Biology subjects

Sorrentino, A.

Publications and source records attributed to Sorrentino, A..

8 recordsLinked to original sources

bioRxiv2026

Multifaceted immune resistance landscapes in human oligodendrocytes protect against cytotoxic T cells and are dysregulated in MS brain cell subsets

Multiple sclerosis (MS) is a progressive neuroinflammatory demyelinating disease of the central nervous system (CNS) that remains incurable. Autoreactive myelin-specific T cells contribute to immunopathology by directly targeting and damaging oligodendrocytes in situ. In oligodendrocytes, several immune-modulatory functions have been described that can ameliorate immune damage. However, a systematic discovery of cell-intrinsic mechanisms that protect oligodendrocytes against T cell-derived cytotoxic mechanisms has not been performed. We used human MO3.13 oligodendrocytic cells and human antigen-specific cytotoxic T cells to conduct a high-throughput (HTP) RNAi-based screen with altogether 4155 genes to identify oligodendrocyte-intrinsic immune resistance genes (IRGs). The screen revealed 133 candidate IRGs. Among them, we validated 32, which exerted a strong immuno-protective phenotype. We studied IRG expression landscapes in human brain cell subsets from postmortem brain tissues of MS and control individuals. This revealed clustered expression of IRGs in a cell-type and oligodendrocyte subset-specific manner and differential IRG expression between MS patients and controls in distinct oligodendrocyte subclusters. ChEA3 analysis revealed cell type-specific expression of transcription factors that can drive expression of respective IRGs. Explorative molecular mode of action analyses of five selected IRGs, STK11, KCNH8, ABCA2, SLC1A3 and CHRNA1 revealed that these prevented death receptor-mediated apoptosis induced by T cell-derived cytotoxic molecules. In particular, they controlled TRAIL-induced apoptosis by suppressing JNK1 activation through interfering with several upstream pathways regulating metabolic, potassium, cholesterol, glutamate and acetylcholine homeostasis. In addition, STK11, ABCA2, and CHRNA1 regulated TRAIL-R2 surface expression contributing to increased TRAIL-sensitivity whereas KCNH8 expression in oligodendrocytes inhibited secretion of inflammatory cytokines by cytotoxic T cells. Taken together, we here demonstrate the existence of multiple co-expressed IRGs in human oligodendrocytes that regulate multifaceted mechanisms of T cell resistance and are dysregulated in oligodendrocyte subsets of MS patients.

immunology↗

bioRxiv2025

Extracellular glutamine is essential in cell division and flagellar function in bloodstream forms of Trypanosoma brucei

Trypanosoma brucei is the etiologic agent of African trypanosomiasis, also known as sleeping sickness. In the mammalian host, T. brucei is present as replicative and non-replicative bloodstream forms (BSF) referred to as long slender and stumpy, respectively. In the insect vector, the developmental forms are procyclic (PCF), epimastigote, and metacyclic trypomastigote. It is well established that BSF use glucose as the main energy source, and PCF can use glucose but, in its absence, uses amino acids, mainly proline. Due to these facts, the metabolism of amino acids has been well studied in PCF, but less attention has been given to it in BSF. In the present work, we unveil the participation of glutamine (Gln), the most abundant amino acid in the human blood, in BSF proliferation. According to the data presented herein, in the absence of extracellular Gln, cell cycle progress, as well as kinetoplast and flagella distribution and function among daughter cells, are widely compromised, yielding polyploid multiflagellated cells with reduced motility. In addition, the Gln-poor medium resulted in cells with a massive alteration in the proteome glutamylation. These alterations were reverted when Gln was added to the culture media. An analysis of the glutamylproteome of cells incubated in Gln-poor medium, followed by a Gene Ontology (GO) analysis, suggested a relationship between glutamylation and biological processes such as gene expression and regulation, cell cycle, and bioenergetics metabolism, in addition to cytoskeleton dynamics in BSF of T. brucei.

cell biology↗

bioRxiv2024

Controlled pH Alteration Enables Guanine Accumulation and Drives Crystallization within Iridosomes

Many animals exhibit remarkable colors produced by the constructive interference of light reflected from arrays of intracellular guanine crystals. These systems are utilized for various purposes, including vision, camouflage, communication, and thermal regulation. Each guanine crystal forms within a membrane-bound organelle called an iridosome, where precise control over crystal formation occurs. While the presence of guanine crystals in iridosomes is well-documented, the mechanisms facilitating the accumulation of water-insoluble guanine and driving its crystallization remain unclear. Here, we employ advanced imaging and spectroscopy techniques to characterize the maturation of iridosomes in zebrafish iridophores during development. Using cryo-electron microscopy, we found that amorphous guanine accumulates in early-stage iridosomes. Synchrotron-based soft X-ray microscopy studies revealed that, unlike mature crystals, the accumulated guanine is initially in its protonated state. Live imaging with a pH sensor demonstrated that early-stage iridosomes are acidic and that their pH gradually approaches neutrality during maturation. Additionally, the application of a V-ATPase inhibitor reduced the acidity of iridosomes and significantly decreased crystal formation, suggesting the involvement of V-ATPase in regulating the organelle pH. Our findings reveal new insights into the molecular mechanisms facilitating guanine accumulation and crystallization within iridosomes, emphasizing the pivotal role of pH alternations in the precise formation of biogenic crystals.

cell biology↗

bioRxiv2023

Tuning Minimum-Norm regularization parameters for optimal MEG connectivity estimation

The accurate characterization of cortical functional connectivity from Magnetoencephalography (MEG) data remains a challenging problem due to the subjective nature of the analysis, which requires several decisions at each step of the analysis pipeline, such as the choice of a source estimation algorithm, a connectivity metric and a cortical parcellation, to name but a few. Recent studies have emphasized the importance of selecting the regularization parameter in minimum norm estimates with caution, as variations in its value can result in significant differences in connectivity estimates. In particular, the amount of regularization that is optimal for MEG source estimation can actually be suboptimal for coherence-based MEG connectivity analysis. In this study, we expand upon previous work by examining a broader range of commonly used connectivity metrics, including the imaginary part of coherence, corrected imaginary part of Phase Locking Value, and weighted Phase Lag Index, within a larger and more realistic simulation scenario. Our results show that the best estimate of connectivity is achieved using a regularization parameter that is 1 or 2 orders of magnitude smaller than the one that yields the best source estimation. This remarkable difference may imply that previous work assessing source-space connectivity using minimum-norm may have benefited from using less regularization, as this may have helped reduce false positives. Importantly, we provide the code for MEG data simulation and analysis, offering the research community a valuable open source tool for informed selections of the regularization parameter when using minimum-norm for source space connectivity analyses. HighlightsO_LIThe regularization parameter of the Minimum Norm Estimate of neural activity impacts connectivity estimation C_LIO_LIWe study empirically the optimal parameter for connectivity estimation using realistic synthetic datasets C_LIO_LIWe find the optimal parameter for connectivity estimation is systematically smaller than the optimal parameter for source imaging; different connectivity metrics yield the same result C_LIO_LICode and data are available open source. C_LI

neuroscience↗

bioRxiv2021

An in-vivo validation of ESI methods with focal sources

Electrical source imaging (ESI) aims at reconstructing the electrical brain activity from measurements of the electric field on the scalp. Even though the localization of single focal sources should be relatively straightforward, different methods provide diverse solutions due to the different underlying assumptions. Furthermore, their input parameter(s) further affects the solution provided by each method, making localization even more challenging. In addition, validations and comparisons are typically performed either on synthetic data or through post-operative outcomes, in both cases with considerable limitations. We use an in-vivo high-density EEG dataset recorded during intracranial single pulse electrical stimulation, in which the true sources are substantially dipolar and their locations are known. We compare ten different ESI methods under multiple choices of input parameters, to assess the accuracy of the best reconstruction, as well as the impact of the parameters on the localization performance. Best reconstructions often fall within 1 cm from the true source, with more accurate methods outperforming less accurate ones by 1 cm, on average. Expectedly, dipolar methods tend to outperform distributed methods. Sensitivity to input parameters varies widely between methods. Depth weighting played no role for three out of six methods implementing it. In terms of regularization parameters, for several distributed methods SNR=1 unexpectedly turned out to be the best choice among the tested ones. Our data show similar levels of accuracy of ESI techniques when applied to "conventional" (32 channels) and dense (64, 128, 256 channels) EEG recordings. Overall findings reinforce the importance that ESI may have in the clinical context, especially when applied to identify the surgical target in potential candidates for epilepsy surgery.

neuroscience↗

bioRxiv2020

Cellular pathways of calcium transport and concentration towards mineral formation in sea urchin larvae

Sea urchin larvae have an endoskeleton consisting of two calcitic spicules. The primary mesenchyme cells (PMCs) are the cells that are responsible for spicule formation. PMCs endocytose sea water from the larval internal body cavity into a network of vacuoles and vesicles, where calcium ions are concentrated until they precipitate in the form of amorphous calcium carbonate (ACC). The mineral is subsequently transferred to the syncytium, where the spicule forms. Using cryo-soft X-ray microscopy (cryo-SXM) we imaged intra-cellular calcium-containing particles in the PMCs and acquired Ca-L2,3 X-ray absorption near edge spectra (XANES) of these Ca-particles. Using the pre-peak/main peak (L2/ L2) intensity ratio, which reflects the atomic order in the first Ca coordination shell, we determined the state of the calcium ions in each particle. The concentration of Ca in each of the particles was also determined by the integrated area in the main Ca absorption peak. We observed about 700 Ca-particles with order parameters, L2/ L2, ranging from solution to hydrated and anhydrous ACC, and with concentrations ranging between 1-15 M. We conclude that in each cell the calcium ions exist in a continuum of states. This implies that most, but not all water, is expelled from the particles. This cellular process of calcium concentration may represent a widespread pathway in mineralizing organisms. SignificanceOrganisms form mineralized skeletons, many of which are composed of calcium salts. Marine organisms extract calcium ions from sea water. One of the main unresolved issues is how organisms concentrate calcium by more than 3 orders of magnitude, to achieve mineral deposition in their skeleton. Here we determine the calcium state in each of the calcium-containing vesicles inside the spicule-building cells of sea urchin larvae. We show that within one cell there is a wide range of concentrations and states from solution to solid. We hypothesize that calcium concentration increases gradually in each vesicle, starting from sea water levels and until mineral is deposited. This model might well be relevant to other phyla, thus advancing the understanding of biomineralization processes.

biophysics↗

bioRxiv2020

Simultaneous human intracerebral stimulation and HD-EEG: ground-truth for source localization methods

Precisely localizing the sources of brain activity as recorded by EEG is a fundamental procedure and a major challenge for both research and clinical practice. Even though many methods and algorithms have been proposed, their relative advantages and limitations are still not well established. Moreover, these methods involve tuning multiple parameters, for which no principled way of selection exists yet. These uncertainties are emphasized due to the lack of ground-truth for their validation and testing. Here we provide the first open dataset that comprises EEG recorded electrical activity originating from precisely known locations inside the brain of living humans. High-density EEG was recorded as single-pulse biphasic currents were delivered at intensities ranging from 0.1 to 5 mA through stereotactically implanted electrodes in diverse brain regions during pre-surgical evaluation of patients with drug-resistant epilepsy. The uses of this dataset range from the estimation of in vivo tissue conductivity to the development, validation and testing of forward and inverse solution methods.

neuroscience↗

bioRxiv2017

Inverse Modeling For MEG/EEG Data

We provide an overview of the state-of-the-art for mathematical methods that are used to reconstruct brain activity from neurophysiological data. After a brief introduction on the mathematics of the forward problem, we discuss standard and recently proposed regularization methods, as well as Monte Carlo techniques for Bayesian inference. We classify the inverse methods based on the underlying source model, and discuss advantages and disadvantages. Finally we describe an application to the pre-surgical evaluation of epileptic patients.

neuroscience↗