Search

Motivation The advent of highly multiplexed in situ imaging cytometry assays has revolutionized the study of cellular systems, offering unparalleled detail in observing cellular activities and characteristics. These assays provide comprehensive insights by concurrently profiling the spatial distribution and molecular features of numerous cells. In navigating this complex data landscape, unsupervised machine learning techniques, particularly clustering algorithms, have become essential tools. They enable the identification and categorization of cell types and subsets based on their molecular characteristics. Despite their widespread adoption, most clustering algorithms in use were initially developed for cell suspension technologies, leading to a potential mismatch in application. There is a critical gap in the systematic evaluation of these methods, particularly in determining the properties that make them optimal for in situ imaging assays. Addressing this gap is vital for ensuring accurate, reliable analyses and fostering advancements in cellular biology research. Results In our extensive investigation, we evaluated a range of similarity metrics, which are crucial in determining the relationships between cells during the clustering process. Our findings reveal substantial variations in clustering performance, contingent on the similarity metric employed. These variations underscore the importance of selecting appropriate metrics to ensure accurate cell type and subset identification. In response to these challenges, we introduce FuseSOM, a novel ensemble clustering algorithm that integrates hierarchical multiview learning of similarity metrics with self-organizing maps. Through a rigorous stratified subsampling analysis framework, we demonstrate that FuseSOM outperforms existing best-practice clustering methods specifically tailored for in situ imaging cytometry data. Our work not only provides critical insights into the performance of clustering algorithms in this novel context but also offers a robust solution, paving the way for more accurate and reliable in situ imaging cytometry data analysis. Availability and implementation The FuseSOM R package is available on Bioconductor and is available under the GPL-3 license. All the codes for the analysis performed can be found at Github. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the therapeutic effectiveness of the use of photodynamic therapy in chronic traumatic lesions of oral mucosa. Materials and methods: Clinical examination and treatment of 67 patients aged 18-65 years with erosive-ulcerative lesions of oral mucosa were carried out. Treatment of patients in the main group was performed using photodynamic therapy. Treatment of patients of the control group was carried out according to the standard method. The results of treatment were evaluated by clinical and cytological parameters. Results: In all patients of the main group with chronic traumatic erythema, already on the second day of treatment, complaints of pain when talking and eating completely disappeared, and on the third day in 100% of patients the affected mucosa had no pathological changes. In patients with erosive-ulcerative lesions, complete clinical recovery in the main group was observed on the 3-4th day of treatment, in the control group – on the 7-10th day. The results of cytological examination, namely the absence of young epithelial cells of stages 1 and 2 of differentiation, a significant decrease of intermediate maturity cells (stages 3 and 4) and a similar increase of mature cells (stages 5 and 6), indicated the acceleration of mucosal regeneration in patients of the main group compared to the control group. Conclusions: The use of photodynamic therapy in the treatment of traumatic oral mucosa lesions contributed to the acceleration of elimination of clinical manifestations of chronic mechanical injuries and the normalization of parameters of cytological characteristics of epithelial cells in patients of the main group compared to the group of standard treatment. [ABSTRACT FROM AUTHOR]

Surface nano- and microtexturing techniques have been used to enhance osseointegration, but how these surfaces work is not well understood. Using the knowledge gained from the cell and molecular biology fields, tissue engineering studies, and their own work, the authors and other researchers have developed surfaces for in vitro and in vivo control of the function of cells and tissues. In the present article, the authors summarize what they know about the process of cell response to surfaces, and what they have done and can do to develop surfaces that control hard- and soft-tissue formation and integration of implants. This article is intended to add to the clinician’s understanding of cell and surface interactions, explain why certain surfaces are currently used, and describe what surfaces clinicians may see in the future. [ABSTRACT FROM AUTHOR]

Although cancer is commonly perceived as a disease of dedifferentiation, the hallmark of early-stage prostate cancer is paradoxically the loss of more plastic basal cells and the abnormal proliferation of more differentiated secretory luminal cells. However, the mechanism of prostate cancer proluminal differentiation is largely unknown. Through integrating analysis of the transcription factors (TFs) from 806 human prostate cancers, we found that ERG was highly correlated with prostate cancer luminal subtyping. ERG overexpression in luminal epithelial cells inhibited those cells' normal plasticity to transdifferentiate into a basal lineage, and ERG superseded PTEN loss, which favored basal differentiation. ERG KO disrupted prostate cell luminal differentiation, whereas AR KO had no such effects. Trp63 is a known master regulator of the prostate basal lineage. Through analysis of 3D chromatin architecture, we found that ERG bound and inhibited the enhancer activity and chromatin looping of a Trp63 distal enhancer, thereby silencing its gene expression. Specific deletion of the distal ERG binding site resulted in the loss of ERG-mediated inhibition of basal differentiation. Thus, ERG, in its fundamental role in lineage differentiation in prostate cancer initiation, orchestrated chromatin interactions and regulated prostate cell lineage toward a proluminal program., Introduction Tumor initiation, progression, and therapy resistance involve epigenetic reprogramming that leads to aberrant cell lineage specification and transition (1-5). It is critical to understand the underlying mechanisms of cancer [...]

How do V1 cells respond to, adapt to, and combine signals from the two eyes? We tested a simple functional model that has monocular and binocular stages of divisive contrast gain control (CGC) that sit before, and after, binocular summation respectively. Interocular suppression (IOS) was another potential influence on contrast gain. Howarth, Vorobyov & Sengpiel (2009, Cerebral Cortex, 19, 1835-1843) studied contrast adaptation and interocular transfer in cat V1 cells. In our re-analysis we found that ocular dominance (OD) and contrast adaptation at a fixed test contrast were well described by a re-scaling of the unadapted orientation tuning curve - a simple change in response gain. We compared six variants of the basic model, and one model fitted the gain data notably better than the others did. When the dominant eye was tested, adaptation reduced cell response gain more when that eye was adapted than when the other eye was adapted. But when the non-dominant eye was tested, adapting either eye gave about the same reduction in overall gain, and there was an interaction between OD and adapting eye that was well described by the best-fitting model. Two key features of this model are that signals driving IOS arise 'early', before attenuation due to OD, while suppressive CGC signals are 'late' and so affected by OD. We show that late CGC confers a functional advantage: it yields partial compensation for OD, which should reduce ocular imbalance at the input to binocular summation, and improve the cell's sensitivity to variation in stereo disparity. [ABSTRACT FROM AUTHOR]

[Na.sup.+]/[H.sup.+] exchanger isoform one (NHE1) is a mammalian plasma membrane protein that removes intracellular protons, thereby elevating intracellular pH ([pH.sub.i]). NHE1 uses the energy of allowing an extracellular sodium down its gradient into cells to remove one intracellular proton. The ubiquitous protein has several important physiological and pathological influences on mammalian cells as a result of its activity. The three-dimensional structure of human NHE1 (hNHE1) is not known. Here, we modeled NHE1 based on the structure of MjNhaP1 of Methanocaldoccocus jannaschii in combination with biochemical surface accessibility data. hNHE1 contained 12 transmembrane segments including a characteristic [Na.sup.+]/[H.sup.+] antiporter fold of two trans-membrane segments with a helix--extended region--helix conformation crossing each other within the membrane. Amino acids 363-410 mapped principally to the extracellular surface as an extracellular loop (EL5). A large preponderance of amino acids shown to be surface accessible by biochemical experiments mapped near to, or on, the extracellular surface. Docking of [Na.sup.+]/[H.sup.+] exchanger inhibitors to the extracellular surface suggested that inhibitor binding on an extracellular site is made up from several amino acids of different regions of the protein. The results present a novel testable, three-dimensional model illustrating NHE1 structure and accounting for experimental biochemical data. Key words: molecular modeling, MjNhaP1, [Na.sup.+]/[H.sup.+] exchanger, NhaA, NHE1. L'echangeur [Na.sup.+]/[H.sup.+] NHE1 est une proteine de la membrane plasmique des mammiferes qui enleve les protons intracellulaires, elevant ainsi le pH intracellulaire ([pH.sub.i]). NHE1 utilise l'energie generee par l'entree spontanee dans les cellules d'un sodium extracellulaire par gradient pour faire sortir un proton intracellulaire. Cette proteine ubiquiste exerce une influence importante sur les plans physiologiques et pathologiques dans les cellules de mammiferes consequemment a son activite. La structure tridimensionnelle de NHE1 humain (hNHE1) n'est pas connue. Les auteurs ont modelise ici NHE1 a partir de la structure de MjNhaP1 de Methanocaldococcus jannaschii en combinaison avec les donnees biochimiques d'accessibilite de la surface. Le transporteur hNHE1 comprenait 12 segments transmembranaires dont un repli caracteristique de l'antiport [Na.sup.+]/[H.sup.+], formededeux segments transmembranaires dans une conformation helice--region etendue--helice qui se croisental'interieur de la membrane. Les acides amines 363-410 ont ete cartographies principalement a la surface extracellulaire en tant que boucle extracellulaire (EL5). Une forte preponderance d'acides amines accessibles a la surface selon des experiences biochimiques etait cartographiee a proximite ou sur la surface extracellulaire. L'amarrage d'inhibiteurs de l'echangeur [Na.sup.+]/[H.sup.+] a la surface extra-cellulaire suggerait que la liaison de l'inhibiteur sur un site extracellulaire implique plusieurs acides amines de differentes regions de la proteine. Les resultats presentent un nouveau modele tridimensionnel verifiable qui illustre la structure de NHE1 et explique les donnees biochimiques experimentales. [Traduit par la Redaction] Mots-cles : modelisation moleculaire, MjNhaP1, echangeur [Na.sup.+]/[H.sup.+], NhaA, NHE1., Introduction Membranes are key to cellular function. They separate cells from the extracellular environment and allow cells to maintain intracellular compartments of specific content. The plasma membrane of eukaryotic cells [...]

Endocytic organelles maintain their acidic pH using the V-type ATPase proton pump. However, proton accumulation across the membrane generates a voltage and requires the movement of an additional ion, known as a counterion, to dissipate charge buildup. The role of counterion movement in endosomes is not clear, but a subpopulation of early endosomes, clathrin-coated vesicles (CCVs), has previously been shown to use external chloride ([Cl.sup.-]) to allow V-ATPase-dependent acidification. We aimed to determine the identity and function of this presumed [Cl.sup.-] transporting protein. Our sample of highly enriched bovine brain CCVs exhibited V-type ATPase-facilitated acidification in the presence of external [Cl.sup.-], independent of the monovalent cations present. While unsuccessful at identifying the mechanism of anion transport, we used glutamate-facilitated acidification, density gradients, and mass spectrometry to show that most brain CCVs are synaptic vesicles, complementing results from earlier studies that argued similarity only on the basis on protein content. The source of [Cl.sup.-]-dependent acidification in brain CCVs may be vGLUT1, a synaptic vesicle glutamate transporter with known [Cl.sup.-]- permeability, although CCVs in other tissues are likely to utilize different proteins to facilitate acidification. Key words: acidification, chloride, endosome, membrane, transport. Les organites d'endocytose maintiennent leur pH acide a l'aide d'une pompe a proton, l'ATPase de type V. Toutefois, l'accumulation de protons a travers la membrane genere une difference de potentiel et requiert le mouvement d'un ion additionnel, appele contre-ion, qui dissipe l'accumulation de la charge. Le role du mouvement du contre-ion dans les endosomes n'est pas clair, mais une sous-population d'endosomes precoces, les vesicules recouvertes de clathrine (VRC), s'averent utiliser le chlorure ([Cl.sup.-]) externe pour permettre l'acidification dependante de l'ATPase de type V. L'objectif des auteurs etait de determiner l'identite et la fonction de cette proteine de transport de [Cl.sup.-] presumee. Leur echantillon hautement enrichi en VRC de cerveau bovin montrait une acidification facilitee par l'ATPase de type V en presence de [Cl.sup.-] externe, independante de la presence de cations monovalents. Meme s'ils n'ont pu identifier le mecanisme de transport d'anions, ils ont utilise une acidification facilitee par le glutamate, des gradients de densite et la spectrometrie de masse pour montrer que la plupart des VRC du cerveau consistent en vesicules synaptiques, completant les resultats d'etudes anterieures dont les conclusions basees seulement sur le contenu en proteines etaient similaires. La source de l'acidification dependante du [Cl.sup.-] dans les VRC du cerveau pourrait etre vGLUT1, untransporteurdeglutamate des vesicules synaptiques dont la permeabilite au [Cl.sup.-] est connue, memesiles VRC d'autres tissus utilisent probablement des proteines differentes pour faciliter l'acidification. [Traduit par la Redaction] Mots-cles : acidification, chlorure, endosome, membrane, transport., Introduction Cells utilize the endosomal pathway to perform vital functions including protein sorting, trafficking, and cell signaling. The initial step of the pathway involves endocytic vesicles, largely originating from Clathrin-coated [...]

The human solute carrier 26 (SLC26) gene family of anion transporters consists of 10 members (SLC26A1-A11, A10 being a pseudogene) that encode membrane glycoproteins with 14 transmembrane segments and a C-terminal cytoplasmic sulfate transporter anti-sigma antagonist domain. Thus far, mutations in eight members of the SLC26 family (A1-A6, A8, and A9) have been linked to diseases in humans. Our goal is to characterize the role of N-glycosylation and the effect of mutations in SLC26A2 and A3 proteins on their functional expression in transfected HEK-293 cells. We found that certain mutants were retained in the endoplamic reticulum via an interaction with the lectin chaperone calnexin. Some could escape protein quality control and traffic to the cell surface upon removal of the N-glycosylation sites. Furthermore, we found that loss of N-glycosylation reduced expression of SLC26A2 at the cell surface. Loss of N-glycosylation had no effect on the stability of SLC26A3, yet resulted in a profound decrease in transport activity. Thus, N-glycosylation plays three roles in the functional expression of SLC26 proteins: (1) to retain misfolded proteins in the endoplamic reticulum, (2) to stabilize the protein at the cell surface, and (3) to maintain the transport protein in a functional state. Key words: anion transport, calnexin, glycoproteins, membrane proteins, protein trafficking, solute carriers (SLC), SLC26, transporters. La famille de transporteurs d'anions SLC26 (<< solute carrier 26 >>) chez l'humain comprend 10 membres (SLC26A1-A11, A10 etant un pseudogene) qui codent des glycoproteines comportant 14 segments transmembranaires et un domaine C-terminal cytoplasmique STAS (<< sulfate transporter anti-sigma6 >>). Jusqu'a present, des mutations au sein de huit membres de la famille SLC26 (A1-A6, A8 et A9) ont ete reliees a des maladies chez l'humain. L'objectif des auteurs consiste a caracteriser le role de la N-glycosylation et l'effet des mutations de SLC26A2 et A3 sur leur expression fonctionnelle chez les cellules HEK-293 transfectees. Ils ont trouve que certains mutants etaient gardes a l'interieur du reticulum endoplasmique par leur interaction avec la calnexine, une lectine chaperon. Certains d'entre eux pouvaient echapper au controle de qualite des proteines et se rendre a la surface cellulaire a la suite de la suppression des sites de N-glycosylation. Qui plus est, ils ont trouve que la perte de N-glycosylation reduisait l'expression de SLC26A2 a la surface cellulaire. La perte de N-glycosylation n'avait pas d'effet sur la stabilite de SLC26A3, mais donnait lieu, neanmoins, a une forte diminution de l'activite de transport. Ainsi, la N-glycosylation joue trois roles dans l'expression fonctionnelle des proteines SCL26 : (1) retenir les proteines mal repliees dans le reticulum endoplasmique, (2) stabiliser la proteine a la surface cellulaire et (3) maintenir la proteine de transport dans un etat fonctionnel. [Traduit par la Redaction] Mots-cles : transport d'anion, calnexine, glycoproteines, proteines membranaires, transport des proteines, transporteurs de solutes (SLC), SLC26, transporteurs., Introduction Solute carrier (SLC) proteins comprise some 456 members subdivided into 52 families of membrane transporters that play essential roles in human health and disease. Regardless, they are one of [...]

The expansion of brain size is accompanied by a relative enlargement of the subventricular zone during development. Epithelial-like neural stem cells divide in the ventricular zone at the ventricles of the embryonic brain, self-renew and generate basal progenitors.sup.1 that delaminate and settle in the subventricular zone in enlarged brain regions.sup.2. The length of time that cells stay in the subventricular zone is essential for controlling further amplification and fate determination. Here we show that the interphase centrosome protein AKNA has a key role in this process. AKNA localizes at the subdistal appendages of the mother centriole in specific subtypes of neural stem cells, and in almost all basal progenitors. This protein is necessary and sufficient to organize centrosomal microtubules, and promote their nucleation and growth. These features of AKNA are important for mediating the delamination process in the formation of the subventricular zone. Moreover, AKNA regulates the exit from the subventricular zone, which reveals the pivotal role of centrosomal microtubule organization in enabling cells to both enter and remain in the subventricular zone. The epithelial-to-mesenchymal transition is also regulated by AKNA in other epithelial cells, demonstrating its general importance for the control of cell delamination. The interphase centrosome protein AKNA is necessary and sufficient for the organization of centrosomal microtubules, mediates delamination in the formation of the subventricular zone and regulates exit from this zone., Author(s): Germán Camargo Ortega [sup.1] [sup.2] [sup.3] , Sven Falk [sup.1] [sup.2] , Pia A. Johansson [sup.1] [sup.2] [sup.20] , Elise Peyre [sup.4] , Loïc Broix [sup.4] , Sanjeeb Kumar [...]

Small intestinal mononuclear cells that express CX3CR1 (CX3CR1.sup.+ cells) regulate immune responses.sup.1-5. CX3CR1.sup.+ cells take up luminal antigens by protruding their dendrites into the lumen.sup.1-4,6. However, it remains unclear how dendrite protrusion by CX3CR1.sup.+ cells is induced in the intestine. Here we show in mice that the bacterial metabolites pyruvic acid and lactic acid induce dendrite protrusion via GPR31 in CX3CR1.sup.+ cells. Mice that lack GPR31, which was highly and selectively expressed in intestinal CX3CR1.sup.+ cells, showed defective dendrite protrusions of CX3CR1.sup.+ cells in the small intestine. A methanol-soluble fraction of the small intestinal contents of specific-pathogen-free mice, but not germ-free mice, induced dendrite extension of intestinal CX3CR1.sup.+ cells in vitro. We purified a GPR31-activating fraction, and identified lactic acid. Both lactic acid and pyruvic acid induced dendrite extension of CX3CR1.sup.+ cells of wild-type mice, but not of Gpr31b.sup.-/- mice. Oral administration of lactate and pyruvate enhanced dendrite protrusion of CX3CR1.sup.+ cells in the small intestine of wild-type mice, but not in that of Gpr31b.sup.-/- mice. Furthermore, wild-type mice treated with lactate or pyruvate showed an enhanced immune response and high resistance to intestinal Salmonella infection. These findings demonstrate that lactate and pyruvate, which are produced in the intestinal lumen in a bacteria-dependent manner, contribute to enhanced immune responses by inducing GPR31-mediated dendrite protrusion of intestinal CX3CR1.sup.+ cells.In the mouse intestine, pyruvate and lactate produced from bacterial metabolites enhance immune responses through inducing dendrite protrusion, mediated by GPR31, of small intestinal mononuclear cells that express CX3CR1., Author(s): Naoki Morita [sup.1] [sup.2] [sup.3] , Eiji Umemoto [sup.1] [sup.2] [sup.3] , Setsuko Fujita [sup.4] , Akio Hayashi [sup.4] , Junichi Kikuta [sup.2] [sup.5] , Ikuo Kimura [sup.6] , [...]

Across the animal kingdom, gastrulation represents a key developmental event during which embryonic pluripotent cells diversify into lineage-specific precursors that will generate the adult organism. Here we report the transcriptional profiles of 116,312 single cells from mouse embryos collected at nine sequential time points ranging from 6.5 to 8.5 days post-fertilization. We construct a molecular map of cellular differentiation from pluripotency towards all major embryonic lineages, and explore the complex events involved in the convergence of visceral and primitive streak-derived endoderm. Furthermore, we use single-cell profiling to show that Tal1.sup.-/- chimeric embryos display defects in early mesoderm diversification, and we thus demonstrate how combining temporal and transcriptional information can illuminate gene function. Together, this comprehensive delineation of mammalian cell differentiation trajectories in vivo represents a baseline for understanding the effects of gene mutations during development, as well as a roadmap for the optimization of in vitro differentiation protocols for regenerative medicine. Single-cell profiling is used to create a molecular-level atlas of cell differentiation trajectories during gastrulation and early organogenesis in the mouse., Author(s): Blanca Pijuan-Sala [sup.1] [sup.2] , Jonathan A. Griffiths [sup.3] , Carolina Guibentif [sup.1] [sup.2] , Tom W. Hiscock [sup.3] [sup.4] , Wajid Jawaid [sup.1] [sup.2] , Fernando J. Calero-Nieto [...]

Our understanding of metabolic networks is incomplete, and new enzymatic activities await discovery in well-studied organisms. Mass spectrometric measurement of cellular metabolites reveals compounds inside cells that are unexplained by current maps of metabolic reactions, and existing computational models are unable to account for all activities observed within cells. Additional large-scale genetic and biochemical approaches are required to elucidate metabolic gene function. We have used full-scan mass spectrometry metabolomics of polar small molecules to examine deletion mutants of candidate enzymes in the model yeast Saccharomyces cerevisiae. We report the identification of 25 genes whose deletion results in focal metabolic changes consistent with loss of enzymatic activity and describe the informatic approaches used to enrich for candidate enzymes from uncharacterized open reading frames. Triumphs and pitfalls of metabolic phenotyping screens are discussed, including estimates of the frequency of uncharacterized eukaryotic genes that affect metabolism and key issues to consider when searching for new enzymatic functions in other organisms.Key words: metabolomics, enzyme discovery, discovery metabolite profiling, hexosepyranosyl-citrulline.Notre comprehension des reseaux metaboliques est incomplete et de nouvelles activites enzymatiques tardent a etre decouvertes dans des organismes bien etudies. La mesure par spectrometrie de masse de metabolites cellulaires revele la presence de composes a l'interieur des cellules qui sont inexpliques par la cartographie actuelle des reactions metaboliques, et les modeles computationnels existants sont incapables d'expliquer toutes les activites observees a l'interieur des cellules. De nouvelles approches genetiques et biochimiques a grande echelle sont necessaires pour elucider la fonction des genes du metabolisme. Les auteurs ont utilise la metabolomique en spectrometrie de masse a balayage complet de petites molecules polaires afin d'examiner des mutants de deletion d'enzymes candidates chez la levure modele Saccharomyces cerevisiae. Ils rapportent l'identification de 25 genes dont la deletion donne lieu a des changements metaboliques focalises coherents avec la perte d'activite enzymatique, et decrivent les approches informatiques utilisees pour enrichir le groupe d'enzymes candidates a partie de cadres de lecture ouverts non caracterises. Les succes et les echecs des criblages du phenotypage metabolique sont discutes, dont les estimations de la frequence des genes eucaryotes non caracterises qui affectent le metabolisme, ainsi que les questions cles a considerer lors de la recherche de nouvelles fonctions enzymatiques chez d'autres organismes. [Traduit par la Redaction]Mots-cles : metabolomique, decouverte d'enzymes, profilage metabolique, hexosepyranosyl-citrulline., IntroductionUncharacterized enzymes remain to be discovered even in well-studied genomesMany gaps in the collective understanding of metabolism remain despite decades of work invested by the scientific community to both identify [...]

Cell surface receptors trigger the activation of signaling pathways to regulate key cellular processes, including cell survival and proliferation. Internalization, sorting, and trafficking of activated receptors, therefore, play a major role in the regulation and attenuation of cell signaling. Efficient sorting of endocytosed receptors is performed by the ESCRT machinery, which targets receptors for degradation by the sequential establishment of protein complexes. These events are tightly regulated and malfunction of ESCRT components can lead to abnormal trafficking and sustained signaling and promote tumor formation or progression. In this review, we analyze the modular domain organization of the alternative ESCRT protein HD-PTP and its role in receptor trafficking and tumorigenesis.Key words: HD-PTP, ESCRT, endosomal sorting, receptor trafficking, tumorigenesis.Les recepteurs de la surface cellulaire declenchent l'activation des voies de signalisation qui regulent des processus cellulaires cles, dont la survie et la proliferation cellulaire. L'internalisation, le tri et le trafic des recepteurs actives jouent ainsi un role important dans la regulation et l'attenuation de la signalisation cellulaire. Le tri efficace des recepteurs internalises par endocytose est realise par le complexe ESCRT. Ces proteines ciblent les recepteurs en vue de leur degradation par l'etablissement sequentiel de complexes proteiques. Ces evenements sont etroitement regules, et le fonctionnement defectueux des composantes de ESCRT peut conduire a un trafic anormal et une signalisation prolongee et favorisant la formation ou la progression tumorale. Dans cette synthese, les auteurs analysent l'organisation du domaine modulaire de HD-PTP, une proteine associee a ESCRT, et son role dans le trafic des recepteurs et la tumorigenese. [Traduit par la Redaction]Mots-cles : HD-PTP, ESCRT, tri endosomal, trafic des recepteurs, tumorigenese., IntroductionCell surface receptors are activated by the binding of their cognate ligands. This event leads to receptor ubiquitylation, internalization, and sorting to be either recycled back to the plasma membrane [...]

Signalling through phosphoinositide lipids is essential for regulating many cellular processes, including endosomal trafficking. A number of intracellular pathogens have found ways to subvert host trafficking pathways via exploitation of endosomal phosphoinositides. This review will discuss how pathogens such as bacteria, viruses, and eukaryotic parasites depend on endosomal phosphoinositides for infection as well as the mechanisms through which some are able to actively manipulate these signalling lipids to facilitate invasion, survival, replication, and immune evasion.Key words: endosomal trafficking, phosphoinositides, lipid signalling, host-pathogen interactions.La signalisation par les phosphoinositides est essentielle a la regulation de plusieurs processus cellulaires, y compris le trafic endosomal. Plusieurs agents pathogenes intracellulaires ont developpe des strategies pour deregler les voies de trafic de l'hote au moyen de l'exploitation des phosphoinositides des endosomes. Cette synthese presentera comment des agents pathogenes tels les bacteries, les virus et les parasites eucaryotes dependent des phosphoinositides des endosomes pour infecter leur hote. Elle discutera aussi des mecanismes grace auxquels certains agents sont capables de manipuler les lipides signaletiques pour faciliter leur invasion, leur survie, leur replication et leur evasion du systeme immunitaire. [Traduit par la Redaction]Mots-cles : trafic endosomal, phosphoinositides, signalisation par les lipides, interactions hote-pathogene., IntroductionVesicular trafficking is a defining characteristic of eukaryotic cells. The sorting and transport of macromolecules between cellular compartments is a dynamically regulated process involving precise spatiotemporal signalling events on membranes. [...]

Normal hematopoiesis is sustained through a carefully orchestrated balance between hematopoietic stem cell (HSC) self-renewal and differentiation. The functional importance of this axis is underscored by the severity of disease phenotypes initiated by abnormal HSC function, including myelodysplastic syndromes and hematopoietic malignancies. Major advances in the understanding of transcriptional regulation of primitive hematopoietic cells have been achieved; however, the post-transcriptional regulatory layer that may impinge on their behavior remains underexplored by comparison. Key players at this level include RNA-binding proteins (RBPs), which execute precise and highly coordinated control of gene expression through modulation of RNA properties that include its splicing, polyadenylation, localization, degradation, or translation. With the recent identification of RBPs having essential roles in regulating proliferation and cell fate decisions in other systems, there has been an increasing appreciation of the importance of post-transcriptional control at the stem cell level. Here we discuss our current understanding of RBP-driven post-transcriptional regulation in HSCs, its implications for normal, perturbed, and malignant hematopoiesis, and the most recent technological innovations aimed at RBP-RNA network characterization at the systems level. Emerging evidence highlights RBP-driven control as an underappreciated feature of primitive hematopoiesis, the greater understanding of which has important clinical implications.Key words: hematopoietic stem cells, leukemia stem cells, post-transcriptional regulation, RNA-binding proteins, RNA regulons.L'hematopoiese normale est soutenue par un equilibre soigneusement orchestre entre l'autorenouvelement des cellules souches hematopoietiques (CSH) et leur differenciation. L'importance fonctionnelle de cet axe est mise en evidence par la severite des phenotypes des maladies initiees par une fonction anormale des CSH, dont les syndromes myelodysplasiques et les cancers hematopoietiques. Des percees importantes dans la comprehension de la regulation transcriptionnelle des cellules hematopoietiques primitives ont ete realisees; toutefois, en comparaison, les composantes de la regulation post-transcriptionnelle qui pourraient affecter leur comportement demeurent peu explorees. Les joueurs cles de ce niveau de regulation comprennent les proteines de liaison de l'ARN qui executent un controle hautement coordonne de l'expression genique par la modulation des proprietes de l'ARN dont l'epissage, la polyadenylation, la localisation, la degradation ou la traduction. Avec l'identification recente de proteines de liaison de l'ARN qui jouent un role essentiel dans la regulation de la proliferation et des decisions cellulaires dans d'autres systemes, l'importance du controle post-transcriptionnel a l'echelle des cellules souches est de plus en plus reconnue. Les auteurs discutent ici de la comprehension actuelle de la regulation post-transcriptionnelle assuree par les proteines de liaison de l'ARN dans les CSH, de son implication dans l'hematopoiese normale, perturbee et maligne, de meme que des innovations technologiques les plus recentes visant a caracteriser le reseau ARN-proteines de liaison de l'ARN a l'echelle des systemes. De nouvelles donnees soulignent que le controle exerce par les proteines de liaison de l'ARN constitue une caracteristique negligee de l'hematopoiese primitive, dont une meilleure connaisance aurait d'importantes retombees cliniques. [Traduit par la Redaction]Mots-cles : cellules souches hematopoietiques, cellules souches leucemiques, regulation post-transcriptionnelle, proteines de liaison de l'ARN, regulons d'ARN., IntroductionThe machinery underlying stem cells' capacity to orchestrate their self-maintenance and differentiation can be represented as integrated circuits that are genetically programmed. As demonstrated by the capacity to reprogram somatic [...]

Phagocytosis is an evolutionarily conserved process. In Protozoa, phagocytosis fulfills a feeding mechanism, while in Metazoa, phagocytosis diversified to play multiple organismal roles, including immune defence, tissue homeostasis, and remodeling. Accordingly, phagocytes display a high level of plasticity in their capacity to recognize, engulf, and process targets that differ in composition and morphology. Here, we review how phagocytosis adapts to its multiple roles and discuss in particular the effect of target morphology in phagocytic uptake and phagosome maturation.Key words: phagocytosis, target morphology, phagocytic plasticity, phagosomal maturation, phagocytic cup.La phagocytose est un processus conserve durant l'evolution. Chez les protozoaires, la phagocytose remplit des fonctions alimentaires alors que chez les metazoaires, la phagocytose s'est diversifiee pour remplir de multiples roles dans l'organisme, dont la defense immunitaire, l'homeostasie des tissus et le remodelage. Consequemment, les phagocytes montrent un haut degre de plasticite dans leur capacite a reconnaitre, engloutir et transformer des particules cibles qui varient quant a leur composition et leur morphologie. Les auteurs presentent ici l'adaptation d'un phagocyte a ses multiples roles et discutent plus particulierement de l'effet de la morphologie d'une particule cible dans la captation phagocytaire et la maturation du phagosome. [Traduit par la Redaction]Mots-cles : phagocytose, morphologie de la cible, plasticite phagocytaire, maturation du phagosome, coupe phagocytaire., Overview of phagocytosis and phagosome maturationProtozoa and certain cells within Metazoa have the ability to selectively internalize particles and degrade them intracellularly through a process known as phagocytosis. In this [...]

The aim of the study is to reveal the risk of COVID-19 among pathologists and to examine their views, concerns along with measures to be taken in dealing with COVID-19. The research was carried out in Turkey with online survey method, on 176 participants. According to the findings of the study, participants who served one-on-one to a COVID-19 patient was 47.16%. Number of participants assigned in the polyclinic and clinical processes of coronavirus patients; 63.6%. 24 participant (13.6%) stated that their frozen cases decreased. Substantially, there was a use of protective equipment (88.6%). Cytological specimens were seen to continue 93.7%. There was a competence of 88.6% in terms of protective equipment. It was determined that the anxiety levels of the participants did not change according to age groups, according to the hospital type, working pandemic outpatient clinic and gender variables (p> 0.05). As a result, medical pathologists actively continue their routine services during the pandemic process and also support their other colleagues by working actively in the COVID-19 outpatient clinic. As always, solidarity with our colleagues continues. [ABSTRACT FROM AUTHOR]

Copyright of NaUKMA Research Papers. Biology & Ecology is the property of National University of Kyiv-Mohyla Academy, Faculty of Humanities and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Optogenetics has revolutionised research in cell biology over the past 15 years, yet devices that can effectively stimulate cells using light are often costly and specifically designed for a single experimental set-up with little flexibility. Our novel 'OptoGenie' stimulation device can be conveniently transferred between cell culture incubators for long-term stimulation, electrophysiology rigs for patch-clamp recordings, and optical microscopes for fluorescence imaging of cells. The modular design of the device offers portability between these experimental set-ups, is low cost compared with commercial devices, and provides easy adjustment of the stimulation intensity and frequency. OptoGenie provides an open-source model made from proprietary parts such that researchers without experience with electronics and coding can easily purchase, assemble and customise for their experimental needs. [ABSTRACT FROM AUTHOR]

Copyright of Firat Universitesi Sağlik Bilimleri Tip Dergisi is the property of Firat Universitesiu, Saglik Bilimleri Enstitusu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Microscopic examination of blood smears remains the gold standard for laboratory inspection and diagnosis of malaria. Smear inspection is, however, time-consuming and dependent on trained microscopists with results varying in accuracy. We sought to develop an automated image analysis method to improve accuracy and standardization of smear inspection that retains capacity for expert confirmation and image archiving. Here, we present a machine learning method that achieves red blood cell (RBC) detection, differentiation between infected/uninfected cells, and parasite life stage categorization from unprocessed, heterogeneous smear images. Based on a pretrained Faster Region-Based Convolutional Neural Networks (R-CNN) model for RBC detection, our model performs accurately, with an average precision of 0.99 at an intersection-over-union threshold of 0.5. Application of a residual neural network-50 model to infected cells also performs accurately, with an area under the receiver operating characteristic curve of 0.98. Finally, combining our method with a regression model successfully recapitulates intraerythrocytic developmental cycle with accurate lifecycle stage categorization. Combined with a mobile-friendly web-based interface, called PlasmoCount, our method permits rapid navigation through and review of results for quality assurance. By standardizing assessment of Giemsa smears, our method markedly improves inspection reproducibility and presents a realistic route to both routine lab and future field-based automated malaria diagnosis. [ABSTRACT FROM AUTHOR]

In the present work, we theoretically study a 2D photonic crystal (PC) comprised by double negative (DNG) metamaterial cylinders, showing that such a system presents a superior light-matter interaction when compared with their single negative (SNG) plasmonic PC counterparts, suggesting a route to enhance the performance of sensors and photovoltaic cells. On the other hand, we have observed that depending on the frequency, the mode symmetry resembles either the case of SNG electric (SNG-E) or SNG magnetic (SNG-M) PC, suggesting that either the electric or magnetic character of the DNG metamaterial dominates in each case. [ABSTRACT FROM AUTHOR]

We investigate reversible diffusion-influenced reactions of an isolated pair in two dimensions. To this end, we employ convolution relations that permit deriving the survival probability of the reversible reaction directly in terms of the survival probability of the irreversible reaction. Furthermore, we make use of the mean reaction time approximation to write the irreversible survival probability in restricted spaces as a single exponential. In this way, we obtain exact and approximative expressions in the time domain for the reversible survival probability for three different two dimensional spatial domains: The infinite plane, the annular domain, and the surface of a sphere. Our obtained results should prove useful in the context of membrane-bound reversible diffusion-influenced reactions in cell biology. [ABSTRACT FROM AUTHOR]

In-resin CLEM of Epon embedded samples can greatly simplify the correlation of fluorescent images with electron micrographs. The usefulness of this technique is limited at present by the low number of fluorescent proteins that resist CLEM processing. Additionally, no study has reported the possibility of two-color in-resin CLEM of Epon embedded cells. In this study, we screened for monomeric green and red fluorescent proteins that resist CLEM processing. We identified mWasabi, CoGFP variant 0, and mCherry2; two green and one red fluorescent proteins as alternatives for in-resin CLEM. We expressed mitochondria-localized mCherry2 and histone H2B tagged with CoGFP variant 0 in cells. Green and red fluorescence was detected in 100 nm-thin sections of the Epon-embedded cells. In the same thin sections, we correlated the fluorescent signals to mitochondria and the nucleus using a scanning electron microscope. Similar results were obtained when endoplasmic reticulum-localized mCherry2 and histone H2B tagged with CoGFP variant 0 were expressed in the cells. Two-color in-resin CLEM of two cytoplasmic organelles, mitochondria and endoplasmic reticulum, was also achieved using mitochondria-localized mCherry2 and endoplasmic reticulum-localized mWasabi. In summary, we report three new fluorescent protein-alternatives suitable for in-resin CLEM of Epon-embedded samples, and achieved Epon-based two-color in-resin CLEM. [ABSTRACT FROM AUTHOR]

Background: Visual Inspection with Acetic Acid (VIA) has a low specificity for the detection of cervical lesions. It is therefore, necessary to subject those found positive to cytological assessment so as to avoid referrals for cryotherapy. Objectives: To determine Liquid Based Cytological (LBC) findings in VIA positive women and also estimate the proportion of women who could be spared from cryotherapy. Materials and Methods: This study was a cross sectional descriptive study. Consecutive sampling method was used. A Thin Prep 2000 machine was used to process the LBC samples which were then stained using the Papanicolaou stain. The 2014 Bethesda System was used to report the LBC smears. Results: Of the 205 VIA positive women enrolled in the study, 6 (2.9%) had an unsatisfactory interpretation, 145 (70.7%) had an NILM interpretation, 27 (13.2%) had an ASCUS interpretation, 7 (3.4%) had an LSIL diagnosis, 2 (1.0%) had an ASC-H interpretation and 18 (8.8%) had a HSIL diagnosis. Of the 145 NILM cases, 35 (24%) were reported as inflammatory, 2 (1.4%) had Candida infections and 5 (3.4%) had Bacterial vaginosis. Conclusion: Most (70.7%) VIA positive women had no cytological detectable lesions and therefore were requested for follow up as per protocol. This study recommends subjecting all who are VIA positive to have a cytological test and follow up. [ABSTRACT FROM AUTHOR]

Fluorescence lifetime imaging (FLIM) is a quantitative, intensity-independent microscopical method for measurement of diverse biochemical and physical properties in cell biology. It is a highly effective method for measurements of Förster resonance energy transfer (FRET), and for quantification of protein-protein interactions in cells. Time-domain FLIM-FRET measurements of these dynamic interactions are particularly challenging, since the technique requires excellent photon statistics to derive experimental parameters from the complex decay kinetics often observed from fluorophores in living cells. Here we present a new time-domain multi-confocal FLIM instrument with an array of 64 visible beamlets to achieve parallelised excitation and detection with average excitation powers of ~ 1–2 μW per beamlet. We exemplify this instrument with up to 0.5 frames per second time-lapse FLIM measurements of cAMP levels using an Epac-based fluorescent biosensor in live HeLa cells with nanometer spatial and picosecond temporal resolution. We demonstrate the use of time-dependent phasor plots to determine parameterisation for multi-exponential decay fitting to monitor the fractional contribution of the activated conformation of the biosensor. Our parallelised confocal approach avoids having to compromise on speed, noise, accuracy in lifetime measurements and provides powerful means to quantify biochemical dynamics in living cells. [ABSTRACT FROM AUTHOR]

The marriage of Sally Peris Hughes (1895–1984) and Franz Schrader (1891–1962) in November 1920 launched a highly successful scientific collaboration that lasted over four decades. The Schraders were avid naturalists, adroit experimentalists, and keen theoreticians, and both had long, productive, and fruitful careers in zoology. They offer an extraordinarily rich case study that provides an insightful view of the work carried out in several areas of the life sciences from the 1920s to the 1960s—fieldwork, cytology, cytogenetics, and entomology—as well as critical aspects of the social world of contemporary science. By focusing on the fieldwork the couple carried out in Mexico and Central America in the late 1920s and early 1930s, this paper seeks to illuminate how this collaborative scientific marriage embodies a collective, complex, and integrated personal and social arrangement that served to enhance both knowledge production and disciplinary development in several areas of science. It also reveals ways in which marriage could serve as a means to help both parties navigate and negotiate restrictive sociocultural norms and institutional arrangements in science involving gender, power, and authority in the early twentieth century. [ABSTRACT FROM AUTHOR]

Copyright of NaUKMA Research Papers. Biology & Ecology is the property of National University of Kyiv-Mohyla Academy, Faculty of Humanities and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recently, the coherent generation of GHz acoustic waves using ultrashort laser pulses has demonstrated the ability to probe the sound velocity in vegetal cells and in cell-mimicking soft micro-objects with micrometer resolution, opening tremendous potentialities for single-cell biology. However, manipulating biological media in physiological conditions is often a technical challenge when using a laser-based setup. In this article, we present a new opto-acoustic bio-transducer composed of a thin metal film sputtered on a transparent heat sink that allows reducing importantly the laser-induced cellular stresses, and offers a wide variety of optical configurations. In particular, by exploiting the acoustic reflection coefficient at the sample-transducer interface and the photoacoustic interaction inside the transparent sample, the density and compressibility of the sample can be probed simultaneously. Using an ad hoc signal analysis based on Hilbert and wavelet transforms, these quantities are measured accurately for a reference fluid. Similar analysis performed in a single vegetal cell also suggests high sensitivity to the state of the transducer-cell interface, and notably to the presence of the plasma membrane that encloses the cell vacuole. [ABSTRACT FROM AUTHOR]

Elastic systems that are spatially heterogeneous in their mechanical response pose special challenges for molecular simulations. Standard methods for sampling thermal fluctuations of a system’s size and shape proceed through a series of homogeneous deformations, whose magnitudes can be severely restricted by its stiffest parts. Here we present a Monte Carlo algorithm designed to circumvent this difficulty, which can be prohibitive in many systems of modern interest. By deforming randomly selected subvolumes alone, it naturally distributes the amplitude of spontaneous elastic fluctuations according to intrinsic heterogeneity. We describe in detail implementations of such “slice moves” that are consistent with detailed balance. Their practical application is illustrated for crystals of two-dimensional hard disks and random networks of cross-linked polymers. [ABSTRACT FROM AUTHOR]

Gap junctions establish direct pathways for cell-to-cell communication through the assembly of twelve connexin subunits that form intercellular channels connecting neighbouring cells. Co-assembly of different connexin isoforms produces channels with unique properties and enables communication across cell types. Here we used single-particle cryo-electron microscopy to investigate the structural basis of connexin co-assembly in native lens gap junction channels composed of connexin 46 and connexin 50 (Cx46/50). We provide the first comparative analysis to connexin 26 (Cx26), which--together with computational studies--elucidates key energetic features governing gap junction permselectivity. Cx46/50 adopts an open-state conformation that is distinct from the Cx26 crystal structure, yet it appears to be stabilized by a conserved set of hydrophobic anchoring residues. 'Hot spots' of genetic mutations linked to hereditary cataract formation map to the core structural-functional elements identified in Cx46/50, suggesting explanations for many of the disease-causing effects.Cryo-electron microscopy structures of connexin channels composed of connexin 46 and connexin 50 in an open-state reveal features that govern permselectivity and the location of mutated residues linked to herediatry cataracts., Author(s): Janette B. Myers [sup.1] , Bassam G. Haddad [sup.1] , Susan E. O'Neill [sup.1] , Dror S. Chorev [sup.2] , Craig C. Yoshioka [sup.3] , Carol V. Robinson [sup.2] [...]

Fundamental biological processes are carried out by curved epithelial sheets that enclose a pressurized lumen. How these sheets develop and withstand three-dimensional deformations has remained unclear. Here we combine measurements of epithelial tension and shape with theoretical modelling to show that epithelial sheets are active superelastic materials. We produce arrays of epithelial domes with controlled geometry. Quantification of luminal pressure and epithelial tension reveals a tensional plateau over several-fold areal strains. These extreme strains in the tissue are accommodated by highly heterogeneous strains at a cellular level, in seeming contradiction to the measured tensional uniformity. This phenomenon is reminiscent of superelasticity, a behaviour that is generally attributed to microscopic material instabilities in metal alloys. We show that in epithelial cells this instability is triggered by a stretch-induced dilution of the actin cortex, and is rescued by the intermediate filament network. Our study reveals a type of mechanical behaviour--which we term active superelasticity--that enables epithelial sheets to sustain extreme stretching under constant tension.Theoretical modelling in combination with measurements of tension and shape in epithelial domes of controlled geometry reveals a plateau of tension in tissue that is maintained by heterogeneous strain across cells., Author(s): Ernest Latorre [sup.1] [sup.2] , Sohan Kale [sup.2] , Laura Casares [sup.1] , Manuel Gómez-González [sup.1] , Marina Uroz [sup.1] , Léo Valon [sup.1] , Roshna V. Nair [sup.3] [...]

Starvation poses a fundamental challenge to cell survival. Whereas the role of autophagy in promoting energy homeostasis in this setting has been extensively characterized.sup.1, other mechanisms are less well understood. Here we reveal that glyceraldehyde 3-phosphate dehydrogenase (GAPDH) inhibits coat protein I (COPI) transport by targeting a GTPase-activating protein (GAP) towards ADP-ribosylation factor 1 (ARF1) to suppress COPI vesicle fission. GAPDH inhibits multiple other transport pathways, also by targeting ARF GAPs. Further characterization suggests that this broad inhibition is activated by the cell during starvation to reduce energy consumption. These findings reveal a remarkable level of coordination among the intracellular transport pathways that underlies a critical mechanism of cellular energy homeostasis.During starvation, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) targets GTPase-activating proteins to inhibit multiple intracellular transport pathways, thereby promoting energy homeostasis., Author(s): Jia-Shu Yang [sup.1] , Jia-Wei Hsu [sup.1] , Seung-Yeol Park [sup.1] , Jian Li [sup.1] , William M. Oldham [sup.2] , Galina V. Beznoussenko [sup.3] , Alexander A. Mironov [...]

Adipocyte development and differentiation have an important role in the aetiology of obesity and its co-morbidities.sup.1,2. Although multiple studies have investigated the adipogenic stem and precursor cells that give rise to mature adipocytes.sup.3-14, our understanding of their in vivo origin and properties is incomplete.sup.2,15,16. This is partially due to the highly heterogeneous and unstructured nature of adipose tissue depots.sup.17, which has proven difficult to molecularly dissect using classical approaches such as fluorescence-activated cell sorting and Cre-lox lines based on candidate marker genes.sup.16,18. Here, using the resolving power of single-cell transcriptomics.sup.19 in a mouse model, we reveal distinct subpopulations of adipose stem and precursor cells in the stromal vascular fraction of subcutaneous adipose tissue. We identify one of these subpopulations as CD142.sup.+ adipogenesis-regulatory cells, which can suppress adipocyte formation in vivo and in vitro in a paracrine manner. We show that adipogenesis-regulatory cells are refractory to adipogenesis and that they are functionally conserved in humans. Our findings point to a potentially critical role for adipogenesis-regulatory cells in modulating adipose tissue plasticity, which is linked to metabolic control, differential insulin sensitivity and type 2 diabetes. Single-cell transcriptomics reveals that, in mice and humans, a population of cells in the stromal vascular fraction of adipose tissue regulates adipogenesis by suppressing adipocyte formation in a paracrine manner., Author(s): Petra C. Schwalie [sup.1] , Hua Dong [sup.2] , Magda Zachara [sup.1] , Julie Russeil [sup.1] , Daniel Alpern [sup.1] , Nassila Akchiche [sup.2] , Christian Caprara [sup.3] , [...]

Mammalian cells integrate mitogen and stress signalling before the end of G1 phase to determine whether or not they enter the cell cycle.sup.1-4. Before cells can replicate their DNA in S phase, they have to activate cyclin-dependent kinases (CDKs), induce an E2F transcription program and inactivate the anaphase-promoting complex (APC/C.sup.CDH1, also known as the cyclosome), which is an E3 ubiquitin ligase that contains the co-activator CDH1 (also known as FZR, encoded by FZR1). It was recently shown that stress can return cells to quiescence after CDK2 activation and E2F induction but not after inactivation of APC/C.sup.CDH1, which suggests that APC/C.sup.CDH1 inactivation is the point of no return for cell-cycle entry.sup.3. Rapid inactivation of APC/C.sup.CDH1 requires early mitotic inhibitor 1 (EMI1).sup.3,5, but the molecular mechanism that controls this cell-cycle commitment step is unknown. Here we show using human cell models that cell-cycle commitment is mediated by an EMI1-APC/C.sup.CDH1 dual-negative feedback switch, in which EMI1 is both a substrate and an inhibitor of APC/C.sup.CDH1. The inactivation switch triggers a transition between a state with low EMI1 levels and high APC/C.sup.CDH1 activity during G1 and a state with high EMI1 levels and low APC/C.sup.CDH1 activity during S and G2. Cell-based analysis, in vitro reconstitution and modelling data show that the underlying dual-negative feedback is bistable and represents a robust irreversible switch. Our study suggests that mammalian cells commit to the cell cycle by increasing CDK2 activity and EMI1 mRNA expression to trigger a one-way APC/C.sup.CDH1 inactivation switch that is mediated by EMI1 transitioning from acting as a substrate of APC/C.sup.CDH1 to being an inhibitor of APC/C.sup.CDH1.The transition between early mitotic inhibitor 1 acting as a substrate of the APC/C and as an inhibitor of the same complex results in an irreversible switch that mediates human cell-cycle commitment., Author(s): Steven D. Cappell [sup.1] [sup.2] , Kevin G. Mark [sup.3] [sup.4] , Damien Garbett [sup.1] , Lindsey R. Pack [sup.1] , Michael Rape [sup.3] [sup.4] , Tobias Meyer [sup.1] [...]

Tissues that undergo rapid cellular turnover, such as the mammalian haematopoietic system or the intestinal epithelium, are dependent on stem and progenitor cells that proliferate to provide differentiated cells to maintain organismal health. Stem and progenitor cells, in turn, are thought to rely on signals and growth factors provided by local niche cells to support their function and self-renewal. Several cell types have been hypothesized to provide the signals required for the proliferation and differentiation of the intestinal stem cells in intestinal crypts.sup.1-6. Here we identify subepithelial telocytes as an important source of Wnt proteins, without which intestinal stem cells cannot proliferate and support epithelial renewal. Telocytes are large but rare mesenchymal cells that are marked by expression of FOXL1 and form a subepithelial plexus that extends from the stomach to the colon. While supporting the entire epithelium, FOXL1.sup.+ telocytes compartmentalize the production of Wnt ligands and inhibitors to enable localized pathway activation. Conditional genetic ablation of porcupine (Porcn), which is required for functional maturation of all Wnt proteins, in mouse FOXL1.sup.+ telocytes causes rapid cessation of Wnt signalling to intestinal crypts, followed by loss of proliferation of stem and transit amplifying cells and impaired epithelial renewal. Thus, FOXL1.sup.+ telocytes are an important source of niche signals to intestinal stem cells.Subepithelial telocytes are identified as a source of Wnt signals that enable proliferation and differentiation of intestinal stem cells, an essential function for maintenance of the intestinal epithelium., Author(s): Michal Shoshkes-Carmel [sup.1] , Yue J. Wang [sup.1] , Kirk J. Wangensteen [sup.1] , Beáta Tóth [sup.2] , Ayano Kondo [sup.1] , Efi E. Massassa [sup.2] , Shalev Itzkovitz [...]

Despite intense interest in discovering drugs that cause G-protein-coupled receptors (GPCRs) to selectively stimulate or block arrestin signalling, the structural mechanism of receptor-mediated arrestin activation remains unclear.sup.1,2. Here we reveal this mechanism through extensive atomic-level simulations of arrestin. We find that the receptor's transmembrane core and cytoplasmic tail--which bind distinct surfaces on arrestin--can each independently stimulate arrestin activation. We confirm this unanticipated role of the receptor core, and the allosteric coupling between these distant surfaces of arrestin, using site-directed fluorescence spectroscopy. The effect of the receptor core on arrestin conformation is mediated primarily by interactions of the intracellular loops of the receptor with the arrestin body, rather than the marked finger-loop rearrangement that is observed upon receptor binding. In the absence of a receptor, arrestin frequently adopts active conformations when its own C-terminal tail is disengaged, which may explain why certain arrestins remain active long after receptor dissociation. Our results, which suggest that diverse receptor binding modes can activate arrestin, provide a structural foundation for the design of functionally selective ('biased') GPCR-targeted ligands with desired effects on arrestin signalling.Molecular dynamics simulations and site-directed fluorescence spectroscopy show that the transmembrane core and cytoplasmic tail of G-protein-coupled receptors independently and cooperatively activate arrestin., Author(s): Naomi R. Latorraca [sup.1] [sup.2] [sup.3] [sup.4] , Jason K. Wang [sup.2] , Brian Bauer [sup.5] , Raphael J. L. Townshend [sup.2] , Scott A. Hollingsworth [sup.1] [sup.2] [sup.3] [...]

The cell microenvironment, which is critical for stem cell maintenance, contains both cellular and non-cellular components, including secreted growth factors and the extracellular matrix.sup.1-3. Although Notch and other signalling pathways have previously been reported to regulate quiescence of stem cells.sup.4-9, the composition and source of molecules that maintain the stem cell niche remain largely unknown. Here we show that adult muscle satellite (stem) cells in mice produce extracellular matrix collagens to maintain quiescence in a cell-autonomous manner. Using chromatin immunoprecipitation followed by sequencing, we identified NOTCH1/RBPJ-bound regulatory elements adjacent to specific collagen genes, the expression of which is deregulated in Notch-mutant mice. Moreover, we show that Collagen V (COLV) produced by satellite cells is a critical component of the quiescent niche, as depletion of COLV by conditional deletion of the Col5a1 gene leads to anomalous cell cycle entry and gradual diminution of the stem cell pool. Notably, the interaction of COLV with satellite cells is mediated by the Calcitonin receptor, for which COLV acts as a surrogate local ligand. Systemic administration of a calcitonin derivative is sufficient to rescue the quiescence and self-renewal defects found in COLV-null satellite cells. This study reveals a Notch-COLV-Calcitonin receptor signalling cascade that maintains satellite cells in a quiescent state in a cell-autonomous fashion, and raises the possibility that similar reciprocal mechanisms act in diverse stem cell populations.Muscle stem cell quiescence in mice is maintained by a Notch-Collagen V-CALCR signalling pathway that is activated and sustained in a cell-autonomous fashion., Author(s): Meryem B. Baghdadi [sup.1] [sup.2] [sup.3] , David Castel [sup.4] [sup.5] , Léo Machado [sup.6] , So-ichiro Fukada [sup.7] , David E. Birk [sup.8] , Frederic Relaix [sup.6] , [...]

Fibroblasts are a dynamic cell type that achieve selective differentiated states to mediate acute wound healing and long-term tissue remodeling with scarring. With myocardial infarction injury, cardiomyocytes are replaced by secreted extracellular matrix proteins produced by proliferating and differentiating fibroblasts. Here, we employed 3 different mouse lineage tracing models and stage-specific gene profiling to phenotypically analyze and classify resident cardiac fibroblast dynamics during myocardial infarction injury and stable scar formation. Fibroblasts were activated and highly proliferative, reaching a maximum rate within 2 to 4 days after infarction injury, at which point they expanded 3.5-fold and were maintained long term. By 3 to 7 days, these cells differentiated into myofibroblasts that secreted abundant extracellular matrix proteins and expressed smooth muscle [alpha]-actin to structurally support the necrotic area. By 7 to 10 days, myofibroblasts lost proliferative ability and smooth muscle [alpha]-actin expression as the collagen-containing extracellular matrix and scar fully matured. However, these same lineage-traced initial fibroblasts persisted within the scar, achieving a new molecular and stable differentiated state referred to as a matrifibrocyte, which was also observed in the scars of human hearts. These cells express common and unique extracellular matrix and tendon genes that are more specialized to support the mature scar., Introduction Fibroblasts are a unique cell type of mesenchymal origin that are present in essentially all tissues and organs, where they regulate extracellular matrix (ECM) production and acute wound healing [...]

Author(s): Zahra Assur Sanghai [1]; Linamarie Miller [1, 2]; Kelly R. Molloy [3]; Jonas Barandun [1]; Mirjam Hunziker [1]; Malik Chaker-Margot [1, 2]; Junjie Wang [3]; Brian T. Chait [3]; [...]

Author(s): Joana Carrelha [1, 2]; Yiran Meng [1, 2]; Laura M. Kettyle [3, 4]; Tiago C. Luis [1, 2]; Ruggiero Norfo [1, 2]; Vernica Alcolea [1, 2]; Hanane Boukarabila [1, [...]

Genetics, experience, environment, and health can all affect the anatomic and physiologic components of the olfactory system and thereby influence olfactory performance. Large individual differences exist among subjects with respect to olfactory sensitivity and identification ability, which may result in both qualitative and quantitative differences in perceptual ability. [ABSTRACT FROM AUTHOR]