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Centrosomes are the major microtubule organising centres of animal cells. Deregulation in their number occurs in cancer and was shown to trigger tumorigenesis in mice. However, the incidence, consequence and origins of this abnormality are poorly understood. Here, we screened the NCI-60 panel of human cancer cell lines to systematically analyse centriole number and structure. Our screen shows that centriole amplification is widespread in cancer cell lines and highly prevalent in aggressive breast carcinomas. Moreover, we identify another recurrent feature of cancer cells: centriole size deregulation. Further experiments demonstrate that severe centriole over-elongation can promote amplification through both centriole fragmentation and ectopic procentriole formation. Furthermore, we show that overly long centrioles form over-active centrosomes that nucleate more microtubules, a known cause of invasiveness, and perturb chromosome segregation. Our screen establishes centriole amplification and size deregulation as recurrent features of cancer cells and identifies novel causes and consequences of those abnormalities. Cancer cells are characterised by abnormalities in the number of centrosomes and this phenotype is linked with tumorigenesis. Here the authors report centriole length deregulation in a subset of cancer cell lines and suggest a link with subsequent alterations in centriole numbers and chromosomal instability.

Bacillus thuringiensis (Bt) bacteria produce different pore forming toxins with insecticidal activity, including Cry and Vip3 proteins. While both Cry and Vip3 cause insect death by forming pores in susceptible lepidopteran larval midgut cells, their mechanisms of action differ. The Vip3Aa protoxin adopts a tetramer-structure, where each monomer has five distinct domains. Upon proteolytic activation, the Vip3 tetramer undergoes a large conformational change forming a syringe like structure that is ready for membrane insertion and pore formation. Here we show that Vip3Aa protoxin had low binding to Spodoptera frugiperda brush border membrane vesicles (BBMV) unlike the activated toxin that bound specifically in a concentration dependent way, suggesting that a structural change upon Vip3Aa proteolytic activation is required for efficient receptor binding. Consistently, the Vip3Aa protoxin showed no toxicity to Sf9 cells compared to the activated toxin. In contrast, Cry1Fa protoxin and its activated toxin, were both highly toxic to Sf9 cells. To identify the region of Vip3 involved in binding to BBMV proteins, different overlapping peptides from Vip3Aa covering domains III, IV and V were expressed, and binding analysis were performed against BBMV, showing that domain III is the primary binding domain. Additionally, domains III, IV and V amino acid residues that become exposed upon activation of Vip3Aa were identified. Mutagenesis of these exposed residues revealed three amino acids (K385, K526 and V529) located in two structural adjacent loops, domain III loop β5-β6 and loop α11-β16 that connects domains III and IV, that are crucial for binding to the midguts of S . frugiperda larvae and for toxicity. Our results demonstrate that proteolytic activation of Vip3Aa exposes a receptor binding region essential for its toxicity.

Wound healing is a biological process that requires a complex regulation to maintaining the function of skin. However, many factors can alter this process, resulting in non-healing wounds. An option for the treatment of this kind of wound is the use of stem cell secretome (S), since it has been shown that it promotes the tissue repair-regeneration processes. For this reason, this work focused on develop a polymeric matrix in hydrogel state, based on jellyfish collagen (CLG), polyurethane and S from mesenchymal stem cells (MSCs) from human amniotic membrane, and its in vitro evaluation in wound closure. Two types of polyurethane matrix were analyzed; the first one was crosslinking with polyurethane derived from hexamethylene diisocyanate (HDI), and the second one was crosslinking with polyurethane derived from isophorone diisocyanate (IPDI), giving rise to two different polymeric matrices, CLG-P(HDI)-S and CLG-P(IPDI)-S containing 0.5 wt.% of S for each matrix. The results suggest that the incorporation to S in the polymeric matrices generates interactions in the hydrogel state matrices, promoting amorphous surfaces, which seems to indicate that the S is encapsulated by physical or electrostatic interactions with polymeric chains. The CLG-P(HDI)-S showed a spherical structure, while the CLG-P(IPDI)-S exhibited a planar structure, which is related to the chemical structure of polyurethane crosslinker, these structural characteristics gave the polymeric matrices, suitable physicochemical, mechanical and biological properties for accelerating the wound healing process in an in vitro scratch assay, and thus could be a promising scaffold for wound management for non-healing wounds. Graphical abstract

Key Points Polo-like kinases (PLKs) are a family of Ser/Thr kinases that have a pivotal role in cell cycle progression, the centrosome cycle, mitosis and cellular responses to DNA damage, which makes them attractive targets for treatments against several diseases. PLK1 is the most ancestral and best-conserved member of the family; it is found in most eukaryotic organisms, except for higher land plants. PLK4 is the most divergent member of the family. PLK2, PLK3 and PLK5 have evolved very recently, probably from a PLK1 gene duplication in vertebrates. PLK1 and PLK4 have distinct structural organizations and are phosphorylated at different residues, which correlate with different mode of actions. The amino-terminal kinase domain and carboxy-terminal polo box domains that characterize PLKs are crucial for regulation of their kinase catalytic activity in time and space, and for controlling subcellular PLK localization. Recent studies show non-canonical functions for PLKs in asymmetric cell division and cilia disassembly. PLKs function in centriole and centrosome biogenesis; PLK1 integrates various external stimuli with cell cycle inputs to coordinate mitotic progression and the centrosome cycle, whereas PLK4 drives centriole assembly. PLK2 and PLK3 have roles in DNA replication and in the DNA damage response and are also expressed in non-proliferative tissues, in which they have a role in cell differentiation and homeostasis (for example, PLK2 and PLK5 regulate neuronal activity). Members of the polo-like kinase (PLK) family are crucial regulators of cell cycle progression, centriole duplication, mitosis, cytokinesis and the DNA damage response. Recent structural and molecular studies have revealed how such processes depend on the tight regulation of PLK abundance, activity, localization and interactions with other proteins, and how dysregulation may be associated with disease. Members of the polo-like kinase (PLK) family are crucial regulators of cell cycle progression, centriole duplication, mitosis, cytokinesis and the DNA damage response. PLKs undergo major changes in abundance, activity, localization and structure at different stages of the cell cycle. They interact with other proteins in a tightly controlled spatiotemporal manner as part of a network that coordinates key cell cycle events. Their essential roles are highlighted by the fact that alterations in PLK function are associated with cancers and other diseases. Recent knowledge gained from PLK crystal structures, evolution and interacting molecules offers important insights into the mechanisms that underlie their regulation and activity, and suggests novel functions unrelated to cell cycle control for this family of kinases.

The modification of collagen derived from jellyfish to generate hydrogels with high biocompatibility is in recent trend, since this type of collagen does not present allergenic effects or transmission of zoonosis in humans. Therefore, developing novel strategies that allow tailoring their properties for regenerative medicine and biomedical applications is a current research challenge. In this work, the generation of interpenetrating polymeric matrices (IPN) in the hydrogel state composed of jellyfish collagen ( C. andromeda ) and polyurethane is proposed; for this, dispersions of trifunctional polyurethane prepolymers (TPU) derived from glycerol ethoxylate and hexamethylene diisocyanate (P(HDI)) or isophorone diisocyanate (P(IPDI)) are used as interpenetrating agents for marine collagen chains. The evaluation of the structural modification produced by the chemical structure of the TPU on the properties and the in vitro biocompatibility of the matrices in the hydrogel state is addressed. The results indicate that IPN hydrogels based on P(HDI) show a structure based on microspheric agglomerates with interconnected porosity, while those generated from P(IPDI) exhibit a smooth structure with irregular porosity. The interpenetration of jellyfish collagen with P(HDI) produces an improvement in the storage modulus of 16,972%, enhancing the swelling in acidic, physiological and basic media; as well as delaying proteolytic degradation. Both novel matrices do not present cytotoxic effects for monocytes and fibroblasts, evaluated for up to 48 h of incubation, indicating that they have excellent in vitro biocompatibility, in addition they present enhanced hemocompatility and capacity to inhibit the growth of E. coli ; due to this, these matrices in hidrogel state can be applied in strategies for the design of dressings for regenerative medicine applications.

The preparation of hydrogels based on biopolymers like collagen and gum arabic gives a chance to provide novel options that can be used in biomedical field. Through a polymeric semi-interpenetration technique, collagen-based polymeric matrices can be associated with gum arabic while controlling its physicochemical and biological properties. To create novel hydrogels with their potential use in the treatment of wounds, the semi-interpenetration process, altering the concentration (0–40% by wt) of gum arabic in a collagen matrix is explored. The ability of gum arabic to create intermolecular hydrogen bonds in the collagen matrix enables the development of semi-interpenetrating polymeric networks (semi-IPN)-based hydrogels with a faster gelation time and higher crosslinking. Amorphous granular surfaces with linked porosity are present in matrices with 30% (by wt) of gum arabic, enhancing the storage modulus and thermal degradation resistance. The hydrogels swell to very high extent in hydrolytic and proteolytic environments, good hemocompatibility, and suppression of growth of pathogens like E. coli, and all it is enhanced by gum arabic included them, in addition to enabling the controlled release of ketorolac. The chemical composition of theses semi-IPN matrices have no deleterious effects on monocytes or fibroblasts, promoting their proliferation, and lowering alpha tumor necrosis factor (α-TNF) secretion in human monocytes. Graphical abstract

Humans and other vertebrates define body axis left-right asymmetry in the early stages of embryo development. The mechanism behind left-right establishment is not fully understood. Symmetry breaking occurs in a dedicated organ called the left-right organizer (LRO) and involves motile cilia generating fluid-flow therein. However, it has been a matter of debate whether the process of symmetry breaking relies on a chemosensory or a mechanosensory mechanism (Shinohara et al., 2012). Novel tailored manipulations for LRO fluid extraction in living zebrafish embryos allowed us to pinpoint a physiological developmental period for breaking left-right symmetry during development. The shortest critical time-window was narrowed to one hour and characterized by a mild counterclockwise flow. The experimental challenge consisted in emptying the LRO of its fluid, abrogating simultaneously flow force and chemical determinants. Our findings revealed an unprecedented recovery capacity of the embryo to re-fil and re-circulate new LRO fluid. The embryos that later developed laterality problems were found to be those that had lower anterior angular velocity and thus less anterior-posterior heterogeneity. Next, aiming to test the presence of any secreted determinant, we replaced the extracted LRO fluid by a physiological buffer. Despite some transitory flow homogenization, laterality defects were absent unless viscosity was altered, demonstrating that symmetry breaking does not depend on the nature of the fluid content but is rather sensitive to fluid mechanics. Altogether, we conclude that the zebrafish LRO is more sensitive to fluid dynamics for symmetry breaking.

Mammalian sperm delve into the female reproductive tract to fertilize the female gamete. The available information about how sperm regulate their motility during the final journey to the fertilization site is extremely limited. In this work, we investigated the structural and functional changes in the sperm flagellum after acrosomal exocytosis (AE) and during the interaction with the eggs. The evidence demonstrates that the double helix actin network surrounding the mitochondrial sheath of the midpiece undergoes structural changes prior to the motility cessation. This structural modification is accompanied by a decrease in diameter of the midpiece and is driven by intracellular calcium changes that occur concomitant with a reorganization of the actin helicoidal cortex. Midpiece contraction occurs in a subset of cells that undergo AE, and live-cell imaging during in vitro fertilization showed that the midpiece contraction is required for motility cessation after fusion is initiated. These findings provide the first evidence of the F-actin network’s role in regulating sperm motility, adapting its function to meet specific cellular requirements during fertilization, and highlighting the broader significance of understanding sperm motility.

The insecticidal Cry11Aa and Cyt1Aa proteins are produced by Bacillus thuringiensis as crystal inclusions. They work synergistically inducing high toxicity against mosquito larvae. It was proposed that these crystal inclusions are rapidly solubilized and activated in the gut lumen, followed by pore formation in midgut cells killing the larvae. In addition, Cyt1Aa functions as a Cry11Aa binding receptor, inducing Cry11Aa oligomerization and membrane insertion. Here, we used fluorescent labeled crystals, protoxins or activated toxins for in vivo localization at nano-scale resolution. We show that after larvae were fed solubilized proteins, these proteins were not accumulated inside the gut and larvae were not killed. In contrast, if larvae were fed soluble non-toxic mutant proteins, these proteins were found inside the gut bound to gut-microvilli. Only feeding with crystal inclusions resulted in high larval mortality, suggesting that they have a role for an optimal intoxication process. At the macroscopic level, Cry11Aa completely degraded the gastric caeca structure and, in the presence of Cyt1Aa, this effect was observed at lower toxin-concentrations and at shorter periods. The labeled Cry11Aa crystal protein, after midgut processing, binds to the gastric caeca and posterior midgut regions, and also to anterior and medium regions where it is internalized in ordered “net like” structures, leading finally to cell break down. During synergism both Cry11Aa and Cyt1Aa toxins showed a dynamic layered array at the surface of apical microvilli, where Cry11Aa is localized in the lower layer closer to the cell cytoplasm, and Cyt1Aa is layered over Cry11Aa. This array depends on the pore formation activity of Cry11Aa, since the non-toxic mutant Cry11Aa-E97A, which is unable to oligomerize, inverted this array. Internalization of Cry11Aa was also observed during synergism. These data indicate that the mechanism of action of Cry11Aa is more complex than previously anticipated, and may involve additional steps besides pore-formation activity.

Spermatozoa of marine invertebrates are attracted to their conspecific female gamete by diffusive molecules, called chemoattractants, released from the egg investments in a process known as chemotaxis. The information from the egg chemoattractant concentration field is decoded into intracellular Ca2+ concentration ([Ca2+]i) changes that regulate the internal motors that shape the flagellum as it beats. By studying sea urchin species-specific differences in sperm chemoattractant-receptor characteristics we show that receptor density constrains the steepness of the chemoattractant concentration gradient detectable by spermatozoa. Through analyzing different chemoattractant gradient forms, we demonstrate for the first time that Strongylocentrotus purpuratus sperm are chemotactic and this response is consistent with frequency entrainment of two coupled physiological oscillators: i) the stimulus function and ii) the [Ca2+]i changes. We demonstrate that the slope of the chemoattractant gradients provides the coupling force between both oscillators, arising as a fundamental requirement for sperm chemotaxis.