Biology subjects

Spinelli, S.

Publications and source records attributed to Spinelli, S..

5 recordsLinked to original sources

bioRxiv2025

IgM hyposialylation drives podocyte injury in pediatric and young adult patients with podocytopathies.

IntroductionAltered immunoglobulin glycosylation has been implicated in antibody-mediated podocytopathies, yet the functional impact of IgM sialylation remains unclear. Previous evidence suggested that circulating cationic or hyposialylated IgM may contribute to podocyte injury in idiopathic nephrotic syndrome (iNS). MethodsSerum IgM from pediatric and young adult patients with podocytopathies, membranous nephropathy (MN), lupus nephritis (LN), and healthy controls were analyzed by lectin-based ELISA using a panel of six biotinylated lectins to detect terminal N-glycan residues. Among these, Sambucus nigra agglutinin (SNA) binds 2,6-linked sialic acid, and Ricinus communis agglutinin I (RCA-I) recognizes {beta}1,4-linked galactose. Serum levels of the 2,6-sialyltransferase ST6GAL1 and the sialidases neuraminidase-1 (NEU1) and neuraminidase-3 (NEU3) were quantified. Cultured human podocytes were exposed to patient-derived, control, or enzymatically modified IgM (desialylated/resialylated) and analyzed by confocal microscopy, quantitative proteomics, phosphoproteomics, and metabolic assays. ResultsIgM from patients with podocytopathies showed reduced SNA binding, which inversely correlated with proteinuria (r = -0.69, P < 0.0001) and with serum sialidases NEU1/NEU3 (r = -0.67/-0.59, P < 0.0001). In paired samples, SNA reactivity decreased during relapse and normalized in remission, indicating dynamic modulation with disease activity. ST6GAL1 was undetectable in all groups. In contrast, PLA2R1-positive MN, in which pathogenic antibodies target podocyte PLA2R1, displayed reduced RCA-I binding. Podocytes exposed to hyposialylated or desialylated IgM exhibited actin disorganization, loss of nephrin signal, increased lipid peroxidation, and decreased ATP synthesis. In contrast, resialylated IgM preserved morphology and metabolism comparable to controls. Proteomic and phosphoproteomic profiling revealed enrichment of MAPK, mTOR, AMPK, and cytoskeletal remodeling pathways. ConclusionsIgM hyposialylation, driven by extracellular sialidases up-regulation, correlates with disease activity and promotes oxidative stress, mitochondrial dysfunction, and cytoskeletal remodeling in podocytes, identifying immune glycan remodeling as a modifiable determinant of podocyte injury and a potential biomarker of disease activity. Translational StatementAltered glycosylation of circulating immunoglobulins is emerging as a key mechanism underlying glomerular injury. Here, we demonstrate that hyposialylated IgM, resulting from elevated serum sialidases NEU1 and NEU3, directly induces podocyte cytoskeletal disorganization, oxidative stress, and metabolic impairment. In contrast, enzymatic resialylation maintains podocyte morphology and function at levels indistinguishable from controls, indicating that sialic acid loss is a modifiable determinant of podocyte injury. Clinically, reduced IgM sialylation correlates with proteinuria and disease activity in idiopathic nephrotic syndrome, supporting its potential as a biomarker of relapse and remission. Targeting the sialidase-sialic acid pathway may therefore represent a promising strategy to preserve podocyte integrity and improve outcomes in antibody-negative podocytopathies.

pathology↗

bioRxiv2024

Hemogenic endothelium of the vitelline and umbilical arteries is the major contributor to mouse fetal lympho-myelopoiesis

Embryonic hematopoiesis consists of distinct waves originating in rapid succession from different anatomical locations. Hematopoietic progenitors appearing earlier than definitive hematopoietic stem cells (HSCs) play key roles in fetal and postnatal life. However, their precise origin, identity and the extent of their contribution need further clarification. To this aim, we took advantage of a genetic fate-mapping strategy in mice that allows labeling and tracking of distinct subsets of hemogenic endothelium (HE). Time-course labeling of hematopoietic progenitors emerging from HE between E8.5 and E9.5, before intra-embryonic definitive HSC generation, revealed a major fetal lympho-myeloid contribution which declined in the adult. Lineage tracing coupled with whole-mount imaging and single-cell RNA sequencing located its source within hematopoietic clusters of vitelline and umbilical arteries. Functional assays confirmed the transient nature of these progenitors. We therefore unveiled a hitherto unidentified early wave of fetal-restricted hematopoietic stem/progenitor cells poised for differentiation that provide a major contribution to pre-natal hematopoiesis.

developmental biology↗

bioRxiv2024

Disruption of autism-associated Pcdh9 gene leads to transcriptional alterations, synapses overgrowth and aberrant excitatory transmission in the CA1

Protocadherins are cell adhesion molecules with crucial role in cell-cell contacts, whose mutations or altered expression have been implicated in multiple brain disorders. In particular, growing evidence links genetic alterations in Protocadherin 9 (PCDH9) gene with Autism Spectrum Disorder (ASD) and Major Depression Disorder (MDD). Furthermore, Pcdh9 deletion induces neuronal defects in the mouse somatosensory cortex, accompanied by sensorimotor and memory impairment. However, the synaptic and molecular mechanisms underlying Pcdh9 physiological function and its involvement in brain pathology remain largely unknown. To this aim, we conducted a comprehensive investigation of PCDH9 role in the mouse hippocampus at the ultrastructural, biochemical, transcriptomic, electrophysiological and network level. We show that PCDH9 mainly localizes at glutamatergic synapses and its expression peaks in the first week after birth, a crucial time window for synaptogenesis. Strikingly, Pcdh9 KO neurons exhibit oversized presynaptic terminal and postsynaptic density (PSD) in the CA1. Synapse overgrowth is sustained by the broad up-regulation of synaptic genes and the dysregulation of key drivers of synapse morphogenesis, as revealed by single-nucleus RNAseq. Synaptic and transcriptional defects are accompanied by increased EPSC frequency and disturbances in the hippocampal network activity of Pcdh9 KO mice. In conclusion, our work indicates that Pcdh9 regulates the morphology and function of excitatory synapses in the CA1, thereby affecting glutamatergic transmission in hippocampal circuitries.

neuroscience↗

bioRxiv2022

Balanced SET levels favor the correct enhancer repertoire during cell fate acquisition

Within the chromatin, distal elements interact with promoters to regulate specific transcriptional programs. Histone acetylation, interfering with the net charges of the nucleosomes, is a key player in this regulation. Here, we report that the onco-protein SET is a critical determinant for the levels of histone acetylation within enhancers. We disclose that conditions in which SET is accumulated, including the severe Schinzel-Giedion Syndrome (SGS), are characterized by a failure in the usage of the distal regulatory regions typically employed during fate commitment. This is accompanied by the usage of alternative enhancers leading to a massive rewiring of the distal control of the gene transcription. This represents a (mal)adaptive mechanism that, on one side, allows to achieve a certain degree of differentiation, while on the other affects the fine and corrected maturation of the cells. Thus, we propose the differential in cis-regulation as a contributing factor to the pathological basis of the SET-related disorders in humans, including SGS, neurodevelopmental disorders, myeloproliferative diseases, and cancer.

developmental biology↗

bioRxiv2018

Phase transition and amyloid formation by a viral protein as an additional molecular mechanism of virus-induced cell toxicity

Henipaviruses are severe human pathogens responsible for severe encephalitis. Their V protein is a key player in the evasion of the host innate immune response. We have previously reported a biophysical characterization of the Henipavirus V proteins and shown that they interact with DDB1, a cellular protein that is a component of the ubiquitin ligase E3 complex. Here, we serendipitously discovered that the Hendra virus V protein undergoes a liquidhydrogel phase transition. By combining experimental and bioinformatics approaches, we have identified the V region responsible for this phenomenon. This region (referred to as PNT3), which falls within the long intrinsically disordered region of V, was further investigated using a combination of biophysical and structural approaches. ThioflavinT and Congo red binding assays, together with negative-staining electron microscopy studies, show that this region forms amyloid-like, {beta}-enriched structures. Such structures are also formed in mammal cells transfected to express PNT3. Those cells also exhibit a reduced viability in the presence of a stress agent. Interestingly, mammal cells expressing a rationally designed, non-amyloidogenic PNT3 variant (PNT33A), appear to be much less sensitive to the stress agent, thus enabling the establishment of a link between fibril formation and cell toxicity. The present findings therefore pinpoint a so far never reported possible mechanism of virus-induced cell toxicity.

biophysics↗