Biology subjects

Rebollo, E.

Publications and source records attributed to Rebollo, E..

9 recordsLinked to original sources

bioRxiv2024

HUMAN SPINAL CORD ORGANOIDS REVEAL CELL INTERCALATION AS A CONSERVED MECHANISM FOR SECONDARY NEURULATION

Human pluripotent stem cells (hPSCs) have enabled major advances in neural organoid research, yet reconstructing spinal cord development in vitro remains challenging, as it requires mimicking the early environment of body axis elongation. Here, by exposing hPSCs to defined extrinsic signals, we directed their self-organizing capacity to generate organoids that recapitulate the transcriptional profile, cellular composition, and tissue architecture of the early human posterior spinal cord. Furthermore, we refined our culture system to more closely model the in vivo morphogenetic events of secondary neurulation. Using this approach, we identified cell intercalation--regulated by Yes-associated protein (YAP) activity--as a key morphogenetic mechanism driving de novo lumen formation and resolution. These biomimetic models provide a powerful platform to investigate the molecular and mechanical processes underlying human spinal cord development and offer new opportunities to elucidate the origins of neural tube defects, among the most common congenital defects.

developmental biology↗

bioRxiv2023

Imaging analysis of six human histone H1 variants reveals universal enrichment of H1.2, H1.3, and H1.5 at the nuclear periphery and nucleolar H1X presence

Histone H1 participates in chromatin condensation and regulates nuclear processes. Human somatic cells may contain up to seven histone H1 variants, although their functional heterogeneity is not fully understood. Here, we have profiled the differential nuclear distribution of the somatic H1 repertoire in human cells through imaging techniques including super-resolution microscopy. H1 variants exhibit characteristic distribution patterns in both interphase and mitosis. H1.2, H1.3, and H1.5 are universally enriched at the nuclear periphery in all cell lines analyzed and co-localize with compacted DNA. H1.0 shows a less pronounced peripheral localization, with apparent variability among different cell lines. On the other hand, H1.4 and H1X are distributed throughout the nucleus, being H1X universally enriched in high-GC regions and abundant in the nucleoli. Interestingly, H1.4 and H1.0 show a more peripheral distribution in cell lines lacking H1.3 and H1.5. The differential distribution patterns of H1 suggest specific functionalities in organizing lamina-associated domains or nucleolar activity, which is further supported by a distinct response of H1X or phosphorylated H1.4 to the inhibition of rDNA transcription. Moreover, H1 variants depletion affects chromatin structure in a variant-specific manner. Concretely, H1.2 knock-down, either alone or combined, triggers a global chromatin decompaction. Overall, imaging has allowed us to distinguish H1 variants distribution beyond the segregation in two groups denoted by previous ChIP-seq determinations. Our results support H1 variants heterogeneity and suggest that variant-specific functionality can be shared between different cell types.

cell biology↗

bioRxiv2023

Quantification of extracellular matrix components in immunolabeled tissue samples

In recent years, the interaction between cells and the extracellular matrix (ECM) has become a new focus in understanding tissue morphogenesis, regeneration, and disease. However, the lack of specific techniques to study the ECM composition in preserved tissue structures remains a major obstacle to explaining ECM changes in response to extrinsic stimuli. To overcome this, we propose a novel strategy that uses multidimensional fluorescence microscopy and computational tools to quantify ECM composition in immunolabeled tissues and/or cell-derived matrices (CDM). This approach includes a detailed protocol for densitometric fluorescence calibration and procedures for image acquisition, processing, and automated quantification. Using this method, we present new data comparing collagen types I, III, and IV, and fibronectin contents in various tissues. These results emphasize the importance of studying ECM composition in situ under both normal homeostatic and disease conditions. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=135 SRC="FIGDIR/small/535641v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@1203e08org.highwire.dtl.DTLVardef@1c88c1borg.highwire.dtl.DTLVardef@1664ac2org.highwire.dtl.DTLVardef@b63154_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2021

A novel Alex3/Gαq protein complex regulating mitochondrial dynamics, dendritic complexity, and neuronal survival

In neurons, mitochondrial dynamics and trafficking are essential to provide the energy required for neurotransmission and neuronal activity. Recent studies point to GPCR and G proteins as important regulators of mitochondrial dynamics and energy metabolism. Here we show that activation of Gq negatively regulates mitochondrial dynamics and trafficking in neurons. Gq interacts with the mitochondrial trafficking protein Alex3. By generating a CNS-specific armcx3 knock-out mouse line, we demonstrate that Alex3 is required for Gq effects on mitochondrial dynamics and trafficking, and dendritic growth. Armcx3-deficient mice present decreased OXPHOS complex and ER stress response protein levels, which correlate with increased neuronal death, motor neuron and neuromuscular synaptic loss, and severe motor alterations. Finally, we show that Alex3 disassembles from the Miro1/Gq complex upon calcium rise. These data uncover a novel Alex3/Gq complex that regulates neuronal mitochondrial dynamics and neuronal death and allows the control of mitochondrial functions by GPCRs.

cell biology↗

bioRxiv2021

Neural crest-related NXPH1/α-NRXN signaling opposes neuroblastoma malignancy by inhibiting metastasis

Neuroblastoma is a pediatric cancer that can present as low- or high-risk tumors (LR-NBs and HR-NBs), the latter group showing poor prognosis due to metastasis and strong resistance to current therapy. NBs are known to originate from alterations to cells in the sympatho-adrenal lineage derived from the neural crest, but whether LR-NBs and HR-NBs differ in the way they exploit the transcriptional program underlying their developmental origin remains unclear. Here, we compared the transcriptional landscapes of primary samples of LR-NBs, HR-NBs and human fetal adrenal gland, and thereby identified the transcriptional signature associated to NB formation that further distinguishes LR-NBs from HR-NBs. The majority of the genes comprising this signature belong to the core sympatho-adrenal developmental program, are associated with favorable patient prognosis and with diminished disease progression. The top candidate gene of this list, Neurexophilin-1 (NXPH1), encodes a ligand of the transmembrane receptors -Neurexins (-NRXNs). Our functional in vivo and in vitro assays reveal that NXPH1/-NRXN signaling has a dual impact on NB behavior: whereas NXPH1 and -NRXN1 promote NB tumor growth by stimulating cell proliferation, they conversely inhibit the ability of NB cells to form metastases. Our findings uncover a module of the neural crest-derived sympatho-adrenal developmental program that opposes neuroblastoma malignancy by impeding metastasis, and pinpoint NXPH1/-NRXN signaling as a promising target to treat HR-NBs.

neuroscience↗

bioRxiv2021

Kazrin C entraps early endosomes at the pericentriolar region and facilitates endocytic recycling

Kazrin is a protein widely expressed in vertebrates whose depletion causes a myriad of developmental defects, in part derived from altered cell adhesion, impaired cell migration and failure to undergo Epidermal to Mesenchymal Transition (EMT). However, the primary molecular role of kazrin, which might contribute to all these functions, has not been elucidated yet. We previously identified one of its isoforms, kazrin C, as a protein that potently inhibits clathrin-mediated endocytosis when overexpressed. We now generated kazrin knock out Mouse Embryonic Fibroblasts (MEFs) to investigate its endocytic function. We found that kazrin depletion delays perinuclear enrichment of internalized material, indicating a role in endocytic traffic from Early (EE) to Recycling Endosomes (REs). Consistently, we found that the C-terminal domain of kazrin C, predicted to be an Intrinsically Disordered Region (IDR), directly interacts with several components of the EEs, and that kazrin depletion impairs centripetal motility of EEs. Further, we noticed that the N-terminus of kazrin C shares homology with dynein/dynactin adaptors and that it directly interacts with the dynactin complex and the dynein Light Intermediate Chain 1 (LIC1). Altogether, the data indicate that one of the primary kazrin functions is to facilitate endocytic recycling via the perinuclear endocytic compartment, by promoting microtubule and dynein/dynactin-dependent transport of EEs or EE-derived transport intermediates to the RE.

cell biology↗

bioRxiv2021

Light-dependent inhibition of clathrin-mediated endocytosis in yeast

Clathrin-mediated endocytosis (CME) is an essential cellular process, which is evolutionarily conserved among eukaryotes. Yeast constitutes a powerful genetic model to dissect the complex endocytic machinery, yet there is a lack of pharmacological agents that could complement genetics in selectively and reversibly interfere with CME in these organisms. TL2 is a light-regulated peptide inhibitor that targets the AP2/{beta}-arrestin interaction and that can photocontrol CME with high spatiotemporal precision in mammalian cells. Here, we study endocytic protein dynamics by live-cell imaging of the fluorescently tagged coat-associated protein Sla1-GFP and demonstrate that TL2 retains its inhibitory activity in S. cerevisiae spheroplasts, thus providing a unique tool for acute and reversible CME modulation in yeast.

cell biology↗

bioRxiv2020

eEF1A2 controls local translation and actin dynamics in structural synaptic plasticity

Synaptic plasticity involves structural modifications in dendritic spines. Increasing evidence suggests that structural plasticity is modulated by local protein synthesis and actin remodeling in a synapsis-specific manner. However, the precise molecular mechanisms connecting synaptic stimulation to these processes in dendritic spines are still unclear. In the present study, we demonstrate that the configuration of phosphorylation sites in eEF1A2, an essential translation elongation factor in neurons, is a key modulator of structural plasticity in dendritic spines. A mutant that cannot be phosphorylated stimulates translation but reduces actin dynamics and spine density. By contrast, the phosphomimetic variant loosens its association with F-actin and becomes inactive as a translation elongation factor. Metabotropic glutamate receptor signaling triggers a transient dissociation of eEF1A2 from its GEF protein in dendritic spines, in a phospho-dependent manner. We propose that eEF1A2 establishes a crosstalk mechanism that coordinates local translation and actin dynamics during spine remodeling.

neuroscience↗

bioRxiv2018

Impaired development of neocortical circuits contributes to the neurological alterations in DYRK1A haploinsufficiency syndrome

Autism spectrum disorders are early onset neurodevelopmental disorders characterized by deficits in social communication and restricted repetitive behaviors, yet they are quite heterogeneous in terms of their genetic basis and phenotypic manifestations. Recently, de novo pathogenic mutations in DYRK1A, a chromosome 21 gene associated to neuropathological traits of Down syndrome, have been identified in patients presenting a recognizable syndrome included in the autism spectrum. These mutations produce DYRK1A kinases with partial or complete absence of the catalytic domain, or they represent missense mutations located within this domain. Here, we undertook an extensive biochemical characterization of the DYRK1A missense mutations reported to date and show that most of them, but not all, result in enzymatically dead DYRK1A proteins. We also show that haploinsufficient Dyrk1a+/- mutant mice mirror the neurological traits associated with the human pathology, such as defective social interactions, stereotypic behaviors and epileptic activity. These mutant mice present altered proportions of excitatory and inhibitory neocortical neurons and synapses. Moreover, we provide evidence that alterations in the production of cortical excitatory neurons are contributing to these defects. Indeed, by the end of the neurogenic period, the expression of developmental regulated genes involved in neuron differentiation and/or activity is altered. Therefore, our data indicate that altered neocortical neurogenesis could critically affect the formation of cortical circuits, thereby contributing to the neuropathological changes in DYRK1A haploinsufficiency syndrome.

neuroscience↗