Publications

autocatalytic microtubule nucleation determines the size and mass of xenopus laevis egg extract spindles.	regulation of size and growth is a fundamental problem in biology. a prominent example is the formation of the mitotic spindle, where protein concentration gradients around chromosomes are thought to regulate spindle growth by controlling microtubule nucleation. previous evidence suggests that microtubules nucleate throughout the spindle structure. however, the mechanisms underlying microtubule nucleation and its spatial regulation are still unclear. here, we developed an assay based on laser ab ...	29323637
reference gene identification and validation for quantitative real-time pcr studies in developing xenopus laevis.	reference genes are essential for gene expression analysis when using real-time quantitative pcr (rt-qpcr). xenopus laevis is a popular amphibian model for studying vertebrate embryogenesis and development. further, x. laevis is ideal for studying thyroid signaling due to its thyroid dependent metamorphosis, a stage comparable to birth in humans. when using pcr based studies, a primary concern is the choice of reference genes. commonly used references are eef1a1, odc1, rpl8, and actnb, although ...	29323148
cranial neural crest transplants.	the transplantation of cranial neural crest (cnc) expressing green fluorescent protein (gfp) in xenopus laevis has allowed researchers not only to assess cnc migration in vivo but also to address many other experimental questions. coupled with loss- or gain-of-function experiments, this technique can be used to characterize the function of specific genes during cnc migration and differentiation. although targeted injection can also be used to assess gene function during cnc migration, cnc transp ...	29321285
cranial neural crest explants.	the cranial neural crest (cnc) explant assay was originally designed to assess the basic requirements for cnc migration in vitro. this protocol describes the key parameters of cnc explants in xenopus laevis, with a focus on how to extirpate cnc cells and assay their migration in vitro. the protocol can be adapted according to the needs of the experimenter, some examples of which are discussed here.	29321283
nucleus assembly and import in xenopus laevis egg extract.	xenopus egg extract represents a powerful cell-free biochemical tool for studying organelle assembly and function. large quantities of cytoplasm can be isolated, and biochemical manipulation of extract composition and cell cycle state is relatively straightforward. in this protocol, we describe the reconstitution of nuclear assembly by adding a chromatin source to interphasic x. laevis egg extract. intact nuclei assemble within 30-45 min of initiating the reaction, followed by nuclear growth. we ...	29321282
analysis of mitotic checkpoint function in xenopus egg extracts.	accurate sister chromatid segregation is pivotal in the faithful transmission of genetic information during each cell division. to ensure accurate segregation, eukaryotic organisms have evolved a "mitotic (or spindle assembly) checkpoint" to prevent premature advance to anaphase before successful attachment of every chromosome to the microtubules of the mitotic spindle. an unattached kinetochore generates a diffusible signal that inhibits ubiquitination of substrates such as cyclin b and securin ...	29321280
whole-mount immunofluorescence for visualizing endogenous protein and injected rna in xenopus oocytes.	asymmetric distribution of mrna and protein is a hallmark of cell polarity in many systems. the xenopus laevis oocyte provides many technical advantages to studying such polarity. thousands of oocytes at different stages of maturity can be harvested from a single ovary and, owing to their relatively large size, even the youngest oocytes can be manually microinjected. microinjection of fluorescently labeled rna combined with immunofluorescence of endogenous proteins can provide insight into the c ...	29321279
paternal chromosome loss and metabolic crisis contribute to hybrid inviability in xenopus.	hybridization of eggs and sperm from closely related species can give rise to genetic diversity, or can lead to embryo inviability owing to incompatibility. although central to evolution, the cellular and molecular mechanisms underlying post-zygotic barriers that drive reproductive isolation and speciation remain largely unknown. species of the african clawed frog xenopus provide an ideal system to study hybridization and genome evolution. xenopus laevis is an allotetraploid with 36 chromosomes ...	29320479
molecular determinants of α3β4 nicotinic acetylcholine receptors inhibition by triterpenoids.	in a previous work, we reported the regulatory role of the triterpenoids on 5-hydroxytryptamine (5-ht)3a receptors activity in xenopus laevis oocytes (eur. j. pharmacol., 615, 2009, lee et al.). in the present report, we studied the modulation of triterpenoids on the activity of the human nicotinic acetylcholine receptor type α3β4. two-electrode voltage clamp experiments were used to test acetylcholine mediated inward current (iach). treatment with triterpenoids (dehydroeburicoic acid, 6α-hydrox ...	29311484
exploring the underlying mechanisms of xenopus laevis embryonic cell cycle.	cell cycle is an indispensable process in the proliferation and development. despite significant efforts, global quantification and physical understanding are still challenging. in this study, we explored the mechanisms of xenopus laevis embryonic cell cycle by quantifying the underlying landscape and flux. we uncovered the mexican hat landscape of the xenopus laevis embryonic cell cycle with several local basins and barriers on the oscillation path. the local basins characterize the different p ...	29310435
nanoscale correlated disorder in out-of-equilibrium myelin ultrastructure.	ultrastructural fluctuations at nanoscale are fundamental to assess properties and functionalities of advanced out-of-equilibrium materials. we have taken myelin as a model of supramolecular assembly in out-of-equilibrium living matter. myelin sheath is a simple stable multilamellar structure of high relevance and impact in biomedicine. although it is known that myelin has a quasi-crystalline ultrastructure, there is no information on its fluctuations at nanoscale in different states due to limi ...	29281257
a triad of residues is functionally transferrable between 5-ht3 serotonin receptors and nicotinic acetylcholine receptors.	cys-loop receptors are pentameric ligand-gated ion channels that facilitate communication within the nervous system. upon neurotransmitter binding, these receptors undergo an allosteric activation mechanism connecting the binding event to the membrane-spanning channel pore, which expands to conduct ions. some of the earliest steps in this activation mechanism are carried out by residues proximal to the binding site, the relative positioning of which may reflect functional differences among membe ...	29298898
dioxin exposure alters molecular and morphological responses to thyroid hormone in xenopus laevis cultured cells and prometamorphic tadpoles.	amphibian metamorphosis is driven by thyroid hormone (th). we used prometamorphic tadpoles and a cell line of the african clawed frog (xenopus laevis) to examine immediate effects of dioxin exposure on th. gene expression patterns suggest cross-talk between the thyroid hormone receptor (tr) and aryl hydrocarbon receptor (ahr) signaling pathways. in xlk-wg cells, expression of cytochrome p450 1a6 (cyp1a6), an ahr target, was induced 1000-fold by 100 nm tcdd (2, 3, 7, 8 tetrachlorodibenzo-p-dioxin ...	29294139
a transgenic reporter under control of an es1 promoter/enhancer marks wound epidermis and apical epithelial cap during tail regeneration in xenopus laevis tadpole.	rapid wound healing and subsequent formation of the apical epithelial cap (aec) are believed to be required for successful appendage regeneration in amphibians. despite the significant role of aec in limb regeneration, its role in tail regeneration and the mechanisms that regulate the wound healing and aec formation are not well understood. we previously identified xenopus laevis es1, which is preferentially expressed in wounded regions, including the aec after tail regeneration. in this study w ...	29291984
hyperinnervation improves xenopus laevis limb regeneration.	xenopus laevis (an anuran amphibian) shows limb regeneration ability between that of urodele amphibians and that of amniotes. xenopus frogs can initiate limb regeneration but fail to form patterned limbs. regenerated limbs mainly consist of cone-shaped cartilage without any joints or branches. these pattern defects are thought to be caused by loss of proper expressions of patterning-related genes. this study shows that hyperinnervation surgery resulted in the induction of a branching regenerate. ...	29291977
optimization of mass spectrometric parameters improve the identification performance of capillary zone electrophoresis for single-shot bottom-up proteomics analysis.	the effects of ms1 injection time, ms2 injection time, dynamic exclusion time, intensity threshold, and isolation width were investigated on the numbers of peptide and protein identifications for single-shot bottom-up proteomics analysis using cze-ms/ms analysis of a xenopus laevis tryptic digest. an electrokinetically pumped nanospray interface was used to couple a linear-polyacrylamide coated capillary to a q exactive hf mass spectrometer. a sensitive method that used a 1.4 th isolation width, ...	29291811
unravelling the mechanisms that determine the uptake and metabolism of magnetic single and multicore nanoparticles in a xenopus laevis model.	multicore superparamagnetic nanoparticles have been proposed as ideal tools for some biomedical applications because of their high magnetic moment per particle, high specific surface area and long term colloidal stability. through controlled aggregation and packing of magnetic cores it is possible to obtain not only single-core but also multicore and hollow spheres with internal voids. in this work, we compare toxicological properties of single and multicore nanoparticles. both types of particle ...	29242877
anosmin-1 is essential for neural crest and cranial placodes formation in xenopus.	during embryogenesis vertebrates develop a complex craniofacial skeleton associated with sensory organs. these structures are primarily derived from two embryonic cell populations the neural crest and cranial placodes, respectively. neural crest cells and cranial placodes are specified through the integrated action of several families of signaling molecules, and the subsequent activation of a complex network of transcription factors. here we describe the expression and function of anosmin-1 (ano ...	29277616
the progestin norethisterone affects thyroid hormone-dependent metamorphosis of xenopus laevis tadpoles at environmentally relevant concentrations.	previously, levonorgestrel (lng) has been shown to be an endocrine disruptor of the amphibian thyroid system. in the present study, we investigated whether anti-thyroidal effects are a common property of progestins other than lng. premetamorphic xenopus laevis tadpoles were exposed to norethisterone (net) and dienogest die (each at 0.1-10nm) and lng (10nm) until completion of metamorphosis. lng and net at all concentrations caused a significant developmental retardation whereas die did not impai ...	29268119
roles for xenopus aquaporin-3b (aqp3.l) during gastrulation: fibrillar fibronectin and tissue boundary establishment in the dorsal margin.	aquaporins and aquaglyceroporins are a large family of membrane channel proteins that allow rapid movement of water and small, uncharged solutes into and out of cells along concentration gradients. recently, aquaporins have been gaining recognition for more complex biological roles than the regulation of cellular osmotic homeostasis. we have identified a specific expression pattern for xenopus aqp3b (also called aqp3.l) during gastrulation, where it is localized to the sensorial (deep) layer of ...	29113748
effect of imidacloprid on the survival of xenopus tadpoles challenged with wild type frog virus 3.	the sensitivity of amphibians to ranavirus may be increased by exposure to other environmental stressors, including chemical contaminants. neonicotinoid insecticides comprise 27% of the global insecticide market and have been detected in wetlands and other aquatic habitats. the present study focused on the effects of exposure of pre-metamorphic xenopus laevis to the neonicotinoid, imidacloprid (imi) on sensitivity to frog virus 3 (fv3) infection. it was hypothesized that exposure of tadpoles to ...	29179150
regulation of kv1.4 potassium channels by pkc and ampk kinases.	over the last years extensive kinase-mediated regulation of a number of voltage-gated potassium (kv) channels important in cardiac electrophysiology has been reported. this includes regulation of kv1.5, kv7.1 and kv11.1 cell surface expression, where the kinase-mediated regulation appears to center around the ubiquitin ligase nedd4-2. in the present study we examined whether kv1.4, constituting the cardiac ito,s current, is subject to similar regulation. in the epithelial madin-darby canine kidn ...	29168928
identification of isthmin 1 as a novel clefting and craniofacial patterning gene in humans.	orofacial clefts are one of the most common birth defects, affecting 1-2 per 1000 births, and have a complex etiology. high-resolution array-based comparative genomic hybridization has increased the ability to detect copy number variants (cnvs) that can be causative for complex diseases such as cleft lip and/or palate. utilizing this technique on 97 nonsyndromic cleft lip and palate cases and 43 cases with cleft palate only, we identified a heterozygous deletion of isthmin 1 in one affected case ...	29162626
functional differences in transport properties of natural hkt1;1 variants influence shoot na+ exclusion in grapevine rootstocks.	under salinity, vitis spp. rootstocks can mediate salt (nacl) exclusion from grafted v. vinifera scions enabling higher grapevine yields and production of superior wines with lower salt content. until now, the genetic and mechanistic elements controlling sodium (na+ ) exclusion in grapevine were unknown. using a cross between two vitis interspecific hybrid rootstocks, we mapped a dominant quantitative trait locus (qtl) associated with leaf na+ exclusion (nae) under salinity stress. the nae locus ...	29160564
the extraordinary biology and development of marsupial frogs (hemiphractidae) in comparison with fish, mammals, birds, amphibians and other animals.	the study of oogenesis and early development of frogs belonging to the family hemiphractidae provide important comparison to the aquatic development of other frogs, such as xenopus laevis, because reproduction on land characterizes the hemiphractidae. in this review, the multinucleated oogenesis of the marsupial frog flectonotus pygmaeus (hemiphractidae) is analyzed and interpreted. in addition, the adaptations associated with the incubation of embryos in the pouch of the female marsupial frog g ...	29305906
phosphoregulation of k+ -cl- cotransporters during cell swelling: novel insights.	the k+ -cl- cotransporters (kccs) belong to the cation-cl- cotransporter family and consist of four isoforms and many splice variants. their main role is to promote electroneutral efflux of k+ and cl- ions across the surface of many cell types and, thereby, to regulate intracellular ion concentration, cell volume, and epithelial salt movement. these transport systems are induced by an increase in cell volume and are less active at lower intracellular [cl- ] (cli ), but the mechanisms at play are ...	28276587
the regulation of heat shock proteins in response to dehydration in xenopus laevis.	african clawed frogs (xenopus laevis) endure bouts of severe drought in their natural habitats and survive the loss of approximately 30% of total body water due to dehydration. to investigate molecular mechanisms employed by x. laevis during periods of dehydration, the heat shock protein response, a vital component of the cytoprotective stress response, was characterized. using western immunoblotting and multiplex technology, the protein levels of hsp27, hsp40, hsp60, hsp70, hsc70, and hsp90 wer ...	28676984
sequence and timing of early cranial skeletal development in xenopus laevis.	xenopus laevis is widely used as a model organism in biological research. morphological descriptions of the larval cartilaginous skeleton are more than half a century old and comprehensive studies of early cartilage differentiation and development are missing. a proper understanding of early cranial skeletal development in x. laevis requires a detailed description that can function as a baseline for experimental studies. this basis makes it possible to evaluate skeletal defects produced by exper ...	28960402
aprotinin prevents proteolytic epithelial sodium channel (enac) activation and volume retention in nephrotic syndrome.	volume retention in nephrotic syndrome has been linked to activation of the epithelial sodium channel (enac) by proteolysis of its γ-subunit following urinary excretion of serine proteases such as plasmin. here we tested whether pharmacological inhibition of urinary serine protease activity might protect from enac activation and volume retention in nephrotic syndrome. urine from both nephrotic mice (induced by doxorubicin injection) and nephrotic patients exhibited high aprotinin-sensitive serin ...	29042083
xenbase: a genomic, epigenomic and transcriptomic model organism database.	xenbase (www.xenbase.org) is an online resource for researchers utilizing xenopus laevis and xenopus tropicalis, and for biomedical scientists seeking access to data generated with these model systems. content is aggregated from a variety of external resources and also generated by in-house curation of scientific literature and bioinformatic analyses. over the past two years many new types of content have been added along with new tools and functionalities to reflect the impact of high-throughpu ...	29059324
site-directed unnatural amino acid mutagenesis to investigate potassium channel pharmacology in xenopus laevis oocytes.	unnatural amino acid mutagenesis is a useful tool enabling detailed investigation of ion channel structure-function relationships and pharmacology. methods have been developed to apply this technique to different heterologous systems for electrophysiological studies, with each system offering unique advantages and limitations. synthesis of aminoacylated-trna followed by injection into xenopus laevis oocytes is beneficial because it allows for the incorporation of a wide range of unnatural sidech ...	29058197
aurora a activation in mitosis promoted by bugz.	protein phase separation or coacervation has emerged as a potential mechanism to regulate biological functions. we have shown that coacervation of a mostly unstructured protein, bugz, promotes assembly of spindle and its matrix. bugz in the spindle matrix binds and concentrates tubulin to promote microtubule (mt) assembly. it remains unclear, however, whether bugz could regulate additional proteins to promote spindle assembly. in this study, we report that bugz promotes aurora a (aura) activatio ...	29074706
effect of isothiocyanates, bitc and peitc, on stress protein accumulation, protein aggregation and aggresome-like structure formation in xenopus a6 kidney epithelial cells.	numerous studies have elucidated the health benefits of organosulfur compounds, known as isothiocyanates (itcs), derived from cruciferous vegetables. as electrophiles, itcs have the ability to directly bind and modify thiol-containing compounds such as glutathione and cellular protein, including tubulin. while the biochemical effects of itcs have been well characterized, less information is available regarding their effects on the accumulation of stress-inducible heme oxygenase-1 (ho-1), heat sh ...	29100952
glut characterization using frog xenopus laevis oocytes.	xenopus laevis oocytes are a useful heterologous expression system for expressing glucose transporters (gluts) and examining their functions. in this chapter, we provide a detailed protocol on oocyte extraction and preparation for glut9 protein expression. furthermore, we describe the determination of glut9 overexpression level by biotinylation and western blotting analysis. finally, we also describe how glut9-expressing oocytes can be used to measure urate kinetics by radioisotopes as well as t ...	29218516
models of convergent extension during morphogenesis.	convergent extension (ce) is a fundamental and conserved collective cell movement that forms elongated tissues during embryonic development. thus far, studies have demonstrated two different mechanistic models of collective cell movements during ce. the first, termed the crawling mode, was discovered in the process of notochord formation in xenopus laevis embryos, and has been the established model of ce for decades. the second model, known as the contraction mode, was originally reported in stu ...	28906063
negative modulation of the gabaa ρ1 receptor function by l-cysteine.	l-cysteine is an endogenous sulfur-containing amino acid with multiple and varied roles in the central nervous system, including neuroprotection and the maintenance of the redox balance. however, it was also suggested as an excitotoxic agent implicated in the pathogenesis of neurological disorders such as parkinson's and alzheimer's disease. l-cysteine can modulate the activity of ionic channels, including voltage-gated calcium channels and glutamatergic nmda receptors, whereas its effects on ga ...	29023772
functional properties and mechanism of action of pptq, an allosteric agonist and low nanomolar positive allosteric modulator at gabaa receptors.	the former sedative-hypnotic and recreational drug methaqualone (quaalude) is a moderately potent, non-selective positive allosteric modulator (pam) at gabaa receptors (gabaars) (hammer et al., 2015). in the present study, we have identified a novel methaqualone analog, 2-phenyl-3-(p-tolyl)quinazolin-4(3h)-one (pptq), in a screening of 67 analogs at five αβ2γ2s gabaar subtypes and delineated its functional properties and mechanism of action at wild-type and mutant gabaars expressed in xenopus la ...	29155148
hmg-box factor soxd/sox15 and homeodomain-containing factor xanf1/hesx1 directly interact and regulate the expression of xanf1/hesx1 during early forebrain development in xenopus laevis.	the homeodomain-containing transcription factor anf (also known as rpx/hesx1 in mammals) plays an important role during the forebrain development in vertebrates. here we demonstrate the ability of the xenopus laevis anf, xanf1/hesx1, to directly bind sry-related hmg-box-containing transcription factor soxd/sox15 and to cooperate with the latter during regulating of the expression of xanf1/hesx1 own gene. as we have shown by gst pull-down, emsa and the luciferase reporter assays, xanf1/hesx1 and ...	28918251