Biology subjects

Mattei, F.

Publications and source records attributed to Mattei, F..

5 recordsLinked to original sources

bioRxiv2026

Seasonal patterns in Synechococcus pigment diversity at two temperate sites with contrasting oceanic regimes

Competition for light has driven extensive pigment diversification among phytoplankton species, yet how this diversity shapes their spatiotemporal distribution in the field has been little studied so far. The cyanobacterium Synechococcus is an ideal model for addressing this issue, since this group has colonized most light spectral niches in marine environments. Here, we used an approach based on marker read recruitment from metagenomes to analyze the seasonal succession of Synechococcus pigment types (PTs) at two time-series stations off French coasts exhibiting contrasting oceanic regimes. Marked seasonality was observed at both sites. The shallow, permanently mixed English Channel site SOMLIT-Astan was characterized by an alternation between green-light specialists (PT 3a) peaking in spring, and chromatic acclimaters type A (PT 3dA) accounting for most of the Synechococcus community in winter. In contrast, the pigment diversity was much higher at the deep Mediterranean station BOUSSOLE. In the upper layer, the two main PTs were the blue light specialists (PT 3c), which dominated the community in summer and fall, and PT 3dA cells, which were more abundant in spring. The third most abundant PT was chromatic acclimaters type B (PT 3dB), which accounted for up to 15% of the surface community in late fall. Strikingly, PT 3dA was dominant at depth during most of the year. Multivariate analyses between PT abundances, clade abundances and environmental factors, notably water color indexes, suggested new associations between PTs to specific clades and ecological niches. This study provides novel insights for refining distribution models of Synechococcus PTs and phytoplankton groups in general.

microbiology↗

bioRxiv2025

Competition for light color between marine Synechococcus strains with fixed and variable pigmentation

Competition between phytoplankton species for light has triggered an extensive diversification of photosynthetic pigments. In Synechococcus cyanobacteria, three major pigment types occur in the ocean: blue light (BL) specialists that have a high ratio of the BL-absorbing chromophore phycourobilin (PUB) to the green light (GL)-absorbing chromophore phycoerythrobilin (PEB), GL specialists that have a low PUB:PEB ratio, and cells that modify their PUB:PEB ratio to match the ambient color, a process called Type IV chromatic acclimation (CA4). The abundance of CA4-capable cells in marine ecosystems suggests that CA4 confers a fitness advantage in certain light conditions compared to cells with fixed pigmentation. This hypothesis was tested by performing mono- and co-cultures of a BL specialist, a GL specialist and a CA4-capable strain in chemostats under different light conditions. Monocultures enabled us to parameterize a resource competition model that was used to predict competition between the three pigment types in co-cultures. In line with the model predictions, the BL specialist won in low blue light and the GL specialist won in low and high green light. Interestingly, we found that while the CA4-capable strain was at a disadvantage at low light, it was able to outcompete specialists in high blue light. IMPORTANCESynechococcus cyanobacteria are ubiquitous and abundant in the lit layer of most marine ecosystems. This ubiquity relies in part on the wide pigment diversity of their light-harvesting complexes, with three main pigment types thriving in open ocean waters: green light specialists, blue light specialists and chromatic acclimaters, the latter being capable of matching their pigment content to the ambient spectral field. Here, we simulated the competition for light color that occurs between these pigment types in the field by co-culturing them in various light color and intensity conditions, and compared the resulting data to that of a competition model. This study provides new insights on how this key group of phytoplankton colonized the various spectral niches of the marine environment.

microbiology↗

bioRxiv2024

Complementary methods for the study of interactions between eosinophils and cancer cells.

Eosinophils are a rare immune cell subset with important roles in Th2 immunity and, recently, in cancer. Interleukin IL-33 (IL-33) is well recognized for its important roles in the activation of eosinophils in Th2 immunity. On the other hand, IL-33 has been recently discovered to play central roles in cancer, in particular by activating eosinophils and increase their degranulation consequent to an intrinsic tumor cell killing function. We propose a dual approach methodology to extrapolate functional interactions of eosinophils with tumor cells, as a result of eosinophil stimulation. Human eosinophils (Eos) isolated from the blood of healthy donors by dextran sedimentation followed by magnetic sorting are exposed to IL-33 (Eos33) or IL-5 (Eos5, control) for 18 h. These pre-conditioned cells are then co-cultured with A375P melanoma cells to monitor cell-cell interactions. Acoustic focusing flow cytometry analysis is employed to evaluate the presence of Eos-tumor cell conjugates after 1h incubation of human eosinophils and A375P melanoma cells. Moreover, a 24 h time-lapse video recording approach is employed to obtain single cell tracking Eos profiles. This allows to quantitatively determine the interaction extent of Eos33, as opposed to Eos5 (control condition), with tumor cells. In conclusion, our protocols easily and quickly allow the extrapolation of relevant kinematic and biologically relevant parameters for tumor reactive eosinophils. Furthermore, these methods are adaptable to various models with other types of immune cell subsets and cancer cells and can be implemented on different video microscopy platforms and advanced flow cytometry systems.

cancer biology↗

bioRxiv2024

Combined in vitro differentiation and cell sorting-based isolation of highly pure mouse bone marrow-derived basophils.

Basophils constitute a rare population of granulocytes with key functions in allergies, immunodeficiencies and cancer. The scarcity of basophils in the human blood and tissues constitutes a considerable limit for the study of these cells. Interleukin-3 (IL-3) is a cytokine that stimulates both the differentiation and the expansion of basophils from bone marrow (BM) precursors by positively regulating the expression of the IL3Ra receptor. We have standardized an in vitro differentiation protocol of mouse basophils (mBaso) from BM precursors through culture in presence of IL-3 for 10 days followed by cell sorting. At the end of the 10-day differentiation, a considerable number of mBaso can be obtained and cell sorting procedures further improved the isolation of an extraordinarily pure (>98%) and vital Fc{varepsilon}R1+ CD11c- c-kit- mBaso population. Phenotypic analysis revealed that terminally differentiated (day 10) unsorted mBaso cultured for 24 hours showed a decrease in basophilic lineage (c-kit-) and an increase of mastocytic lineage (c-kit+) and reduced the expression of basophil markers Fc{varepsilon}RI, CD49b and CD200R either in absence of stimuli or following activation with the alarmin IL-33, indicating cell dedifferentiation. In contrast, terminally differentiated and Fc{varepsilon}R1+ CD11c- c-kit- sorted mBaso do not dedifferentiate in mast cells when placed in culture, and responded to IL-33 stimulation by up-regulating the activation marker CD63 without down-modulation of Fc{varepsilon}RI and CD200R3. These evidences highlight that in vitro differentiation followed by cell sorting is a useful method to obtain elevated numbers of highly pure mBaso that preserve their lineage markers and thus are suitable for conducting the desired functional studies.

cell biology↗

bioRxiv2024

Organ-on-Chip immunostaining method for three-dimensional identification and study of immune cells responding to drug-treated tumor cells

Epigenetic deregulation is implied in cancer initiation and resistance to antitumor drugs. In melanoma, aberrant DNA hypermethylation is frequently observed, resulting in the silencing of several genes involved in cell cycle regulation, apoptosis, tumor growth and drug resistance. DNA hypomethylating agents have been recently evaluated in both preclinical and clinical studies as a strategy to restore tumor suppressor genes and to increase immune recognition by tumors, highlighting their potential in pre-clinical models of melanoma. Advanced microfluidic system for the culture of complex three-dimensional cell, tissue and organ models have proven utility for oncoimmunology studies and drug testing. Here we present a protocol employing ad hoc fabricated microfluidic devices to reproduce a three-dimensional (3D) tumor microenvironment (TME) to study two aspects of the crosstalk between immune and cancerous cells under the effect of Decitabine (DAC), a DNMT inhibitor (DNMTi). First, we evaluated the preferential migration of immune cells towards treated and non-treated melanoma cells inside the chip. Next, we identified a specific subpopulation of migrated immune cells, with an on-chip immunostaining protocol resulting in the acquisition and evaluation of 3D images on a Laser-Scanning Confocal Microscopy (LSCM) station for in-depth characterization of tumor-immune interactions. This protocol may find broad application for pre-clinical drug testing in cancer studies.

cancer biology↗