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Leon, F.

Publications and source records attributed to Leon, F..

10 recordsLinked to original sources
bioRxiv2026

Understanding cognitive function in post-COVID-19 condition with fatigue: an interdisciplinary multimodal investigation

Lingering cognitive symptoms of post-COVID-19 condition (PCC) continue to challenge our understanding, highlighting the need for interdisciplinary research. We investigated whether individuals with PCC and fatigue differ from matched controls across neurocognitive, neuroimaging, and immunological measures, integrating these findings with qualitative phenomenological analyses through multimodal cross-analysis. Individuals with PCC and clinically significant fatigue (n=34), and age-, sex-, and education-matched controls recovered from COVID-19 without PCC (n=37) were included. Assessments encompassed physician evaluation, neuropsychological and functional tests, structural and functional MRI, immunological tests, and qualitative phenomenological analysis of interviews. Data were analyzed using established methods and an interdisciplinary cross-analysis to examine persistent cognitive symptoms in PCC. Group comparisons revealed subtle differences between individuals with PCC and controls, while neurocognitive performance and immunological markers remained within normative ranges. Modest differences in white matter, myelin related, and global brain measures were observed, alongside differences in associations between network connectivity and neurocognitive performance across groups, suggesting reduced network resilience rather than domain specific deficits. This pattern resonated with qualitative phenomenological findings: altered experiences of concentrating and difficulties to execute decisions and actions, despite preserved performance on standard neurocognitive tests. These findings suggest that cognitive symptoms in post-COVID-19 fatigue are associated with subtle neurobiological alterations not captured by standard cognitive assessments. In this highly fatigued sample, converging neuroimaging, neurocognitive and immunological findings point toward reduced network efficiency rather than overt cognitive impairment. Qualitative phenomenological analysis further highlighted altered modes of being in the world characterized by increased cognitive effort and difficulties executing decisions and actions.

neuroscience↗
bioRxiv2026

A novel clonal and axenic isolation pipeline for the human gut protist Blastocystis reveals within-subtype strain coexistence

Blastocystis is the most prevalent protist in the human gut microbiome, but its study is impeded by limitations in existing cultivation methods that hinder routine axenic and clonal isolation. These barriers have left open the question of whether multiple strains of a protist species can coexist within a single host, as observed within the bacterial gut microbiota. To address this, we introduce egg-based monophasic (EBM) medium, a novel optically clear liquid medium that supports exponential growth of Blastocystis from low inoculum densities in standard tissue-culture plates and flasks, a capability not supported by existing media formulations tested here. Using EBM medium, we established a modular axenization and clonal isolation pipeline and recovered axenic and clonally isolated cultures representing Blastocystis subtypes 1-4 from human and non-human primate hosts. To investigate within-host strain diversity, we sequenced a subtype 1 culture before and after clonal isolation. The non-clonal culture yielded a 21 Mb assembly with gene copy distribution and allelic polymorphism patterns consistent with multiple strains, whereas its clonal derivative yielded a 15 Mb assembly with patterns consistent with a single strain. These results indicate that the original culture contained multiple closely related strains co-colonizing one host. We identified the same genomic signature in published xenic cultures established from single human donors, supporting the presence of strain-level diversity within Blastocystis subtypes. Our pipeline provides a scalable platform for Blastocystis cultivation, imaging, and clonal isolation, enabling investigation of strain-level diversity that may be obscured in non-clonal cultures.

microbiology↗
bioRxiv2026

Chronic Activity-Based Anorexia triggers a glial response in the hippocampus independent of intestinal epithelial Toll-Like Receptor 4

Anorexia nervosa is characterized by maladaptive eating behavior and cognitive dysfunction, which could be explained by a neuroinflammation. A gut dysbiosis could link gastrointestinal alterations to central dysfunctions, particularly via the toll-like receptor 4 (TLR4), which has been shown to play a key role in the activity-based anorexia (ABA) model. We aimed to evaluate the neuroinflammation and its behavioral consequences in the ABA model, and to decipher the role of the microbiota-gut-brain axis, and more specifically of TLR4, in these alterations of the central nervous system. We show that chronic restriction is more strongly associated with gut inflammation, cecal microbiota alteration and neuroinflammatory processes in the hippocampus than acute restriction. The hippocampal glial response is characterized by a loss of astrocyte density, and an increased number of deramified microglia. We further demonstrate that these alterations are independent of TLR4 expressed by intestinal epithelial cells. In conclusion, our results highlight that the chronicity of ABA-associated undernutrition alters the response of glial cells in the hippocampus that is linked with changes in microbiota composition, highlighting the importance of faster diagnosis and treatment of AN.

neuroscience↗
bioRxiv2025

Sex-dependent effects of intestinal epithelial TLR4 deletion induced before activity-based anorexia

RationaleA role for the microbiota-gut-brain axis in the pathophysiology of anorexia nervosa (AN) has emerged in the last decade. An alteration of intestinal Toll-like receptor type 4 (TLR4) has been reported in the activity-based anorexia (ABA) model with an increase in its expression at the cell surface of colonic epithelial cells. In addition, inducible TLR4 invalidation in intestinal epithelial cells (IECs) was associated with behavioral and energy balance changes in ABA mice. The aim of this study was to assess the intestinal response, e.g. inflammation, gut barrier function and gut microbiota composition, to TLR4 invalidation in IEC in ABA mice. MethodsMale and female Villin-CreERT2-TLR4 LoxP C57Bl/6 mice were injected with tamoxifen to induce a specific invalidation of TLR4 in IECs (TLR4IEC-/- mice). Then, wild-type (wt) and TLR4IEC-/- mice were subjected or not to the ABA protocol which combines an access to a running wheel and a progressively limited access to food. After 12 days, colon samples were collected and the expression of 44 mRNAs encoding proteins involved in inflammatory response, gut barrier function and homeostatic regulation was measured by qPCR. Results were compared by a two-way ANOVA (ABA x TLR4IEC-/-). Gut microbiota composition was analysed by 16S rRNA Illumina sequencing. ResultsIn both male and female ABA TLR4IEC-/- mice, the kinetics of body weight loss was slowed down. In addition, male and female ABA TLR4IEC-/- mice showed an increase and a decrease in food intake, respectively. In males, TLR4 invalidation in IEC was associated with a reduction of Tlr2, Ticam1, Myd88, Tnf, I{kappa}B, Irf3, Cxcr3 and Tgf{beta} mRNA expression and fecal calprotectin levels under control conditions but not in response to the ABA model. In females, Myd88, Il6, Cxcl1 and Ccl2 mRNA levels were increased by TLR4IEC invalidation in control mice but not in ABA, except for Ccl2. TLR4 invalidation also affected the expression of genes involved in gut barrier function in control and ABA mice in a sex-dependent manner. Male mice exhibited more marked alterations. For instance, male CT TLR4IEC-/- showed a decrease of numerous targets (Ocln, Marveld2, F11r, Tjp1, Cldn7, Cldn12, Cldn15). ABA TLR4IEC-/- mice did not exhibit this decrease but other changes were observed such as an increase in Cldn3 and Cldn7 mRNA levels. Finally, TLR4IEC invalidation in control mice, but not in ABA, altered the gut microbiota in a sex dependent manner with an increase in the abundance of Parasutterella and Desulfovibrio genera in females and males, respectively. Interestingly, the ABA model per se induced an increase in the abundance of the Lactobacillus genus in both sexes, which was not observed in ABA TLR4IEC-/-. ConclusionsOur study shows for the first time the impact of inducible TLR4 invalidation in IEC on the intestinal response. We highlighted numerous colonic alterations regarding epithelial permeability, mucosal inflammation and gut microbiota composition, in control and ABA conditions: all were partially reversed in ABA TLR4IEC-/-. TLR4 invalidation in IEC also induced changes in energy homeostasis in response to the ABA model both in female and male mice. Further studies are warranted to deeply evaluate the underlying mechanisms.

physiology↗
bioRxiv2024

Cell-type-specific expression of a DCYTB ortholog enables the choanoflagellate Salpingoeca rosetta to utilize ferric colloids

Marine microeukaryotes have evolved diverse cellular features that link their life histories to surrounding environments. How those dynamic life histories intersect with the ecological functions of microeukaryotes remains a frontier to understand their roles in essential biogeochemical cycles1,2. Choanoflagellates, phagotrophs that cycle nutrients through filter feeding, provide models to explore this intersection, for many choanoflagellate species transition between life history stages by differentiating into distinct cell types3-6. Here we report that cell differentiation in the marine choanoflagellate Salpingoeca rosetta endows one of its cell types with the ability to utilize insoluble ferric colloids for improved growth through the expression of a cytochrome b561 iron reductase (cytb561a). This gene is an ortholog of the mammalian duodenal cytochrome b561 (DCYTB) that reduces ferric cations prior to their uptake in gut epithelia7 and is part of an iron utilization toolkit that choanoflagellates and their closest living relatives, the animals, inherited from a last common eukaryotic ancestor. In a database of oceanic metagenomes8,9, the abundance of cytb561a transcripts from choanoflagellates positively correlates with upwellings, which are a major source of ferric colloids in marine environments10. As this predominant form of iron11,12 is largely inaccessible to cell-walled microbes13,14, choanoflagellates and other phagotrophic eukaryotes may serve critical ecological roles by first acquiring ferric colloids through phagocytosis and then cycling this essential nutrient through iron utilization pathways13-15. These findings provide insight into the ecological roles choanoflagellates perform and inform reconstructions of early animal evolution where functionally distinct cell types became an integrated whole at the origin of animal multicellularity16-22.

evolutionary biology↗
bioRxiv2022

Directed Biosynthesis of Mitragynine Stereoisomers

Mitragyna speciosa ("Kratom") is used as a natural remedy for pain and management of opioid dependence. The pharmacological properties of Kratom have been linked to a complex mixture of monoterpene indole alkaloids, most notably mitragynine. Here, we report the central biosynthetic steps responsible for the scaffold formation of mitragynine and related corynanthe-type alkaloids. We illuminate the mechanistic basis by which the key stereogenic centre of this scaffold is formed. These discoveries were leveraged for the enzymatic production of mitragynine, the C-20 epimer speciogynine, and a series of fluorinated analogues.

biochemistry↗
bioRxiv2022

An RFX transcription factor regulated ciliogenesis in the progenitors of choanoflagellates and animals

Little is known about the origins of the transcriptional modules that coordinate cell-type specific functions in animals. The controlled expression of one cellular feature - the cilium - was likely critical during early animal evolution. Two key transcription factors, RFX and FoxJ1, coordinate ciliogenesis in animals but are absent from the genomes of most other ciliated eukaryotes, raising the question of how the transcriptional regulation of ciliogenesis has evolved. To reconstruct the evolution of the RFX/FoxJ1 transcriptional module and its role in the regulation of ciliogenesis, we investigated RFX and FoxJ1 function in one of the closest living relatives of animals, the choanoflagellate Salpingoeca rosetta. Targeted disruption of the S. rosetta RFX homolog cRFXa resulted in delayed cell proliferation and aberrant ciliogenesis, marked by the collapse and resorption of nascent cilia. Ciliogenesis genes and foxJ1 were significantly down-regulated in cRFXa mutants, consistent with a pre-animal ancestry for this transcriptional module. We also found that cRFXa protein preferentially binds to a sequence motif that is enriched in the promoters of S. rosetta ciliary genes and matches the sequence motif bound by animal RFX proteins. These findings suggest that RFX coordinated ciliogenesis before the divergence of animals and choanoflagellates, and that the deployment of this module may have provided a mechanism to differentiate ciliated and non-ciliated cell types in early animal evolution.

evolutionary biology↗
bioRxiv2021

Plant growth and phytoactive alkaloid synthesis in Mitragyna speciosa (kratom) in response to varying radiance

The dose-dependent consumptive effect of kratom and its potential application as an alternative source of medicine to mitigate opioid withdrawal symptoms has brought considerable attention to this plant. Increased interest in the application and use of kratom has emerged globally, including North America. Although the chemistry and pharmacology of major kratom alkaloids, mitragynine and 7-hydroxymitragynine, are well documented, foundational information on the impact of plant production environment on growth and kratom alkaloids synthesis is unavailable. To directly address this need, kratom plant growth, leaf chlorophyll content, and alkaloid concentration were evaluated under three lighting conditions: outdoor full sun, greenhouse unshaded, and greenhouse shaded. Nine kratom alkaloids were quantified using an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. Contents of six alkaloids to include: mitragynine, speciogynine, speciociliatine, mitraphylline, coynantheidine, and isocorynantheidine were not significantly impacted by lighting conditions, whereas 7-hydroxymitragynine was below the lower limit of quantification across all treatments. However, paynantheine concentration per leaf dry mass was increased by 40% and corynoxine was increased by 111% when grown under shade conditions in a greenhouse compared to outdoor full sun. Additionally, total alkaloid yield per plant was maximized when plants were under such conditions. Greenhouse cultivation generally promoted height and width extension, leaf number, leaf area, average leaf size, and total leaf dry mass, compared to outdoor full sun condition. Rapid, non-destructive chlorophyll evaluation correlated well (r2 = 0.68) with extracted chlorophyll concentrations. Given these findings, production efforts where low-light conditions can be implemented are likely to maximize plant biomass and total leaf alkaloid production.

plant biology↗
bioRxiv2018

How symbiosis and ecological context influence the variable expression of transgenerational wing induction upon fungal infection of aphids

Aphids, like most animals, mount a diverse set of defenses against pathogens. For aphids, two of the best studied defenses are symbiont-conferred protection and transgenerational wing induction. Aphids can harbor bacterial symbionts that provide protection against pathogens, parasitoids and predators, as well as against other environmental stressors. In response to signals of danger, aphids also protect not themselves but their offspring by producing more winged than unwinged offspring as a way to ensure that their progeny may be able to escape deteriorating conditions. Such transgenerational wing induction has been studied most commonly as a response to overcrowding of host plants and presence of predators, but recent evidence suggests that pea aphids (Acyrthosiphon pisum) may also begin to produce a greater proportion of winged offspring when infected with fungal pathogens. Here, we explore this phenomenon further by asking how protective symbionts, pathogen dosage and environmental conditions influence this response. Overall, while we find some evidence that protective symbionts can modulate transgenerational wing induction in response to fungal pathogens, we observe that transgenerational wing induction in response to fungal infection is highly variable. That variability cannot be explained entirely by symbiont association, by pathogen load or by environmental stress, leaving the possibility that a complex interplay of genotypic and environmental factors may together influence this trait.

evolutionary biology↗