Biology subjects

Fernandez-Monreal, M.

Publications and source records attributed to Fernandez-Monreal, M..

5 recordsLinked to original sources

bioRxiv2025

Synchrotron XRF imaging reveals manganese accumulation in the Golgi and post-synapses of neurons and enhanced uptake in astrocytes

Manganese is an essential trace metal for humans, but excessive exposure can cause neurotoxicity, including parkinsonian syndromes, cognitive deficits, and has also been implicated in the pathogenesis of neurodegenerative diseases. Globally, tens of millions of people are exposed to elevated manganese levels through drinking water, exceeding the WHO recommended guideline. Despite its public health significance, the cellular and subcellular mechanisms underlying manganese neurotoxicity remain poorly defined, particularly its distribution across brain cell types and its specific intracellular targets. In this study, we investigated manganese accumulation in primary cultures of hippocampal neurons and astrocytes. Using a correlative imaging approach that combined cryo-fluorescence light microscopy with synchrotron X-ray fluorescence imaging, we mapped and quantified manganese at subcellular resolution. Our analysis revealed that manganese preferentially accumulates in the Golgi apparatus of both neurons and astrocytes. In neurons, manganese was also detected in dendrites at the postsynaptic density, suggesting a role in synaptic vulnerability. Quantitative elemental analysis showed that astrocytes accumulated 3 times more manganese than neurons. Furthermore, when neurons were co-cultured with astrocytes, their manganese uptake was significantly reduced, indicating a possible protective or buffering role of astrocytes. These findings identify key cellular and subcellular targets of manganese and highlight the Golgi apparatus as a major regulator of manganese neurotoxicity. This work provides a foundation for understanding cell type-specific responses to manganese exposure and may inform the development of targeted neuroprotection strategies. Significance statementManganese neurotoxicity impact millions of people worldwide. Understanding how manganese distributes within brain cells is critical for addressing its neurotoxic effects. This study identifies the Golgi apparatus and postsynaptic density as key sites of manganese accumulation and reveals astrocytes as major regulators of neuronal manganese uptake. These findings provide a cellular framework for developing targeted strategies to mitigate manganese-induced neurotoxicity.

neuroscience↗

bioRxiv2024

Root Expansion Microscopy (ROOT-ExM): A streamlined super resolution method for plants

Expansion microscopy (ExM) has revolutionized biological imaging by physically enlarging samples, surpassing the light diffraction limit and enabling nanoscale visualization using standard microscopes. While extensively employed across a wide range of biological samples, its application to plant tissues is sparse. In this work, we present ROOT-ExM, an expansion method suited for stiff and intricate multicellular plant tissues, focusing on the primary root of Arabidopsis thaliana. ROOT-ExM achieves isotropic expansion with a fourfold increase in resolution, enabling super-resolution microscopy comparable to STimulated Emission Depletion (STED) microscopy. Labelling is achieved through immunolocalization, compartment-specific dyes, and native fluorescence preservation, while N-Hydroxysuccinimide (NHS) ester-dye conjugates reveal the ultrastructural context of cells alongside specific labelling. We successfully applied ROOT-ExM to image various cellular structures, including the Golgi apparatus, the endoplasmic reticulum, the cytoskeleton, and wall-embedded structures such as plasmodesmata. When combined with lattice light sheet microscopy (LLSM), ROOT-ExM achieves 3D quantitative analysis of nanoscale cellular process, revealing increased vesicular fusion in close proximity of the cell plate during cell division. Achieving super-resolution fluorescence imaging in plant biology remains a formidable challenge. Our findings underscore that ROOT-ExM provides a remarkable, cost-effective solution to this challenge, paving the way for unprecedented insights into plant cellular subcellular architecture. One sentence summaryROOT-ExM achieves super-resolution expansion microscopy in plants

plant biology↗

bioRxiv2023

ER-to-Golgi trafficking via a dynamic intermediate cis-Golgi tubular network in Arabidopsis

Endoplasmic Reticulum (ER)-to-Golgi trafficking is a central process of the secretory system of eukaryotic cells that ensures proper spatiotemporal sorting of proteins and lipids1-5. However, the nature of the ER-Golgi Intermediate Compartments (ERGIC) and the molecular mechanisms mediating the transition between the ERGIC and the Golgi, as well as the universality of these processes amongst Eukaryotes, remain undiscovered. Here, we took advantage of the plant cell system in which the Golgi is highly dynamic and in close vicinity to the ER6-9. We discovered that the ERGIC is composed from at least two distinct subpopulations of cis-Golgi. A subpopulation is a reticulated tubulo-vesicular network mostly independent from the Golgi, highly dynamic at the ER-Golgi interface and crossed by ER-induced release of luminal cargos at early stage. Another subpopulation is more stable, cisterna-like and mostly associated to the Golgi. Our results identified that the generation and dynamics of the ER-Golgi intermediate tubulo-vesicular network is regulated by the acyl-chain length of sphingolipids as well as the contacts it establishes with existing Golgi cisternae. Our study is a major twist in the understanding of the Golgi by identifying that the ERGIC in plants is a Golgi-independent highly dynamic tubular network from which arise more stable cisternae-like Golgi structures. This novel model presents a mechanism for early secretory trafficking adapted to respond to developmental and environmental stimuli, including susceptibility or resistance to diseases, autophagy or cell-reprograming.

cell biology↗

bioRxiv2021

High-resolution imaging and manipulation of endogenous AMPA receptor surface mobility during synaptic plasticity and learning

Regulation of synaptic neurotransmitter receptor content is a fundamental mechanism for tuning synaptic efficacy during experience-dependent plasticity and behavioral adaptation. However, experimental approaches to track and modify receptor movements in integrated experimental systems are limited. Exploiting AMPA-type glutamate receptors (AMPAR) as a model, we generated a knock-in mouse expressing the biotin acceptor peptide (AP) tag on the GluA2 extracellular N-terminus. Cell-specific introduction of biotin ligase allows the use of monovalent or tetravalent avidin variants to respectively monitor or manipulate the surface mobility of endogenous AMPAR containing biotinylated AP-GluA2 in neuronal subsets. AMPAR immobilization precluded the expression of long-term potentiation and formation of contextual fear memory, allowing for target-specific control of the expression of synaptic plasticity and animal behavior. The AP tag knock-in model offers unprecedented access to resolve and control the spatiotemporal dynamics of endogenous receptors, and opens new avenues to study the molecular mechanisms of synaptic plasticity and learning.

neuroscience↗

bioRxiv2019

Gamma-protocadherin localization at the synapse corresponds to parameters of synaptic maturation

Clustered protocadherins (Pcdhs) are a large family of ~60 cadherin-like proteins (divided into the subclasses , {beta}, and {gamma}) that compose a surface "barcode" in individual neurons. The code is generated through combinatorial expression via epigenetic regulation at a large gene cluster that encodes the molecules. During early neural development, Pcdhs were shown to mediate dendrite self-avoidance in some neuronal types through a still uncharacterized anti-adhesive mechanism. Pcdhs were also shown to be important for dendritic complexity in cortical neurons likely through a pro-adhesive mechanism. Pcdhs have also been postulated to participate in synaptogenesis and the specificity of connectivity. Some synaptic defects were noted in knockout animals, including synaptic number and physiology, but the role of these molecules in synaptic development is not understood. The effects of Pcdh knockout on dendritic patterning may present a confound to studying synaptogenesis. We have shown previously in vivo and in cultures that Pcdh-{gamma}s are highly enriched in intracellular compartments located in dendrites and spines with localization at only a few synaptic clefts. To gain insight into how Pcdh-{gamma}s might affect synapses, we compared synapses that harbored endogenous Pcdh-{gamma}s versus those that did not for parameters of synaptic maturation including pre- and postsynaptic size, postsynaptic perforations, and spine morphology by light microscopy in cultured hippocampal neurons and by serial section immuno-electron microscopy in hippocampal CA1. In mature neurons, synapses immunopositive for Pcdh-{gamma}s were found to be larger in diameter with more frequent perforations. Analysis of spines in cultured neurons revealed that mushroom spines were more frequently immunopositive for Pcdh-{gamma}s at their tips than thin spines. Taken together, these results suggest that Pcdh-{gamma} function at the synapse may be related to promotion of synaptic maturation and stabilization.

neuroscience↗