Morphological Polarity Research Articles

Bi6Fe2Ti3O18 ferroelectrics with various morphologies under mild conditions by crystal growth control for promoted adsorption-piezo-photocatalytic degradation performances

Bi6Fe2Ti3O18 (BFTO) Aurivillius phase layered perovskite ferroelectric materials with spontaneous polarization and piezoelectric effect, have garnered significant attention in photocatalysis owing to their unique advantage of enhancing electron-hole separation. Herein, morphological engineering is used to improve the photocatalytic, piezo-catalytic, and piezo-photocatalytic activities of BFTO, and BFTO nanocrystallites with diverse morphologies such as nanosheet, nanoparticle, nanosheets-assembled flower-like structures were successfully synthesized using a hydrothermal method under mild conditions. Among these structures, the flower-like BFTO sample exhibits efficient absorption of visible light, excellent adsorption performance, enhanced piezoelectric response, and effective carrier separation, thereby contributing to its superior adsorption-photocatalytic, adsorption-piezo-catalytic, and adsorption-piezo-photocatalytic activities for Rhodamine B. Furthermore, corona poling was further applied to enhance the macroscopic polarization and piezoelectric response of the BFTO photocatalyst, thereby leading to more effective separation of photogenerated carriers in the polarized samples. The polarized BFTO microflowers exhibit excellent photocatalytic, piezo-catalytic, and piezo-photocatalytic activities with reaction rate constants of 0.222 min−1, 0.168 min−1, and 0.255 min−1. Based on the results of piezoresponse force microscopy and finite element simulation, the greater piezoelectric response was confirmed in the polarized flower-like BFTO compared to the other samples. Overall, the synergistic effect of morphology control and polarization engineering is effective for achieving Bi-based Aurivillius phase layered perovskite photocatalyst with excellent adsorption-photocatalytic and adsorption-piezo-photocatalytic performances.

Corrosion behavior of Q345 and Q235 steels in simulated neutral soil solution

Abstract Q345 and Q235 steels are widely used in infrastructure and manufacturing. Examining the corrosion behavior of two types of steel in a neutral soil environment can facilitate the assessment of the service life of the steel machinery, thereby mitigating potential corrosion failures. In order to investigate the corrosion and mechanism of Q345 and Q235 steels in the neutral soil solution, an electrochemical test, scanning electron microscopy, and X-ray diffraction were employed to analyze the corrosion morphology, corrosion product, and electrochemical polarization curves. The results showed that no visible pitting pits were observed on the surfaces of Q345 steel and Q235 steel. The corrosion types were mainly overall corrosion in the simulated neutral soil solution. The microstructure of Q235’s corrosion product exhibits greater compactness, facilitating the formation of Fe3O4. This compound demonstrates excellent binding ability with the metal matrix and hinders the continuous corrosion of the steel. Q235 steel has better corrosion resistance with a lower corrosion rate than Q345 steel in the simulated neutral soil solution. These findings contribute valuable information for material selection considerations in manufacturing machinery in neutral soil environments.

Tuning the microstructure, morphology, and electrical polarization behavior in BNT-BKT through hydrothermal method

Tuning the microstructure, morphology, and electrical polarization behavior in BNT-BKT through hydrothermal method

Species Delimitation of Some Melanargia Species (Lepidoptera, Nymphalidae, Satyrinae) in The Southeastern Anatolia Region Based On The mtCOI Gene

Among the Palearctic species, butterflies of the genus Melanargia are known for their black and white wing patterns. The morphological character polarization of this genus is full of varying combinations of subgenus, species complex, and subspecies status. Its taxonomy is open to debate, especially in species and subspecies categories, with definitions mostly based on wing color. In recent years, cryptic species, phenotypically masked species, and species with intense intraspecific variation have been identified through the determination of lineages under the leadership of molecular systematics. The mtCOI gene, which is especially described as a species signature, is an important DNA barcode used for Lepidoptera. In the presented study, the mtCOI gene sequence of the populations of Melanargia larissa, M.grumi, M.hylata, M.syriaca, and M.russiae species in the southeastern Anatolia region was determined for the first time. To determine the boundaries of these species, gene characterization and genetic distances were carried out according to the Kimura-2 Parameter, and putative species analyses were carried out by the ABGD method. Trees were constructed with Maximum likelihood and Bayesian inference algorithms to determine the phylogenetic relationships between species of the genus. In light of these analyses, it has been shown that the genetic distance of morphological species M. larissa, M. grumi, M.hylata, and M. syriaca is not at the species level and that M.larissa maintains its species status according to the principle of priority. In addition, the M.russiae population presented in this study forms a monophyletic clade with other populations of the same species in the phylogenetic tree, proving that this taxon is a stable species.

Mitochondrial morphology dynamics and ROS regulate apical polarity and differentiation in Drosophila follicle cells.

Mitochondrial morphology dynamics regulate signaling pathways during epithelial cell formation and differentiation. The mitochondrial fission protein Drp1 affects the appropriate activation of EGFR and Notch signaling-driven differentiation of posterior follicle cells in Drosophila oogenesis. The mechanisms by which Drp1 regulates epithelial polarity during differentiation are not known. In this study, we show that Drp1-depleted follicle cells are constricted in early stages and present in multiple layers at later stages with decreased levels of apical polarity protein aPKC. These defects are suppressed by additional depletion of mitochondrial fusion protein Opa1. Opa1 depletion leads to mitochondrial fragmentation and increased reactive oxygen species (ROS) in follicle cells. We find that increasing ROS by depleting the ROS scavengers, mitochondrial SOD2 and catalase also leads to mitochondrial fragmentation. Further, the loss of Opa1, SOD2 and catalase partially restores the defects in epithelial polarity and aPKC, along with EGFR and Notch signaling in Drp1-depleted follicle cells. Our results show a crucial interaction between mitochondrial morphology, ROS generation and epithelial cell polarity formation during the differentiation of follicle epithelial cells in Drosophila oogenesis.

Comparative Evaluation of Anticancer Activity of Natural Methoxylated Flavones Xanthomicrol and Eupatilin in A375 Skin Melanoma Cells.

Melanoma is a skin cancer caused by the malignant transformation of melanocytes and cutaneous melanoma represents the most aggressive and deadliest type of skin cancer with an increasing incidence worldwide. The main purpose of the present research was to evaluate the anticancer effects of the natural bioactive compounds xanthomicrol (XAN) and eupatilin (EUP) in human A375 malignant skin melanoma cells, a cell line widely used as an in vitro model of cutaneous melanoma. XAN and EUP are lipophilic methoxylated flavones with antioxidant, anti-inflammatory, and antitumor properties. The effects of XAN and EUP on cell viability, morphology, lipid profile, oxidative status, apoptosis, and mitochondrial membrane polarization were determined and compared in A375 cells. At 24 h-incubation (MTT assay), XAN significantly reduced viability at the dose range of 2.5-200 μM, while EUP showed a significant cytotoxicity from 25 μM. Moreover, both methoxylated flavones induced (at 10 and 25 μM, 24 h-incubation) marked cell morphological alterations (presence of rounded and multi-nucleated cells), signs of apoptosis (NucView 488 assay), and a noteworthy mitochondrial membrane depolarization (MitoView 633 assay), coupled to a marked lipid profile modulation, including variations in the ratio of phospholipid/cholesterol and a decrease in the oleic, palmitic, and palmitoleic acid amounts. Moreover, a remarkable time-dependent ROS generation (2',7'-dichlorodihydrofluorescein diacetate assay) was observed during 3 h-incubation of A375 cancer cells in the presence of XAN and EUP (10 and 25 μM). Our results confirm the potential antitumor effect of natural EUP and XAN in cutaneous melanoma by the activation of multiple anticancer mechanisms.

Sonochemically synthesized black phosphorus nanoparticles: a promising candidate for piezocatalytic antibacterial activity with enhanced dielectric properties.

The drawbacks inherent to traditional antibacterial therapies, coupled with the escalating prevalence of multi-drug resistant (MDR) microorganisms, have prompted the imperative need for novel antibacterial strategies. Accordingly, the emerging field of piezocatalysis in semiconductors harnesses mechanical stress to drive chemical reactions by utilizing piezo-generated free charge carriers, presenting a promising technology. To the best of our knowledge, this study is the first to provide a comprehensive overview of the eradication of pathogenic S. aureus bacteria using few-layer black phosphorus (SCBP) piezo catalyst under mechanical stimuli, along with the exploration of temperature dependent dielectric properties. The synthesis of the piezo catalysts involved a one-step cost-effective sonochemical method, and its structural, morphological, elemental, optical, and overall polarization properties were thoroughly characterized and compared with the traditional method-derived product (TABP). The synthesis-introduced defects, reduced crystalline diameters, modified bandgap (1.76 eV), nanoparticle aggregation, photoluminescence quenching, along with interfacial polarization, synergistically contribute to SCBP's exceptional dielectric response (4.596 × 107 @40 Hz), which in turn enhanced the piezocatalytic activity. When subjected to soft ultrasound stimulation at 15 kHz, the piezo catalyst SCBP demonstrated significant ROS-mediated antibacterial activity, resulting in a ∼94.7% mortality rate within 40 minutes. The impact of this study extends to cost-effective energy storage devices and advances in antibacterial therapy, opening new dimensions in both fields.

Regulated Behavior in Living Cells with Highly Aligned Configurations on Nanowrinkled Graphene Oxide Substrates: Deep Learning Based on Interplay of Cellular Contact Guidance.

Micro-/nanotopographical cues have emerged as a practical and promising strategy for controlling cell fate and reprogramming, which play a key role as biophysical regulators in diverse cellular processes and behaviors. Extracellular biophysical factors can trigger intracellular physiological signaling via mechanotransduction and promote cellular responses such as cell adhesion, migration, proliferation, gene/protein expression, and differentiation. Here, we engineered a highly ordered nanowrinkled graphene oxide (GO) surface via the mechanical deformation of an ultrathin GO film on an elastomeric substrate to observe specific cellular responses based on surface-mediated topographical cues. The ultrathin GO film on the uniaxially prestrained elastomeric substrate through self-assembly and subsequent compressive force produced GO nanowrinkles with periodic amplitude. To examine the acute cellular behaviors on the GO-based cell interface with nanostructured arrays of wrinkles, we cultured L929 fibroblasts and HT22 hippocampal neuronal cells. As a result, our developed cell-culture substrate obviously provided a directional guidance effect. In addition, based on the observed results, we adapted a deep learning (DL)-based data processing technique to precisely interpret the cell behaviors on the nanowrinkled GO surfaces. According to the learning/transfer learning protocol of the DL network, we detected cell boundaries, elongation, and orientation and quantitatively evaluated cell velocity, traveling distance, displacement, and orientation. The presented experimental results have intriguing implications such that the nanotopographical microenvironment could engineer the living cells' morphological polarization to assemble them into useful tissue chips consisting of multiple cell types.

Gd-doped bismuth ferrite nanocomposite: A promising candidate for piezocatalytic degradation of organic dyes and pathogenic E. coli

This work portrays a detailed depiction of degrading two separate carcinogenic organic dyes (Rhodamine B and Eriochrome black T) along with the ablation of pathogenic E. coli bacteria by employing a gadolinium-doped bismuth ferrite (GBF) piezo catalyst. The piezo catalyst has been prepared by a facile two-step solvothermal route and characterized for structural, morphological, elemental, and overall polarization properties. An irregular cubic structure is found (∼15-50 nm), confirming the nano-scale nature of the synthesized samples. Notably, the synthesized nano powder exhibits high remnant polarization (0.92 μC cm−2) which is further confirmed by the density functional theory (DFT). Such tremendously high polarizability has been further exploited to eradicate both dyes. Under the soft ultrasound stimulation (15 kHz), the piezo catalyst (GBF1) shows an extraordinary degradation efficiency (97.6% for RhB and 91.3% for EBT). The reusability of the piezo catalyst has been checked for several cycles, and after the cyclic test, post-analysis of the sample has also been done which indicates the stability of the catalyst very well. Moreover, a remarkable antibacterial activity has been found for the GBF1 sample having a mortality of almost ∼ 99.33% in 30 mins. Additionally, the strong remanent magnetization of the catalyst (10.564×10−4 emu/g) makes the extraction of the catalyst possible by using a simple magnetic field. This extraction method has significant potential for rapidly cleaning waterbodies to prevent secondary pollution. Henceforth, the as-synthesized piezo catalyst (GBF1) could aid in future water treatment projects and can be translated from the bench to the bedside, if properly improvised.

Inversin-deficient (inv) mice do not establish a polarized duct system in the liver and pancreas.

Inversin-deficient (inv) mice have anomalies in liver and pancreatic development in addition to an inverted left-right axis of the body. The present study was undertaken to unveil mechanisms of bile and pancreatic duct development from immunohistochemical analyses of anomalies in inv mice. Intrahepatic bile ducts having proximodistal polarity in size and the height of their epithelia, and ductules were formed in livers of wild-type neonates. By contrast, in inv mice, ductal plates, precursor structures of intrahepatic bile ducts and ductules, persisted without the proximodistal polarity. Their epithelial cells did not acquire planar cell polarity (PCP) in terms of expression of tight junction proteins although they expressed bile duct markers, HNF1β and SOX9. They had an apicobasal polarity from expression of basal laminar components. Enlargement of the hepatic artery and poor connective tissue development, including the abnormal deposition of the extracellular matrices, were also noted in inv mice, suggesting that bile duct development was coupled to that of the hepatic artery and portal vein. In pancreata of inv neonates, neither the main pancreatic duct was formed, nor dilated duct-like structures had the morphological polarity from the connecting point with the common bile duct. Lumina of acini was dilated, and centroacinar cells changed their position in the acini to their neck region. Immunohistochemical analyses of tight junction proteins suggested that epithelial cells of the duct-like structures did not have a PCP. Thus, Invs may be required for the establishment of the PCP of the whole duct system in the liver and pancreas.

Utility of Right-Electrocardiogram Chest Leads in Localization of Accessory Pathways in Patients with Wolf-Parkinson-White Syndrome

Abstract Background Prediction of the precise location of an Accessory Pathway (AP) prior to the ablation procedure is of clinical importance. Several algorithms have been published to localize the AP on a surface 12-lead electrocardiogram (ECG). Most of them are based on analysis of delta wave morphology or QRS polarity. However, they are somewhat complicated, and an accurate determination of the delta wave morphology or QRS polarity are occasionally difficult, and their accuracy are still limited. Recently a new published algorithm using right-sided ECG chest leads for the prediction site of an AP is figured out and still under study for measuring its accuracy. Aim of the Work The aim of this study is to evaluate the accuracy of the utility of rightsided ECG Chest leads in the localization of APs in patients with manifest pre-excitation pattern in 12-lead ECG in prospective manner. Patients and Methods This study included 35 patients in whom successful ablation of manifest Wolff-Parkinson-White (WPW) syndrome was performed in prospective manner. Standard 12-lead ECG and right-sided chest ECG waveforms were recorded before the procedure. Results There were 13, 10, and 12 patients with left, right, and septal APs, respectively. All left AP patients had type A (RS morphology) in V1 and 12 of them in V4R leads, only 1 had type B in V4R lead. Of the 10 right AP patients, 5 had type B (rS morphology) in V1 while all 10 patients had type B in V4R. Of the 12 septal AP patients, 9 had type C (QS or Qr morphology) in V1, while 2 of the 12 patients had type B, and 1 of 12 patients had type A. All the 12 septal AP patients had type C in V4R. Conclusions The QRS morphology of V1 and V4R leads could predict the site of AP in patients with WPW syndrome with overall accuracy of 85.7% and 98%, respectively. Abbreviations AP: Accessory Pathway; ECG: Electrocardiogram; EPS: Electrophysiology study; RF: Radiofrequency; WPW: Wolff-Parkinson-White

Organ function is preserved despite reorganization of niche architecture in the hair follicle.

The ability of stem cells to build and replenish tissues depends on support from their niche. Although niche architecture varies across organs, its functional importance is unclear. During hair follicle growth, multipotent epithelial progenitors build hair via crosstalk with their remodeling fibroblast niche, thedermal papilla, providing a powerful model to functionally interrogate niche architecture. Through mouse intravital imaging, we show that dermal papilla fibroblasts remodel individually and collectively to form a morphologically polarized, structurally robust niche. Asymmetric TGF-β signaling precedes morphological niche polarity, and loss of TGF-β signaling in dermal papilla fibroblasts leads them to progressively lose their stereotypic architecture, instead surrounding the epithelium. The reorganized niche induces the redistribution of multipotent progenitors but nevertheless supports their proliferation and differentiation. However, the differentiated lineages and hairs produced by progenitors are shorter. Overall, our results reveal that niche architecture optimizes organ efficiency but is not absolutely essential for organ function.

Celsr2-mediated morphological polarization and functional phenotype of reactive astrocytes in neural repair.

Neural repair is highly influenced by reactive astrocytes. Atypical cadherin Celsr2 regulates neuron development and axon regeneration, while its role in glial cells remains unexplored. In this study, we show that Celsr2 is highly expressed in spinal astrocytes of adult mice, and knockout of Celsr2 results in reactive astrocytes with longer protrusions preferentially orientated towards lesion borders in culture scratch assay and injured spinal cord, and elevation of total and active Cdc42 and Rac1 protein in western blots. Inactivation of Celsr2 enhances calcium influx in reactive astrocytes in time-lapse imaging. Morphological phenotypes of cultured Celsr2-/- astrocytes are rescued by Cdc42 or Rac1 inhibitors. Following spinal cord injury (SCI), Celsr2-/- mice exhibit smaller lesion cavity and glial scar, enhanced fiber regeneration, weaker microglial response, and improved functional recovery than control animals. Similar phenotypes are found in mice with conditional knockout of Celsr2 in astrocytes. In Celsr2-/- mice, astrocyte phenotype is changed and neuroinflammation is alleviated after injury. Inhibiting Cdc42/Rac1 activities compromises astrocyte polarization and the improvement of neural repair and functional recovery in Celsr2-/- mice with SCI. In conclusion, Celsr2 regulates morphological polarization and functional phenotype of reactive astrocytes and inactivating Celsr2 is a potential therapeutic strategy for neural repair.

Innovative Forward Fusion Feature Selection Algorithm for Sentiment Analysis Using Supervised Classification

Sentiment analysis is considered one of the significant trends of the recent few years. Due to the high importance and increasing use of social media and electronic services, the need for reviewing and enhancing the provided services has become crucial. Revising the user services is based mainly on sentiment analysis methodologies for analyzing users’ polarities to different products and applications. Sentiment analysis for Arabic reviews is a major concern due to high morphological linguistics and complex polarity terms expressed in the reviews. In addition, the users can present their orientation towards a service or a product by using a hybrid or mix of polarity terms related to slang and standard terminologies. This paper provides a comprehensive review of recent sentiment analysis methods based on lexicon or machine learning (ML). The comparison provides a clear vision of the number of classes, the used dialect, the annotated algorithms, and their performance. The proposed methodology is based on cross-validation of Arabic data using a k-fold mechanism that splits the dataset into training and testing folds; subsequently, the data preprocessing is executed to clean sentiments from unwanted terms that can affect data analysis. A vectorization of the dataset is then applied using TF–IDF for counting word and polarity terms. Furthermore, a feature selection stage is processed using Pearson, Chi2, and Random Forest (RF) methods for mapping the compatibility between input and target features. This paper also proposed an algorithm called the forward fusion feature for sentiment analysis (FFF-SA) to provide a feature selection that applied different machine learning (ML) classification models for each chunk of k features and accumulative features on the Arabic dataset. The experimental results measured and scored all accuracies between the feature importance method and ML models. The best accuracy is recorded with the Naïve Bayes (NB) model with the RF method.

Hair cell morphological patterns and polarity organization in the sea lamprey vestibular cristae.

The inner ear of the sea lamprey was examined by scanning electron microscopy, antibody labeling with tubulin, Myo7a, Spectrin, and Phalloidin stain to elucidate the canal cristae organization and the morphology and polarity of the hair cells. We characterized the hair cell stereocilia bundles and their morphological polarity with respect to the kinocilia. We identified three types of hair cells. In Type 1 hair cells, the kinocilia were slightly longer than the tallest stereocilia. This type was located along the medial bank of the crista and their polarity, based on kinocilia location, was uniformly pointed ampullipetally. Type 2 hair cells that had kinocilia that were much longer than the stereocilia, were most abundant in the central region of the crista. This type of hair cell displayed variable polarity. Type 3 hair cells had extremely long kinocilia (~40-50 μm long) and with extremely short stereocilia. They were mostly located in the lateral zone crista and displayed ampullipetal polarity. Myo7a and tubulin antibodies revealed that hair cells and vestibular afferents are distributed across the canal cristae in the lamprey, covering the area of cruciate eminence; a feature that is absent in more derived vertebrates. Spectrin shows hair cells of varying polarities in the central zone. In this zone, some cells followed the main polarity vector (lateral) like those in medial and lateral zones, whereas other cells displayed polarities that carried up to 40° from the main polarity vector.

Cytoskeletal fractionation identifies LMO7 as a positive regulator of fibroblast polarization and directed migration

Cell migration is a cytoskeleton-driven cellular process involved in physiological and pathological events such as embryonic development and cancer metastasis. Fibroblasts have often been used to elucidate the mechanism of cell migration due to their high morphological polarity and migratory activity. We recently reported that human lung fibroblasts migrate straight for a long duration without external stimuli, which phenomenon we named intrinsic and directed migration (IDM) of fibroblasts. In this study, we explored proteins involved in IDM in order to elucidate the molecular mechanism. First, we focused on the differences in morphology and migratory behaviors between normal and immortalized fibroblasts—the former exhibit obvious polarity and IDM; the latter exhibit poorly polarized morphology and random migration. We compared the abundance of proteins functioning as the cytoskeletal components between them through proteomic analysis and found that LIM domain only protein 7 (LMO7) is overwhelmingly incorporated into the cytoskeletons of normal fibroblasts. Depletion of LMO7 inhibited the directed migration of normal fibroblast on the fibronectin (FN)-rich surface, suggesting that LMO7 is important for IDM. Moreover, on the FN-free surface, LMO7-depleted fibroblasts often failed to establish morphological polarity and hardly migrated. Thus, the present study identified LMO7 as a positive regulator of fibroblast polarization and IDM, especially in an environment where integrin-mediated substrate attachment is insufficient.

Electrochemical sensor based on ion-selective membrane of silica/polyaniline nano-composites for selective determination of uranyl ions

Life threatening impacts of uranium have necessitated its detection and determination in economically feasible way before it arrives in living bodies. Therefore, a new form of UO22+ ion-selective electrode has been fabricated based on membrane of silica/polyaniline core-shell nano-composites, in-spite of traditionally used ionophores, because of intrinsically conducting nature of polyaniline. For the synthesis of these nano-composites, silica has been extracted from rice straw in its cristobalite form, whereas the layer of polyaniline shell has been grafted on silica nanoparticles through in-situ chemical oxidative polymerization technique by cautiously maintaining the electro-active nature of these core-shell nano-composites. The chemical composition, purity, topography, morphology and surface polarity of this nano-composite assembly have been studied through various spectroscopic techniques such as, FT-IR, EDS, FESEM, UV–Vis, DLS and Raman spectroscopy. The results confirm that silica/polyaniline nano-composites have been synthesized with desired semi-cavities and electrostatic surface charge, which is responsible for binding with target cation, i.e., UO22+for its potentiometric determination in aqueous medium even in the presence of interfering metal ions. The designed potentiometric sensor has shown fast and stable linear response in concentration range of 1 × 10−6 to 1 × 10−2 M with the limit of detection of 1.4 × 10−7 M which is 100-folds lower than the detection limit calculated using spectrofluorometry. In addition to this, the proposed UO22+ion-selective electrode has been successfully employed as an indicator electrode for the determination of uranyl ions in complexometric titration and for the estimation of UO22+ions in real life based environmental sample, i.e., soil.

FGF-mediated establishment of left-right asymmetry requires Rab7 function in the dorsal mesoderm in Xenopus.

Gastrulation denotes a very important developmental process, which includes significant structural tissue rearrangements and patterning events that shape the emerging vertebrate organism. At the end of gastrulation, the three body axes are spatially defined while the left-right axis still lacks any molecular or morphological polarity. In most vertebrates, this is established during neurulation by a symmetry breaking LR organizer. However, this mesoderm-derived structure depends on proper induction and specification of the mesoderm, which in turn requires involvement of several signaling pathways. Endocytosis and the endosomal machinery offer manifold platforms for intracellular pathway regulation, especially late endosomes claim increasing attention. The late endosomal regulator Rab7 has been linked to mesoderm specification during gastrulation. Distinct axial defects due to compromised dorsal mesoderm development in rab7-deficient Xenopus embryos suggested a requirement of Rab7 for FGF-dependent mesoderm patterning and LR asymmetry. Here we specifically addressed such a role of Rab7, demonstrating a functional requirement for LR organizer development and symmetry breakage. Using different FGF/MAPK pathway components we show that Rab7 participates in dorsal mesoderm patterning. We suggest a hierarchical classification of Rab7 upstream of MAPK-dependent mesoderm specification, most probably at the level of the small GTPase Ras. Thus, this study affords an insight on how the Rab7-regulated endosomal machinery could participate in signal transduction to enable correct mesoderm specification and left-right asymmetry.

BARS Influences Neuronal Development by Regulation of Post-Golgi Trafficking.

Neurons are highly polarized cells requiring precise regulation of trafficking and targeting of membrane proteins to generate and maintain different and specialized compartments, such as axons and dendrites. Disruption of the Golgi apparatus (GA) secretory pathway in developing neurons alters axon/dendritic formation. Therefore, detailed knowledge of the mechanisms underlying vesicles exiting from the GA is crucial for understanding neuronal polarity. In this study, we analyzed the role of Brefeldin A-Ribosylated Substrate (CtBP1-S/BARS), a member of the C-terminal-binding protein family, in the regulation of neuronal morphological polarization and the exit of membrane proteins from the Trans Golgi Network. Here, we show that BARS is expressed during neuronal development in vitro and that RNAi suppression of BARS inhibits axonal and dendritic elongation in hippocampal neuronal cultures as well as largely perturbed neuronal migration and multipolar-to-bipolar transition during cortical development in situ. In addition, using plasma membrane (PM) proteins fused to GFP and engineered with reversible aggregation domains, we observed that expression of fission dominant-negative BARS delays the exit of dendritic and axonal membrane protein-containing carriers from the GA. Taken together, these data provide the first set of evidence suggesting a role for BARS in neuronal development by regulating post-Golgi membrane trafficking.

From apolar gastrula to polarized larva: Embryonic development of a marine hydroid, Dynamena pumila.

In almost all metazoans examined to this respect, the axial patterning system based on canonical Wnt (cWnt) signaling operates throughout the course of development. In most metazoans, gastrulation is polar, and embryos develop morphological landmarks of axial polarity, such as blastopore under control/regulation from cWnt signaling. However, in many cnidarian species, gastrulation is morphologically apolar. The question remains whether сWnt signaling providing the establishment of a body axis controls morphogenetic processes involved in apolar gastrulation. In this study, we focused on the embryonic development of Dynamena pumila, a cnidarian species with apolar gastrulation. We thoroughly described cell behavior, proliferation, and ultrastructure and examined axial patterning in the embryos of this species. We revealed that the first signs of morphological polarity appear only after the end of gastrulation, while molecular prepatterning of the embryo does exist during gastrulation. We have shown experimentally that in D. pumila, the direction of the oral-aboral axis is highly robust against perturbations in cWnt activity. Our results suggest that morphogenetic processes are uncoupled from molecular axial patterning during gastrulation in D. pumila. Investigation of D. pumila might significantly expand our understanding of the ways in which morphological polarization and axial molecular patterning are linked in Metazoa.