Modulation of DNA conformation in electrolytic nanodroplets.

The behavior of deoxyribonucleic acid (DNA) molecules in confinement is of profound importance in various bioengineering and medical applications. In the present study, all-atom molecular dynamics simulation is utilized to investigate the transition of the double-strand DNA (dsDNA) conformation in the electrolytic nanodroplet. Three typical conformations, i.e., C-shaped, folded S-shaped, and double C-shaped, are observed for different droplet sizes and ionic concentrations. To reveal the physics underlying this phenomenon, the characteristics of the dsDNA molecules, such as the overcharging intensity, the end-to-end distance, the radius of gyration, etc. are analyzed in detail based on the numerical results. It is found that the transition can be ascribed to the buckling of the polymer molecules under the compression due to the confinement of the nanodroplet, and it can be modulated by the ionic concentration in the electrolyte. Generally, nanoscale confinement dominates dsDNA behavior over the electrostatic effects in smaller nanodroplets, while the latter becomes more important for larger nanodroplets. This competition results in the persistence length increasing with the nanodroplet radii. Based on these discussions, a non-dimensional elasto-capillary number µ is proposed to classify the dsDNA conformations into three regions.

Investigating the Regulation of Neural Differentiation and Injury in PC12 Cells Using Microstructure Topographic Cues.

In this study, we designed and manufactured a series of different microstructure topographical cues for inducing neuronal differentiation of cells in vitro, with different topography, sizes, and structural complexities. We cultured PC12 cells in these microstructure cues and then induced neural differentiation using nerve growth factor (NGF). The pheochromocytoma cell line PC12 is a validated neuronal cell model that is widely used to study neuronal differentiation. Relevant markers of neural differentiation and cytoskeletal F-actin were characterized. Cellular immunofluorescence detection and axon length analysis showed that the differentiation of PC12 cells was significantly different under different isotropic and anisotropic topographic cues. The expression differences of the growth cone marker growth-associated protein 43 (GAP-43) and sympathetic nerve marker tyrosine hydroxylase (TH) genes were also studied in different topographic cues. Our results revealed that the physical environment has an important influence on the differentiation of neuronal cells, and 3D constraints could be used to guide axon extension. In addition, the neurotoxin 6-hydroxydopamine (6-OHDA) was used to detect the differentiation and injury of PC12 cells under different topographic cues. Finally, we discussed the feasibility of combining the topographic cues and the microfluidic chip for neural differentiation research.

A potential barrier in the diffusion of nanoparticles in ordered polymer networks.

Diffusion of nanoparticles (NPs) in a polymer matrix is of significant importance in diverse research fields, such as bio-engineering and nano-technology. Although the prediction of the effective diffusivity has been extensively explored, it remains a great challenge for theoretical investigation. In the present study, the single-particle Dissipative Particle Dynamics (DPD) is employed to study the diffusion of nanoparticles in an unentangled ordered polymer network. To explore the main mechanism of the diffusion of nanoparticles, detailed microscopic information of the interaction between the polymer and nanoparticles is analyzed, in which the deformation of the network due to crosslink deviation induced by nanoparticle squeezing is observed, and the failed hopping or bounce-back of a nanoparticle can be identified based on its trajectories. It is suggested that, besides the potential well trapping the NPs due to the network, an additional energy induced by the deformation of the local structure of the polymer network during failed hopping should be included in constructing the potential barrier. Then the Nonlinear Langevin equation (NLE) and Kramer's theory are utilized to predict the effective diffusivity DL using the modified potential well. It is found that the theoretical prediction of diffusivity based on this idea is in good agreement with the simulation results of DPD. This study might be helpful for extending our understanding of the diffusion of nanoparticles in complex environments.

Positive feedback of SuFu negating protein 1 on Hedgehog signaling promotes colorectal tumor growth.

Hedgehog (Hh) signaling plays a critical role in embryogenesis and tissue homeostasis, and its deregulation has been associated with tumor growth. The tumor suppressor SuFu inhibits Hh signaling by preventing the nuclear translocation of Gli and suppressing cell proliferation. Regulation of SuFu activity and stability is key to controlling Hh signaling. Here, we unveil SuFu Negating Protein 1 (SNEP1) as a novel Hh target, that enhances the ubiquitination and proteasomal degradation of SuFu and thus promotes Hh signaling. We further show that the E3 ubiquitin ligase LNX1 plays a critical role in the SNEP1-mediated degradation of SuFu. Accordingly, SNEP1 promotes colorectal cancer (CRC) cell proliferation and tumor growth. High levels of SNEP1 are detected in CRC tissues and are well correlated with poor prognosis in CRC patients. Moreover, SNEP1 overexpression reduces sensitivity to anti-Hh inhibitor in CRC cells. Altogether, our findings demonstrate that SNEP1 acts as a novel feedback regulator of Hh signaling by destabilizing SuFu and promoting tumor growth and anti-Hh resistance.

USP33 regulates c-Met expression by deubiquitinating SP1 to facilitate metastasis in hepatocellular carcinoma.

AIMS: Deubiquitinase ubiquitin-specific protease 33 (USP33) is abnormally expressed in various tumors and participates in tumor progression. However, the expression and biological role of USP33 in hepatocellular carcinoma (HCC) are still unclear. MAIN METHODS: We performed immunohistochemistry, western blotting, and qRT-PCR analysis to determine the expression of USP33 in HCC. We then analyzed the effects of USP33 expression on the prognosis of HCC. The roles of USP33 in regulating HCC cell migration and invasion were further explored in vitro. Animal studies were performed to investigate the effects of USP33 on tumor metastasis. RNA sequencing and luciferase reporter and immunofluorescence assays were used to identify the activation of the specificity protein 1 (SP1)/c-Met axis. KEY FINDINGS: Here, for the first time, we reported an abnormal increase in the expression of USP33 in HCC tissues and that USP33 may act as a prognostic biomarker for HCC patients. We found that USP33 knockdown inhibited the invasion and metastasis in HCC cells both in vitro and in vivo, which was partly dependent on c-Met. Further investigations revealed that USP33 regulated c-Met expression by enhancing the protein stability of the transcription factor SP1 in HCC cells. Mechanistically, USP33 directly bound SP1 and decreased its ubiquitination, thereby upregulating c-Met expression. SIGNIFICANCE: Our results reveal that USP33 acts as the deubiquitinating enzyme of SP1 and contributes to HCC invasion and metastasis through activation of the SP1/c-Met axis. These data indicate a previously unknown function of USP33, which may provide potential targets for the treatment of HCC patients.

The critical role of dysregulated Hh-FOXM1-TPX2 signaling in human hepatocellular carcinoma cell proliferation.

BACKGROUND: Aberrant activation of the Hedgehog (Hh) signaling pathway is frequently observed in hepatocellular carcinoma (HCC), nevertheless, the precise molecular mechanism remains unclear. Forkhead box M1 (FOXM1), a target of the Hh pathway, is a key oncofetal transcription factor and a master cell cycle regulator. Targeting protein for Xenopus kinesin-like protein 2 (TPX2) is an oncogene critical for mitosis. However, how these molecular events affect HCC progression remains unclear. METHODS: Realtime PCR, immunohistochemistry, western blotting, and analyses of datasets TCGA and Gene Expression Omnibus (GEO) were conducted to assess the expression of TPX2 and FOXM1 at the mRNA and protein levels in HCC samples or HCC cells. Expression and knockdown of TPX2 and FOXM1 were performed to assess their role in regulating HCC cell proliferation in vitro and in vivo. Dual luciferase report assay and chromosome immunoprecipitation (ChIP) were investigated to seek the FOXM1 binding sites in the promoter of TPX2. RESULTS: Specific antagonists (cyclopamine and GANT61) of the Hh pathway down-regulated TPX2, whereas activation of Hh signaling stimulated TPX2 expression. Furthermore, TPX2 over-expression accelerated HCC cell proliferation when upstream events of Hh signaling were inhibited, and TPX2 knockdown significantly alleviated Sonic Hh ligand (Shh)-induced HCC cell proliferation. Reporter assays and ChIP showed that FOXM1 bound to the TPX2 promoter, confirming that TPX2 is a direct downstream target of FOXM1. Xenograft model further verified the cell function and expression regulation of TPX2 and FOXM1 in vivo. Furthermore, FOXM1 regulated TPX2 activity to drive HCC proliferation. Immunohistochemical (IHC) analysis indicated that FOXM1 and TPX2 were highly-expressed in HCC samples and cohort study revealed that FOXM1 and TPX2 may act as negative predictors for the prognosis of patients with HCC. CONCLUSIONS: TPX2 acts as a novel downstream target and effector of the Hh pathway, and Hh signaling contributes to HCC proliferation via regulating the FOXM1-TPX2 cascade, suggesting that this signaling axis may be a novel therapeutic target for HCC.

PRMT2 accelerates tumorigenesis of hepatocellular carcinoma by activating Bcl2 via histone H3R8 methylation.

Protein arginine methyltransferases (PRMTs) have been implicated in the development of various cancers. PRMT2, a member of the type I PRMT family, is overexpressed in multiple tumors. However, the expression and role of PRMT2 in hepatocellular carcinoma (HCC) have not been studied. Here, we discovered that PRMT2 expression is elevated in HCC tissues compared to the corresponding non-tumor tissues, and PRMT2 overexpression is an independent predictor of poor prognosis in HCC patients. Depletion of PRMT2 in HCC cell lines inhibited their cell growth and induced apoptosis. Mechanistic investigations showed that PRMT2 is responsible for H3R8 asymmetric methylation (H3R8me2a). H3R8me2a enrichment at the Bcl2 promoter increases its accessibility to STAT3, promoting Bcl2 gene expression. In addition, our results confirmed that the catalytically inactive mutant of PRMT2 or the type I PRMT inhibitor MS023 impaired the pro-tumorigenic functions of PRMT2 in HCC cells. Overall, our findings showed that PRMT2 functions as an oncogenic gene in HCC, revealing its potential as a novel therapeutic target in HCC.

Autophagy regulator Atg9 is degraded by the proteasome.

Autophagy is a highly conserved biological process essential to protein, cellular and organismal homeostasis. As autophagy plays a critical role in cellular responses to various external and internal stimuli, it is important to understand the mechanism underlying autophagy regulation. Here, we monitor the stability of 17 key autophagy factors in the yeast S. cerevisiae and show that Atg9 and Atg14 are degraded under normal growth conditions. Whereas Atg14 is regulated by both the proteasome and autophagy, Atg9 turnover is normally mediated by the proteasome but impeded upon starvation or rapamycin treatment. Interestingly, distinct segments of Atg9 confer instability, suggesting that multiple pathways are involved in Atg9 degradation. Our results provide the foundation to further elucidate the physiological significance of Atg9 turnover and also the interplay between two major proteolytic systems (i.e., autophagy and the proteasome).

Comparative transcriptome analysis of panicle development under heat stress in two rice (Oryza sativa L.) cultivars differing in heat tolerance.

Heat stress inhibits rice panicle development and reduces the spikelet number per panicle. This study investigated the mechanism involved in heat-induced damage to panicle development and spikelet formation in rice cultivars that differ in heat tolerance. Transcriptome data from developing panicles grown at 40 °C or 32 °C were compared for two rice cultivars: heat-tolerant Huanghuazhan and heat-susceptible IR36. Of the differentially expressed genes (DEGs), 4,070 heat stress-responsive genes were identified, including 1,688 heat-resistant-cultivar-related genes (RHR), 707 heat-susceptible-cultivar-related genes (SHR), and 1,675 common heat stress-responsive genes (CHR). A Gene Ontology (GO) analysis showed that the DEGs in the RHR category were significantly enriched in 54 gene ontology terms, some of which improved heat tolerance, including those in the WRKY, HD-ZIP, ERF, and MADS transcription factor families. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the DEGs in the RHR and SHR categories were enriched in 15 and 11 significant metabolic pathways, respectively. Improved signal transduction capabilities of endogenous hormones under high temperature seemed to promote heat tolerance, while impaired starch and sucrose metabolism under high temperature might have inhibited young panicle development. Our transcriptome analysis provides insights into the different molecular mechanisms of heat stress tolerance in developing rice.

FOXM1 promotes hepatocellular carcinoma progression by regulating KIF4A expression.

BACKGROUND: Forkhead box M1 (FOXM1) is a proliferation-associated transcription factor of the forkhead box proteins superfamily, which includes four isoforms FOXM1a, b, c, and d. FOXM1 has been implicated in hepatocellular carcinoma (HCC) progression, but the underlying molecular mechanism remains elusive. In this study, we aim to clarify the molecular basis for FOXM1-mediated HCC progression. METHODS: Bioinformatic analysis was used to explore the differentially expressed genes predicting HCC proliferation. The expression of FOXM1 and kinesin family member (KIF)4A was confirmed by western blotting and immunohistochemistry in HCC tissues. Kaplan-Meier survival analysis was conducted to analyze the clinical impact of FOXM1 and KIF4A on HCC. The effect of FOXM1 on the regulation of KIF4A expression was studied in cell biology experiments. The interaction between KIF4A and FOXM1 was analyzed by chromatin immunoprecipitation and luciferase experiments. A series of experiments was performed to explore the functions of FOXM1/KIF4A in HCC progression, such as cell proliferation, cell growth, cell viability, and cell cycle. A xenograft mouse model was used to explore the regulatory effect of FOXM1-KIF4A axis on HCC tumor growth. RESULTS: FOXM1 and KIF4A were overexpressed in human primary HCC tissues compared to that in matched adjacent normal liver tissue and are significant risk factors for HCC recurrence and shorter survival. We found that KIF4A was dominantly regulated by FOXM1c among the four isoforms, and further identified KIF4A as a direct downstream target of FOXM1c. Inhibiting FOXM1 decreased KIF4A expression in HCC cells, whereas its overexpression had the opposite effect. FOXM1-induced HCC cell proliferation was dependent on elevated KIF4A expression as KIF4A knockdown abolished FOXM1-induced proliferation of HCC cells both in vitro and in vivo. CONCLUSION: The FOXM1-KIF4A axis mediates human HCC progression and is a potential therapeutic target for HCC treatment.

Reduced bioactive gibberellin content in rice seeds under low temperature leads to decreased sugar consumption and low seed germination rates.

GA is important for rice seed germination, and seed embryo growth relies on sugar supplementation via starch hydrolysis in the endosperm. Low temperature reduces the seed germination rates of rice; however, the mechanism of GA metabolism and its impact on sugar utilization of germinating seeds under low temperature conditions remain poorly understood. In this study, low-temperature (15 °C) treatment delayed rice (Oryza sativa L.) seed germination, promoted GA deactivation, inhibited GA signal transduction, and increased ABA synthesis in the seed compared with normal treatment (30 °C). Under low temperature conditions, the soluble sugar content in endosperm was reduced along with depression of the specific activity levels of α-amylase (EC 3.2.1.1) and ß-amylase (EC 3.2.1.2), but the soluble sugar content was increased in the embryo compared with the control treatment. Low temperature treatment promoted sugar transportation from endosperm to embryo and reduced the activity levels of enzymes involved in glycolysis and the tricarboxylic acid cycle, which participated in sugar consumption. Exogenous GA3 application (10 µM) prompted GA signal transduction and inhibited ABA synthesis, while enhancing starch hydrolysis and sugar consumption to boost rice seed germination under low temperature conditions. In conclusion, a deficiency of bioactive GAs in rice seeds exposed to low temperature led to a decrement in starch hydrolysis and sugar consumption, thus inhibit seed germination.

DNA Confined in a Nanodroplet: A Molecular Dynamics Study.

As a major genetic material, the configuration and the mechanical properties of a double-stranded DNA (dsDNA) molecule in confinement are crucial for the application of nanotechnology and biological engineering. In the present paper, molecular dynamics simulation is utilized to study the configuration of dsDNA in a nanodroplet on a graphene substrate. The results show that the semiflexible dsDNA molecule changes its configuration with radius of gyration ( Rg) of a few nanometers because of the confined space, that is, the Rg of the dsDNA molecule decreases with the reduction of the nanodroplet size. In comparison, the dsDNA in the bulk usually has a persistent length of tens of nanometers. Especially, if the nanodroplet is small enough, the dsDNA molecule might form a loop structure inside. The dsDNA molecule affects the wetting properties of the graphene substrate. It is found that the graphene becomes more hydrophilic in smaller systems containing the dsDNA molecule, whereas for larger droplets, the changes of the contact angles are not significant with the presence of dsDNA. Moreover, the results indicate that for larger droplets, the line tension of the droplet containing DNA is positive and greater than that without DNA; for smaller droplets, the line tension becomes negative because the dsDNA is compressed and bent in the confinement, and has the potential to expand outwards. The worm-like chain model is used to study the bending energy of a dsDNA molecule in a droplet. The results address that the bending energy of the non-loop-structured dsDNA decreases as the droplet becomes larger, and it is larger than that of loop-structured dsDNA, as the loop structure efficiently prevents the DNA from bending in the vertical direction.

Nanoscale cavitation in perforation of cellular membrane by shock-wave induced nanobubble collapse.

The collapse of the bubble induced by the shock wave leads to nano-jet, which is able to perforate cellular membranes. This phenomenon is investigated by Martini coarse-grained molecular dynamic (CG-MD) simulations in the present study. It is found that the occurrence of cavitation nucleation at the nanoscale can be observed during the perforation process. The cavitation locates near the puncture of the cell membrane and its ultimate evolutionary form presents a ring-like structure. The volume of the cavitation is calculated for different initial bubble sizes, and it is found that the maximum volume of the cavitation area has a correlation with the initial bubble size. To understand the underlying physics of the cavitation phenomenon, the classical nucleation theory based on the Rayleigh-Plesset equation is applied to the non-equilibrium nanoscale system after the pressure field is obtained by using the Irving-Kirkwood-Noll procedure. The consistence between the results of CG-MD and the theory reveals that the average pressure of the local environment plays a crucial role in cavitation occurrence on the non-equilibrium system subjected to strong inertia, e.g., shock wave and nano-jet.

A Simple PCR-based Strategy for the Introduction of Point Mutations in the Yeast Saccharomyces cerevisiae via CRISPR/Cas9.

The methods currently employed for in vivo site-directed mutagenesis in yeast are laborious and/or inefficient. Recent developments of the CRISPR-based approaches hold great promise for genome editing, but its application in the yeast S. cerevisiae remains a time-consuming affair. The rate-limiting step in CRISPR-mediated genetic engineering in yeast is the incorporation of the guide sequences, which target Cas9 to relevant chromosomal locus, into the relevant yeast vectors. Here we present a PCR-based strategy to introduce specific point mutation into the yeast CDC48 gene via CRISPR. Our method eliminates the need for special dam- strain and markedly shortens the elaborate multi-step cloning process, leading to significant savings in time, labor and cost.

Aberrant activation of hedgehog signaling promotes cell proliferation via the transcriptional activation of forkhead Box M1 in colorectal cancer cells.

BACKGROUND: Recent evidence suggests that the aberrant activation of Hedgehog (Hh) signaling by Gli transcription factors is characteristic of a variety of aggressive human carcinomas, including colorectal cancer (CRC). Forkhead box M1 (FoxM1) controls the expression of a number of cell cycle regulatory proteins, and FoxM1 expression is elevated in a broad range of human malignancies, which suggests that it plays a crucial role in tumorigenesis. However, the mechanisms underlying FoxM1 expression are not fully understood. Here, we aim to further investigate the molecular mechanism by which Gli1 regulates FoxM1 in CRC. METHODS: Western blotting and immunohistochemistry (IHC) were used to evaluate FoxM1 and Gli1 protein expression, respectively, in CRC tissues and matched adjacent normal mucosa. BrdU (5-bromo-2'-deoxyuridine) and clone formation assays were used to clarify the influence of FoxM1 on CRC cell growth and proliferation. Chromatin immunoprecipitation (ChIP) and luciferase experiments were performed to explore the potential mechanisms by which Gli1 regulates FoxM1. Additionally, the protein and mRNA expression levels of Gli1 and FoxM1 in six CRC cell lines were measured using Western blotting and real-time PCR. Finally, the effect of Hh signaling on the expression of FoxM1 was studied in cell biology experiments, and the effects of Hh signaling activation and FoxM1 inhibition on the distribution of CRC cells among cell cycle phases was assessed by flow cytometry. RESULTS: Gli1 and FoxM1 were abnormally elevated in human CRC tissues compared with matched adjacent normal mucosa samples, and FoxM1 is a downstream target gene of the transcription factor Gli1 in CRC and promoted CRC cell growth and proliferation. Moreover, the aberrant activation of Hh signaling promoted CRC cell proliferation by directly binding to the promoter of FoxM1 and transactivating the activity of FoxM1 in CRC cells. CONCLUSION: The dysregulation of the Hh-Gli1-FoxM1 axis is essential for the proliferation and growth of human CRC cells and offers a potent target for therapeutic intervention in CRC.

Nerve growth factor receptor negates the tumor suppressor p53 as a feedback regulator.

Cancer develops and progresses often by inactivating p53. Here, we unveil nerve growth factor receptor (NGFR, p75NTR or CD271) as a novel p53 inactivator. p53 activates NGFR transcription, whereas NGFR inactivates p53 by promoting its MDM2-mediated ubiquitin-dependent proteolysis and by directly binding to its central DNA binding domain and preventing its DNA-binding activity. Inversely, NGFR ablation activates p53, consequently inducing apoptosis, attenuating survival, and reducing clonogenic capability of cancer cells, as well as sensitizing human cancer cells to chemotherapeutic agents that induce p53 and suppressing mouse xenograft tumor growth. NGFR is highly expressed in human glioblastomas, and its gene is often amplified in breast cancers with wild type p53. Altogether, our results demonstrate that cancers hijack NGFR as an oncogenic inhibitor of p53.

Hydrodynamic modeling of Bicoid morphogen gradient formation in Drosophila embryo.

Bicoid is a maternal polarity determinant that mediates the anterior-posterior (AP) patterning in early Drosophila embryo. During oogenesis, its mRNA deposits at the anterior pole of the embryo and then translates to establish the Bicoid morphogen gradient soon after fertilization. Previous investigations indicated that the patterning is induced by the spatial gradient of Bicoid morphogen concentration, where the cytoplasmic convection plays a crucial role. The present study examines the effect of advection transport on the formation of the Bicoid morphogen gradient using direct simulation of the cytoplasmic streaming described by Navier-Stokes equations, in which the cytoplasm behaves as an incompressible Newtonian fluid. To simulate the cytoplasmic streaming originated from membrane contractions, the flow is driven by slip velocities along the cortex and the anterior-posterior axis of the cell. Results show that the Bicoid concentration distribution we obtained provides a quantitatively consistent picture with the experiment measurements, as well as the diffusive length scale. The competition among the diffusion, advection and degradation is analyzed when the cytoplasmic streaming is considered. It is found that the advection yields wavy phenomenon in the profiles of the Bicoid concentration at small diffusion coefficients, which might have important effects on the embryonic development. After the driven velocities is switched off, the interior flow evanesces gradually due to the viscous drag, the Bicoid degradation will overwhelm the advection effect.

Manipulation of a neutral and nonpolar nanoparticle in water using a nonuniform electric field.

The manipulation of nanoparticles in water is of essential importance in chemical physics, nanotechnology, medical technology, and biotechnology applications. Generally, a particle with net charges or charge polarity can be driven by an electric field. However, many practical particles only have weak and even negligible charge and polarity, which hinders the electric field to exert a force large enough to drive these nanoparticles directly. Here, we use molecular dynamics simulations to show that a neutral and nonpolar nanoparticle in liquid water can be driven directionally by an external electric field. The directed motion benefits from a nonuniform water environment produced by a nonuniform external electric field, since lower water energies exist under a higher intensity electric field. The nanoparticle spontaneously moves toward locations with a weaker electric field intensity to minimize the energy of the whole system. Considering that the distance between adjacent regions of nonuniform field intensity can reach the micrometer scale, this finding provides a new mechanism of manipulating nanoparticles from the nanoscale to the microscale.

Inhibition of Hedgehog signaling pathway impedes cancer cell proliferation by promotion of autophagy.

Multiple lines of evidence implicate that aberrant activation of Hedgehog (Hh) signaling is involved in a variety of human cancers. However, the molecular mechanisms underlying how cancer cells respond to Hh inhibition remain to be elucidated. In this study, we found that blockade of Hh signaling suppresses cell proliferation in human cancer cells. Microarray analysis revealed that differentially expressed genes (DEGs) in human cancer cells are enriched in autophagy pathway in response to the inhibition of Hh signaling. Interestingly, inhibition of Hh signaling induced autophagy, whereas activation of Hh signaling by ligand treatments prevented the induction of autophagy. In addition, inhibition of autophagy by 3-methyladenine (3-MA) partially suppressed cytotoxicity induced by inhibition of Hh signaling. Finally, in autophagy deficient cells, cytotoxic effect triggered by inhibition of Hh signaling was partially reversed, indicating the modulation of autophagy by Hh signaling is autophagy-specific. These results suggest that inhibition of Hh signaling impedes cancer cell proliferation in part through induction of autophagy.

Hydrodynamic flow in the vicinity of a nanopore induced by an applied voltage.

Continuum simulation is employed to study ion transport and fluid flow through a nanopore in a solid-state membrane under an applied potential drop. The results show the existence of concentration polarization layers on the surfaces of the membrane. The nonuniformity of the ionic distribution gives rise to an electric pressure that drives vortical motion in the fluid. There is also a net hydrodynamic flow through the nanopore due to an asymmetry induced by the membrane surface charge. The qualitative behavior is similar to that observed in a previous study using molecular dynamic simulations. The current-voltage characteristics show some nonlinear features but are not greatly affected by the hydrodynamic flow in the parameter regime studied. In the limit of thin Debye layers, the electric resistance of the system can be characterized using an equivalent circuit with lumped parameters. Generation of vorticity can be understood qualitatively from elementary considerations of the Maxwell stresses. However, the flow strength is a strongly nonlinear function of the applied field. Combination of electrophoretic and hydrodynamic effects can lead to ion selectivity in terms of valences and this could have some practical applications in separations.