Distinct Molecular Evolutionary Mechanisms Underlie the Functional Diversification of the Wnt and TGFβ Signaling Pathways

The canonical Wnt pathway is one of the oldest and most functionally diverse of animal intercellular signaling pathways. Though much is known about loss-of-function phenotypes for Wnt pathway components in several model organisms, the question of how this pathway achieved its current repertoire of functions has not been addressed. Our phylogenetic analyses of 11 multigene families from five species belonging to distinct phyla, as well as additional analyses employing the 12 Drosophila genomes, suggest frequent gene duplications affecting ligands and receptors as well as co-evolution of new ligand–receptor pairs likely facilitated the expansion of this pathway’s capabilities. Further, several examples of recent gene loss are visible in Drosophila when compared to family members in other phyla. By comparison the TGFβ signaling pathway is characterized by ancient gene duplications of ligands, receptors, and signal transducers with recent duplication events restricted to the vertebrate lineage. Overall, the data suggest that two distinct molecular evolutionary mechanisms can create a functionally diverse developmental signaling pathway. These are the recent dynamic generation of new genes and ligand–receptor interactions as seen in the Wnt pathway and the conservative adaptation of ancient pre-existing genes to new roles as seen in the TGFβ pathway. From a practical perspective, the former mechanism limits the investigator’s ability to transfer knowledge of specific pathway functions across species while the latter facilitates knowledge transfer.     

Opposing Nodal and BMP Signals Regulate Left–Right Asymmetry in the Sea Urchin Larva

Nodal and BMP signals are important for establishing left-right (LR) asymmetry in vertebrates. In sea urchins, Nodal signaling prevents the formation of the rudiment on the right side. However, the opposing pathway to Nodal signaling during LR axis establishment is not clear. Here, we revealed that BMP signaling is activated in the left coelomic pouch, specifically in the veg2 lineage, but not in the small micromeres. By perturbing BMP activities, we demonstrated that BMP signaling is required for activating the expression of the left-sided genes and the formation of the left-sided structures. On the other hand, Nodal signals on the right side inhibit BMP signaling and control LR asymmetric separation and apoptosis of the small micromeres. Our findings show that BMP signaling is the positive signal for left-sided development in sea urchins, suggesting that the opposing roles of Nodal and BMP signals in establishing LR asymmetry are conserved in deuterostomes.     

Plasminogen Activator Inhibitor-1 Is a Transcriptional Target of the Canonical Pathway of Wnt/β-Catenin Signaling

Plasminogen activator inhibitor-1 (PAI-1) is a multifunctional glycoprotein that plays a critical role in the pathogenesis of chronic kidney and cardiovascular diseases. Although transforming growth factor (TGF)-β1 is a known inducer of PAI-1, how it controls PAI-1 expression remains enigmatic. Here we investigated the mechanism underlying TGF-β1 regulation of PAI-1 in kidney tubular epithelial cells (HKC-8). Surprisingly, overexpression of Smad2 or Smad3 in HKC-8 cells blocked PAI-1 induction by TGF-β1, whereas knockdown of them sensitized the cells to TGF-β1 stimulation, suggesting that Smad signaling is not responsible for PAI-1 induction. Blockade of several TGF-β1 downstream pathways such as p38 MAPK or JNK, but not phosphatidylinositol 3-kinase/Akt and ERK1/2, only partially inhibited PAI-1 expression. TGF-β1 stimulated β-catenin activation in tubular epithelial cells, and ectopic expression of β-catenin induced PAI-1 expression, whereas inhibition of β-catenin abolished its induction. A functional T cell factor/lymphoid enhancer-binding factor-binding site was identified in the promoter region of the PAI-1 gene, which interacted with T cell factor upon β-catenin activation. Deletion or site-directed mutation of this site abolished PAI-1 response to β-catenin or TGF-β1 stimulation. Similarly, ectopic expression of Wnt1 also activated PAI-1 expression and promoter activity. In vivo, PAI-1 was induced in kidney tubular epithelia in obstructive nephropathy. Delivery of Wnt1 gene activated β-catenin and promoted PAI-1 expression after obstructive injury, whereas blockade of Wnt/β-catenin signaling by Dickkopf-1 gene inhibited PAI-1 induction. Collectively, these studies identify PAI-1 as a direct downstream target of Wnt/β-catenin signaling and demonstrate that PAI-1 induction could play a role in mediating the fibrogenic action of this signaling.     

Early Activation of FGF and Nodal Pathways Mediates Cardiac Specification Independently of Wnt/β-Catenin Signaling

Background

Cardiac induction, the first step in heart development in vertebrate embryos, is thought to be initiated by anterior endoderm during gastrulation, but what the signals are and how they act is unknown. Several signaling pathways, including FGF, Nodal, BMP and Wnt have been implicated in cardiac specification, in both gain- and loss-of-function experiments. However, as these pathways regulate germ layer formation and patterning, their specific roles in cardiac induction have been difficult to define.

Methodology/Principal Findings

To investigate the mechanisms of cardiac induction directly we devised an assay based on conjugates of anterior endoderm from early gastrula stage Xenopus embryos as the inducing tissue and pluripotent ectodermal explants as the responding tissue. We show that the anterior endoderm produces a specific signal, as skeletal muscle is not induced. Cardiac inducing signal needs up to two hours of interaction with the responding tissue to produce an effect. While we found that the BMP pathway was not necessary, our results demonstrate that the FGF and Nodal pathways are essential for cardiogenesis. They were required only during the first hour of cardiogenesis, while sustained activation of ERK was required for at least four hours. Our results also show that transient early activation of the Wnt/β-catenin pathway has no effect on cardiogenesis, while later activation of the pathway antagonizes cardiac differentiation.

Conclusions/Significance

We have described an assay for investigating the mechanisms of cardiac induction by anterior endoderm. The assay was used to provide evidence for a direct, early and transient requirement of FGF and Nodal pathways. In addition, we demonstrate that Wnt/β-catenin pathway plays no direct role in vertebrate cardiac specification, but needs to be suppressed just prior to differentiation.     

Study and Simulation of Reaction–Diffusion Systems Affected by Interacting Signaling Pathways

Possible effects of interaction (cross-talk) between signaling pathways is studied in a system of Reaction-Diffusion (RD) equations. Furthermore, the relevance of spontaneous neurite symmetry breaking and Turing instability has been examined through numerical simulations. The interaction between Retinoic Acid (RA) and Notch signaling pathways is considered as a perturbation to RD system of axon-forming potential for N2a neuroblastoma cells. The present work suggests that large increases to the level of RA-Notch interaction can possibly have substantial impacts on neurite outgrowth and on the process of axon formation. This can be observed by the numerical study of the homogeneous system showing that in the absence of RA-Notch interaction the unperturbed homogeneous system may exhibit different saddle-node bifurcations that are robust under small perturbations by low levels of RA-Notch interactions, while large increases in the level of RA-Notch interaction result in a number of transitions of saddle-node bifurcations into Hopf bifurcations. It is speculated that near a Hopf bifurcation, the regulations between the positive and negative feedbacks change in such a way that spontaneous symmetry breaking takes place only when transport of activated Notch protein takes place at a faster rate.     

Long-distance ABA Signaling and Its Relation to Other Signaling Pathways in the Detection of Soil Drying and the Mediation of the Plant’s Response to Drought

In this article we review evidence for a variety of long-distance signaling pathways involving hormones and nutrient ions moving in the xylem sap. We argue that ABA has a central role to play, at least in root-to-shoot drought stress signaling and the regulation of functioning, growth, and development of plants in drying soil. We also stress the importance of changes in the pH of the leaf cell apoplast as influenced both by edaphic and climatic variation, as a regulator of shoot growth and functioning, and we show how changes in xylem and apoplastic pH can affect the way in which ABA regulates stomatal behavior and growth. The sensitivity to drought of the pH/ABA sensing and signaling mechanism is emphasized. This allows regulation of plant growth, development and functioning, and particularly shoot water status, as distinct from stress lesions in growth and other processes as a reaction to perturbations such as soil drying.     

Summer-autumn ichthyoplankton of the Sea of Okhotsk and the Sea of Japan and special traits of feeding of fish larvae and fry in 2003–2004

In summer-autumn of 2003–2004, the ichthyoplankton of the Sea of Okhotsk comprised 35 species. In this period the most widely distributed and numerous were larvae of the lord Hemilepidotus gilberti, the Pacific stout sand lance Ammodytes hexapterus, and the Sakhalin dab Limanda sakhalinensis. The maximum catches of fish larvae were attributed to coastal waters off eastern Sakhalin and to the shelf of the northern part of the Sea of Okhotsk. In November of 2003, the ichthyoplankton of the Sea of Japan was represented by fish larvae belonging mainly to the boreal ichthyocomplex. The catches consisted predominantly of larvae of the arabesque greenling Pleurogrammus azonus, the ronquil Bathymaster derjugini, and the rockfish Sebastes owstoni. Fish larvae and fry in the northwestern part of the Sea of Japan were caught principally within 43°–45° N and 137°–139° E above the depth 1500–2000 m. The food spectrum of fish larvae in the Sea of Okhotsk and the Sea of Japan comprised over 20 plankters of various size belonging to seven taxa. Irrespective of fish species, the food items common of all fish were copepods Pseudocalanus minutus and Oithona similis. The daily rations were calculated for mass species (Hemilepidotus gilberti, Ammodytes hexapterus, Hexagrammos stelleri, Pleurogrammus azonus, Bathymaster derjugini, and Sebastes owstoni). The larvae of all considered species in the Sea of Japan and in the Sea of Okhotsk fed predominantly in the light period of the day.     

Production characteristics of bacteria and phytoplankton in the Sea of Okhotsk and Bering Sea during spring–summer

Production parameters for bacterioplankton were assessed during the spring–summer period in the western parts of the Sea of Okhotsk and the Bering Sea, as well as in northwestern Pacific Ocean. The lowest values of bacterial production were observed in early June during the spring phytoplankton bloom (0.08 mg C day^–1 m^–3), while the maximum values (up to 55 mg C day^–1 m^–3) occurred in late July?early August, 1.5 to 2 months after the bloom. The concentration of dissolved organic matter, the substrate for bacterioplankton, was assessed using satellite data. The ratio between bacterial and primary production in the surface samples varied from 0.5% at the peak of phytoplankton bloom to 180% at the peak of bacterioplankton development.     

Abnormal Resting-State Activities and Functional Connectivities of the Anterior and the Posterior Cortexes in Medication-Na?ve Patients with Obsessive-Compulsive Disorder

Background

Obsessive-compulsive disorder (OCD) is a mental illness characterized by the loss of control. Because the cingulate cortex is believed to be important in executive functions, such as inhibition, we used functional magnetic resonance imaging (fMRI) techniques to examine whether and how activity and functional connectivity (FC) of the cingulate cortex were altered in drug-naïve OCD patients.

Methods

Twenty-three medication-naïve OCD patients and 23 well-matched healthy controls received fMRI scans in a resting state. Functional connectivities of the anterior cingulate (ACC) and the posterior cingulate (PCC) to the whole brain were analyzed using correlation analyses based on regions of interest (ROI) identified by the fractional amplitude of low-frequency fluctuation (fALFF). Independent Component Analysis (ICA) was used to identify the resting-state sub-networks.

Results

fALFF analysis found that regional activity was increased in the ACC and decreased in the PCC in OCD patients when compared to controls. FC of the ACC and the PCC also showed different patterns. The ACC and the PCC were found to belong to different resting-state sub-networks in ICA analysis and showed abnormal FC, as well as contrasting correlations with the severity of OCD symptoms.

Conclusions

Activity of the ACC and the PCC were increased and decreased, respectively, in the medication-naïve OCD patients compared to controls. Different patterns in FC were also found between the ACC and the PCC with respect to these two groups. These findings implied that the cardinal feature of OCD, the loss of control, may be attributed to abnormal activities and FC of the ACC and the PCC.     

Structural and Functional Integration of the PLCγ Interaction Domains Critical for Regulatory Mechanisms and Signaling Deregulation

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Highlights? Domains from PLCγ regulatory region show structural and functional integration ? Only cSH2 domain interacts with the PLC-core forming a high affinity surface ? Activation involves removal of autoinhibition and dissociation from the receptor ? Disease-linked mutations map to the autoinhibitory interface     

Interaction of NF-κB and Wnt/β-catenin Signaling Pathways in Alzheimer’s Disease and Potential Active Drug Treatments

The most important neuropathological features of Alzheimer's disease (AD) are extracellular amyloid-β protein (Aβ) deposition, tau protein hyperphosphorylation and activation of neurometabolic reaction in the brain accompanied by neuronal and synaptic damage, and impaired learning and memory function. According to the amyloid cascade hypothesis, increased Aβ deposits in the brain to form the core of the senile plaques that initiate cascade reactions, affecting the synapses and stimulating activation of microglia, resulting in neuroinflammation. A growing number of studies has shown that NF-κB and Wnt/β-catenin pathways play important roles in neurodegenerative diseases, especially AD. In this review, we briefly introduce the connection between neuroinflammation-mediated synaptic dysfunction in AD and elaborated on the mechanism of these two signaling pathways in AD-related pathological changes, as well as their interaction. Based on our interest in natural compounds, we also briefly introduce and conduct preliminary screening of potential therapeutics for AD.

     

Involvement of the Wnt/β-Catenin Signaling Pathway in the Cellular and Molecular Mechanisms of Fibrosis in Endometriosis

Background

During the development and progression of endometriotic lesions, excess fibrosis may lead to scarring, chronic pain, and altered tissue function. However, the cellular and molecular mechanisms of fibrosis in endometriosis remain to be clarified.

Objectives

The objective of the present study was to investigate whether the Wnt/β-catenin signaling pathway was involved in regulating the cellular and molecular mechanisms of fibrosis in endometriosis in vitro and to evaluate whether fibrosis could be prevented by targeting the Wnt/β-catenin pathway in a xenograft model of endometriosis in immunodeficient nude mice.

Methods

Seventy patients (40 with and 30 without endometriosis) with normal menstrual cycles were recruited. In vitro effects of small-molecule antagonists of the Tcf/β-catenin complex (PKF 115-584 and CGP049090) on fibrotic markers (alpha smooth muscle actin, type I collagen, connective tissue growth factor, fibronectin) and collagen gel contraction were evaluated in endometrial and endometriotic stromal cells from patients with endometriosis. In vitro effects of activation of the Wnt/β-catenin signaling pathway by treatment with recombinant Wnt3a on profibrotic responses were evaluated in endometrial stromal cells of patients without endometriosis. The effects of CGP049090 treatment on the fibrosis of endometriotic implants were evaluated in a xenograft model of endometriosis in immunodeficient nude mice.

Results

Treatment with PKF 115-584 and CGP049090 significantly decreased the expression of alpha smooth muscle actin, type I collagen, connective tissue growth factor and fibronectin mRNAs in both endometriotic and endometrial stromal cells with or without transforming growth factor-β1 stimulation. Both endometriotic and endometrial stromal cell-mediated contraction of collagen gels was significantly decreased by treatment with PKF 115-584 and CGP049090 as compared to that of untreated cells. The animal experiments showed that CGP049090 prevented the progression of fibrosis and reversed established fibrosis in endometriosis.

Conclusion

Aberrant activation of the Wnt/β-catenin pathway may be involved in mediating fibrogenesis in endometriosis.     

Chronic Stress Suppresses the Expression of Cutaneous Hypothalamic–Pituitary–Adrenocortical Axis Elements and Melanogenesis

Chronic stress can affect skin function, and some skin diseases might be triggered or aggravated by stress. Stress can activate the central hypothalamic–pituitary–adrenocortical (HPA) axis, which causes glucocorticoid levels to increase. The skin has HPA axis elements that react to environmental stressors to regulate skin functions, such as melanogenesis. This study explores the mechanism whereby chronic stress affects skin pigmentation, focusing on the HPA axis, and investigates the role of glucocorticoids in this pathway. We exposed C57BL/6 male mice to two types of chronic stress, chronic restraint stress (CRS) and chronic unpredictable mild stress (CUMS). Mice subjected to either stress condition showed reduced melanogenesis. Interestingly, CRS and CUMS triggered reductions in the mRNA expression levels of key factors involved in the HPA axis in the skin. In mice administered corticosterone, decreased melanin synthesis and reduced expression of HPA axis elements were observed. The reduced expression of HPA axis elements and melanogenesis in the skin of stressed mice were reversed by RU486 (a glucocorticoid receptor antagonist) treatment. Glucocorticoids had no significant inhibitory effect on melanogenesis in vitro. These results suggest that, high levels of serum corticosterone induced by chronic stress can reduce the expression of elements of the skin HPA axis by glucocorticoid-dependent negative feedback. These activities can eventually result in decreased skin pigmentation. Our findings raise the possibility that chronic stress could be a risk factor for depigmentation by disrupting the cutaneous HPA axis and should prompt dermatologists to exercise more caution when using glucocorticoids for treatment.     

The Gut–Brain Axis and Peroxisome Proliferator-Activated Receptors in the Regulation of Epileptogenesis

Journal of Evolutionary Biochemistry and Physiology - A large proportion of patients with epilepsy suffer from pharmacoresistant forms of the disease, and this makes the search for new treatments...     

Effect of Intracerebroventricular Administration of Apelin-13 on the Hypothalamus–Pituitary–Thyroid Axis and Peripheral Uncoupling Proteins

Apelin, a ligand for G protein-coupled APJ receptor, is a peptide hormone. Although apelin and APJ receptors are determined in hypothalamus and thyroid gland its role in the hypothalamus–pituitary–thyroid (HPT) axis and mechanism of action on energy metabolism is not clear. This suggests that apelin may play a role in the HPT axis and energy metabolism. This study was designed to determine possible effects of centrally administered apelin-13 on the HPT axis and energy metabolism. A total of 40 adult male Sprague Dawley rats were divided into four groups (n?=?10 each group). Intact rats served as control group while the sham group received vehicle of apelin. Apelin-13 was injected intracerebroventricularly at the doses of 1 and 10 nmol, for 7 days in the rats in the experimental group. At the end of the experimental protocol, animals were decapitated and brain, blood, white and brown adipose tissues samples were collected. There was no significant difference between the groups in terms of hypothalamic TRH mRNA levels. Serum TSH levels were significantly higher in all groups compared to the control group (p?<?0.05). Serum fT3 and fT4 levels were significantly lower in apelin-13 administered groups (p?<?0.05). Moreover, apelin-13 administered groups had lower levels of UCP1 mRNA in white and brown adipose tissues. UCP3 mRNA expression in muscle tissue was also lower in apelin-13 treated groups (p?<?0.05). These results indicates that apelin-13 exhibits a decreasing effect on energy consumption through a mechanism involving the peripheral rather than central arms of the HPT axis.