Publications

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an inhibitor of thyroid hormone synthesis protects tail skin grafts transplanted to syngenic adult frogs.tail regression in amphibian tadpoles during metamorphosis is one of the most dynamic morphological changes in animal development and is induced by thyroid hormone (th). it has been proposed that tail resorption is driven by immunological rejection in xenopus laevis, based on experimental evidence showing that larval skin grafts become atrophic on syngenic recipient adult frogs. this led to the hypothesis that tail regression is induced by an immunological rejection against larval skin-specific ...201728990472
design of light-sensitive nmdars by genetically encoded photo-cross-linkers.genetic code expansion exploiting unnatural amino acids (uaas) is a powerful technique to create novel protein function in vivo. here, we provide a protocol for the incorporation of two uv-sensitive crosslinking uaas into nmda receptors (nmdars), a type of glutamate-gated ion channels mediating fast synaptic transmission. through heterologous expression in xenopus laevis oocytes, we have identified light-sensitive nmdars of glun2b subtype by using the two-electrode voltage electrophysiology meas ...201728986874
permeant-specific gating of connexin 30 hemichannels.gap junctions confer interconnectivity of the cytoplasm in neighboring cells via docking of two connexons expressed in each of the adjacent membranes. undocked connexons, referred to as hemichannels, may open and connect the cytoplasm with the extracellular fluid. the hemichannel configuration of connexins (cxs) displays isoform-specific permeability profiles that are not directly determined by the size and charge of the permeant. to further explore ca2+-mediated gating and permeability features ...201728982982
the effect of food properties on grasping and manipulation in the aquatic frog xenopus laevis.the ability to grasp an object is fundamental from an evolutionary perspective. involved in many daily activities, grasping has been extensively studied in primates and other mammals. yet other groups of tetrapods, including anurans, have also evolved significant forelimb prehensile capacities that are often thought to have originated in an arboreal context. in addition, grasping is also observed in aquatic species. but how aquatic frogs use their forelimbs to capture and manipulate prey remains ...201728982969
desynchronizing embryonic cell division waves reveals the robustness of xenopus laevis development.the early xenopus laevis embryo is replete with dynamic spatial waves. one such wave, the cell division wave, emerges from the collective cell division timing of first tens and later hundreds of cells throughout the embryo. here, we show that cell division waves do not propagate between neighboring cells and do not rely on cell-to-cell coupling to maintain their division timing. instead, intrinsic variation in division period autonomously and gradually builds these striking patterns of cell divi ...201728978482
the slc2a14 gene, encoding the novel glucose/dehydroascorbate transporter glut14, is associated with inflammatory bowel disease.background: variations in intestinal antioxidant membrane transporters are implicated in the initiation and progression of inflammatory bowel disease (ibd). facilitated glucose transporter member 14 (glut14), encoded by the solute carrier family 2 member 14 (slc2a14) gene, is a putative transporter for dehydroascorbic acid and glucose. although information on the gene is limited, shorter and longer glut14 isoforms have been identified. we hypothesized that glut14 mediates glucose and dehydroasco ...201728971850
differential cytolocation and functional assays of the two major human slc30a8 (znt8) isoforms.the non-synonymous single nucleotide polymorphism (snp) rs13266634 in human zinc transporter 8, znt8 (slc30a8), leads to a r325 variant, which is associated with an increased risk of developing type 2 diabetes (t2d). although the molecular details remain unknown, the mutation is thought to alter the kinetics of zinc transport into insulin granules in pancreatic β-cells. nevertheless, analysis of znt8 sequences from several animals shows that the amino acid at position 325 is poorly conserved. ap ...201728965566
interaction of excitatory amino acid transporters 1 - 3 (eaat1, eaat2, eaat3) with n-carbamoylglutamate and n-acetylglutamate.inborn deficiency of the n-acetylglutamate synthase (nags) impairs the urea cycle and causes neurotoxic hyperammonemia. oral administration of n-carbamoylglutamate (ncg), a synthetic analog of n-acetylglutamate (nag), successfully decreases plasma ammonia levels in the affected children. due to structural similarities to glutamate, ncg may be absorbed in the intestine and taken up into the liver by excitatory amino acid transporters (eaats).201729055942
maturation of xenopus laevis oocytes under cadmium and lead exposures: cell biology investigations.since amphibians are recognised as good models to assess the quality of environments, only few studies have dealt with the impacts of chemical contaminants on their gametes, while toxic effects at this stage will alter all the next steps of their life cycle. therefore, we propose to investigate the oocyte maturation of xenopus laevis in cadmium- and lead-contaminated conditions. the impacts of cadmium and lead ions were explored on events involved in the hormone-dependent process of maturation. ...201729053961
rare gabra3 variants are associated with epileptic seizures, encephalopathy and dysmorphic features.genetic epilepsies are caused by mutations in a range of different genes, many of them encoding ion channels, receptors or transporters. while the number of detected variants and genes increased dramatically in the recent years, pleiotropic effects have also been recognized, revealing that clinical syndromes with various degrees of severity arise from a single gene, a single mutation, or from different mutations showing similar functional defects. accordingly, several genes coding for gabaa rece ...201729053855
comparative early life stage toxicity of the african clawed frog, xenopus laevis following exposure to selected herbicide formulations applied to eradicate alien plants in south africa.the rise in pesticides application has increased the need for better understanding of their ecological impacts. the global amphibian declines, for example, have been positively correlated with pesticides use. the differential susceptibility in the developmental stages of amphibians to chemical substances are still largely unknown. we examined the 96-h differential toxicity responses of embryos, premetamorphic and transitional larval stage of xenopus laevis, to six formulated aquatic herbicide pr ...201729051999
a molecular atlas of the developing ectoderm defines neural, neural crest, placode, and nonneural progenitor identity in vertebrates.during vertebrate neurulation, the embryonic ectoderm is patterned into lineage progenitors for neural plate, neural crest, placodes and epidermis. here, we use xenopus laevis embryos to analyze the spatial and temporal transcriptome of distinct ectodermal domains in the course of neurulation, during the establishment of cell lineages. in order to define the transcriptome of small groups of cells from a single germ layer and to retain spatial information, dorsal and ventral ectoderm was subdivid ...201729049289
geraniin is a diuretic by inhibiting the na+:k+:2cl- cotransporter, nkcc2.geranium seemannii peyr is a perennial plant endemic in central mexico that has been widely used for its diuretic effect, but the responsible compound of this effect is unknown as well as the mechanism by which the diuretic effect is achieved. geraniin is one of the compounds isolated from this kind of geranium. this study was designed to determinate whether geraniin possesses diuretic activity and to elucidate the mechanism of action. geraniin was extracted and purified from geranium seemannii ...201729046296
inheritance of histones h3 and h4 during dna replication in vitro.nucleosomes are believed to carry epigenetic information through the cell cycle, including through dna replication. it has been known for decades that parental histones are reassembled on newly replicated chromatin, but the mechanisms underlying histone inheritance and dispersal during dna replication are not fully understood. we monitored the fate of histones h3 or h4 from a single nucleosome through dna replication in two in vitro systems. in the sv40 system, histones assembled on a single nuc ...201729091772
abnormal creatine transport of mutations in monocarboxylate transporter 12 (mct12) found in patients with age-related cataract can be partially rescued by exogenous chaperone cd147.membrane transporters influence biological functions in the ocular lens. here, we investigate the monocarboxylate transporter 12 (mct12), also called creatine transporter 2 (crt2), which is found in the ocular lens and is involved in cataract. as the age-related form affects about half of the population world-wide, understanding relevant pathomechanisms is a prerequisite for exploring non-invasive treatments. we screened the coding exons of the gene slc16a12 in 877 patients from five cohorts, in ...201729088427
active site voltage clamp fluorometry of the sodium glucose cotransporter hsglt1.in the human sodium glucose cotransporter (hsglt1) cycle, the protein undergoes conformational changes where the sugar-binding site alternatively faces the external and internal surfaces. functional site-directed fluorometry was used to probe the conformational changes at the sugar-binding site. residues (y290, t287, h83, and n78) were mutated to cysteines. the mutants were expressed in xenopus laevis oocytes and tagged with environmentally sensitive fluorescent rhodamines [e.g., tetramethylrhod ...201729087341
elicitation of xenopus laevis tadpole and adult frog peritoneal leukocytes.peritoneal lavage of xenopus laevis tadpoles and adult frogs is a reliable way of isolating resident and/or recruited innate immune populations. this protocol details the isolation of tadpole and adult amphibian (xenopus laevis) peritoneal leukocytes. the isolated cells are comprised predominantly of innate immune populations and chiefly of mononuclear and polymorphonuclear granulocytes. as described here, these cells are typically elicited by peritoneal injections of animals with heat-killed es ...201729084862
bioconcentration and metabolism of pyriproxyfen in tadpoles of african clawed frogs, xenopus laevis.bioconcentration and metabolism of pyriproxyfen uniformly labeled with 14c at the phenoxyphenyl ring were studied using tadpoles of african clawed frog, xenopus laevis, exposed to water at the nominal concentrations of 3 and 300 ppb for 22 days under the flow-through conditions, with a following 3 day depuration phase. neither meaningful mortality nor abnormal behavior was observed in control and exposure groups throughout the study. after the rapid uptake to tadpoles, pyriproxyfen was extensive ...201729084385
development of xenopus laevis bipotential gonads into testis or ovary is driven by sex-specific cell-cell interactions, proliferation rate, cell migration and deposition of extracellular matrix.information on the mechanisms orchestrating sexual differentiation of the bipotential gonads into testes or ovaries in amphibians is limited. the aim of this study was to investigate the development of xenopus laevis gonad, to identify the earliest signs of sexual differentiation, and to describe mechanisms driving these processes. we used light and electron microscopy, immunofluorescence and cell tracing. in order to identify the earliest signs of sexual differentiation the sex of each tadpole ...201729080791
reactivation of larval keratin gene (krt62.l) in blastema epithelium during xenopus froglet limb regeneration.limb regeneration is considered a form of limb redevelopment because of the molecular and morphological similarities. forming a regeneration blastema is, in essence, creating a developing limb bud in an adult body. this reactivation of a developmental process in a mature body is worth studying. xenopus laevis has a biphasic life cycle that involves distinct larval and adult stages. these distinct developmental stages are useful for investigating the reactivation of developmental processes in pos ...201729079423
biophysical characterization of genetically encoded voltage sensor asap1: dynamic range improvement.recent work has introduced a new fluorescent voltage sensor, asap1, which can monitor rapid trains of action potentials in cultured neurons. this indicator is based on the gallus gallus voltage-sensitive phosphatase with the phosphatase domain removed and a circularly permuted gfp placed in the s3-s4 linker. however, many of the biophysical details of this indicator remain unknown. in this work, we study the biophysical properties of asap1. using the cut-open voltage clamp technique, we have sim ...201729108650
influence of the rdl a301s mutation in the brown planthopper nilaparvata lugens on the activity of phenylpyrazole insecticides.we discovered the a301s mutation in the rdl gaba-gated chloride channel of fiprole resistant rice brown planthopper, nilaparvata lugens populations by dna sequencing and snp calling via rnaseq. ethiprole selection of two field n. lugens populations resulted in strong resistance to both ethiprole and fipronil and resulted in fixation of the a301s mutation, as well as the emergence of another mutation, q359e in one of the selected strains. to analyse the roles of these mutations in resistance to p ...201729107231
identification of novel cis-regulatory elements of eya1 in xenopus laevis using bac recombineering.the multifunctional eya1 protein plays important roles during the development of cranial sensory organs and ganglia, kidneys, hypaxial muscles and several other organs in vertebrates. eya1 is encoded by a complex locus with candidate cis-regulatory elements distributed over a 329 kbp wide genomic region in xenopus. consequently, very little is currently known about how expression of eya1 is controlled by upstream regulators. here we use a library of xenopus tropicalis genomic sequences in bacter ...201729101371
frizzled-7 is required for xenopus heart development.wnt signalling regulates cardiogenesis during specification of heart tissue and the morphogenetic movements necessary to form the linear heart. wnt11-mediated non-canonical signalling promotes early cardiac development whilst wnt11-r, which is expressed later, also signals through the non-canonical pathway to promote heart development. it is unclear which frizzled proteins mediate these interactions. frizzled-7 (fzd7) is expressed during gastrulation in the mesodermal cells fated to become heart ...201729101100
4-aminopyridine: a pan voltage-gated potassium channel inhibitor that enhances kv 7.4 currents and inhibits noradrenaline-mediated contraction of rat mesenteric small arteries.kv 7.4 and kv 7.5 channels are regulators of vascular tone. 4-aminopyridine (4-ap) is considered a broad inhibitor of voltage-gated potassium (kv ) channels, with little inhibitory effect on kv 7 family members at mmol concentrations. however, the effect of 4-ap on kv 7 channels has not been systematically studied. the aim of this study was to investigate the pharmacological activity of 4-ap on kv 7.4 and kv 7.5 channels and characterize the effect of 4-ap on rat resistance arteries.201729156097
a nonredundant role for the trpm6 channel in neural tube closure.in humans, germline mutations in trpm6 cause autosomal dominant hypomagnesemia with secondary hypocalcemia disorder. loss of trpm6 in mice also perturbs cellular magnesium homeostasis but additionally results in early embryonic lethality and neural tube closure defects. to define the mechanisms by which trpm6 influences neural tube closure, we functionally characterized the role of trpm6 during early embryogenesis in xenopus laevis. the expression of xenopus trpm6 (xtrpm6) is elevated at the ons ...201729142255
developmental changes in spinal neuronal properties, motor network configuration and neuromodulation at free-swimming stages of xenopus frog tadpoles.we describe a novel preparation of the isolated brainstem and spinal cord from pro-metamorphic tadpole stages of the south african clawed frog (xenopus laevis) that permits whole cell patch-clamp recordings from neurons in the ventral spinal cord. previous research on earlier stages of the same species has provided one of the most detailed understandings of the design and operation of a cpg circuit. here we have addressed how development sculpts complexity from this more basic circuit. the prepa ...201729142093
it's not all black and white: visual scene parameters influence optokinetic reflex performance in xenopus laevis tadpoles.the maintenance of visual acuity during active and passive body motion is ensured by gaze-stabilizing reflexes that aim at minimizing retinal image slip. for the optokinetic reflex (okr), large-field visual motion of the surround forms the essential stimulus that activates eye movements. properties of the moving visual world influence cognitive motion perception and the estimation of visual image velocity. therefore, the performance of brainstem-mediated visuo-motor behaviors might also depend o ...201729141881
overland movement in african clawed frogs (xenopus laevis): empirical dispersal data from within their native range.dispersal forms are an important component of the ecology of many animals, and reach particular importance for predicting ranges of invasive species. african clawed frogs (xenopus laevis) move overland between water bodies, but all empirical studies are from invasive populations with none from their native southern africa. here we report on incidents of overland movement found through a capture-recapture study carried out over a three year period in overstrand, south africa. the maximum distance ...201729134157
specific inhibition of gpcr-independent g protein signaling by a rationally engineered protein.activation of heterotrimeric g proteins by cytoplasmic nonreceptor proteins is an alternative to the classical mechanism via g protein-coupled receptors (gpcrs). a subset of nonreceptor g protein activators is characterized by a conserved sequence named the gα-binding and activating (gba) motif, which confers guanine nucleotide exchange factor (gef) activity in vitro and promotes g protein-dependent signaling in cells. gba proteins have important roles in physiology and disease but remain greatl ...201729133411
towards functional selectivity for α6β3γ2 gabaa receptors: a series of novel pyrazoloquinolinones.the gabaa receptors are ligand-gated ion channels, which play an important role in neurotransmission. their variety of binding sites serves as an appealing target for many clinically relevant drugs. here, we explored the functional selectivity of modulatory effects at specific extracellular α+/β- interfaces, using a systematically varied series of pyrazoloquinolinones.201729127702
wall following in xenopus laevis is barrier-driven.the tendency of animals to follow boundaries within their environment can serve as a strategy for spatial learning or defensive behaviour. we examined whether xenopus laevis tadpoles and froglets employ such a strategy by characterizing their swimming pattern in a square tank with shallow water. trajectories obtained from video recordings were analysed for proximity to the nearest wall. with the exception of young larvae, the vast majority of animals (both tadpoles and froglets) spent a dispropo ...201729119247
nuclear pore complex plasticity during developmental process as revealed by super-resolution microscopy.nuclear pore complex (npc) is of paramount importance for cellular processes since it is the unique gateway for molecular exchange through the nucleus. unraveling the modifications of the npc structure in response to physiological cues, also called nuclear pore plasticity, is key to the understanding of the selectivity of this molecular machinery. as a step towards this goal, we use the optical super-resolution microscopy method called direct stochastic optical reconstruction microscopy (dstorm) ...201729116248
the rice high-affinity k+ transporter oshkt2;4 mediates mg2+ homeostasis under high-mg2+ conditions in transgenic arabidopsis.rice (oryza sativa; background nipponbare) contains nine hkt (high-affinity k+ transport)-like genes encoding membrane proteins belonging to the superfamily of ktr/trk/hkt. oshkts have been proposed to include four selectivity filter-pore-forming domains homologous to the bacterial k+ channel kcsa, and are separated into oshkt1s with na+-selective activity and oshkt2s with na+-k+ symport activity. as a member of the oshkt2 subfamily, oshkt2;4 renders mg2+ and ca2+ permeability for yeast cells an ...201729114257
xenopus laevis as a model organism for the study of spinal cord formation, development, function and regeneration.the spinal cord is the first central nervous system structure to develop during vertebrate embryogenesis, underscoring its importance to the organism. because of its early formation, accessibility to the developing spinal cord in amniotes is challenging, often invasive and the experimental approaches amenable to model systems like mammals are limited. in contrast, amphibians, in general and the african-clawed frog xenopus laevis, in particular, offer model systems in which the formation of the s ...201729218002
interaction of purinergic p2x4 and p2x7 receptor subunits.p2x4 and p2x7 are members of the p2x receptor family, comprising seven isoforms (p2x1-p2x7) that form homo- and heterotrimeric non-specific cation channels gated by extracellular atp. p2x4 and p2x7 are widely coexpressed, particularly in secretory epithelial cells and immune and inflammatory cells, and regulate inflammation and nociception. although functional heteromerization has been established for p2x2 and p2x3 subunits expressed in sensory neurons, there are contradictory reports regarding ...201729213241
spindle-to-cortex communication in cleaving frog eggs.during cytokinesis, the mitotic spindle communicates with the cell cortex to position a cleavage furrow that will cut through the cell in the plane defined by the metaphase plate. we investigated the molecular basis of this communication in xenopus laevis eggs, where the signal has to travel ∼400 µm in ∼30 min to reach the cortex from the first anaphase spindle. at anaphase onset, huge microtubule asters grow out from the poles of the spindle and meet at the plane previously defined by the metap ...201729196560
the ectodomain of cadherin-11 binds to erbb2 and stimulates akt phosphorylation to promote cranial neural crest cell migration.during development, a multi-potent group of cells known as the cranial neural crest (cnc) migrate to form craniofacial structures. proper migration of these cells requires proteolysis of cell adhesion molecules, such as cadherins. in xenopus laevis, preventing extracellular cleavage of cadherin-11 impairs cnc migration. however, overexpression of the soluble cleavage product (ec1-3) is capable of rescuing this phenotype. the mechanism by which ec1-3 promotes cnc migration has not been investigat ...201729190819
tissue-specific gene inactivation in xenopus laevis: knockout of lhx1 in the kidney with crispr/cas9.studying genes involved in organogenesis is often difficult because many of these genes are also essential for early development. the allotetraploid frog, xenopus laevis, is commonly used to study developmental processes, but because of the presence of two homeologs for many genes, it has been difficult to use as a genetic model. few studies have successfully used crispr in amphibians, and currently there is no tissue-targeted knockout strategy described in xenopus the goal of this study is to d ...201729187504
evaluating the longevity of surgically extracted xenopus laevis oocytes for the study of nematode ligand-gated ion channels.xenopus laevis oocytes have been extensively used as a heterologous expression system for the study of ion channels. while used successfully worldwide as tool for expressing and characterizing ion channels from a wide range of species, the limited longevity of oocytes once removed from the animal can pose significant challenges. in this study, we evaluate a simple and useful method that extends the longevity of xenopus oocytes after removal from the animal and quantitatively assessed the reliabi ...201729185074
quantification of size effect on protein rotational mobility in cells by 19f nmr spectroscopy.protein diffusion in living cells might differ significantly from that measured in vitro. little is known about the effect of globular protein size on rotational diffusion in cells because each protein has distinct surface properties, which result in different interactions with cellular components. to overcome this problem, the b1 domain of protein g (gb1) and several concatemers of the protein were labeled with 5-fluorotryptophan and studied by 19f nmr in escherichia coli cells, xenopus laevis ...201729184995
the r81t mutation in the nicotinic acetylcholine receptor of aphis gossypii is associated with neonicotinoid insecticide resistance with differential effects for cyano- and nitro-substituted neonicotinoids.the cotton aphid, aphis gossypii glover, is one of the most agriculturally important insect pests. neonicotinoid insecticides and sulfoxaflor have generally shown excellent control of a. gossypii, but these aphids have recently developed resistance against neonicotinoid insecticides. we previously characterized a field-collected a. gossypii kushima clone that showed higher resistance to nitro-substituted neonicotinoids, such as imidacloprid, than to cyano-substituted neonicotinoids, such as acet ...201729183611
targeted base editing via rna-guided cytidine deaminases in xenopus laevis embryos.genome editing using programmable nucleases such as crispr/cas9 or cpf1 has emerged as powerful tools for gene knock-out or knock-in in various organisms. while most genetic diseases are caused by point mutations, these genome-editing approaches are inefficient in inducing single-nucleotide substitutions. recently, cas9-linked cytidine deaminases, named base editors (bes), have been shown to convert cytidine to uridine efficiently, leading to targeted single-base pair substitutions in human cell ...201729179261
fmrp regulates neurogenesis in vivo in xenopus laevis tadpoles.fragile x syndrome (fxs) is the leading known monogenic form of autism and the most common form of inherited intellectual disability. fxs results from silencing the fmr1 gene during embryonic development, leading to loss of fragile x mental retardation protein (fmrp), an rna-binding protein that regulates mrna transport, stability, and translation. fxs is commonly thought of as a disease of synaptic dysfunction, however, fmrp expression is lost early in embryonic development, well before most sy ...201725844398
extinction of an introduced warm-climate alien species, xenopus laevis, by extreme weather events.invasive, non-native species represent a major threat to biodiversity worldwide. the african amphibian xenopus laevis is widely regarded as an invasive species and a threat to local faunas. populations originating at the western cape, south africa, have been introduced on four continents, mostly in areas with a similar mediterranean climate. some introduced populations are also established in cooler environments where persistence for many decades suggests a capacity for long-term adaptation. in ...201726430383
methylmercury exposure during early xenopus laevis development affects cell proliferation and death but not neural progenitor specification.methylmercury (mehg) is a widespread environmental toxin that preferentially and adversely affects developing organisms. to investigate the impact of mehg toxicity on the formation of the vertebrate nervous system at physiologically relevant concentrations, we designed a graded phenotype scale for evaluating xenopus laevis embryos exposed to mehg in solution. embryos displayed a range of abnormalities in response to mehg, particularly in brain development, which is influenced by both mehg concen ...201725496965
a staging table of post-ovipositional development for the south american collared lizard tropidurus torquatus (squamata: tropiduridae).the mouse, chicken, african clawed frog, and zebrafish are considered ¨model organisms¨ due to their extensive embryological and genetic characterization. however, they are far from representative of known diversity, impairing phylogenetic analyses of developmental patterns. since squamates have historically received limited attention in developmental studies, we here describe the developmental sequence for tropidurus torquatus, and provide the first post-ovipositional developmental series for t ...201727741560
isolation and functional characterization of cslsi1, a silicon transporter gene in cucumis sativus.cucumber (cucumis sativus) is a widely grown cucurbitaceous vegetable that exhibits a relatively high capacity for silicon (si) accumulation, but the molecular mechanism for silicon uptake remains to be clarified. here we isolated and characterized cslsi1, a gene encoding a silicon transporter in cucumber (cv. mch-4). cslsi1 shares 55.70 and 90.63% homology with the lsi1s of a monocot and dicot, rice (oryza sativa) and pumpkin (cucurbita moschata), respectively. cslsi1 was predominantly expresse ...201727701737
targeting functional noncoding rnas.noncoding rnas have essential biochemical functions in different areas of cellular metabolism, including protein synthesis, rna splicing, protein secretion, and dna replication. we have successfully used morpholino antisense oligonucleotides for the functional inactivation of small noncoding rnas required for dna replication (y rnas in vertebrates and stem-bulge rnas in nematodes). here we discuss specific issues of targeting functional noncoding rnas for inactivation by morpholino antisense oli ...201728364241
h(+)-dependent inorganic phosphate uptake in trypanosoma brucei is influenced by myo-inositol transporter.trypanosoma brucei is an extracellular protozoan parasite that causes human african trypanosomiasis or "sleeping sickness". during the different phases of its life cycle, t. brucei depends on exogenous inorganic phosphate (pi), but little is known about the transport of pi in this organism. in the present study, we showed that the transport of (32)pi across the plasma membrane follows michaelis-menten kinetics and is modulated by ph variation, with higher activity at acidic ph. bloodstream forms ...201728185085
two spatially and temporally distinct ca(2+) signals convey arabidopsis thaliana responses to k(+) deficiency.in plants, potassium (k(+) ) homeostasis is tightly regulated and established against a concentration gradient to the environment. despite the identification of ca(2+) -regulated kinases as modulators of k(+) channels, the immediate signaling and adaptation mechanisms of plants to low-k(+) conditions are only partially understood. to assess the occurrence and role of ca(2+) signals in arabidopsis thaliana roots, we employed ratiometric analyses of ca(2+) dynamics in plants expressing the ca(2+) ...201727579668
polar localization of the nip5;1 boric acid channel is maintained by endocytosis and facilitates boron transport in arabidopsis roots.boron uptake in arabidopsis thaliana is mediated by nodulin 26-like intrinsic protein (nip)5;1, a boric acid channel that is located preferentially on the soil side of the plasma membrane in root cells. however, the mechanism underlying this polar localization is poorly understood. here, we show that the polar localization of nip5;1 in epidermal and endodermal root cells is mediated by the phosphorylation of thr residues in the conserved tpg (thrprogly) repeat in the n-terminal region of nip5;1. ...201728341806
models of amphibian myogenesis - the case of bombina variegata.several different models of myogenesis describing early stages of amphibian paraxial myotomal myogenesis are known. myoblasts of xenopus laevis and hymenochirus boettgeri change their position from perpendicular to parallel, in relation to axial organs, and differentiate into mononucleate myotubes. in bombina variegate the myotomal myoblasts change their shape from round to elongate and then differentiate into mononuclear, morphologically mature myotubes. in pelobates fuscus and triturus vulgari ...201728287243
cloning and expression analysis of zygote arrest 1 (zar1) in new zealand white rabbits.zygote arrest 1 (zar1) is an oocyte-specific maternal-effect gene. previous studies indicate that zar1 plays important role in early embryo development, but little is known about its function in rabbit. the objectives of this study were to clone the new zealand white rabbit zar1 gene and to investigate its expression in various organs in groups of animals with different reproductive traits.we obtained a 709-bp zar1 cdna fragment consisting of an 8-bp exon 1, 161-bp exon 2, 75-bp exon 3, 271-bp e ...201728360383
aquaglyceroporins are the entry pathway of boric acid in trypanosoma brucei.the boron element possesses a range of different effects on living beings. it is essential to beneficial at low concentrations, but toxic at excessive concentrations. recently, some boron-based compounds have been identified as promising molecules against trypanosoma brucei, the causative agent of sleeping sickness. however, until now, the boron metabolism and its access route into the parasite remained elusive. the present study addressed the permeability of t. brucei aquaglyceroporins (tbaqps) ...201728087364
functional characterisation and cell specificity of bvsut1, the transporter that loads sucrose into the phloem of sugar beet (beta vulgaris l.) source leaves.sugar beet (beta vulgaris l.) is one of the most important sugar-producing plants worldwide and provides about one third of the sugar consumed by humans. here we report on molecular characterisation of the bvsut1 gene and on the functional characterisation of the encoded transporter. in contrast to the recently identified tonoplast-localised sucrose transporter bvtst2.1 from sugar beet taproots, which evolved within the monosaccharide transporter (mst) superfamily, bvsut1 represents a classical ...201728075052
sucrose transporter localization and function in phloem unloading in developing stems.how sucrose transporters (suts) regulate phloem unloading in monocot stems is poorly understood and particularly so for species storing high suc concentrations. to this end, sorghum bicolor suts sbsut1 and sbsut5 were characterized by determining their transport properties heterologously expressed in yeast or xenopus laevis oocytes, and their in planta cellular and subcellular localization. the plasma membrane-localized sbsut1 and sbsut5 exhibited a strong selectivity for suc and high suc affini ...201727986867
hepatitis e virus orf3 is a functional ion channel required for release of infectious particles.hepatitis e virus (hev) is the leading cause of enterically transmitted viral hepatitis globally. of hev's three orfs, the function of orf3 has remained elusive. here, we demonstrate that via homophilic interactions orf3 forms multimeric complexes associated with intracellular endoplasmic reticulum (er)-derived membranes. hev orf3 shares several structural features with class i viroporins, and the function of hev orf3 can be maintained by replacing it with the well-characterized viroporin influe ...201728096411
the malaria parasite's lactate transporter pffnt is the target of antiplasmodial compounds identified in whole cell phenotypic screens.in this study the 'malaria box' chemical library comprising 400 compounds with antiplasmodial activity was screened for compounds that perturb the internal ph of the malaria parasite, plasmodium falciparum. fifteen compounds induced an acidification of the parasite cytosol. two of these did so by inhibiting the parasite's formate nitrite transporter (pffnt), which mediates the h+-coupled efflux from the parasite of lactate generated by glycolysis. both compounds were shown to inhibit lactate tra ...201728178359
immune roles of amphibian (xenopus laevis) tadpole granulocytes during frog virus 3 ranavirus infections.infections by frog virus 3 (fv3) and other ranaviruses (rvs) are contributing to the amphibian declines, while the mechanisms controlling anuran tadpole susceptibility and adult frog resistance to rvs, including the roles of polymorphonuclear granulocytes (pmns) during anti-fv3 responses, remain largely unknown. since amphibian kidneys represent an important fv3 target, the inability of amphibian (xenopus laevis) tadpoles to mount effective kidney inflammatory responses to fv3 is thought to cont ...201728238879
amphibian (xenopus laevis) tadpoles and adult frogs mount distinct interferon responses to the frog virus 3 ranavirus.infections of amphibians by frog virus 3 (fv3) and other ranavirus genus members are significantly contributing to the amphibian declines, yet much remains unknown regarding amphibian antiviral immunity. notably, amphibians represent an important step in the evolution of antiviral interferon (ifn) cytokines as they are amongst the first vertebrates to possess both type i and type iii ifns. accordingly, we examined the roles of type i and iii ifns in the skin of fv3-challenged amphibian xenopus l ...201728081430
long term effects of carbaryl exposure on antiviral immune responses in xenopus laevis.water pollutants associated with agriculture may contribute to the increased prevalence of infectious diseases caused by ranaviruses. we have established the amphibian xenopus laevis and the ranavirus frog virus 3 (fv3) as a reliable experimental platform for evaluating the effects of common waterborne pollutants, such as the insecticide carbaryl. following 3 weeks of exposure to 10 ppb carbaryl, x. laevis tadpoles exhibited a marked increase in mortality and accelerated development. exposure at ...201727988452
an inducible amphipathic helix within the intrinsically disordered c-terminus is not required for protein biosynthesis, trafficking, or garp2 interaction, but can participate in membrane curvature generation by peripherin-2/rds.peripherin-2/rds is required for biogenesis of vertebrate photoreceptor outer segment organelles. its localization at the high curvature rim domains of outer segment disk membranes suggests that it may act to shape these structures; however, the molecular function of this protein is not yet resolved. here, we apply biochemical, biophysical, and imaging techniques, to elucidate the role(s) played by the protein's intrinsically disordered c-terminal domain, and an incipient amphipathic α-helix con ...201728325841
effects of amphibian phylogeny, climate and human impact on the occurrence of the amphibian-killing chytrid fungus.chytridiomycosis, due to the fungus batrachochytrium dendrobatidis (bd), has been associated with the alarming decline and extinction crisis of amphibians worldwide. because conservation programs are implemented locally, it is essential to understand how the complex interactions among host species, climate and human activities contribute to bd occurrence at regional scales. using weighted phylogenetic regressions and model selection, we investigated geographic patterns of bd occurrence along a l ...201728055125
trrap is a central regulator of human multiciliated cell formation.the multiciliated cell (mcc) is an evolutionarily conserved cell type, which in vertebrates functions to promote directional fluid flow across epithelial tissues. in the conducting airway, mccs are generated by basal stem/progenitor cells and act in concert with secretory cells to perform mucociliary clearance to expel pathogens from the lung. studies in multiple systems, includingxenopus laevisepidermis, murine trachea, and zebrafish kidney, have uncovered a transcriptional network that regulat ...201829588376
embryonic lethality is not sufficient to explain hourglass-like conservation of vertebrate embryos.understanding the general trends in developmental changes during animal evolution, which are often associated with morphological diversification, has long been a central issue in evolutionary developmental biology. recent comparative transcriptomic studies revealed that gene expression profiles of mid-embryonic period tend to be more evolutionarily conserved than those in earlier or later periods. while the hourglass-like divergence of developmental processes has been demonstrated in a variety o ...201829568479
characterization of pax3 and sox10 transgenic xenopus laevis embryos as tools to study neural crest development.the neural crest is a multipotent population of cells that originates a variety of cell types. many animal models are used to study neural crest induction, migration and differentiation, with amphibians and birds being the most widely used systems. a major technological advance to study neural crest development in mouse, chick and zebrafish has been the generation of transgenic animals in which neural crest specific enhancers/promoters drive the expression of either fluorescent proteins for use ...201829522707
molecular and functional characterization of the gulf toadfish serotonin transporter (sert; slc6a4).the serotonin transporter (sert) functions in the uptake of the neurotransmitter serotonin (5-ht) from the extracellular milieu and is the molecular target of the selective serotonin reuptake inhibitors (ssris), a common group of antidepressants. the current study comprehensively assesses the sequence, tissue distribution, transport kinetics, and physiological function of a teleost sert. the 2,022-bp toadfish sert sequence encodes a protein of 673 amino acids, which shows 83% similarity to zebra ...201829487159
fam60al as a novel factor involved in reprogramming of somatic cell nuclear transfer in zebrafish (danio rerio).the main reason for abnormal development of cloned animals or embryos, and inefficient animal cloning, is a poor understanding of the reprogramming mechanism. to better comprehend reprogramming and subsequent generation of pluripotent stem cells, we must investigate factors related to reprogramming of somatic cells as nuclear donors. as we know,fam60al(family with sequence similarity 60, member a, like) is a coding gene only found in zebrafish and frog (xenopus laevis) among vertebrates. however ...201829483827
chemical screening using cell-freexenopusegg extract.most drug screening methods use purified proteins, cultured cells, and/or small model organisms such asxenopus, zebrafish, flies, or nematodes. these systems have proven successes in drug discovery, but they also have weaknesses. although purified cellular components allow for identification of compounds with activity against specific targets, such systems lack the complex biological interactions present in cellular and organismal screens. in vivo systems overcome these weaknesses, but the lack ...201829475996
expression of the adhesion g protein-coupled receptor a2 (adgra2) during xenopus laevis development.the adhesion g protein-coupled receptor a2 (adgra2) is a seven transmembrane receptor that has been described to be a regulator for angiogenesis in mice. furthermore, the zebrafish ouchless mutant is unable to develop dorsal root ganglia through a disrupted trafficking of adgra2. besides rna sequencing data, nothing is reported about adgra2 in the south african crawled frog xenopus laevis. in this study, we investigated for the first time the spatio-temporal expression of adgra2 during early xen ...201829462671
physiological effects of kdm5c on neural crest migration and eye formation during vertebrate development.lysine-specific histone demethylase 5c (kdm5c) belongs to the jumonji family of demethylases and is specific for the di- and tri-demethylation of lysine 4 residues on histone 3 (h3k4 me2/3). kdm5c is expressed in the brain and skeletal muscles of humans and is associated with various biologically significant processes. kdm5c is known to be associated with x-linked mental retardation and is also involved in the development of cancer. however, the developmental significance of kdm5c has not been e ...201830522514
ivermectin promotes peripheral nerve regeneration during wound healing.peripheral nerves have the capacity to regenerate due to the presence of neuroprotective glia of the peripheral nervous system, schwann cells. upon peripheral nerve injury, schwann cells create a permissive microenvironment for neuronal regrowth by taking up cytotoxic glutamate and secreting neurotrophic signaling molecules. impaired peripheral nerve repair is often caused by a defective schwann cell response after injury, and there is a critical need to develop new strategies to enhance nerve r ...201830411007
i spy with my little eye: a simple behavioral assay to test color sensitivity on digital displays.passive and interactive virtual reality (vr) environments are becoming increasingly popular in the field of behavioral neuroscience. while the technique was originally developed for human observers, corresponding applications have been adopted for the research of visual-driven behavior and neural circuits in animals. rgb color reproduction using red, green and blue primary color pixels is generally calibrated for humans, questioning if the distinct parameters are also readily transferable to oth ...201830127095
biological concerns on the selection of animal models for teratogenic testing.during pregnancy fetus can be exposed to a variety of chemicals which may induce abortion and malformations. due to the amounts of new substances coming into the market every year, a high demand for a rapid, reliable, and cost-effective method to detect potential toxicity is necessary. different species have been used as animal models for teratogen screening, most of them sharing similar development processes with humans. however, the application of embryology knowledge to teratology is hampered ...201829896687
transgenic xenopus laevis line for in vivo labeling of nephrons within the kidney.xenopus laevis embryos are an established model for studying kidney development. the nephron structure and genetic pathways that regulate nephrogenesis are conserved between xenopus and humans, allowing for the study of human disease-causing genes. xenopus embryos are also amenable to large-scale screening, but studies of kidney disease-related genes have been impeded because assessment of kidney development has largely been limited to examining fixed embryos. to overcome this problem, we have g ...201829642376
pharmacological profile of vestibular inhibitory inputs to superior oblique motoneurons.vestibulo-ocular reflexes (vor) are mediated by three-neuronal brainstem pathways that transform semicircular canal and otolith sensory signals into motor commands for the contraction of spatially specific sets of eye muscles. the vestibular excitation and inhibition of extraocular motoneurons underlying this reflex is reciprocally organized and allows coordinated activation of particular eye muscles and concurrent relaxation of their antagonistic counterparts. here, we demonstrate in isolated p ...201829556714
divergent axial morphogenesis and earlyshhexpression in vertebrate prospective floor plate.the notochord has organizer properties and is required for floor plate induction and dorsoventral patterning of the neural tube. this activity has been attributed to sonic hedgehog (shh) signaling, which originates in the notochord, forms a gradient, and autoinducesshhexpression in the floor plate. however, reported data are inconsistent and the spatiotemporal development of the relevantshhexpression domains has not been studied in detail. we therefore studied the expression dynamics ofshhin rab ...201829423139
cloning and spatiotemporal expression of xenopus laevis apolipoprotein ci.apolipoprotein ci (apoci) belongs to the apolipoprotein superfamily, members of which are involved in lipid transport, uptake and homeostasis. excessive apoci has been implicated in atherosclerosis and alzheimer's disease in humans. in this study we report the isolation of xenopus laevis apoci and describe the expression pattern of this gene during early development, using reverse transcription polymerase chain reaction and whole mount in situ hybridization. xenopus apoci is enriched in the dors ...201829346450
investigation of non-cb1, non-cb2 win55212-2-sensitive g-protein-coupled receptors in the brains of mammals, birds, and amphibians.previous studies have found non-cb1 non-cb2 g-protein-coupled receptors in rodents that are activated by the aminoalkylindole cannabinoid agonist win55212-2. this work obtained evidence for the presence or absence of similar receptors in the brains of other mammals, birds and amphibians.201830376752
cardiovascular pharmacology of k2p17.1 (task-4, talk-2) two-pore-domain k+ channels.k2p17.1 (task-4, talk-2) potassium channels are expressed in the heart and represent potential targets for pharmacological management of atrial and ventricular arrhythmias. reduced k2p17.1 expression was found in atria and ventricles of heart failure (hf) patients. modulation of k2p17.1 currents by antiarrhythmic compounds has not been comprehensively studied to date. the objective of this study was to investigate acute effects of clinically relevant antiarrhythmic drugs on human k2p17.1 channel ...201830008082
combined effects of mutations in loop c and the loop d-e-g triangle on neonicotinoid interactions with drosophila dα1/chicken β2 hybrid nachrs.neonicotinoid insecticides interact with the orthosteric sites of nicotinic acetylcholine receptors (nachrs) formed at the interfaces of (a) two adjacent α subunits and (b) α and non-α subunits. however, little is known of the detailed contributions of these two orthosteric sites to neonicotinoid actions. we therefore applied voltage-clamp electrophysiology to the dα1/chicken β2 hybrid nachr expressed in xenopus laevis oocytes to explore the agonist actions of imidacloprid and thiacloprid on wil ...201830704712
the publications of embryologist lev v. beloussov.a list of papers and books of the late lev v. beloussov was compiled and is available in word and endnote supplements. the breadth of his work is briefly described.201830321582
bapx1 is required for jaw joint development in amphibians.the acquisition of a movable jaw and a jaw joint are key events in gnathostome evolution. jaws are derived from the neural crest derived pharyngeal skeleton and the transition from jawless to jawed vertebrates consists of major morphological changes, which must have a genetic foundation. recent studies on the effects of bapx1 knockdown in fish and chicken indicate that bapx1 has acquired such a role in primary jaw joint development during vertebrate evolution, but evidence from amphibians is mis ...201830168254
spindle assembly in egg extracts of the marsabit clawed frog, xenopus borealis.egg extracts of the african clawed frog xenopus laevis have provided a cell-free system instrumental in elucidating events of the cell cycle, including mechanisms of spindle assembly. comparison with extracts from the diploid western clawed frog, xenopus tropicalis, which is smaller at the organism, cellular and subcellular levels, has enabled the identification of spindle size scaling factors. we set out to characterize the marsabit clawed frog, xenopus borealis, which is intermediate in size b ...201829573195
cell cycles during early steps of amphibian embryogenesis: a review.the published data on cell cycles during the initial (pregastrular) period of embryonic development in representatives of the class amphibia have been critically discussed. we have also used the literature data on ontogenetic diversity of these animals. the relatively small eggs of two principal model species for amphibian embryology, the mexican axolotl and the african clawed frog, undergo the extensive series of rapid synchronous cleavage divisions, after which the midblastula transition (mbt) ...201830240720
the tmem16a channel mediates the fast polyspermy block in xenopus laevis.in externally fertilizing animals, such as sea urchins and frogs, prolonged depolarization of the egg immediately after fertilization inhibits the entry of additional sperm-a phenomenon known as the fast block to polyspermy. in the african clawed frog xenopus laevis, this depolarization is driven by ca2+-activated cl- efflux. although the prominent ca2+-activated cl- currents generated in immature x. laevis oocytes are mediated by x. laevis transmembrane protein 16a (xtmem16a) channels, little i ...201830012842
skin regeneration of amphibians: a novel model for skin regeneration as adults.adult mammals do not regenerate the dermis of the skin but form a scar after a deep skin injury. since a scar causes serious medical problems, skin regeneration, instead of formation of a scar, has been strongly desired from a clinical point of view. recent studies have suggested multiple origins of myofibroblasts, which are scar-forming cells in skin wound healing of mammals. while amphibians have skin structures that are basically common to mammals as tetrapods, both urodele and anuran amphibi ...201829947057
bapx1 upregulation is associated with ectopic mandibular cartilage development in amphibians.the emergence of novel structures during evolution is crucial for creating variation among organisms, but the underlying processes which lead to the emergence of evolutionary novelties are poorly understood. the gnathostome jaw joint is such a novelty, and the incorporation of bapx1 expression into the intermediate first pharyngeal arch may have played a major role in the evolution of this joint. knockdown experiments revealed that loss of bapx1 function leads to the loss of the jaw joint, becau ...201829942645
musashi and plasticity of xenopus and axolotl spinal cord ependymal cells.the differentiated state of spinal cord ependymal cells in regeneration-competent amphibians varies between a constitutively active state in what is essentially a developing organism, the tadpole of the frog xenopus laevis, and a quiescent, activatable state in a slowly growing adult salamander ambystoma mexicanum, the axolotl. ependymal cells are epithelial in intact spinal cord of all vertebrates. after transection, body region ependymal epithelium in both xenopus and the axolotl disorganizes ...201829535610
morphological and transcriptomic analyses reveal three discrete primary stages of postembryonic development in the common fire salamander, salamandra salamandra.the postembryonic development of amphibians has been characterized as divided into three predominant periods, hereafter named primary developmental stages: premetamorphosis (prem), prometamorphosis (prom), metamorphic climax (meta), and completion of metamorphosis (postm), largely based on examination of anuran development. here, we categorized the postembryonic development of larvae of a poisonous fire salamander (salamandra salamandra) by integrating morphology and gene expression (transcripto ...201829504232
a role for sox9 in post-transcriptional processes: insights from the amphibian oocyte.sox9 is a member of the gene family of sox transcription factors, which is highly conserved among vertebrates. it is involved in different developmental processes including gonadogenesis. in all amniote species examined thus far, sox9 is expressed in the sertoli cells of the male gonad, suggesting an evolutionarily conserved role in testis development. however, in the anamniotes, fishes and amphibians, it is also expressed in the oocyte but the significance of such an expression remains to be el ...201829740094
effects of copper on the early development of xenopus laevis: the case of cuso4 and bordeaux mixture solutions. 201830701063
time-lapse imaging of cell death in cell culture and whole living organisms using turn-on deep-red fluorescent probes.cell death is a central process in developmental biology and also an important indicator of disease status and treatment efficacy. two related fluorescent probes are described that are molecular conjugates of one or two zinc dipicolylamine (zndpa) coordination complexes with an appended solvatochromic benzothiazolium squaraine dye. the probes were designed to target the anionic phospholipid, phosphatidylserine (ps), that is exposed on the surface of dead and dying cells. a series of spectrometri ...201830858977
ventx1.1 as a direct repressor of early neural gene zic3 in xenopus laevis.from xenopus embryo studies, the bmp4/smad1-targeted gene circuit is a key signaling pathway for specifying the cell fate between the ectoderm and neuro-ectoderm as well as the ventral and dorsal mesoderm. in this context, several bmp4/smad1 target transcriptional factors have been identified as repressors of the neuro-ectoderm. however, none of these direct target transcription factors in this pathway, including gata1b, msx1 and ventx1.1 have yet been proven as direct repressors of early neuro- ...201830590909
development of a rapid functional assay that predicts glut1 disease severity.to examine the genotype to phenotype connection in glucose transporter type 1 (glut1) deficiency and whether a simple functional assay can predict disease outcome from genetic sequence alone.201830588498
xenopus hybrids provide insight into cell and organism size control.determining how size is controlled is a fundamental question in biology that is poorly understood at the organismal, cellular, and subcellular levels. the xenopus species, x. laevis and x. tropicalis differ in size at all three of these levels. despite these differences, fertilization of x. laevis eggs with x. tropicalis sperm gives rise to viable hybrid animals that are intermediate in size. we observed that although hybrid and x. laevis embryogenesis initiates from the same sized zygote and pr ...201830564147
alteration of the retinoid acid-cbp signaling pathway in neural crest induction contributes to enteric nervous system disorder.hirschsprung disease (hscr) and/or hypoganglionosis are common pediatric disorders that arise from developmental deficiencies of enteric neural crest cells (enccs). retinoid acid (ra) signaling has been shown to affect neural crest (nc) development. however, the mechanisms underlying ra deficiency-induced hscr or hypoganglionosis are not well-defined. in this report, we found that in hscr patient bowels, the ra nuclear receptor rarα and its interacting coregulator creb-binding protein (cbp) were ...201830560112
modeling underwater hearing and sound localization in the frog xenopus laevis.animals that are small compared to sound wavelengths face the challenge of localizing a sound source since the main cues to sound direction-interaural time differences (itd) and interaural level differences (ild)-both depend on size. remarkably, the majority of terrestrial vertebrates possess internally coupled ears (ice) with an air-filled cavity connecting the two eardrums and producing an inherently directional middle-ear system. underwater, longer wavelengths and faster sound-speed reduce bo ...201830522324
silurana chromosomal evolution: a new piece to the puzzle.the african clawed frogs of the subgenus silurana comprise both diploid and tetraploid species. the root of the polyploidization event leading to the extant xenopus calcaratus, x. mellotropicalis, and x. epitropicalis is not fully understood so far. in x. mellotropicalis, we previously proposed 2 evolutionary scenarios encompassing complete (scenario a) or incomplete (scenario b) translocation of a heterochromatic block from chromosome 9 to 2 in a diploid ancestor. to resolve this puzzle, we per ...201830537723
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