Standardization of a silver stain to reveal mesoscale myelin in histological preparations of the mammalian brain.

BACKGROUND: The brain is built of neurons supported by myelin, a fatty substance that improves cellular communication. Noninvasive magnetic resonance imaging (MRI) is now able to measure brain structure like myelin and requires histological validation. NEW METHOD: Here we present work in small and large biomedical model mammals to standardize a silver impregnation method as a high-throughput histological myelin visualization procedure. Specifically, we built a new staining well plate to increase batch size, and then systematically varied the staining and clearing cycles to describe the staining response curve across taxa and conditions. We compared tissues fixed by immersion or perfusion, mounted versus free-floating, and cut as thicker or thinner slices, with two-weeks of post-fixation. RESULTS: The staining response curves show optimal staining with a single exposure across taxa when incubation and clearing epochs are held to within 3-9 min. We show that clearing was slower in mounted vs free-floating tissue, and that staining was faster and caused fracturing earlier in thinner sliced and smaller volumes of tissue. COMPARISON WITH EXISTING METHODS: We developed a batch processing approach to increase throughput while ensuring reproducibility and demonstrate the optimal conditions for fine myelinated fiber morphology visualization with short cycles (<9 minutes). CONCLUSIONS: We present our optimized protocol to reveal mesoscale neuroanatomical myelin content in histology across mammals. This standard staining procedure will facilitate multiscale analyses of myelin content across development as well as in the presence of injury or disease.

Predictions of novel Schistosoma mansoni - human protein interactions consistent with experimental data.

Infection by the human blood fluke, Schistosoma mansoni involves a variety of cross-species protein- protein interactions. The pathogen expresses a diverse arsenal of proteins that facilitate the breach of physical and biochemical barriers present in skin evasion of the immune system, and digestion of human plasma proteins including albumin and hemoglobin, allowing schistosomes to reside in the host for years. However, only a small number of specific interactions between S. mansoni and human proteins have been identified. We present and apply a protocol that generates testable predictions of S. mansoni-human protein interactions. In this study, we have preliminary predictions of novel interactions between schistosome and human proteins relevant to infection and the ability of the parasite to evade the immune system. We applied a computational whole-genome comparative approach to predict potential S. mansoni-human protein interactions based on similarity to known protein complexes. We first predict S. mansoni -human protein interactions based on similarity to known protein complexes. Putative interactions were then scored and assessed using several contextual filters, including the use of annotation automatically derived from literature using a simple natural language processing methodology. Next, in vitro experiments were carried out between schistosome and host proteins to validate several prospective predictions. Our method predicted 7 out of the 10 previously known cross-species interactions involved in pathogenesis between S. mansoni and its human host. Interestingly, two novel putative interactions involving Schistosoma proteins, the cercarial elastase SmCE, and the adult tegument surface protein Sm29, were also predicted and experimentally characterized. Preliminary data suggest that elafin, a host endogenous serine protease inhibitor, may be a novel substrate for SmCE. Additionally, CD59, an inhibitor of the membrane attack complex, could interact with Sm29. Furthermore, the application framework provides an integrated methodology for investigation of host-pathogen interactions and an extensive source of orthogonal data for experimental analysis. We have made the predictions available for community perusal.

The in situ synthesis of PbS nanocrystals from lead(II) n-octylxanthate within a 1,3-diisopropenylbenzene-bisphenol A dimethacrylate sulfur copolymer.

The synthesis of lead sulfide nanocrystals within a solution processable sulfur 'inverse vulcanization' polymer thin film matrix was achieved from the in situ thermal decomposition of lead(II) n-octylxanthate, [Pb(S2COOct)2]. The growth of nanocrystals within polymer thin films from single-source precursors offers a faster route to networks of nanocrystals within polymers when compared with ex situ routes. The 'inverse vulcanization' sulfur polymer described herein contains a hybrid linker system which demonstrates high solubility in organic solvents, allowing solution processing of the sulfur-based polymer, ideal for the formation of thin films. The process of nanocrystal synthesis within sulfur films was optimized by observing nanocrystal formation by X-ray photoelectron spectroscopy and X-ray diffraction. Examination of the film morphology by scanning electron microscopy showed that beyond a certain precursor concentration the nanocrystals formed were not only within the film but also on the surface suggesting a loading limit within the polymer. We envisage this material could be used as the basis of a new generation of materials where solution processed sulfur polymers act as an alternative to traditional polymers.

Recombinant human heterodimeric IL-15 complex displays extensive and reproducible N- and O-linked glycosylation.

Human interleukin 15 (IL-15) circulates in blood as a stable molecular complex with the soluble IL-15 receptor alpha (sIL-15Rα). This heterodimeric IL-15:sIL-15Rα complex (hetIL-15) shows therapeutic potential by promoting the growth, mobilization and activation of lymphocytes and is currently evaluated in clinical trials. Favorable pharmacokinetic properties are associated with the heterodimeric formation and the glycosylation of hetIL-15, which, however, remains largely uncharacterized. We report the site-specific N- and O-glycosylation of two clinically relevant large-scale preparations of HEK293-derived recombinant human hetIL-15. Intact IL-15 and sIL-15Rα and derived glycans and glycopeptides were separately profiled using multiple LC-MS/MS strategies. IL-15 Asn79 and sIL-15Rα Asn107 carried the same repertoire of biosynthetically-related N-glycans covering mostly α1-6-core-fucosylated and ß-GlcNAc-terminating complex-type structures. The two potential IL-15 N-glycosylation sites (Asn71 and Asn112) located at the IL-2 receptor interface were unoccupied. Mass analysis of intact IL-15 confirmed its N-glycosylation and suggested that Asn79-glycosylation partially prevents Asn77-deamidation. IL-15 contained no O-glycans, whereas sIL-15Rα was heavily O-glycosylated with partially sialylated core 1 and 2-type mono- to hexasaccharides on Thr2, Thr81, Thr86, Thr156, Ser158, and Ser160. The sialoglycans displayed α2-3- and α2-6-NeuAc-type sialylation. Non-human, potentially immunogenic glycoepitopes (e.g. N-glycolylneuraminic acid and α-galactosylation) were not displayed by hetIL-15. Highly reproducible glycosylation of IL-15 and sIL-15Rα of two batches of hetIL-15 demonstrated consistent manufacturing and purification. In conclusion, we document the heterogeneous and reproducible N- and O-glycosylation of large-scale preparations of the therapeutic candidate hetIL-15. Site-specific mapping of these molecular features is important to evaluate the consistent large-scale production and clinical efficacy of hetIL-15.

Direct and continuous synthesis of VO2 nanoparticles.

Monoclinic VO2 nanoparticles are of interest due to the material's thermochromic properties, however, direct synthesis routes to VO2 nanoparticles are often inaccessible due to the high synthesis temperatures or long reaction times required. Herein, we present a two-step synthesis route for the preparation of monoclinic VO2 nanoparticles using Continuous Hydrothermal Flow Synthesis (CHFS) followed by a short post heat treatment step. A range of particle sizes, dependent on synthesis conditions, were produced from 50 to 200 nm by varying reaction temperatures and the residence times in the process. The nanoparticles were characterised by powder X-ray diffraction, Raman and UV/Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The nanoparticles were highly crystalline with rod and sphere-like morphologies present in TEM micrographs, with the size of both the rod and spherical particles being highly dependent on both reaction temperature and residence time. SEM micrographs showed the surface of the powders produced from the CHFS process to be highly uniform. The samples were given a short post synthesis heat treatment to ensure that they were phase pure monoclinic VO2, which led to them exhibiting a large and reversible switch in optical properties (at near-IR wavelengths), which suggests that if such materials can be incorporated into coatings or in composites, they could be used for fenestration in architectural applications.

Intramuscular delivery of heterodimeric IL-15 DNA in macaques produces systemic levels of bioactive cytokine inducing proliferation of NK and T cells.

Interleukin-15 (IL-15) is a common γ-chain cytokine that has a significant role in the activation and proliferation of T and NK cells and holds great potential in fighting infection and cancer. We have previously shown that bioactive IL-15 in vivo comprises a complex of the IL-15 chain with the soluble or cell-associated IL-15 receptor alpha (IL-15Rα) chain, which together form the IL-15 heterodimer. We have generated DNA vectors expressing the heterodimeric IL-15 by optimizing mRNA expression and protein trafficking. Repeated administration of these DNA plasmids by intramuscular injection followed by in vivo electroporation in rhesus macaques resulted in sustained high levels of IL-15 in plasma, with no significant toxicity. Administration of DNAs expressing heterodimeric IL-15 also resulted in an increased frequency of NK and T cells undergoing proliferation in peripheral blood. Heterodimeric IL-15 led to preferential expansion of CD8(+)NK cells, all memory CD8(+) T-cell subsets and effector memory CD4(+) T cells. Expression of heterodimeric IL-15 by DNA delivery to the muscle is an efficient procedure to obtain high systemic levels of bioactive cytokine, without the toxicity linked to the high transient cytokine peak associated with protein injection.

A case of progressive multifocal leukoencephalopathy in a lupus patient treated with belimumab.

Belimumab is a monoclonal antibody against soluble B-lymphocyte stimulator, an essential growth factor for B-cell maturation and activation, which was approved by the US FDA in 2011 for patients with active autoantibody-positive systemic lupus erythematosus (SLE) who have failed standard treatment. Here we present the case of a 40-year-old woman with SLE diagnosed with progressive multifocal leukoencephalopathy (PML) on belimumab. After a total of 10 infusions of belimumab, from August 2012 through April 2013, in April 2013 she developed progressive neurologic decline with episodic dystonia and autonomic symptoms. Her imaging showed multifocal, confluent regions of T2 hyperintensity in the white matter bilaterally, and CSF JCV PCR returned positive. Based on the patient's clinically mild SLE and the timing of symptom onset, belimumab likely played a key role in the development of PML. Trials of belimumab for other autoimmune diseases are ongoing; as applications for this novel drug broaden, careful monitoring for this potentially fatal adverse effect is warranted.

Electrosynthesis of Rh2(dpf)4(R) where dpf = N,N'-diphenylformamidinate anion and R = CH3, C2H5, C3H7, C4H9 or C5H11.

The electrosynthesis of Rh(2)(dpf)(4)(R) where dpf is the N,N'-diphenylformamidinate anion and R = CH(3), C(2)H(5), C(3)H(7), C(4)H(9) or C(5)H(11) was carried out in THF containing 0.2 M tetra-n-butylammonium perchlorate (TBAP) and one of several alkyl iodides represented as RI. The initial step in the reaction involved a one-electron reduction of the Rh(2)(4+) unit in Rh(2)(dpf)(4) to its Rh(2)(3+) form followed by a homogeneous reaction involving electrogenerated [Rh(2)(dpf)(4)](-) and the alkyl iodide in solution to give Rh(2)(dpf)(4)(R). The homogeneously generated Rh(2)(5+) product was then immediately reduced by a second electron at the potential where [Rh(2)(dpf)(4)(R)](-) is generated, giving [Rh(2)(dpf)(4)(R)](-) which contains a Rh(2)(4+) center as a final product of an electrochemical ECE mechanism. The electrosynthesized [Rh(2)(dpf)(4)(CH(3))](-) derivative could be reoxidized to Rh(2)(dpf)(4)(CH(3)) on the reverse potential sweep and both forms of the CH(3) bonded derivative were in situ characterized by cyclic voltammetry combined with UV-visible and/or ESR spectroscopy. The reversible Rh(2)(4+/3+) process of Rh(2)(dpf)(4) is located at E(1/2) = -1.11 V in THF, 0.2 M TBAP while the electrogenerated Rh(2)(dpf)(4)(R) products are substantially easier to reduce, with E(p) values for the Rh(2)(5+/4+) couples ranging from -0.50 to -0.54 V vs. SCE depending upon the specific R group.

Molecular mechanism underlying the association of Coronin-7 with Golgi membranes.

Coronin-7 (Crn7) is a ubiquitous mammalian WD40-repeat protein that localizes to the Golgi complex, interacts with AP-1 adaptor complex via binding of a tyrosine-288-based sorting signal to the mu1-subunit of AP-1, and participates in the maintenance of the Golgi structure and function. Here, we define the requirements for the recruitment of Crn7 from the cytosol to the Golgi. We establish that Src activity is indispensable for the interaction of Crn7 with Golgi membranes. Crn7 binds Src in vivo and can be phosphorylated by recombinant Src in vitro. We demonstrate that tyrosine-758 is the major Src phosphorylation site. Further, to be targeted to membranes Crn7 requires the presence of cargo in the Golgi complex. Finally, downregulation of the mu1-subunit of AP-1 leads to the dispersal of Crn7 from the Golgi membranes. We propose a mechanism whereby sequential events of protein interaction and posttranslational modification result in the membrane targeting of Crn7.

Heparin-binding and patterns of virulence for two recombinant strains of Sindbis virus.

E2 is an important determinant of Sindbis virus neurovirulence. Increased heparan sulfate (HS) binding is associated with rapid clearance of viremia and usually with decreased virulence. However, substitution of histidine for arginine at E2-157 (R157H) or glutamate for lysine at E2-159 (K159E) produces viruses with decreases in heparin-Sepharose binding and increases in viremia but different levels of binding to HS-expressing cells and virulence phenotypes in newborn CD-1 mice (Byrnes, A.P., Griffin, D.E., 2000. Large-plaque mutants of Sindbis virus show reduced binding to heparan sulfate, heightened viremia and slower clearance from the circulation. J. Virol. 74, 644-651). To identify mechanisms of virulence, R157H and K159E were studied in newborn CD-1 and BALB/c mice. Subcutaneous inoculation of R157H caused 100% and K159E 60% mortality in 2-day-old CD-1 mice. R157H caused 25% and K159E no mortality in 2-day-old BALB/c mice. R157H and K159E replicated similarly at the site of inoculation with the same level of viremia, but clearance was slower in CD-1 than BALB/c mice. R157H replicated better than K159E in the central nervous system (CNS) after subcutaneous and intracerebral inoculation and in undifferentiated neurons. These studies show a genetic restriction of replication in newborn BALB/c mice, and that amino acid substitutions affecting binding to proteoglycans may differ in importance for CNS infection and viremia.

The WASp-like protein scar regulates macropinocytosis, phagocytosis and endosomal membrane flow in Dictyostelium.

Scar, a member of the WASp protein family, was discovered in Dictyostelium discoideum during a genetic screen for second-site mutations that suppressed a developmental defect. Disruption of the scar gene reduced the levels of cellular F-actin by 50%. To investigate the role of Scar in endocytosis, phagocytosis and endocytic membrane trafficking, processes that depend on actin polymerization, we have analyzed a Dictyostelium cell line that is genetically null for Scar. Rates of fluid phase macropinocytosis and phagocytosis are significantly reduced in the scar- cell-line. In addition, exocytosis of fluid phase is delayed in these cells and movement of fluid phase from lysosomes to post-lysosomes is also delayed. Inhibition of actin polymerization with cytochalasin A resulted in similar phenotypes, suggesting that Scar-mediated polymerization of the actin cytoskeleton was important in the regulation of these processes. Supporting this conclusion, fluorescence microscopy revealed that some endo-lysosomes were ringed with F-actin in control cells but no F-actin was detected associated with endo-lysosomes in Scar null cells. Disruption of the two genes encoding the actin monomer sequestering protein profilin in wild-type cells causes defects in the rate of pinocytosis and fluid phase efflux. Consistent with a predicted physical interaction between Scar and profilin, disrupting the scar gene in the profilin null background results in greater decreases in the rate of fluid phase internalization and fluid phase release compared to either mutant alone. Taken together, these data support a model in which Scar and profilin functionally interact to regulate internalization of fluid and particles and later steps in the endosomal pathway, probably through regulation of actin cytoskeleton polymerization.

Non-aqueous-phase-liquid breakthrough during evaporative drying of clay barriers.

In this study, an attempt has been made to model a real field scenario, whereby an initially almost saturated clay liner in a waste site is gradually drying, due to evaporation at its lower boundary. A detailed conceptual model that deals with the penetration and breakthrough of non-aqueous-phase-liquid (NAPL) in clay liners is introduced. Water content of clay samples was monitored during ambient evaporation through apertures at the base of sample holders. Clay drying rate served as the primary parameter for the NAPL breakthrough study. The interconnection between drying rates, structural damage formation (cracks and suction) and NAPL penetration is especially addressed. The processes taking place in the clay samples during drying appear to be associated with the capillary effects between the different fluid phases in the vicinity of either the NAPL-clay or the clay-air boundaries. A conceptual model of NAPL penetration and breakthrough of the clay layer has been considered, based on both indirect and direct observations of structural damages produced on either clay boundaries. A mutual interaction between these two boundaries is suggested and discussed. NAPL breakthrough is suggested to take place through cracks initiated on the upper soil surface.

Synthesis, electrochemistry, and spectroscopic characterization of bis-dirhodium complexes linked by axial ligands.

The synthesis and electrochemical and spectroscopic properties of bis-dirhodium complexes containing ap or dpf bridging ligands, (ap)(4)Rh(2)(C triple bond C)(2)Rh(2)(ap)(4) (2) and (dpf)(4)Rh(2)(CNC(6)H(4)NC)Rh(2)(dpf)(4) (4), were investigated (where ap and dpf are the 2-anilinopyridinate and N,N'-diphenylformamidinate ions, respectively). The related "simple" dirhodium species, (ap)(4)Rh(2)(C triple bond C)(2)Si(CH(3))(3) (1) and (dpf)(4)Rh(2)(CNC(6)H(5)) (3), with the same set of bridging ligands were also synthesized and their properties compared to those of the analogous bis-dirhodium complexes. Compound 1 was obtained by mixing (ap)(4)Rh(2)Cl and Li(C triple bond C)(2)Si(CH(3))(3) in refluxing THF for 16 h under vacuum while compound 2 was prepared by a reaction between (ap)(4)Rh(2)(C triple bond C)(2)Li and (ap)(4)Rh(2)Cl under similar conditions. The reaction between (CF(3)COO)(4)Rh(2) and molten Hdpf under vacuum for 24 h leads to the generation of compound 3 with a yield of 65%. The red-orange compound 4 was obtained upon addition of 0.5 equiv of CNC(6)H(4)NC at room temperature to a CH(2)Cl(2) solution containing (dpf)(4)Rh(2) which was synthesized according to a method described previously in the literature. Compound 1 crystallizes in the triclinic space group P1, with a = 10.164(3) A, b = 13.881(3) A, c = 18.805(4) A, alpha = 73.55(2) degrees, beta = 77.89(2) degrees, gamma = 84.85(2) degrees, and Z = 2. Crystals of 2 were not good enough to collect adequate data for X-ray analysis, but the identity of this compound was confirmed, along with its P1; space group. Crystals of 3 and 4 belong to the monoclinic, P2(1)/c space group and the triclinic, P1; space group, respectively, with a = 13.5254(5) A, b = 13.7387(4) A, c = 27.2011(12) A, beta = 102.637(2) degrees, and Z = 4 for 3 and a = 13.866(8) A, b = 14.756(7) A, c = 15.008(6) A, alpha = 79.91(3) degrees, beta = 87.72(4) degrees, gamma = 89.19(4) degrees, and Z = 1 for 4. Compound 1 exhibits a single reversible oxidation at E(1/2) = 0.66 V and a single reversible reduction at E(1/2) = -0.44 V vs SCE in THF, 0.2 M TBAP. Both processes involve a one-electron transfer. Compound 2 undergoes a reversible oxidation at E(1/2) = 0.60 V and two separate one-electron-transfer reductions at E(1/2) = -0.52 and -0.65 V in THF, 0.2 M TBAP. The oxidation involves two overlapped one-electron-transfer processes. Compounds 3 and 4 undergo two reversible oxidations in CH(2)Cl(2), 0.1 M TBAP located at E(1/2) = 0.23 and 1.22 V (3) or 0.22 and 1.20 V (4). Each redox reaction of 3 involves a one-electron-transfer step while each redox reaction of 4 involves two overlapping one-electron transfers. Compound 2 shows interaction between the two dirhodium cores upon reduction, while 4 gives no evidence of electronic interaction between the two dirhodium units during either reduction or oxidation. An ESR signal with axial symmetry was obtained for the neutral compounds 1 and 2, and a similar spectrum was obtained for the singly oxidized products of compounds 3 and 4, thus suggesting the electronic configuration of (sigma)(2)(pi)(4)(delta)(2)(pi)(4)(delta)(1) for the neutral compounds 1 and 2 as well as for the oxidized compounds 3 and 4. The four compounds were also characterized by FTIR and UV-visible spectroscopy as well as by mass spectrometry.

Syntheses, structural determination, and electrochemistry of Ru(2)(Fap)(4)Cl and Ru(2)(Fap)(4)(NO)Cl.

Ru(2)(Fap)(4)Cl and Ru(2)(Fap)(4)(NO)Cl, where Fap is the 2-(2-fluoroanilino)pyridinate anion, were synthesized, and their structural, electrochemical, and spectroscopic properties were characterized. Ru(2)(Fap)(4)Cl, which was obtained by reaction between Ru(2)(O(2)CCH(3))(4)Cl and molten HFap, crystallizes in the monoclinic space group P2(1)/c, with a = 11.2365(4) A, b = 19.9298(8) A, c = 19.0368(7) A, beta = 90.905(1) degrees, and Z = 4. The presence of three unpaired electrons on the Ru(2)(5+) core and the 2.2862(3) A Ru-Ru bond length for Ru(2)(Fap)(4)Cl are consistent with the electronic configuration (sigma)(2)(pi)(4)(delta)(2)(pi*)(2)(delta*)(1). The reaction between Ru(2)(Fap)(4)Cl and NO gas yields Ru(2)(Fap)(4)(NO)Cl, which crystallizes in the orthorhombic space group Pbca, with a = 10.0468(6) A, b = 18.8091(10) A, c = 41.7615(23) A, and Z = 8. The Ru-Ru bond length of Ru(2)(Fap)(4)(NO)Cl is 2.4203(8) A, while its N-O bond length and Ru-N-O bond angle are 1.164(8) A and 155.8(6) degrees, respectively. Ru(2)(Fap)(4)(NO)Cl can be formulated as a formal Ru(2)(II,II)(NO(+)) complex with a linear Ru-N-O group, and the proposed electronic configuration for this compound is (sigma)(2)(pi)(4)(delta)(2)(pi*)(3)(delta*)(1). The binding of NO to Ru(2)(Fap)(4)Cl leads to some structural changes of the Ru(2)(Fap)(4) framework and a stabilization of the lower oxidation states of the diruthenium unit. Also, IR spectroelectrochemical studies of Ru(2)(Fap)(4)(NO)Cl show that NO remains bound to the complex upon reduction and that the first reduction involves the addition of an electron on the diruthenium core and not on the NO axial ligand.

Rotavirus encephalopathy: pathogenesis reviewed.

Two cases of rotavirus gastroenteritis associated with neurological involvement, one with encephalitis (defined by abnormal neurological signs, cerebrospinal fluid (CSF) pleocytosis and detection of rotavirus genomic nucleic acid in the CSF) and one with a non-inflammatory encephalopathy (defined by abnormal neurological signs, an entirely normal CSF and detection of rotavirus genomic nucleic acid in the CSF), are presented and used as a basis to review and explore potential pathogenetic mechanisms, including direct viral replication within neurons and indirect effects of the newly described rotavirus 'enterotoxin'.

Identification of a novel posttranscriptional regulatory element by using a rev- and RRE-mutated human immunodeficiency virus type 1 DNA proviral clone as a molecular trap.

Human immunodeficiency virus (HIV) and all other lentiviruses utilize the essential viral protein Rev, which binds to RRE RNA, to export their unspliced and partially spliced mRNAs from the nucleus. We used a rev- and RRE-defective HIV type 1 (HIV-1) molecular clone in complementation experiments to establish a method for the rapid isolation of posttranscriptional regulatory elements from the mammalian genome by selecting for rescue of virus replication. Viruses rescued by this method contained a novel element with homology to rodent intracisternal A-particle (IAP) retroelements. A functional element was contained within a 247-nucleotide fragment named RNA transport element (RTE), which was able to promote replication of the Rev- and RRE-defective HIV-1 in both human lymphoid cell lines and primary lymphocytes, demonstrating its potent posttranscriptional function. RTE was functional in many cell types, indicating that the cellular factors that recognize RTE are widely expressed and evolutionarily conserved. RTE also promoted RNA export from Xenopus oocyte nuclei. RTE-mediated RNA transport was CRM1 independent, and RTE did not show high affinity for binding to mRNA export factor TAP/NXF1. Since CRM1 and TAP/NXF1 are critical export receptors associated with the two recognized mRNA export pathways, these results suggest that RTE functions via a distinct export mechanism. Taken together, our results identify a novel posttranscriptional control element that uses a conserved cellular export mechanism.

Regulating cellular actin assembly.

Cellular actin assembly is tightly regulated. The study of pathogen motility has led to the identification of several cellular factors that are critical for controlling this process. Pathogens such as Listeria require Ena/VASP and Arp2/3 proteins to translate actin polymerization into movement. Recent work has extended these observations and uncovered some similarities and surprising differences in the way cells and pathogens utilize the actin cytoskeleton.