Non-canonical C-terminal variant of MeCP2 R344W exhibits enhanced degradation rate.

Rett Syndrome (RTT) is a neurodevelopmental disorder caused by pathogenic variants in the MECP2 gene. While the majority of RTT-causing variants are clustered in the methyl-CpG binding domain and NCoR/SMRT interaction domain, we report a female patient with a functionally uncharacterized MECP2 variant in the C-terminal domain, c.1030C>T (R344W). We functionally characterized MECP2-R344W in terms of protein stability, NCoR/SMRT complex interaction, and protein nuclear localization in vitro. MECP2-R344W cells showed an increased protein degradation rate without significant change in NCoR/SMRT complex interaction and nuclear localization pattern, suggesting that enhanced MECP2 degradation is sufficient to cause a Rett Syndrome-like phenotype. This study highlights the pathogenicity of the C-terminal domain in Rett Syndrome, and demonstrates the potential of targeting MECP2 protein stability as a therapeutic approach.

Imbibition-induced ultrafast assembly and printing of colloidal photonic crystals.

HYPOTHESIS: Self-assembly of colloidal particles enables the versatile fabrication of highly ordered structures and materials for optical, sensing, and other applications. Nevertheless, many traditional assembly processes are inefficient, because there exists an inevitable contradiction between time efficiency and crystalline quality. In this work, we introduce an ultrafast, robust, and scalable approach of imbibition-induced assembly. We assume that the instantaneous solvent imbibition induced by the nanoporous media could direct ultrafast self-assembly of colloidal particles into ordered structures. EXPERIMENTS: Self-assembly of colloidal particles from a droplet on a nanoporous substrate was firstly observed and investigated. A phase diagram of the thickness of the colloidal crystal as a function of the printing speed and the particle volume fraction was presented through systematic experiments. FINDINGS: The nanoporous substrate can induce strong capillary flow that will directthe rapid self-assemblyof particles intocolloidalcrystals. The imbibition-induced assembly was spatially and temporally combined with the meniscus-guided printing approach, and the printing speed can be improved by two orders of magnitude than the traditional evaporative assembly methods. We finally demonstrate an effective and ultrafast approach for assembling colloidal particles into photonic crystals with controllable sizes and shapes on the macroscale.

Thermal Stability and Decomposition Kinetics of 1-Alkyl-2,3-Dimethylimidazolium Nitrate Ionic Liquids: TGA and DFT Study.

The thermal stability and decomposition kinetics analysis of 1-alkyl-2,3-dimethylimidazole nitrate ionic liquids with different alkyl chains (ethyl, butyl, hexyl, octyl and decyl) were investigated by using isothermal and nonisothermal thermogravimetric analysis combined with thermoanalytical kinetics calculations (Kissinger, Friedman and Flynn-Wall-Ozawa) and density functional theory (DFT) calculations. Isothermal experiments were performed in a nitrogen atmosphere at 240, 250, 260 and 270 °C. In addition, the nonisothermal experiments were carried out in nitrogen and air atmospheres from 30 to 600 °C with heating rates of 5, 10, 15, 20 and 25 °C/min. The results of two heating modes, three activation energy calculations and density functional theory calculations consistently showed that the thermal stability of 1-alkyl-2,3-dimethylimidazolium nitrate ionic liquids decreases with the increasing length of the alkyl chain of the substituent on the cation, and then the thermal hazard increases. This study could provide some guidance for the safety design and use of imidazolium nitrate ionic liquids for engineering.

Translational and rotational critical-like behaviors in the glass transition of colloidal ellipsoid monolayers.

Critical-like behaviors have been found in translational degrees of freedom near the glass transition of spherical particle systems mainly with local polycrystalline structures, but it is not clear if criticality exists in more general glassy systems composed of nonspherical particles without crystalline structures. Here, through experiments and simulations, we show critical-like behaviors in both translational and rotational degrees of freedom in monolayers of monodisperse colloidal ellipsoids in the absence of crystalline orders. We find rich features of the Ising-like criticality in structure and slow dynamics at the ideal glass transition point ϕ0, showing the thermodynamic nature of glass transition at ϕ0 A dynamic criticality is found at the mode-coupling critical point ϕc for the fast-moving clusters whose critical exponents increase linearly with fragility, reflecting a dynamic glass transition. These results cast light on the glass transition and explain the mystery that the dynamic correlation lengths diverge at two different temperatures.

Capsaicin Inhibits the Expression of Melanogenic Proteins in Melanocyte via Activation of TRPV1 Channel: Identifying an Inhibitor of Skin Melanogenesis.

Chili pepper belongs to the genus Capsicum of Solanaceae family. Capsaicin is the primary capsaicinoid in placenta and flesh of chili pepper fruit, which has been shown to have various pharmacological functions, including gastric protection, anti-inflammation, and obesity treatment. Here, we revealed that capsaicin as well as chilli extract was able to inhibit synthesis of melanin in melanocytes. In cultured melanocytes, the melanin content was reduced to 54 ± 6.55% and 42 ± 7.41% with p < 0.001 under treatment of 50 µM capsaicin for 24 and 72 h, respectively. In parallel, the protein levels of tyrosinase and tyrosinase-related protein-1 were reduced to 62 ± 8.35% and 48 ± 8.92% with p < 0.001. Such an inhibitory effect of capsaicin was mediated by activation of transient receptor potential vanilloid 1-induced phosphorylation of extracellular signal-regulated kinase. This resulted in a degradation of microphthalmia-associated transcription factor, leading to reduction of melanogenic enzymes and melanin. These results revealed that capsaicin could be an effective inhibitor for skin melanogenesis. Hence, chili pepper, as our daily food, has potential in dermatological application, and capsaicin should be considered as a safe agent in treating hyperpigmentation problems.

Solar light induces expression of acetylcholinesterase in skin keratinocytes: Signalling mediated by activator protein 1 transcription factor.

Acetylcholinesterase (AChE) hydrolyses acetylcholine to choline and acetate, playing an important role in terminating the neurotransmission in brain and muscle. Recently, the non-neuronal functions of AChE have been proposed in different tissues, in which there are various factors to regulate the expression of AChE. In mammalian skin, AChE was identified in melanocytes and keratinocytes. Our previous study has indicated that AChE in keratinocyte affects the process of solar light-induced skin pigmentation; however, the expression of AChE in keratinocytes in responding to sunlight remains unknown. Here, we provided several lines of evidence to support a notion that AChE could be upregulated at transcriptional and translational levels in keratinocytes when exposed to solar light. The light-mediated AChE expression was triggered by Ca2+, supported by an induction of Ca2+ ionophore A23187 and a blockage by Ca2+ chelator BAPTA-AM. In addition, this increase on AChE transcriptional expression was eliminated by mutagenesis on the activating protein 1 (AP1) site in ACHE gene. Hence, the solar light-induced AChE expression is mediated by Ca2+ signalling through AP1 site. This finding supports the role of solar light in affecting the cholinergic system in skin cells, and which may further influence the dermatological function.

Shexiang Baoxin Pill, a Traditional Chinese Herbal Formula, Rescues the Cognitive Impairments in APP/PS1 Transgenic Mice.

BACKGROUND: Shexiang Baoxin Pill (SBP), a formulated traditional Chinese medicine (TCM), has been widely used to treat cardiovascular diseases for years. This herbal mixture has been shown to promote differentiation of cultured neuronal cells. Here, we aimed to investigate the effects of SBP in attenuating cognitive impairment in APP/PS1 transgenic mice. METHODS: Ethanol and water extracts of SBP, denoted as SBPEtOH and SBPwater, were standardized and applied onto cultured rat pheochromocytoma PC12 cells. The potential effect of SBPEtOH extract in attenuating the cognitive impairments in APP/PS1 transgenic mice was shown by following lines of evidence: (i) inhibition of Aß fibril formation, (ii) suppression of secretions of cytokines, and (iii) improvement of behavioral tests by Morris water maze. RESULTS: SBPwater and SBPEtOH inhibited the formation of ß-amyloid fibrils and protected the Aß-induced cytotoxicity in cultured PC12 cells. In APP/PS1 transgenic mice, the treatment of SBPEtOH inhibited expressions of NO, NOS, AChE, as well as aggregation of Aß. Besides, the levels of pro-inflammatory cytokines were suppressed by SBP treatment in the transgenic mice. Importantly, the behavioral tests by Morris Water maze indicated that SBP attenuated cognitive impairments in APP/PS1 transgenic mice. CONCLUSION: The current result has supported the notion that SPB might ameliorate the cognitive impairment through multiple targets, suggesting that SBP could be considered as a promising anti-AD agent.

Shexiang Baoxin Pill, a Formulated Chinese Herbal Mixture, Induces Neuronal Differentiation of PC12 Cells: A Signaling Triggered by Activation of Protein Kinase A.

Background: Shexiang Baoxin Pill (SBP) is a well-known composite formula of traditional Chinese medicine (TCM), which is commonly used today in treating cardiovascular diseases. SBP consists of seven materials thereof, including Moschus, extract of Ginseng Radix et Rhizoma, Bovis Calculus Artifactus, Cinnamomi Cortex, Styrax, Bufonis Venenum, and Borneolum Syntheticum. Here, we are investigating the potential roles of SBP in inducing neuron differentiation, i.e., seeking possible application in neurodegenerative diseases. Methods: Water and ethanol extracts of SBP, denoted as SBPwater and SBPEtOH, respectively, as well as its individual herbal materials, were standardized and applied onto cultured rat pheochromocytoma PC12 cells. The potential effect of SBP extracts in neuronal differentiation was suggested by following parameters: (i) induction of neurite outgrowth of PC12 cells, (ii) increase of neurofilament expression, and (iii) activation of transcription of neurofilament. Results: The treatments of SBPwater and SBPEtOH, or extracts from individual herbal materials, with or without low concentration of nerve growth factor (NGF), could potentiate the differentiation of cultured PC12 cells. The differentiation was indicated by increase of neurite outgrowth, as well as expression of neurofilaments. In addition, application of H89, a protein kinase A (PKA) inhibitor, suppressed the SBP-induced neurofilament expressions, as well as the phosphorylation of cAMP-responsive element binding protein (CREB) in cultures. Conclusion: SBP is proposed to possess trophic activity in modulating neuronal differentiation of PC12 cells, and this induction is shown to be mediated partly by a cAMP-PKA signaling pathway. These results indicate the neurite-promoting SBP could be useful in developing potential drug in treating or preventing neurodegenerative diseases.

Arnicolide D exerts anti-melanoma effects and inhibits the NF-κB pathway.

BACKGROUND: Melanoma is a lethal cancer. NF-κB has been validated as a molecular target for melanoma treatment. Current therapies for melanoma have limitations. Novel targeted therapeutics are needed. Arnicolide D (Ar-D), a sesquiterpene lactone isolated from the dried whole plant of Centipeda minima (L.) A. Br. et Aschers., has been reported to inhibit NF-κB activity in colorectal cancer cells. PURPOSE: To investigate the anti-melanoma effects of Ar-D in vitro and in vivo; and to determine whether Ar-D inhibits the NF-κB pathway in melanoma cells. METHODS: A B16F10 allograft mouse model and two melanoma cell lines (A375 and B16F10) were used to investigate the anti-melanoma effects of Ar-D in vivo and in vitro. Dacarbazine was used as a positive control. Cell viability was assessed by MTT and crystal violet staining assays. Cell cycle arrest and apoptosis were analyzed by flow cytometry. Protein levels were determined by Immunoblotting. RESULTS: In vivo assays showed that the average tumor weight in Ar-D-treated group (4 mg/kg, i.p, 15 days) was reduced by 53.7%, when compared with the control group. In vitro studies demonstrated that Ar-D reduced cell viability, induced G2/M cell cycle arrest and apoptosis, elevated levels of cell cycle regulatory proteins p53 and p21, and lowered levels of G2/M checkpoint proteins Cdc2 and Cyclin B1 in melanoma cells. Mechanistically, Ar-D inhibited the activity of IKKα/ß, the degradation of IκBα, and the phosphorylation and expression of NF-κB p65 in melanoma cells. CONCLUSION: Ar-D has anti-melanoma effects, and inhibition of the IKK/IκBα/NF-κB p65 pathway is involved in the effects.

Homogeneous melting near the superheat limit of hard-sphere crystals.

A defect-free crystal can be superheated into a metastable state above its melting point and eventually melts via homogeneous nucleation. Further increasing the temperature leads to the metastable crystal becoming unstable and melting catastrophically once beyond its superheat limit. The homogeneous melting is not well studied near the superheat limit and this limit is difficult to measure accurately, even for the simplest model of hard-sphere crystals. Here our molecular-dynamics simulations identify its superheat limit at volume fraction φlimit = 0.494 ± 0.003, which is higher than the previous theoretical estimations. We found that the hard-sphere crystal at the superheat limit does not satisfy Born's melting criterion, but has a vanishing bulk modulus, i.e. a spinodal instability, which preempts other thermodynamic or mechanical instabilities. At the strong superheating regime, the nucleation deviates from the assumptions in the classical nucleation theory. In contrast to crystallization which often develops nuclei with various intermediate structures, the melting of face-centered cubic (fcc) hard-sphere crystal does not produce intermediate structures such as body-centered cubic (bcc) crystallites although bcc is more stable than fcc at the strong superheating regime. Moreover, we found that the time evolutions of the order parameters and the pressure all exhibit a compressed exponential function, in contrast to the stretched exponential relaxation of supercooled liquids. The compressed exponential functions have the same exponent, which poses a new challenge to theory.

The role of Arabidopsis Actin-Related Protein 3 in amyloplast sedimentation and polar auxin transport in root gravitropism.

Gravitropism is vital for shaping directional plant growth in response to the forces of gravity. Signals perceived in the gravity-sensing cells can be converted into biochemical signals and transmitted. Sedimentation of amyloplasts in the columella cells triggers asymmetric auxin redistribution in root tips, leading to downward root growth. The actin cytoskeleton is thought to play an important role in root gravitropism, although the molecular mechanism has not been resolved. DISTORTED1 (DIS1) encodes the ARP3 subunit of the Arabidopsis Actin-Related Protein 2/3 (ARP2/3) complex, and the ARP3/DIS1 mutant dis1-1 showed delayed root curvature after gravity stimulation. Microrheological analysis revealed that the high apparent viscosity within dis1-1 central columella cells is closely associated with abnormal movement trajectories of amyloplasts. Analysis using a sensitive auxin input reporter DII-VENUS showed that asymmetric auxin redistribution was reduced in the root tips of dis1-1, and the actin-disrupting drug Latrunculin B increased the asymmetric auxin redistribution. An uptake assay using the membrane-selective dye FM4-64 indicated that endocytosis was decelerated in dis1-1 root epidermal cells. Treatment and wash-out with Brefeldin A, which inhibits protein transport from the endoplasmic reticulum to the Golgi apparatus, showed that cycling of the auxin-transporter PIN-FORMED (PIN) proteins to the plasma membrane was also suppressed in dis1-1 roots. The results reveal that ARP3/DIS1 acts in root gravitropism by affecting amyloplast sedimentation and PIN-mediated polar auxin transport through regulation of PIN protein trafficking.

Structural signatures of dynamic heterogeneities in monolayers of colloidal ellipsoids.

When a liquid is supercooled towards the glass transition, its dynamics drastically slows down, whereas its static structure remains relatively unchanged. Finding a structural signature of the dynamic slowing down is a major challenge, yet it is often too subtle to be uncovered. Here we discover the structural signatures for both translational and rotational dynamics in monolayers of colloidal ellipsoids by video microscopy experiments and computer simulations. The correlation lengths of the dynamic slowest-moving clusters, the static glassy clusters, the static local structural entropy and the dynamic heterogeneity follow the same power-law divergence, suggesting that the kinetic slowing down is caused by a decrease in the structural entropy and an increase in the size of the glassy cluster. Ellipsoids with different aspect ratios exhibit single- or double-step glass transitions with distinct dynamic heterogeneities. These findings demonstrate that the particle shape anisotropy has important effects on the structure and dynamics of the glass.

Imaging the homogeneous nucleation during the melting of superheated colloidal crystals.

The nucleation process is crucial to many phase transitions, but its kinetics are difficult to predict and measure. We superheated and melted the interior of thermal-sensitive colloidal crystals and investigated by means of video microscopy the homogeneous melting at single-particle resolution. The observed nucleation precursor was local particle-exchange loops surrounded by particles with large displacement amplitudes rather than any defects. The critical size, incubation time, and shape and size evolutions of the nucleus were measured. They deviate from the classical nucleation theory under strong superheating, mainly because of the coalescence of nuclei. The superheat limit agrees with the measured Born and Lindemann instabilities.

Glass transitions in quasi-two-dimensional suspensions of colloidal ellipsoids.

We observed a two-step glass transition in monolayers of colloidal ellipsoids by video microscopy. The glass transition in the rotational degree of freedom was at a lower density than that in the translational degree of freedom. Between the two transitions, ellipsoids formed an orientational glass. Approaching the respective glass transitions, the rotational and translational fastest-moving particles in the supercooled liquid moved cooperatively and formed clusters with power-law size distributions. The mean cluster sizes diverge in power law as they approach the glass transitions. The clusters of translational and rotational fastest-moving ellipsoids formed mainly within pseudonematic domains and around the domain boundaries, respectively.

Self-diffusion in two-dimensional hard ellipsoid suspensions.

We studied the self-diffusion of colloidal ellipsoids in a monolayer near a flat wall by video microscopy. The image processing algorithm can track the positions and orientations of ellipsoids with subpixel resolution. The translational and rotational diffusions were measured in both the laboratory frame and the body frame along the long and short axes. The long-time and short-time diffusion coefficients of translational and rotational motions were measured as functions of the particle concentration. We observed the nondiffusive crossover region in the intermediate time regime due to the caging of neighboring particles. Both the beginning and the ending times of the intermediate regime exhibit power-law dependence on concentration. The long-time and short-time diffusion anisotropies change nonmonotonically with concentration and reach minima in the semidilute regime because the motions along long axes are caged at lower concentrations than the motions along short axes. The time derivatives of mean-square displacements change linearly with the inverse of time in the intermediate time regimes at various particle densities. This indicates that their relaxation functions decay as 1/t which provides new challenges in theory. The effects of coupling between rotational and translational Brownian motions were demonstrated and the two time scales corresponding to anisotropic particle shape and anisotropic neighboring environment were measured.

Rapidly infrared-assisted cooperatively self-assembled highly ordered multiscale porous materials.

In this paper, cooperative self-assembly (CSA) of colloidal spheres with different sizes was studied. It was found that a complicated jamming effect makes it difficult to achieve an optimal self-assembling condition for construction of a well-ordered stacking of colloidal spheres in a relatively short growth time by CSA. Through the use of a characteristic infrared (IR) technique to significantly accelerate local evaporation on the growing interface without changing the bulk growing environment, a concise three-parameter (temperature, pressure, and IR intensity) CSA method to effectively overcome the jamming effect has been developed. Mono- and multiscale inverse opals in a large range of lattice scales can be prepared within a growth time (15-30 min) that is remarkably shorter than the growth times of several hours for previous methods. Scanning electron microscopy images and transmittance spectra demonstrated the superior crystalline and optical qualities of the resulting materials. More importantly, the new method enables optimal conditions for CSA without limitations on sizes and materials of multiple colloids. This strategy not only makes a meaningful advance in the applicability and universality of colloidal crystals and ordered porous materials but also can be an inspiration to the self-assembly systems widely used in many other fields, such as nanotechnology and molecular bioengineering.