Biology subjects

Guglielmi, L.

Publications and source records attributed to Guglielmi, L..

9 recordsLinked to original sources

bioRxiv2026

Ventricular Forebrain Organoids Reproduce Macroscale Geometry of the Developing Telencephalon

During development, the size of the neuroepithelial cell pool plays a key role in establishing brain size, determining the numbers of derived progenitors and subsequent neuronal cell types. While early histogenesis is well modelled in brain organoids, the organ-scale geometry of the telencephalon is not accurately recapitulated. Herein, we present a new approach for generating ventral and dorsal forebrain organoids which develop a large ventricular neuroepithelium, characteristic of the closed telencephalic vesicle. Using a growth medium that supports aerobic glycolysis and is typically used for endothelial cells, we modulate neuroepithelial expansion to induce a more anatomically accurate neuroepithelial layer which, upon maturation, thickens physiologically to generate the typical neurogenic layered architecture. In addition, we present a new method for embedding organoids in miniature collagen spheres which mimics native extracellular matrix, stabilizes the ventricular geometry for dynamic culture conditions, and provides a means for incorporating vascular cells for neurovascular development. Finally, we demonstrate that human organoids grown under these conditions exhibit dramatically enlarged ventricles and delayed maturation compared to mouse. Together, this approach provides a model of the forebrain neuroepithelium with morphogenetic macroscale geometry and tissue architecture, suitable for investigating neurodevelopment and disease.

bioengineering↗

bioRxiv2026

Selective targeting of RalA with intrabodies impairs Triple Negative Breast Cancer metastasis

This study successfully developed and validated isoform-specific intrabodies targeting the highly homologous Ral oncoproteins, key effectors in cancer progression. Phage display was used to isolate single-chain variable fragment (scFv) clones that recognize specifically RalA (C1-A, G5-A), RalB (F6-B), or both paralogs (A12-AB). Using lentiviral transduction, these intrabodies were stably expressed as GFP fusions in murine breast cancer 4T1 cells. The anti-RalA clones C1-A and A12-AB demonstrated clear colocalization with RalA, confirming their binding activity inside the cell. We further confirmed their activity in cells by analyzing Ral-dependent pathways. All intrabodies targeting RalA (C1-A, G5-A, A12-AB) but not the one specific to RalB inhibited mitochondrial fission, a known RalA function. All clones, except the pan-Ral one, altered the endo-lysosome pathway by decreasing lysosome number. Furthermore, the RalA-specific C1-A clone reduced lysosomes size, and uniquely and strongly reduced extracellular vesicle secretion, highlighting its distinct inhibitory potential. In an orthotopic Triple-Negative Breast Cancer (TNBC) mouse model, The C1-A RalA specific clone significantly but weakly reduced primary tumor growth, but exerted a powerful anti-metastatic effect, dramatically reducing lung metastases, with a complete abolition of metastases observed in 2/5 mice. In summary, these potent, isoform-specific Ral intrabodies act as effective intracellular inhibitors, successfully modulating RalA-specific functions in cells and offering a promising therapeutic strategy for significantly suppressing tumor growth and metastasis in vivo.

cancer biology↗

bioRxiv2026

Characterization of the p38α MAPK allosteric inhibition by a single chain Fv antibody

Most of the available p38 kinase inhibitors target the highly conserved ATP-binding site, thus explaining their off-target effects and toxicity. Here, we report the use of single-chain fragment variable (scFv) antibodies to identify new highly specific inhibitors. Using phage display, we selected five anti-p38 scFv antibodies among which one fully inhibited p38 kinase activity in vitro. We showed that this scFv did not affect ATP binding, while still acting as a competitive inhibitor of ATP hydrolysis. When expressed as intrabody in the nucleus of the THP-1 human monocytic cell line, the scFv inhibited the function of endogenous p38 and induced a significant decrease in lipopolysaccharide-induced tumor necrosis factor production. To gain insight into the mechanisms by which the scFv induced p38 inhibition, the scFv epitope was mapped by deep mutational scanning of p38 displayed on yeast surface and high-throughput selection by flow cytometry of p38 mutants no longer bound by the scFv. By this approach, we showed that the inhibitory scFv interacts with two helices within the C-terminal lobe of the kinase distant from the ATP-binding pocket and the docking groove. Altogether, our data show that the scFv antibody behaves as an allosteric inhibitor, constraining and maintaining p38 in an inactive form.

biochemistry↗

bioRxiv2024

Calcium dynamics tune developmental tempo to generate evolutionarily divergent axon tract lengths

The human brain has undergone an evolutionary expansion in size, both in terms of cell numbers and the size of cellular structures, including axon tracts. Human brain development also progresses slowly and takes particularly long. However, the functional relevance of slowed timing, and whether it is responsible for these changes in size, remains unknown. Here, we investigate this by studying axon tract development in human and mouse brain organoids. We demonstrate that human axon tracts grow [~]2x more slowly than those of mice, reflecting their slowed tempo, but that this actually leads to shorter human axons, not longer. To overcome the effect of slowed tempo, human axons have a more prolonged growth duration that enables them to project farther despite their slower growth rate. Using a combination of single-cell RNA sequencing and live imaging, we demonstrate that the prolonged duration involves a different mechanism to that controlling tempo and is driven by calcium dynamics. Human axons exhibit a reduced calcium influx compared to mouse, mediated by L-Type voltage-gated calcium channels. Stimulating this calcium influx in human neurons triggers earlier cessation of growth, leading to shorter axon tracts similar to those of mouse. We further show that increasing calcium speeds up the transition to the synaptogenesis stage. Thus, calcium regulation sets the timing of transitions to disproportionately extend developmental duration, thereby enabling evolutionary expansion of human neurons.

developmental biology↗

bioRxiv2024

A minimally guided organoid model for cross-species comparisons of cerebellar development

The human cerebellum has undergone significant evolutionary expansion compared to other species, contributing to both motor and cognitive skills. However, the mechanisms underlying this process remain largely unknown as interrogating human cerebellar development alongside other species has to date been unfeasible. To address this, we developed a minimally guided cerebellar organoid protocol that combines unguided neural induction with precise temporal calibration of posteriorizing morphogens. This approach effectively overrides default telencephalic fate in cerebral organoids and induces stable cerebellar identities. Cerebellar organoids derived from both human and mouse ESCs exhibit species-specific size differences at comparable developmental stages and show robust induction of cerebellar master regulators and progenitor cell types. This model provides a powerful tool for investigating the mechanisms underlying cerebellar development in the context of both evolution and disease.

developmental biology↗

bioRxiv2024

Investigation of Lipid-PEG Anchorage of Proteins onto Mesenchymal Stem Cell Derived Extracellular Vesicles for Intracellular Delivery: A Quantitative Assessment

Despite biomolecule delivery is a natural function of Extracellular Vesicles (EVs), low loading of exogenous macromolecules such as proteins into EVs limits their interest as convincing protein delivery systems for health applications. In this context, lipid-anchorage of exogenous cargo into EV membrane recently emerged as a promising option to enable their vectorization into cells. Nevertheless, this option was not explored for protein intracellular delivery, and further characterization of critical parameters governing the association of a lipid-anchored cargo protein to EVs stills needed to confirm the relevance of this anchorage strategy. Therefore, we sought to identify these parameters in a precise and quantitative manner, using bulk and single nanoparticle analysis methods to identify protein loading capacity and subsequent intracellular delivery. We identified incubation temperature, cargo concentration, Lipid Anchor (LA) structure (lipid nature, linker) and EV origin as critical factors influencing maximal EV loading capacity. Precise control of these parameters enabled to load cargo protein close to EV saturation without hindering cellular delivery. Structural properties of LA influenced not only cargo protein/EV association, but also intracellular delivery into different carcinoma cell lines. By thoroughly characterizing Lipid-PEG-protein anchorage, this study evidences the interest of this tunable and controllable approach for efficient EV protein delivery. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=58 SRC="FIGDIR/small/610030v3_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@1fed681org.highwire.dtl.DTLVardef@1b4d728org.highwire.dtl.DTLVardef@1998e3aorg.highwire.dtl.DTLVardef@488be3_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2022

An improved Erk biosensor reveals oscillatory Erk dynamics driven by mitotic erasure during early development

Erk signaling dynamics elicit distinct cellular responses in a variety of contexts. The early zebrafish embryo is an ideal model to explore the role of Erk signaling dynamics in vivo, as a gradient of activated diphosphorylated Erk (P-Erk) is induced by Fgf signaling at the blastula embryonic margin. Here we describe an improved Erk-specific biosensor which we term modified Erk Kinase Translocation Reporter (modErk-KTR). We demonstrate the utility of this biosensor in vitro and in developing zebrafish and Drosophila embryos. Moreover, we show that Fgf/Erk signaling is dynamic and coupled to tissue growth during both early zebrafish and Drosophila development. Signaling is rapidly extinguished just prior to mitosis, which we refer to as mitotic erasure, inducing periods of inactivity, thus providing a source of heterogeneity in an asynchronously dividing tissue. Our modified reporter and transgenic lines represent an important resource for interrogating the role of Erk signaling dynamics in vivo.

developmental biology↗

bioRxiv2022

Nodal signaling establishes a competency window for stochastic cell fate switching

Specification of the germ layers by Nodal signaling has long been regarded as an archetype of how graded morphogens induce different cell fates. However, this deterministic model cannot explain why only a subset of cells at the margin of the early zebrafish embryo adopt the endodermal fate, while their immediate neighbours, experiencing similar signaling profiles, become mesoderm. Combining pharmacology, quantitative imaging and single cell transcriptomics, we demonstrate that sustained Nodal signaling establishes a bipotential progenitor state where cells initially fated to become mesoderm can switch to an endodermal fate. Switching is a random event, the likelihood of which is modulated by Fgf signaling. This inherently imprecise mechanism nevertheless leads to robust endoderm formation because of buffering at later stages. Thus, in contrast to previous deterministic models of morphogen action, Nodal establishes a temporal window when cells are competent to undergo a stochastic cell fate switch, rather than determining fate itself.

developmental biology↗

bioRxiv2022

Global hypo-methylation in a subgroup of glioblastoma enriched for an astrocytic signature is associated with increased invasion and altered immune landscape

We describe a new molecular subgroup of glioblastoma, the most prevalent malignant adult brain tumour, harbouring a bias towards hypomethylation at defined differentially methylated regions. This epigenetic signature correlates with an enrichment for an astrocytic gene signature, which together with the identification of enriched predicted binding sites of transcription factors known to cause demethylation and to be involved in astrocytic/glial lineage specification, point to a shared ontogeny between this glioblastoma subgroup and astroglial progenitors. At functional level, increased invasiveness, at least in part mediated by SRPX2, and macrophage infiltration characterise this glioblastoma subgroup.

cancer biology↗