Biology subjects

Munoz, O.

Publications and source records attributed to Munoz, O..

7 recordsLinked to original sources

bioRxiv2024

Cell State-Specific Cytoplasmic Material Properties Control Spindle Architecture and Scaling

Mitotic spindles are dynamically intertwined with the cytoplasm they assemble in. How the physicochemical properties of the cytoplasm affect spindle architecture and size remains largely unknown. Using quantitative biochemistry in combination with adaptive feedback microscopy, we investigated mitotic cell and spindle morphology during neural differentiation of embryonic stem cells. While tubulin biochemistry and microtubule dynamics remained unchanged, spindles changed their scaling behaviour: in differentiating cells, spindles were significantly smaller than those in equally-sized undifferentiated stem cells. Integrating quantitative phase imaging, biophysical perturbations and theory, we found that as cells differentiated, their cytoplasm became more dilute. The concomitant decrease in free tubulin activated CPAP (centrosomal P4.1-associated protein) to enhance the centrosomal nucleation capacity. As a consequence, in differentiating cells, microtubule mass shifted towards spindle poles at the expense of the spindle bulk, explaining the differentiation-associated switch in spindle architecture. This study shows that cell state-specific cytoplasmic density tunes mitotic spindle architecture. Thus, we reveal physical properties of the cytoplasm as a major determinant in organelle size control.

cell biology↗

bioRxiv2023

Escape problem of magnetotactic bacteria - physiological magnetic field strength help magnetotactic bacteria navigate in simulated sediments

Bacterial motility is typically studied in bulk solution, while their natural habitats often are complex environments. Here, we produced microfluidic channels that contained sediment-mimicking obstacles to study swimming of magnetotactic bacteria in a near-realistic environment. Magnetotactic bacteria are microor-ganisms that form chains of nanomagnets and that orient in Earths magnetic field. The obstacles were produced based on micro-computer tomography reconstructions of bacteria-rich sediment samples. We characterized the swimming of the cells through these channels and found that swimming throughput was highest for physiological magnetic fields. This observation was confirmed by extensive computer simulations using an active Brownian particle model, which were parameterized based on experimental trajectories, in particular with the trajectories near the sediment-mimicking obstacles, from which the interactions of the swimming bacteria with the obstacles were determined. The simulations were used to quantify the swimming throughput in detail. They showed the behavior seen in experiments, but also exhibited considerable variability between different channel geometries. The simulations indicate that swimming at strong fields is impeded by the trapping of bacteria in "corners" that require transient swimming against the magnetic field for escape. At weak fields, the direction of swimming is almost random, making the process inefficient as well. We confirmed the trapping effect in our experiments and showed that lowering the field strength allows the bacteria to escape. We hypothesize that over the course of evolution, magnetotactic bacteria have thus evolved to produce magnetic properties that are adapted to the geomagnetic field in order to balance movement and orientation in such crowded environments.

biophysics↗

bioRxiv2023

Conserved nucleocytoplasmic density homeostasis drives cellular organization across eukaryotes

The packing and confinement of macromolecules in the cytoplasm and nucleoplasm has profound implications for cellular biochemistry. How intracellular density distributions vary and affect cellular physiology remains largely unknown. Here, we show that the nucleus is less dense than the cytoplasm and that living systems establish and maintain a constant density ratio between these compartments. Using label-free biophotonics and theory, we show that nuclear density is set by a pressure balance across the nuclear envelope in vitro, in vivo and during early development. Nuclear transport establishes a specific nuclear proteome that exerts a colloid osmotic pressure, which, assisted by entropic chromatin pressure, draws water into the nucleus. Using C. elegans, we show that while nuclear-to-cytoplasmic (N/C) volume ratios change during early development, the N/C density ratio is robustly maintained. We propose that the maintenance of a constant N/C density ratio is the biophysical driver of one of the oldest tenets of cell biology: the N/C volume ratio. In summary, this study reveals a previously unidentified homeostatic coupling of macromolecular densities that drives cellular organization with implications for pathophysiologies such as senescence and cancer.

biophysics↗

bioRxiv2023

KDM6 demethylases mediate EWSR1-FLI1-driven oncogenic transformation in Ewing Sarcoma

Ewing Sarcoma (EwS) is an aggressive bone and soft tissue tumor driven by the fusion oncoprotein EWSR1-FLI1. This aberrant transcription factor binds to GGAA microsatellites, causing epigenetic reprogramming through the formation of active neo-enhancers in a permissive cellular context. Inhibition of the oncogene remains challenging and current efforts instead seek to exploit emergent epigenetic treatments targeting EWSR1-FLI1 cofactors. Here, stemming from the genome-wide redistribution of H3K27me3 upon expression of EWSR1-FLI1 in pediatric hMSC, we unravel the contribution of the H3K27me3 demethylases KDM6A and KDM6B in transcriptional activation at EWSR1-FLI1 enhancers. We found that KDM6A has a demethylase-independent role in recruiting the SWI/SNF member BRG1 at EWSR1-FLI1-primed enhancers containing single GGAA motif, which is critical for EwS tumor growth. Conversely, KDM6B demethylates H3K27me3 at EWSR1-FLI1-active enhancers containing multimeric GGAA repeats and its deletion synergizes with EZH2 inhibitors. Our results highlight KDM6 demethylases as EWSR1-FLI1 cofactors with potential for future targeted therapies.

cancer biology↗

bioRxiv2021

c-MAF maintains the transcriptional program of enterocyte zonation and the balance of absorptive/intestinal secretory cell types

Small intestinal villi are structural and functional units uniquely adapted to the nutrient absorption in higher vertebrates. Villus enterocytes are organized in spatially resolved "zones" dedicated to specialized tasks such anti-bacterial protection, and absorption of amino-acids, carbohydrates and lipids. The molecular mechanisms specifying villus zonation are incompletely understood. We report that inactivation of transcription factor c-MAF, highly expressed in mature lower and mid-villus enterocytes, perturbed the entire villus zonation program, by increasing the expression of regulators of carbohydrate and bile acid metabolism and transport, while suppressing genes related to amino acid and lipid absorption. Maf inactivation under homeostatic conditions expanded tuft cells and led to compensatory gut lengthening, preventing body weight loss. However, delayed enterocyte maturation in the absence of Maf impaired body weight recovery after acute intestinal injury, resulting in reduced survival. Our results identify c-MAF as a novel regulator of small intestinal villus zonation program, while highlighting the importance of coordination between stem/progenitor and differentiation programs for intestinal regeneration. Summaryc-MAF is expressed in differentiated enterocytes. c-MAF loss alters enterocyte zonation leading to a compensatory gut remodelling and tuft cell expansion. Upon acute intestinal injury mice deficient for c-MAF cannot recover due to lack of nutrient transport and compensatory lengthening.

cell biology↗

bioRxiv2021

Integrating digital and field surveillance to complement efforts to manage epidemic diseases of livestock: African swine fever as a case study

The SARS-CoV-2 pandemic has unveiled the importance of stakeholders and ordinary citizens in managing infectious disease emergencies. Efficient management of infectious diseases requires a top-down approach which must be complemented with a bottom-up response to be effective. Here we investigate a novel approach to surveillance for transboundary animal diseases using African Swine fever as a model. We were able to collect data at a population level on information-seeking behavior and at a local level through a targeted questionnaire-based survey to relevant stakeholders such as farmers and veterinary authorities. Our study shows how information-seeking behavior and resulting public attention during an epidemic, can be addressed through novel data streams from digital platforms such as Wikipedia. We also bring evidence on how field surveys aimed at local workers (e.g. farmers) and public authorities remain a crucial tool to assess more in-depth preparedness and awareness among front-line actors. We conclude that they should be used in combination to maximize the outcome of surveillance and prevention activities for selected transboundary animal diseases.

scientific communication and education↗

bioRxiv2018

Diverse Escherichia coli lineages, from domestic animals and humans in a household, carry colistin resistance gene mcr-1 in Ecuador

The aim of this study was to investigate the presence of Escherichia coli carrying mcr-1 gene in domestic animals close to a child who suffered a peritoneal infection by a mcr-1 positive E. coli. Rectal or cloacal swabs and fecal samples from domestic animals were plated on selective media to isolate colistin-resistant E. coli and isolates were submitted to detection of mcr-1 gene, pulsed field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), replicon typing and S1-PFGE. Four mcr-1 positive E. coli isolates (from chicken, turkey and dog) were recovered. No shared PFGE pattern or MLST sequence type were observed among isolates. A 60Kb IncI1{gamma} mcr-1-carrying plasmid was detected in all isolates. Our results suggest that mcr-1 gene was horizontally disseminated amongst different lineages of E. coli from domestic animals in the childs household.\n\nImportanceHorizontally transferable colistin resistance (mcr-1 gene) is thought to have originated in domestic animals and transferred to humans through meat and dairy products. In the present report we show evidence that the mcr-1 gene could be transferred to different E. coli strains colonizing different hosts (humans and pets) in the same household.

microbiology↗