms by which the foundation ecosystems provider, Sporobolus alterniflorus, adapts to life in an urbanized environment. To elucidate these mechanisms, we quantified changes in global DNA methylation (% 5-mC) as a result of acute heat stress. Specimens from two differentially impacted populations across an urban to suburban geographical transect formed the basis of this study. These two populations of Sporobolus alterniflora exhibit inverse global DNA methylation patterns when exposed to the same acute heat stress. Our findings suggest that epigenetic mechanisms, such as DNA methylation, control rapid and transient adaptation, in the form of differential stress responses, to distinct environment challenges. Highlights for manuscript submissionO_LI{blacksquare} estuarine grasses native to the Bronx River, NY face stresses associated with low dissolved oxygen and urbanization C_LIO_LI{blacksquare} differentially impacted populations of estuarine grasses exhibit inverse global DNA methylation profiles in response to acute heat stress C_LIO_LI{blacksquare} DNA methylation may represent a mechanism by which plants transiently respond to environmental stressors, and this may represent a form of rapid adaptive evolution C_LIO_LI{blacksquare} stress priming by transgenerational epigenetic modification may enhance fitness in grasses native to the heavily impacted Bronx River estuary C_LI

plant biology↗