Publications

TitleAbstractYear(sorted ascending)
Filter
PMID
Filter
concise review: pursuing self-renewal and pluripotency with the stem cell factor nanog.pluripotent embryonic stem cells and induced pluripotent stem cells hold great promise for future use in tissue replacement therapies due to their ability to self-renew indefinitely and to differentiate into all adult cell types. harnessing this therapeutic potential efficiently requires a much deeper understanding of the molecular processes at work within the pluripotency network. the transcription factors nanog, oct4, and sox2 reside at the core of this network, where they interact and regulat ...201323653415
cranial muscle development in the model organism ambystoma mexicanum: implications for tetrapod and vertebrate comparative and evolutionary morphology and notes on ontogeny and phylogeny.there is still confusion about the homology of several cranial muscles in salamanders with those of other vertebrates. this is true, in part, because of the fact that many muscles present in early ontogeny of amphibians disappear during development and specifically during metamorphosis. resolving this confusion is important for the understanding of the comparative and evolutionary morphology of vertebrates and tetrapods because amphibians are the phylogenetically most plesiomorphic tetrapods, co ...201323650269
accessory limb induction on flank region and its muscle regulation in axolotl.urodele amphibians have high regeneration capability that has been studied for a long time. recently, a new experimental system called the accessory limb model was developed and becomes alternative choice for amphibian limb regeneration study. although the accessory limb model has many advantages, an improvement was needed for some specific analysis, such as studying muscle origin. for that purpose, an accessory limb induction on nonlimb regions was attempted.201323649747
misexpression experiment of tbx5 in axolotl (ambystoma mexicanum) hindlimb blastema.axolotls (ambystoma mexicanum) have the ability to regenerate amputated limbs throughout their life span. in the present study, we attempted to elucidate how axolotls can specify limb type correctly during the regeneration process. we misexpressed tbx5 in regenerating hindlimb blastema, and consequently a forelimb-like hindlimb regenerated from the hindlimb blastema. on the other hand, no change was observed in tbx5-overexpressing forelimb blastema, and thus we considered that tbx5 plays a key r ...201323614983
expression pattern of nogo-a, mag, and ngr in regenerating urodele spinal cord.the mammalian central nervous system is incapable of substantial axon regeneration after injury partially due to the presence of myelin-associated inhibitory molecules including nogo-a and myelin associated glycoprotein (mag). in contrast, axolotl salamanders are capable of considerable axon regrowth during spinal cord regeneration.201323592243
regeneration of soft tissues is promoted by mmp1 treatment after digit amputation in mice.the ratio of matrix metalloproteinases (mmps) to the tissue inhibitors of metalloproteinases (timps) in wounded tissues strictly control the protease activity of mmps, and therefore regulate the progress of wound closure, tissue regeneration and scar formation. some amphibians (i.e. axolotl/newt) demonstrate complete regeneration of missing or wounded digits and even limbs; mmps play a critical role during amphibian regeneration. conversely, mammalian wound healing re-establishes tissue integrit ...201323527099
a new unique form of microrna from human heart, microrna-499c, promotes myofibril formation and rescues cardiac development in mutant axolotl embryos.a recessive mutation "c" in the mexican axolotl, ambystoma mexicanum, results in the failure of normal heart development. in homozygous recessive embryos, the hearts do not have organized myofibrils and fail to beat. in our previous studies, we identified a noncoding myofibril-inducing rna (mir) from axolotls which promotes myofibril formation and rescues heart development.201323522091
comparative rna-seq analysis in the unsequenced axolotl: the oncogene burst highlights early gene expression in the blastema.the salamander has the remarkable ability to regenerate its limb after amputation. cells at the site of amputation form a blastema and then proliferate and differentiate to regrow the limb. to better understand this process, we performed deep rna sequencing of the blastema over a time course in the axolotl, a species whose genome has not been sequenced. using a novel comparative approach to analyzing rna-seq data, we characterized the transcriptional dynamics of the regenerating axolotl limb wit ...201323505351
a hyperpolarization-activated ion current of amphibian oocytes.a comparative analysis of a hyperpolarization-activated ion current present in amphibian oocytes was performed using the two-electrode voltage-clamp technique in xenopus laevis, xenopus tropicalis, and ambystoma mexicanum. this current appears to be driven mainly by cl(-) ions, is independent of ca(2+), and is made evident by applying extremely negative voltage pulses; it shows a slow activating phase and little or no desensitization. the pharmacological profile of the current is complex. the di ...201323440457
excretory nitrogen metabolism in the juvenile axolotl ambystoma mexicanum: differences in aquatic and terrestrial environments.the fully grown but nonmetamorphosed (juvenile) axolotl ambystoma mexicanum was ureogenic and primarily ureotelic in water. a complete ornithine-urea cycle (ouc) was present in the liver. aerial exposure impeded urea (but not ammonia) excretion, leading to a decrease in the percentage of nitrogen excreted as urea in the first 24 h. however, urea and not ammonia accumulated in the muscle, liver, and plasma during aerial exposure. by 48 h, the rate of urea excretion recovered fully, probably due t ...201312529847
activities of acetylcholinesterase, choline acetyltransferase, and catecholamine production in the spinal cord of the axolotl ambystoma mexicanum during forelimb regeneration.amputation of an axolotl limb causes severance of the brachial nerves, followed by their regeneration into a blastema. it is known that these nerves provide a neurotrophic factor to blastemal cells. to approach the problem of the response of spinal cord nerve centers to forelimb amputation, we have studied biosynthetic activities in the nerve centers involved in axonal injury during limb regeneration. we report that the acetylcholinesterase (ache) activity in the spinal cord is elevated 2 days ( ...20137840938
[the era of the axolotls: speculations regarding the neurobiological modifications during the adolescence].the article summarizes a number of recent findings about the brain changes which take place during the adolescence and the youth, their relations with their behavior and some questions are formulated with regard to the deepening of these hypothesis.201417146500
[regeneration of isolated skeletal muscle tissue in the axolotl ambystoma mexicanum]. 20146723509
germline transgenic methods for tracking cells and testing gene function during regeneration in the axolotl. 201427863220
optimized axolotl (ambystoma mexicanum) husbandry, breeding, metamorphosis, transgenesis and tamoxifen-mediated recombination.the axolotl (mexican salamander, ambystoma mexicanum) has become a very useful model organism for studying limb and spinal cord regeneration because of its high regenerative capacity. here we present a protocol for successfully mating and breeding axolotls in the laboratory throughout the year, for metamorphosing axolotls by a single i.p. injection and for axolotl transgenesis using i-scei meganuclease and the mini tol2 transposon system. tol2-mediated transgenesis provides different features an ...201424504478
position-specific induction of ectopic limbs in non-regenerating blastemas on axolotl forelimbs.ectopic retinoic acid (ra) has been hypothesized to reprogram the positional identity of cells in developing and regenerating limbs to a single positional value corresponding to the posterior-ventral-proximal (pvpr) position on the limb. we tested this hypothesis by using ra to reprogram the information of blastema cells that were induced to form at different positions around the limb circumference. we observed that ra treatment of blastemas in anterior and dorsal locations, but not posterior an ...201427499858
experimentally induced metamorphosis in axolotls reduces regenerative rate and fidelity.while most tetrapods are unable to regenerate severed body parts, amphibians display a remarkable ability to regenerate an array of structures. frogs can regenerate appendages as larva, but they lose this ability around metamorphosis. in contrast, salamanders regenerate appendages as larva, juveniles, and adults. however, the extent to which fundamental traits (e.g., metamorphosis, body size, aging, etc.) restrict regenerative ability remains contentious. here we utilize the ability of normally ...201427499857
conservation of position-specific gene expression in axolotl limb skin.urodele amphibians can regenerate their limbs after amputation. after amputation, undifferentiated cells appear on the amputation plane and form regeneration blastema. a limb blastema recreates a complete replica of the original limb. it is well known that disturbance of the location of limb tissues prior to amputation perturbs limb patterning, suggesting that different intact limb tissues carry different location information despite their identical appearance. the cause of such differences in i ...201424410490
evaluation of de novo transcriptome assemblies from rna-seq data.de novo rna-seq assembly facilitates the study of transcriptomes for species without sequenced genomes, but it is challenging to select the most accurate assembly in this context. to address this challenge, we developed a model-based score, rsem-eval, for evaluating assemblies when the ground truth is unknown. we show that rsem-eval correctly reflects assembly accuracy, as measured by ref-eval, a refined set of ground-truth-based scores that we also developed. guided by rsem-eval, we assembled t ...201425608678
evolutionary innovation and conservation in the embryonic derivation of the vertebrate skull.development of the vertebrate skull has been studied intensively for more than 150 years, yet many essential features remain unresolved. one such feature is the extent to which embryonic derivation of individual bones is evolutionarily conserved or labile. we perform long-term fate mapping using gfp-transgenic axolotl and xenopus laevis to document the contribution of individual cranial neural crest streams to the osteocranium in these amphibians. here we show that the axolotl pattern is strikin ...201425434971
notochord-derived hedgehog is essential for tail regeneration in xenopus tadpole.appendage regeneration in amphibians is regulated by the combinatorial actions of signaling molecules. the requirement of molecules secreted from specific tissues is reflected by the observation that the whole process of regeneration can be inhibited if a certain tissue is removed from the amputated stump. interestingly, urodeles and anurans show different tissue dependencies during tail regeneration. the spinal cord is essential for tail regeneration in urodele but not in anuran larva, whereas ...201424941877
stochastic specification of primordial germ cells from mesoderm precursors in axolotl embryos.a common feature of development in most vertebrate models is the early segregation of the germ line from the soma. for example, in xenopus and zebrafish embryos primordial germ cells (pgcs) are specified by germ plasm that is inherited from the egg; in mice, blimp1 expression in the epiblast mediates the commitment of cells to the germ line. how these disparate mechanisms of pgc specification evolved is unknown. here, in order to identify the ancestral mechanism of pgc specification in vertebrat ...201424917499
plasticity for axolotl lens regeneration is associated with age-related changes in gene expression.mexican axolotls lose potential for lens regeneration 2 weeks after hatching. we used microarrays to identify differently expressed genes before and after this critical time, using rna isolated from iris. over 3700 genes were identified as differentially expressed in response to lentectomy between young (7 days post-hatching) and old (3 months post-hatching) axolotl larvae. strikingly, many of the genes were only expressed in the early or late iris. genes that were highly expressed in young iris ...201427499863
implication of two different regeneration systems in limb regeneration.limb regeneration is a representative phenomenon of organ regeneration in urodele amphibians, such as an axolotl. an amputated limb starts regenerating from a remaining stump (proximal) to lost finger tips (distal). in the present case, proximal-distal (pd) reorganization takes place in a regenerating tissue, called a blastema. it has been a mystery how an induced blastema recognizes its position and restores an exact replica of missing parts. recently, a new experimental system called the acces ...201427499860
mapping hematopoiesis in a fully regenerative vertebrate: the axolotl.hematopoietic stem cell (hsc)-derived cells are involved in wound healing responses throughout the body. unfortunately for mammals, wound repair typically results in scarring and nonfunctional reparation. among vertebrates, none display such an extensive ability for adult regeneration as urodele amphibians, including 1 of the more popular models: the axolotl. however, a lack of knowledge of axolotl hematopoiesis hinders the use of this animal for the study of hematopoietic cells in scar-free wou ...201424802774
highly efficient targeted mutagenesis in axolotl using cas9 rna-guided nuclease.among tetrapods, only urodele salamanders, such as the axolotl ambystoma mexicanum, can completely regenerate limbs as adults. the mystery of why salamanders, but not other animals, possess this ability has for generations captivated scientists seeking to induce this phenomenon in other vertebrates. although many recent advances in molecular biology have allowed limb regeneration and tissue repair in the axolotl to be investigated in increasing detail, the molecular toolkit for the study of this ...201424764077
new insights into vertebrate skin regeneration.regeneration biology has experienced a renaissance as clinicians, scientists, and engineers have combined forces to drive the field of regenerative medicine. studies investigating the mechanisms that regulate wound healing in adult mammals have led to a good understanding of the stereotypical processes that lead to scarring. despite comparative studies of fetal wound healing in which no scar is produced, the fact remains that insights from this work have failed to produce therapies that can rege ...201424725426
precise control of mir-125b levels is required to create a regeneration-permissive environment after spinal cord injury: a cross-species comparison between salamander and rat.most spinal cord injuries lead to permanent paralysis in mammals. by contrast, the remarkable regenerative abilities of salamanders enable full functional recovery even from complete spinal cord transections. the molecular differences underlying this evolutionary divergence between mammals and amphibians are poorly understood. we focused on upstream regulators of gene expression as primary entry points into this question. we identified a group of micrornas (mirnas) that are conserved between the ...201424719025
is salamander limb regeneration really perfect? anatomical and morphogenetic analysis of forelimb muscle regeneration in gfp-transgenic axolotls as a basis for regenerative, developmental, and evolutionary studies.the axolotl ambystoma mexicanum is one of the most commonly used model organisms in developmental and regenerative studies because it can reconstitute what is believed to be a completely normal anatomical and functional forelimb/hindlimb after amputation. however, to date it has not been confirmed whether each regenerated forelimb muscle is really a "perfect" copy of the original muscle. this study describes the regeneration of the arm, forearm, hand, and some pectoral muscles (e.g., coracoradia ...201424692358
ectopic blastema induction by nerve deviation and skin wounding: a new regeneration model in xenopus laevis.recently, the accessory limb model (alm) has become an alternative study system for limb regeneration studies in axolotls instead of using an amputated limb. alm progresses limb regeneration study in axolotls because of its advantages. to apply and/or to compare knowledge in axolotl alm studies to other vertebrates is a conceivable next step. first, xenopus laevis, an anuran amphibian, was investigated. a xenopus frog has hypomorphic regeneration ability. its regeneration ability has been consid ...201427499859
two different network topologies yield bistability in models of mesoderm and anterior mesendoderm specification in amphibians.understanding the gene regulatory networks (grns) that underlie development is a major question for systems biology. the establishment of the germ layers is amongst the earliest events of development and has been characterised in numerous model systems. the establishment of the mesoderm is best characterised in the frog xenopus laevis and has been well studied both experimentally and mathematically. however, the xenopus network has significant differences from that in mouse and humans, including ...201424650939
characterization of in vitro transcriptional responses of dorsal root ganglia cultured in the presence and absence of blastema cells from regenerating salamander limbs.during salamander limb regeneration, nerves provide signals that induce the formation of a mass of proliferative cells called the blastema. to better understand these signals, we developed a blastema-dorsal root ganglia (drg) co-culture model system to test the hypothesis that nerves differentially express genes in response to cues provided by the blastema. drg with proximal and distal nerve trunks were isolated from axolotls (ambystoma mexicanum), cultured for five days, and subjected to microa ...201425750744
probability of regenerating a normal limb after bite injury in the mexican axolotl (ambystoma mexicanum).multiple factors are thought to cause limb abnormalities in amphibian populations by altering processes of limb development and regeneration. we examined adult and juvenile axolotls (ambystoma mexicanum) in the ambystoma genetic stock center (agsc) for limb and digit abnormalities to investigate the probability of normal regeneration after bite injury. we observed that 80% of larval salamanders show evidence of bite injury at the time of transition from group housing to solitary housing. among 7 ...201425745564
dynamic evolution of the gnrh receptor gene family in vertebrates.elucidating the mechanisms underlying coevolution of ligands and receptors is an important challenge in molecular evolutionary biology. peptide hormones and their receptors are excellent models for such efforts, given the relative ease of examining evolutionary changes in genes encoding for both molecules. most vertebrates possess multiple genes for both the decapeptide gonadotropin releasing hormone (gnrh) and for the gnrh receptor. the evolutionary history of the receptor family, including anc ...201425344287
successful nucleofection of rat adipose-derived stroma cells with ambystoma mexicanum epidermal lipoxygenase (ambloxe).adipose-derived stroma cells (ascs) are attractive cells for cell-based gene therapy but are generally difficult to transfect. nucleofection has proven to be an efficient method for transfection of primary cells. therefore, we used this technique to transfect ascs with a vector encoding for ambystoma mexicanum epidermal lipoxygenase (ambloxe) which is a promising bioactive enzyme in regenerative processes. thereby, we thought to even further increase the large regenerative potential of the ascs.201425300230
co-operative bmp- and fgf-signaling inputs convert skin wound healing to limb formation in urodele amphibians.urodele amphibians have remarkable organ regeneration capability, and their limb regeneration capability has been investigated as a representative phenomenon. in the early 19th century, nerves were reported to be an essential tissue for the successful induction of limb regeneration. nerve substances that function in the induction of limb regeneration responses have long been sought. a new experimental system called the accessory limb model (alm) has been established to identify the nerve factors ...201425286122
crispr-mediated genomic deletion of sox2 in the axolotl shows a requirement in spinal cord neural stem cell amplification during tail regeneration.the salamander is the only tetrapod that functionally regenerates all cell types of the limb and spinal cord (sc) and thus represents an important regeneration model, but the lack of gene-knockout technology has limited molecular analysis. we compared transcriptional activator-like effector nucleases (talens) and clustered regularly interspaced short palindromic repeats (crisprs) in the knockout of three loci in the axolotl and find that crisprs show highly penetrant knockout with less toxic eff ...201425241743
hematopoietic ontogeny in the axolotl. 201425147373
translational control of tropomyosin expression in vertebrate hearts.the tropomyosin (tm) gene family produces a set of related tm proteins with important functions in striated and smooth muscle, and nonmuscle cells. in vertebrate striated muscle, the thin filament consists largely of actin, tm, the troponin (tn) complex (tn-i, tn-c and tn-t), and tropomodulin (tmod) and is responsible for mediating ca(2+) control of muscle contraction and relaxation. there are four known genes (designated as tpm1, tpm2, tpm3, and tpm4) for tm in vertebrates. the four tm genes ge ...201425125172
axolotls with an under- or oversupply of neural crest can regulate the sizes of their dorsal root ganglia to normal levels.how animals adjust the size of their organs is a fundamental, enduring question in biology. here we manipulate the amount of neural crest (nc) precursors for the dorsal root ganglia (drg) in axolotl. we produce embryos with an under- or over-supply of pre-migratory nc in order to find out if drg can regulate their sizes during development. axolotl embryos are perfectly suitable for this research. firstly, they are optimal for microsurgical manipulations and tissue repair. secondly, they possess, ...201425111151
proteomic analysis of fibroblastema formation in regenerating hind limbs of xenopus laevis froglets and comparison to axolotl.to gain insight into what differences might restrict the capacity for limb regeneration in xenopus froglets, we used high performance liquid chromatography (hplc)/double mass spectrometry to characterize protein expression during fibroblastema formation in the amputated froglet hindlimb, and compared the results to those obtained previously for blastema formation in the axolotl limb.201425063185
leucine-enkephalin-like immunoreactivity is localized in luteinizing hormone-producing cells in the axolotl (ambystoma mexicanum) pituitary.in this study, we used immunohistochemical techniques to determine the cell type of leucine-enkephalin (leu-enk)-immunoreactive cells in the axolotl (ambystoma mexicanum) pituitary. immunoreactive cells were scattered throughout the pars distalis except for the dorso-caudal portion. these cells were immuno-positive for luteinizing hormone (lh), but they were immuno-negative for adrenocorticotrophic, growth, and thyroid-stimulating hormones, as well as prolactin. immunoelectron microscopy demonst ...201424034715
enzymatically active 2',5'-oligoadenylate synthetases are widely distributed among metazoa, including protostome lineage.2',5'-oligoadenylate synthetases (oass) belong to the nucleotidyl transferase family together with poly(a) polymerases, cca-adding enzymes and the recently discovered cyclic-gmp-amp synthase (cgas). mammalian oass have been thoroughly characterized as components of the interferon-induced antiviral system. the oas activity and the respective genes were also discovered in marine sponges where the interferon system is absent. in this study the recombinant oass from several multicellular animals and ...201424184688
fundamental differences in dedifferentiation and stem cell recruitment during skeletal muscle regeneration in two salamander species.salamanders regenerate appendages via a progenitor pool called the blastema. the cellular mechanisms underlying regeneration of muscle have been much debated but have remained unclear. here we applied cre-loxp genetic fate mapping to skeletal muscle during limb regeneration in two salamander species, notophthalmus viridescens (newt) and ambystoma mexicanum (axolotl). remarkably, we found that myofiber dedifferentiation is an integral part of limb regeneration in the newt, but not in axolotl. in ...201424268695
development of fore- and hindlimb muscles in frogs: morphogenesis, homeotic transformations, digit reduction, and the forelimb-hindlimb enigma.here we provide the first detailed description, based on immunohistochemistry and dissections, of the limb muscle development in the direct developing frog eleutherodactylus coqui. we compare e. coqui with other tetrapods and discuss our results in a broad evolutionary and developmental context to address some major questions concerning the origin, evolution, and ontogeny of the tetrapod limbs. our observations and comparisons: (1) support the "in-out" developmental mechanism of the appendicular ...201424254979
is salamander hindlimb regeneration similar to that of the forelimb? anatomical and morphogenetic analysis of hindlimb muscle regeneration in gfp-transgenic axolotls as a basis for regenerative and developmental studies.the axolotl ambystoma mexicanum is one of the most used model organisms in developmental and regenerative studies because it is commonly said that it can reconstitute a normal and fully functional forelimb/hindlimb after amputation. however, there is not a publication that has described in detail the regeneration of the axolotl hindlimb muscles. here we describe and illustrate, for the first time, the regeneration of the thigh, leg and foot muscles in transgenic axolotls that express green fluor ...201424325444
development of fore- and hindlimb muscles in gfp-transgenic axolotls: morphogenesis, the tetrapod bauplan, and new insights on the forelimb-hindlimb enigma.the axolotl is becoming one of the most used model organisms in developmental and regenerative studies but no publication has described in detail the development of its forelimb and hindlimb muscles. we describe and illustrate the ontogeny of these muscles in transgenic axolotls that express gfp in muscle fibers and discuss our results and data previously obtained by us and by other authors about limb regeneration in axolotls and ontogeny in frogs and other tetrapods. our observations and compar ...201424302552
resegmentation in the mexican axolotl, ambystoma mexicanum.the segmental series of somites in the vertebrate embryo gives rise to the axial skeleton. in amniote models, single vertebrae are derived from the sclerotome of two adjacent somites. this process, known as resegmentation, is well-studied using the quail-chick chimeric system, but the presumed generality of resegmentation across vertebrates remains poorly evaluated. resegmentation has been questioned in anamniotes, given that the sclerotome is much smaller and lacks obvious differentiation betwe ...201424127283
retinoic acid modifies positional memory in the anteroposterior axis of regenerating axolotl limbs.the effects of retinoic acid (ra) on anteroposterior (ap) positional memory of regenerating axolotl limbs were tested after removing the anterior or posterior half from the zeugopodium (lower arm or leg). ra (150 micrograms/g body wt) was injected into groups of animals bearing the following types of limbs: (1) anterior and posterior half zeugopodia grafted to the eyesocket and amputated distally 7 days later; (2) unamputated anterior and posterior half zeugopodia in situ; (3) double anterior an ...20143956861
presence and prevalence of batrachochytrium dendrobatidis in commercial amphibians in mexico city.in mexico city, native and exotic amphibians are commonly sold through the pet trade. this study investigates the presence of batrachochytrium dendrobatidis (bd) in native amphibians being sold at two commercial markets and at a herpetarium in mexico city. a total of 238 individuals (6 genera and 12 species) were tested for bd using real-time polymerase chain reaction (pcr) analysis. there were 197 bd-positive individuals (prevalence 82%) from five species of amphibians. hyla eximia from the mar ...201425632670
[prolactin enhancement of absorption of sodium ions in isolated gills from larva of ambystoma mexicanum]. 20144120136
preparation of primary myogenic precursor cell/myoblast cultures from basal vertebrate lineages.due to the inherent difficulty and time involved with studying the myogenic program in vivo, primary culture systems derived from the resident adult stem cells of skeletal muscle, the myogenic precursor cells (mpcs), have proven indispensible to our understanding of mammalian skeletal muscle development and growth. particularly among the basal taxa of vertebrata, however, data are limited describing the molecular mechanisms controlling the self-renewal, proliferation, and differentiation of mpcs ...201424835774
[activities of protein synthesis during the development of lethal nucleocytoplasmic hybrids obtained by nuclear graft between ambystoma mexicanum shaw and ambystoma dumerilii duges (amphibia, urodeles)].a comparative study of proteinograms and zymograms (ldh, mdh) has been carried out at different ontogenic stages, in ambystoma mexicanum (a.m.), ambystoma dumerilii (a.d.) and nucleocytoplasmic hybrids 2 n a.d/cytoplasm am. it appears that 2 n a.d. nucleus, grafted in a.m. cytoplasm expresses only a part of its potentialities, which could account for lethality of the nucleocytoplasmic hybrids.2014809209
a tale of two axolotls.the mexican axolotl (ambystoma mexicanum) is an icon of culture, a revered aquarium pet, and a highly valued animal model in biomedical research. unfortunately, mexican axolotls are critically endangered in their natural xochimilco habitat in mexico city. if axolotls go extinct, current efforts to conserve the xochimilico ecosystem will be undermined, as will efforts to genetically manage the laboratory populations that are needed to sustain research efforts around the world. a concerted global ...201532123398
induction of metamorphosis causes differences in sex-specific allocation patterns in axolotls (ambystoma mexicanum) that have different growth histories.we tested the hypothesis that salamanders growing at different rates would have allocation patterns that differ among male and female metamorphic and larval salamanders. we raised individual axolotls, ambystoma mexicanum, on four food regimes: constant high growth (throughout the experiment), constant low growth (restricted throughout the experiment), high growth switched to low growth (ad libitum switched after 140 d to restricted), and low growth switched to high growth (restricted switched af ...201529755160
pseudotyped retroviruses for infecting axolotl.the ability to introduce dna elements into host cells and analyze the effects has revolutionized modern biology. here we describe a protocol to generate moloney murine leukemia virus (mmlv)-based, replication-incompetent pseudotyped retrovirus capable of infecting axolotls and incorporating genetic information into their genome. when pseudotyped with vesicular stomatitis virus (vsv)-g glycoprotein, the retroviruses can infect a broad range of proliferative axolotl cell types. however, if the ret ...201525740482
vesicular stomatitis virus enables gene transfer and transsynaptic tracing in a wide range of organisms.current limitations in technology have prevented an extensive analysis of the connections among neurons, particularly within nonmammalian organisms. we developed a transsynaptic viral tracer originally for use in mice, and then tested its utility in a broader range of organisms. by engineering the vesicular stomatitis virus (vsv) to encode a fluorophore and either the rabies virus glycoprotein (rabv-g) or its own glycoprotein (vsv-g), we created viruses that can transsynaptically label neuronal ...201525688551
fine structure of the normal, transplanted and postmetamorphic pars distalis of the mexican axolotl, ambystoma mexicanum. 20154699358
[influence of actinomycin d on metamorphosis induced by thyroxine in the axolotl]. 20154954055
induction of spawning in the mexican axolotl (ambystoma mexicanum) by luteinizing hormone. 20154636361
regulation of axolotl (ambystoma mexicanum) limb blastema cell proliferation by nerves and bmp2 in organotypic slice culture.we have modified and optimized the technique of organotypic slice culture in order to study the mechanisms regulating growth and pattern formation in regenerating axolotl limb blastemas. blastema cells maintain many of the behaviors that are characteristic of blastemas in vivo when cultured as slices in vitro, including rates of proliferation that are comparable to what has been reported in vivo. because the blastema slices can be cultured in basal medium without fetal bovine serum, it was possi ...201525923915
comparative and phylogenetic perspectives of the cleavage process in tailed amphibians.the order caudata includes about 660 species and displays a variety of important developmental traits such as cleavage pattern and egg size. however, the cleavage process of tailed amphibians has never been analyzed within a phylogenetic framework. we use published data on the embryos of 36 species concerning the character of the third cleavage furrow (latitudinal, longitudinal or variable) and the magnitude of synchronous cleavage period (up to 3-4 synchronous cell divisions in the animal hemis ...201525180466
gene expression during the first 28 days of axolotl limb regeneration i: experimental design and global analysis of gene expression.while it is appreciated that global gene expression analyses can provide novel insights about complex biological processes, experiments are generally insufficiently powered to achieve this goal. here we report the results of a robust microarray experiment of axolotl forelimb regeneration. at each of 20 post-amputation time points, we estimated gene expression for 10 replicate rna samples that were isolated from 1 mm of heterogeneous tissue collected from the distal limb tip. we show that the lim ...201527168937
cellular dynamics underlying regeneration of appropriate segment number during axolotl tail regeneration.salamanders regenerate their tails after amputation anywhere along their length. how the system faithfully reconstitutes the original number of segments and length is not yet known.201526647066
positional plasticity in regenerating amybstoma mexicanum limbs is associated with cell proliferation and pathways of cellular differentiation.the endogenous ability to dedifferentiate, re-pattern, and re-differentiate adult cells to repair or replace damaged or missing structures is exclusive to only a few tetrapod species. the mexican axolotl is one example of these species, having the capacity to regenerate multiple adult structures including their limbs by generating a group of progenitor cells, known as the blastema, which acquire pattern and differentiate into the missing tissues. the formation of a limb regenerate is dependent o ...201526597593
planar cell polarity-mediated induction of neural stem cell expansion during axolotl spinal cord regeneration.axolotls are uniquely able to mobilize neural stem cells to regenerate all missing regions of the spinal cord. how a neural stem cell under homeostasis converts after injury to a highly regenerative cell remains unknown. here, we show that during regeneration, axolotl neural stem cells repress neurogenic genes and reactivate a transcriptional program similar to embryonic neuroepithelial cells. this dedifferentiation includes the acquisition of rapid cell cycles, the switch from neurogenic to pro ...201526568310
initial characterization of the large genome of the salamander ambystoma mexicanum using shotgun and laser capture chromosome sequencing.vertebrates exhibit substantial diversity in genome size, and some of the largest genomes exist in species that uniquely inform diverse areas of basic and biomedical research. for example, the salamander ambystoma mexicanum (the mexican axolotl) is a model organism for studies of regeneration, development and genome evolution, yet its genome is ~10× larger than the human genome. as part of a hierarchical approach toward improving genome resources for the species, we generated 600 gb of shotgun s ...201526553646
changes in regenerative capacity through lifespan.most organisms experience changes in regenerative abilities through their lifespan. during aging, numerous tissues exhibit a progressive decline in homeostasis and regeneration that results in tissue degeneration, malfunction and pathology. the mechanisms responsible for this decay are both cell intrinsic, such as cellular senescence, as well as cell-extrinsic, such as changes in the regenerative environment. understanding how these mechanisms impact on regenerative processes is essential to dev ...201526512653
linking vertebral number to performance of aquatic escape responses in the axolotl (ambystoma mexicanum).environmental conditions during early development in ectothermic vertebrates can lead to variation in vertebral number among individuals of the same species. it is often seen that individuals of a species raised at cooler temperatures have more vertebrae than individuals raised at warmer temperatures, although the functional consequences of this variation in vertebral number on swimming performance are relatively unclear. to investigate this relationship, we tested how vertebral number in axolot ...201526489369
dynamic membrane depolarization is an early regulator of ependymoglial cell response to spinal cord injury in axolotl.salamanders, such as the mexican axolotl, are some of the few vertebrates fortunate in their ability to regenerate diverse structures after injury. unlike mammals they are able to regenerate a fully functional spinal cord after injury. however, the molecular circuitry required to initiate a pro-regenerative response after spinal cord injury is not well understood. to address this question we developed a spinal cord injury model in axolotls and used in vivo imaging of labeled ependymoglial cells ...201526477559
hyperbaric oxygen promotes proximal bone regeneration and organized collagen composition during digit regeneration.oxygen is critical for optimal bone regeneration. while axolotls and salamanders have retained the ability to regenerate whole limbs, mammalian regeneration is restricted to the distal tip of the digit (p3) in mice, primates, and humans. our previous study revealed the oxygen microenvironment during regeneration is dynamic and temporally influential in building and degrading bone. given that regeneration is dependent on a dynamic and changing oxygen environment, a better understanding of the eff ...201526452224
identification of conserved and novel micrornas during tail regeneration in the mexican axolotl.the mexican axolotl salamander (ambystoma mexicanum) is one member of a select group of vertebrate animals that have retained the amazing ability to regenerate multiple body parts. in addition to being an important model system for regeneration, the axolotl has also contributed extensively to studies of basic development. while many genes known to play key roles during development have now been implicated in various forms of regeneration, much of the regulatory apparatus controlling the underlyi ...201526378530
generation of axolotl hematopoietic chimeras.wound repair is an extremely complex process that requires precise coordination between various cell types including immune cells. unfortunately, in mammals this usually results in scar formation instead of restoration of the original fully functional tissue, otherwise known as regeneration. various animal models like frogs and salamanders are currently being studied to determine the intracellular and intercellular pathways, controlled by gene expression, that elicit cell proliferation, differen ...201526366424
immunodetection of telomerase-like immunoreactivity in normal and regenerating tail of amphibians suggests it is related to their regenerative capacity.the high regenerative power of amphibians suggests that numerous signaling pathways remain active in larvae and adult tissues, including those stimulated by telomerases. the protein component of telomerase (tert) shows high amino acid homology in numerous vertebrates and we have utilized an antibody made for a lizard telomerase to detect a putative telomerase in amphibians tissues based on 60-75% epitope identity. western blotting studies indicate that telomerase is constitutionally present in n ...201526351773
dna methylation dynamics regulate the formation of a regenerative wound epithelium during axolotl limb regeneration.the formation of a blastema during regeneration of an axolotl limb involves important changes in the behavior and function of cells at the site of injury. one of the earliest events is the formation of the wound epithelium and subsequently the apical epidermal cap, which involves in vivo dedifferentiation that is controlled by signaling from the nerve. we have investigated the role of epigenetic modifications to the genome as a possible mechanism for regulating changes in gene expression pattern ...201526308461
primordial germ cells: the first cell lineage or the last cells standing?embryos of many animal models express germ line determinants that suppress transcription and mediate early germ line commitment, which occurs before the somatic cell lineages are established. however, not all animals segregate their germ line in this manner. the 'last cell standing' model describes primordial germ cell (pgc) development in axolotls, in which pgcs are maintained by an extracellular signalling niche, and germ line commitment occurs after gastrulation. here, we propose that this 's ...201526286941
comparative analysis of cartilage marker gene expression patterns during axolotl and xenopus limb regeneration.axolotls (ambystoma mexicanum) can completely regenerate lost limbs, whereas xenopus laevis frogs cannot. during limb regeneration, a blastema is first formed at the amputation plane. it is thought that this regeneration blastema forms a limb by mechanisms similar to those of a developing embryonic limb bud. furthermore, xenopus laevis frogs can form a blastema after amputation; however, the blastema results in a terminal cone-shaped cartilaginous structure called a "spike." the causes of this p ...201526186213
regeneration inducers in limb regeneration.limb regeneration ability, which can be observed in amphibians, has been investigated as a representative phenomenon of organ regeneration. recently, an alternative experimental system called the accessory limb model was developed to investigate early regulation of amphibian limb regeneration. the accessory limb model contributed to identification of limb regeneration inducers in urodele amphibians. furthermore, the accessory limb model may be applied to other species to explore universality of ...201526100345
the axolotl fibula as a model for the induction of regeneration across large segment defects in long bones of the extremities.we tested the ability of the axolotl (ambystoma mexicanum) fibula to regenerate across segment defects of different size in the absence of intervention or after implant of a unique 8-braid pig small intestine submucosa (sis) scaffold, with or without incorporated growth factor combinations or tissue protein extract. fractures and defects of 10% and 20% of the total limb length regenerated well without any intervention, but 40% and 50% defects failed to regenerate after either simple removal of b ...201526098852
using ambystoma mexicanum (mexican axolotl) embryos, chemical genetics, and microarray analysis to identify signaling pathways associated with tissue regeneration.amphibian vertebrates are important models in regenerative biology because they present exceptional regenerative capabilities throughout life. however, it takes considerable effort to rear amphibians to juvenile and adult stages for regeneration studies, and the relatively large sizes that frogs and salamanders achieve during development make them difficult to use in chemical screens. here, we introduce a new tail regeneration model using late stage mexican axolotl embryos. we show that axolotl ...201526092703
mesodermal origin of median fin mesenchyme and tail muscle in amphibian larvae.mesenchyme is an embryonic precursor tissue that generates a range of structures in vertebrates including cartilage, bone, muscle, kidney, and the erythropoietic system. mesenchyme originates from both mesoderm and the neural crest, an ectodermal cell population, via an epithelial to mesenchymal transition (emt). because ectodermal and mesodermal mesenchyme can form in close proximity and give rise to similar derivatives, the embryonic origin of many mesenchyme-derived tissues is still unclear. ...201526086331
epidermal closure regulates histolysis during mammalian (mus) digit regeneration.mammalian digit regeneration progresses through consistent stages: histolysis, inflammation, epidermal closure, blastema formation, and finally redifferentiation. what we do not yet know is how each stage can affect others. questions of stage timing, tissue interactions, and microenvironmental states are becoming increasingly important as we look toward solutions for whole limb regeneration. this study focuses on the timing of epidermal closure which, in mammals, is delayed compared to more rege ...201527499872
dual embryonic origin and patterning of the pharyngeal skeleton in the axolotl (ambystoma mexicanum).the impressive morphological diversification of vertebrates was achieved in part by innovation and modification of the pharyngeal skeleton. extensive fate mapping in amniote models has revealed a primarily cranial neural crest derivation of the pharyngeal skeleton. although comparable fate maps of amphibians produced over several decades have failed to document a neural crest derivation of ventromedial elements in these vertebrates, a recent report provides evidence of a mesodermal origin of one ...201525963195
recurrent turnover of senescent cells during regeneration of a complex structure.cellular senescence has been recently linked to the promotion of age-related pathologies, including a decline in regenerative capacity. while such capacity deteriorates with age in mammals, it remains intact in species such as salamanders, which have an extensive repertoire of regeneration and can undergo multiple episodes through their lifespan. here we show that, surprisingly, there is a significant induction of cellular senescence during salamander limb regeneration, but that rapid and effect ...201525942455
an aryl hydrocarbon receptor from the salamander ambystoma mexicanum exhibits low sensitivity to 2,3,7,8-tetrachlorodibenzo-p-dioxin.structural features of the aryl hydrocarbon receptor (ahr) can underlie species- and population-specific differences in its affinity for 2,3,7,8-tetrachlorodibenzo-p-dioxin (tcdd). these differences often explain variations in tcdd toxicity. frogs are relatively insensitive to dioxin, and xenopus ahrs bind tcdd with low affinity. weak tcdd binding results from the combination of three residues in the ligand-binding domain: a354 and a370, and n325. here we sought to determine whether this mechani ...201525941739
the history of the oldest self-sustaining laboratory animal: 150 years of axolotl research.today the mexican axolotl is critically endangered in its natural habitat in lakes around mexico city, but thrives in research laboratories around the world, where it is used for research on development, regeneration, and evolution. here, we concentrate on the early history of the axolotl as a laboratory animal to celebrate that the first living axolotls arrived in paris in 1864, 150 years ago. maybe surprisingly, at first the axolotl was distributed across europe without being tied to specific ...201525920413
analysis of signal processing in vestibular circuits with a novel light-emitting diodes-based fluorescence microscope.optical visualization of neural network activity is limited by imaging system-dependent technical tradeoffs. to overcome these constraints, we have developed a powerful low-cost and flexible imaging system with high spectral variability and unique spatio-temporal precision for simultaneous optical recording and manipulation of neural activity of large cell groups. the system comprises eight high-power light-emitting diodes, a camera with a large metal-oxide-semiconductor sensor and a high numeri ...201525847143
cooperative regulation of substrate stiffness and extracellular matrix proteins in skin wound healing of axolotls.urodele amphibians (ambystoma mexicanum), unique among vertebrates, can regenerate appendages and other body parts entirely and functionally through a scar-free healing process. the wound epithelium covering the amputated or damaged site forms early and is essential for initiating the subsequent regenerative steps. however, the molecular mechanism through which the wound reepithelializes during regeneration remains unclear. in this study, we developed an in vitro culture system that mimics an in ...201525839038
current advances in tissue repair and regeneration: the future is bright.the fifth embo conference on 'the molecular and cellular basis of regeneration and repair' took place in the peaceful coastal town of sant feliu de guixols (spain) on september 2014. the meeting was organised by emili saló (u. barcelona, spain), kimberly mace (u. manchester, uk), patrizia ferretti (university college london, uk) and michael brand (centre for regenerative therapies dresden, germany) and received the generous support of society for developmental biology, the company of biologists, ...201527499870
the axolotl limb blastema: cellular and molecular mechanisms driving blastema formation and limb regeneration in tetrapods.the axolotl is one of the few tetrapods that are capable of regenerating complicated biological structures, such as complete limbs, throughout adulthood. upon injury the axolotl generates a population of regeneration-competent limb progenitor cells known as the blastema, which will grow, establish pattern, and differentiate into the missing limb structures. in this review we focus on the crucial early events that occur during wound healing, the neural-epithelial interactions that drive the forma ...201527499868
identification of a human mitochondrial rna that promotes tropomyosin synthesis and myocardial differentiation.heart disease is the number one killer in the usa, making cardiogenesis and its related pathways a relevant area of study for improving health and life expectancy. the mexican salamander (axolotl), ambystoma mexicanum, provides an excellent vertebrate animal model for studying myofibrillogenesis due to its naturally occurring cardiac nonfunction mutation. homozygous recessive embryos do not develop normal hearts due to a lack of myofibril formation. in previous studies, myofibril-inducing ribonu ...201525408381
expression of sarcomeric tropomyosin in striated muscles in axolotl treated with shz-1, a small cardiogenic molecule.we evaluated the effect of shz-1, a cardiogenic molecule, on the expression of various tropomyosin (tm) isoforms in the mexican axolotl (ambystoma mexicanum) hearts. qrt-pcr data show a ~1.5-fold increase in cardiac transcripts of the nkx2.5 gene, which plays a crucial role in cardiogenesis in vertebrates. shz-1 augments the expression of transcripts of the total sarcomeric tpm1 (both tpm1α & tpm1κ) and sarcomeric tpm4α. in order to understand the mechanism by which shz-1 augments the expression ...201524958154
positional information in axolotl and mouse limb extracellular matrix is mediated via heparan sulfate and fibroblast growth factor during limb regeneration in the axolotl (ambystoma mexicanum).urodele amphibians are unique among adult vertebrates in their ability to regenerate complex body structures after traumatic injury. in salamander regeneration, the cells maintain a memory of their original position and use this positional information to recreate the missing pattern. we used an in vivo gain-of-function assay to determine whether components of the extracellular matrix (ecm) have positional information required to induce formation of new limb pattern during regeneration. we discov ...201527499874
tissue specific reactions to positional discontinuities in the regenerating axolotl limb.we investigated cellular contributions to intercalary regenerates and 180° supernumerary limbs during axolotl limb regeneration using the cell autonomous gfp marker and exchanged blastemas between white and gfp animals. after distal blastemas were grafted to proximal levels tissues of the intercalary regenerate behaved independently with regard to the law of distal transformation; graft epidermis was replaced by stump epidermis, muscle-derived cells, blood vessels and schwann cells of the distal ...201526755943
sal-site: research resources for the mexican axolotl.sal-site serves axolotl research efforts by providing web access to genomic data and information, and living stocks that are reared and made available by the ambystoma genetic stock center (agsc). in this chapter, we detail how investigators can search for genes of interest among sal-site resources to identify orthologous nucleotide and protein-coding sequences, determine genome positions within the ambystoma meiotic map, and obtain estimates of gene expression. in the near future, additional ge ...201525740497
transcriptomics using axolotls.microarray and rna-sequencing technology now exists for the characterization of the ambystoma mexicanum transcriptome. with sufficient replication, these tools give the opportunity to truly investigate gene expression in a variety of experimental paradigms. analysis of data from the amby002 array and rna-sequencing technology can identify genes that change expression levels in concert with each other, which in turn may reveal mechanisms associated with biological processes and molecular function ...201525740496
generating and identifying axolotls with targeted mutations using cas9 rna-guided nuclease.the crispr/cas9 rna-guided nuclease now enables a reverse genetics approach to investigate the function of genes of interest during regeneration in the axolotl. the process of generating the constructs necessary for targeting a gene of interest is considerably less labor intensive than for other methods of targeted mutagenesis such as zinc finger nucleases or transcription activator-like effector nucleases. here, we describe the identification of targetable sequences in the gene of interest, the ...201525740494
transgenesis in axolotl (ambystoma mexicanum).transgenic animals have been indispensable in elucidating and deciphering mechanisms underlying various biological phenomena. in regeneration, transgenic animals expressing fluorescent protein genes have been crucial for identifying the source cells for regeneration and the mechanism of blastema formation. animals are usually generated by manipulating their genome using various techniques at/in one cell embryo/fertilized egg stage. here, we describe the generation of germline transgenic axolotls ...201525740493
methods for axolotl blood collection, intravenous injection, and efficient leukocyte isolation from peripheral blood and the regenerating limb.the vertebrate immune system comprises both adaptive and innate immune cells with distinct functions during the resolution of inflammation and wound healing after tissue injury. recent evidence implicates a requirement for innate immune cells from the myeloid lineage during the early stages of limb regeneration in the mexican axolotl. understanding the functions of innate and adaptive immune cells in the axolotl has been hampered by a lack of approaches to isolate and analyze these cells. here w ...201525740489
culture and transfection of axolotl cells.the use of cells grown in vitro has been instrumental for multiple aspects of biomedical research and especially molecular and cellular biology. the ability to grow cells from multicellular organisms like humans, squids, or salamanders is important to simplify the analyses and experimental designs to help understand the biology of these organisms. the advent of the first cell culture has allowed scientists to tease apart the cellular functions, and in many situations these experiments help under ...201525740487
Refresh
firstprev
...111213141516171819
nextlast
Displaying items 1501 - 1600 of 1847