👤 Purificación López-García

Osteoarthritis (OA) can be experimentally induced by injecting monoiodoacetate (MIA) in the knee capsule of mice. Our aim was to assess the role of nerve growth factor (NGF)/TrkA axis in OA, identifying differentially expressed genes (DEGs) and functional pathways in knee-innervating dorsal root ganglia (DRG) from wild type (WT) and hypersensitive TrkAP782S knock-in (KI) mice after MIA injection. We performed saline or MIA-injection in knee joints of WT and KI mice and harvested L3-L5 DRGs at 5 and 21 days after injection, pooling males and females (n = 4/group). RNA was extracted, and microarray analysis was performed. Upon comparisons between different groups, identification of DEGs was defined as adjusted P < 0.01. Gene ontology, pathway analysis and protein interactions were conducted using Gene Set Enrichment Analysis over Gene Ontology and REACTOME databases, and STRING database. For each comparison regarding genotype (WT vs KI), numerous DEGs were identified but with limited overlap, being Lingo1, Socs2, and Slc4a4 already related to pain, OA and/or NGF/TrkA axis. Regarding comparisons of early vs late OA (D5 vs D21), many more DEGs were revealed including genes previously implicated in OA such as Gal, Gja1, and Lep. Moreover, we found enriched pathways in the KI_MIA group, such as gene expression, neuronal system and signal transduction, in which NTRK1 and MAPK pathways indicate specificity in the NGF/TrkA axis and in the transition from early to late OA pain. Our results identify new mouse DEGs and pathways that demonstrate the relevance of the NGF/TrkA system in the chronification of OA pain. Show less

Cytokines elicit pleiotropic and non-redundant activities despite strong overlap in their usage of receptors, JAKs and STATs molecules. We use IL-6 and IL-27 to ask how two cytokines activating the same signaling pathway have different biological roles. We found that IL-27 induces more sustained STAT1 phosphorylation than IL-6, with the two cytokines inducing comparable levels of STAT3 phosphorylation. Mathematical and statistical modeling of IL-6 and IL-27 signaling identified STAT3 binding to GP130, and STAT1 binding to IL-27Rα, as the main dynamical processes contributing to sustained pSTAT1 levels by IL-27. Mutation of Tyr613 on IL-27Rα decreased IL-27-induced STAT1 phosphorylation by 80% but had limited effect on STAT3 phosphorgylation. Strong receptor/STAT coupling by IL-27 initiated a unique gene expression program, which required sustained STAT1 phosphorylation and IRF1 expression and was enriched in classical Interferon Stimulated Genes. Interestingly, the STAT/receptor coupling exhibited by IL-6/IL-27 was altered in patients with systemic lupus erythematosus (SLE). IL-6/IL-27 induced a more potent STAT1 activation in SLE patients than in healthy controls, which correlated with higher STAT1 expression in these patients. Partial inhibition of JAK activation by sub-saturating doses of Tofacitinib specifically lowered the levels of STAT1 activation by IL-6. Our data show that receptor and STATs concentrations critically contribute to shape cytokine responses and generate functional pleiotropy in health and disease. Show less

During the process of reprogramming to induced pluripotent stem (iPS) cells, somatic cells switch from oxidative to glycolytic metabolism, a transition associated with profound mitochondrial reorganization. Neither the importance of mitochondrial remodelling for cell reprogramming, nor the molecular mechanisms controlling this process are well understood. Here, we show that an early wave of mitochondrial fragmentation occurs upon expression of reprogramming factors. Reprogramming-induced mitochondrial fission is associated with a minor decrease in mitochondrial mass but not with mitophagy. The pro-fission factor Drp1 is phosphorylated early in reprogramming, and its knockdown and inhibition impairs both mitochondrial fragmentation and generation of iPS cell colonies. Drp1 phosphorylation depends on Erk activation in early reprogramming, which occurs, at least in part, due to downregulation of the MAP kinase phosphatase Dusp6. Taken together, our data indicate that mitochondrial fission controlled by an Erk-Drp1 axis constitutes an early and necessary step in the reprogramming process to pluripotency. Show less

Stramenopiles or heterokonts constitute one of the most speciose and diverse clades of protists. It includes ecologically important algae (such as diatoms or large multicellular brown seaweeds), as well as heterotrophic (e.g., bicosoecids, MAST groups) and parasitic (e.g., Blastocystis, oomycetes) species. Despite their evolutionary and ecological relevance, deep phylogenetic relationships among stramenopile groups, inferred mostly from small-subunit rDNA phylogenies, remain unresolved, especially for the heterotrophic taxa. Taking advantage of recently released stramenopile transcriptome and genome sequences, as well as data from the genomic assembly of the MAST-3 species Incisomonas marina generated in our laboratory, we have carried out the first extensive phylogenomic analysis of stramenopiles, including representatives of most major lineages. Our analyses, based on a large data set of 339 widely distributed proteins, strongly support a root of stramenopiles lying between two clades, Bigyra and Gyrista (Pseudofungi plus Ochrophyta). Additionally, our analyses challenge the Phaeista-Khakista dichotomy of photosynthetic stramenopiles (ochrophytes) as two groups previously considered to be part of the Phaeista (Pelagophyceae and Dictyochophyceae), branch with strong support with the Khakista (Bolidophyceae and Diatomeae). We propose a new classification of ochrophytes within the two groups Chrysista and Diatomista to reflect the new phylogenomic results. Our stramenopile phylogeny provides a robust phylogenetic framework to investigate the evolution and diversification of this group of ecologically relevant protists. Show less

Although inland water bodies are more heterogeneous and sensitive to environmental variation than oceans, the diversity of small protists in these ecosystems is much less well known. Some molecular surveys of lakes exist, but little information is available from smaller, shallower and often ephemeral freshwater systems, despite their global distribution and ecological importance. We carried out a comparative study based on massive pyrosequencing of amplified 18S rRNA gene fragments of protists in the 0.2-5 μm size range in one brook and four shallow ponds located in the Natural Regional Park of the Chevreuse Valley, France. Our study revealed a wide diversity of small protists, with 812 stringently defined operational taxonomic units (OTUs) belonging to the recognized eukaryotic supergroups (SAR--Stramenopiles, Alveolata, Rhizaria--Archaeplastida, Excavata, Amoebozoa, Opisthokonta) and to groups of unresolved phylogenetic position (Cryptophyta, Haptophyta, Centrohelida, Katablepharida, Telonemida, Apusozoa). Some OTUs represented deep-branching lineages (Cryptomycota, Aphelida, Colpodellida, Tremulida, clade-10 Cercozoa, HAP-1 Haptophyta). We identified several lineages previously thought to be marine including, in addition to MAST-2 and MAST-12, already detected in freshwater, MAST-3 and possibly MAST-6. Protist community structures were different in the five ecosystems. These differences did not correlate with geographical distances, but seemed to be influenced by environmental parameters. Show less

Culture-independent molecular methods based on the amplification, cloning and sequencing of small-subunit (SSU) rRNA genes are a powerful tool to study the diversity of prokaryotic and eukaryotic microorganisms for which morphological features are not conspicuous. In recent years, molecular data from environmental surveys have revealed several clades of protists lacking cultured and/or described members. Among them are various clades of marine stramenopiles (heterokonts), which are thought to play an essential ecological role as grazers, being abundant and distributed in oceans worldwide. In this work, we show that Solenicola setigera, a distinctive widespread colonial marine protist, is a member of the environmental clade MArine STramenopile 3 (MAST-3). Solenicola is generally considered as a parasite or an epiphyte of the diatom Leptocylindrus mediterraneus. So far, the ultrastructural, morphological and ecological data available were insufficient to elucidate its phylogenetic position, even at the division or class level. We determined SSU rRNA gene sequences of S. setigera specimens sampled from different locations and seasons in the type locality, the Gulf of Lions, France. They were closely related, though not identical, which, together with morphological differences under electron microscopy, suggest the occurrence of several species. Solenicola sequences were well nested within the MAST-3 clade in phylogenetic trees. Since Solenicola is the first identified member of this abundant marine clade, we propose the name Solenicolida for the MAST-3 phylogenetic group. Show less