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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
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
non-invasive cell tracking of spio labeled cells in an intrinsic regenerative environment: the axolotl limb.non-invasive methods to track the progress of stem cell therapies are important in the development of future regenerative therapies. super-paramagnetic iron oxide particles (spios) have previously been applied to track cells using magnetic resonance imaging (mri) in vivo in non-regenerative animal models. to the best of the author's knowledge, the present study investigated for the first time, the feasibility of tracking spio labeled cells in an intrinsic regenerative environment, the regenerati ...201829545849
noncanonical hox, etv4, and gli3 gene activities give insight into unique limb patterning in salamanders.limb development in salamanders is unique among tetrapods in significant ways. not only can salamanders regenerate lost limbs repeatedly and throughout their lives, but also the preaxial zeugopodial element and digits form before the postaxial ones and, hence, with a reversed polarity compared to all other tetrapods. moreover, in salamanders with free-swimming larval stages, as exemplified by the axolotl (ambystoma mexicanum), each digit buds independently, instead of undergoing a paddle stage. ...201829602205
positive in vitro wound healing effects of functional inclusion bodies of a lipoxygenase from the mexican axolotl.ambloxe is a lipoxygenase, which is up-regulated during limb-redevelopment in the mexican axolotl, ambystoma mexicanum, an animal with remarkable regeneration capacity. previous studies have shown that mammalian cells transformed with the gene of this epidermal lipoxygenase display faster migration and wound closure rate during in vitro wound healing experiments.201829626934
publisher correction: virtual genome walking across the 32 gb ambystoma mexicanum genome; assembling gene models and intronic sequence.a correction to this article has been published and is linked from the html and pdf versions of this paper. the error has been fixed in the paper.201829654245
cancer reversion with oocyte extracts is mediated by cell cycle arrest and induction of tumour dormancy.inducing stable control of tumour growth by tumour reversion is an alternative approach to cancer treatment when eradication of the disease cannot be achieved. the process requires re-establishment of normal control mechanisms that are lost in cancer cells so that abnormal proliferation can be halted. embryonic environments can reset cellular programmes and we previously showed that axolotl oocyte extracts can reprogram breast cancer cells and reverse their tumorigenicity. in this study, we anal ...201829662623
ectopic fgf signaling induces the intercalary response in developing chicken limb buds.intercalary pattern formation is an important regulatory step in amphibian limb regeneration. amphibian limb regeneration is composed of multiple steps, including wounding, blastema formation, and intercalary pattern formation. attempts have been made to transfer insights from regeneration-competent animals to regeneration-incompetent animalsat each step in the regeneration process. in the present study, we focused on the intercalary mechanism in chick limb buds. in amphibian limb regeneration, ...201829721334
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
forever young: endocrinology of paedomorphosis in the mexican axolotl (ambystoma mexicanum).the mexican axolotl (ambystoma mexicanum) is a salamander species that does not undergo metamorphosis, resulting in the retention of juvenile characteristics in the mature breeding stage (paedomorphosis). here we review the endocrinological studies investigating the proximate cause of axolotl paedomorphosis with a focus on the hypothalamo-pituitary-thyroid (hpt) axis. it is well established that axolotl paedomorphosis is a consequence of low activity of the hpt axis. the pituitary hormone thyrot ...201829777689
signaling-dependent control of apical membrane size and self-renewal in rosette-stage human neuroepithelial stem cells.in the developing nervous system, neural stem cells are polarized and maintain an apical domain facing a central lumen. the presence of apical membrane is thought to have a profound influence on maintaining the stem cell state. with the onset of neurogenesis, cells lose their polarization, and the concomitant loss of the apical domain coincides with a loss of the stem cell identity. little is known about the molecular signals controlling apical membrane size. here, we use two neuroepithelial cel ...201829779899
author correction: the axolotl genome and the evolution of key tissue formation regulators.in the originally published version of this article, the sequenced axolotl strain (the homozygous white mutant) was denoted as 'd/d' rather than 'd/d' in fig. 1a and the accompanying legend, the main text and the methods section. the original article has been corrected online.201829795340
variable manifestations in the short toes (s) mutation of the axolotl.we describe a detailed histological analysis of the affected organs in the short toes (s) mutation of the mexican axolotl, ambystoma mexicanum. the s mutant animals displayed a variation in the response to the mutation such as the time of death and the degree of abnormalities of the affected organs (limbs, kidney, ducts, and reproductive structures). in addition to the numerous histological abnormalities characterized here, we also examined the presence of laminin-related molecules in s mutant k ...199329865473
brain-capillary architecture of the newt, triturus cristatus carnifex (caudata: salamandridae): scanning electron-microscopical study of vascular corrosion casts.the brain-microvascular architecture of the newt (triturus cristatus carnifex) was studied by scanning electron-microscopical examination of microvascular corrosion casts. it is characterized at the leptomeningeal level by a superficial network of single vessels that leave the meningeal sheath to form hairpin-shaped capillary loops. these loops penetrate the nervous parenchyma to varying depths and are variously bent, inclined, and twisted. each hairpin-like loop consists of descending and ascen ...199129865580
the vascular structure of the kidney of the neotenous axolotl and its metamorphosed counterpart.the renal vascular and glomerular structures of the kidney of neotenous and experimentally metamorphosed axolotls (ambystoma mexicanum: amphibia, urodela) are investigated using light, transmission electron, and scanning electron microscopy of critical-point dried specimens and vascular corrosion casts. the blood vascular system of the kidney in the axolotl is generally similar to that in other urodeles. the glomeruli are comparatively large and distincly ovoid (mean size 267 × 201 μm). glomerul ...199229865583
lateral-line neuromast development in ambystoma mexicanum and a comparison with rana pipiens.we have examined the embryonic development of the major neuromast lines of the lateral-line system in the urodele ambystoma mexicanum both in vivo (using microsurgical techniques to transplant placodes) and in preserved embryos using scanning electron microscopy (sem). we have compared this to sem observations of embryos of the anuran rana pipiens. we have determined the approximate locations of the lateral-line placodes in a. mexicanum and the approximate timing of both the migration of the lat ...198829879797
an interview with elly tanaka.elly tanaka is a senior scientist at the research institute of molecular pathology in vienna, austria. her lab's research uses the axolotl - which possesses impressive regenerative capacity - to understand the molecular and cellular mechanisms underlying limb and spinal cord regeneration. we met elly in her office in vienna on the occasion of the recent sy-stem symposium (see meeting review by porrello and kirkeby in this issue) to talk about what drew her to regeneration research and the axolot ...201829884656
retinoid x receptor α downregulation is required for tail and caudal spinal cord regeneration in the adult newt.some adult vertebrate species, such as newts, axolotls and zebrafish, have the ability to regenerate their central nervous system (cns). however, the factors that establish a permissive cns environment for correct morphological and functional regeneration in these species are not well understood. recent evidence supports a role for retinoid signaling in the intrinsic ability of neurons, in these regeneration-competent species, to regrow after cns injury. previously, we demonstrated that a specif ...201829926831
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
an integrative framework for salamander and mouse limb regeneration.appendage regeneration is not a simple task. the animal must harness all of its energy and resources to orchestrate perhaps one of the most complicated events since its development. balancing the immune response, wound healing, proliferation, patterning and differentiation is an elegant job, and how some animals achieve that still leaves researchers enchanted today. in this work, we review some of the molecular aspects of regeneration, with a focus on the axolotl, the champion of tetrapod limb r ...201829943379
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
formation of the pronephros and pronephric duct rudiment in the mexican axolotl.in the mexican axolotl (ambystoma mexicanum), the pronephros begins to form at the four-somite stage. it is initially continuous with the posterior-lateral region of somite 2 and the lateral margin of somites 3 and 4. by the seven-somite stage, the pronephros has become compacted, and the cells are now morphologically distinct from the somitic cells. at this stage, a mass of loosely connected cells, apparently originating from the lateral mesoderm, is seen below somites 4 and 5. by the eight-som ...198529976020
changes in the appendicular skeleton during metamorphosis in the axolotl salamander (ambystoma mexicanum).axolotl salamanders (ambystoma mexicanum) remain aquatic in their natural state, during which biomechanical forces on their diarthrodial limb joints are likely reduced relative to salamanders living on land. however, even as sexually mature adults, these amphibians can be induced to metamorphose into a weight-bearing terrestrial stage by environmental stress or the exogenous administration of thyroxine hormone. in some respects, this aquatic to terrestrial transition of axolotl salamanders throu ...201829992565
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
experimentally induced metamorphosis in highly regenerative axolotl (ambystoma mexicanum) under constant diet restructures microbiota.axolotl (ambystoma mexicanum) is a critically endangered salamander species and a model organism for regenerative and developmental biology. despite life-long neoteny in nature and in captive-bred colonies, metamorphosis of these animals can be experimentally induced by administering thyroid hormones (ths). however, microbiological consequences of this experimental procedure, such as host microbiota response, remain largely unknown. here, we systematically compared host bacterial microbiota asso ...201830030457
evaluation of the anesthetic effects of ms222 in the adult mexican axolotl (ambystoma mexicanum).the mexican axolotl (ambystoma mexicanum) is a unique research model in several fields of medicine, where surgical and invasive procedures may be required. as yet, little is known about the efficacy of ms222 (tricaine methanesulfonate), which is the most commonly used anesthetic agent in amphibians. the main objectives of this study were to evaluate the anesthetic effects and physiological changes in adult axolotls following a 20-minute immersion bath, containing progressive ms222 concentrations ...201630050832
comparative transcriptomics of limb regeneration: identification of conserved expression changes among three species of ambystoma.transcriptome studies are revealing the complex gene expression basis of limb regeneration in the primary salamander model - ambystoma mexicanum (axolotl). to better understand this complexity, there is need to extend analyses to additional salamander species. using microarray and rna-seq, we performed a comparative transcriptomic study using a. mexicanum and two other ambystomatid salamanders: a. andersoni, and a. maculatum. salamanders were administered forelimb amputations and rna was isolate ...201930092345
exogenous vitamin d signaling alters skeletal patterning, differentiation, and tissue integration during limb regeneration in the axolotl.urodele amphibians such as the axolotl regenerate complete limbs as adults, and understanding how the "blueprint", or pattern, of the regenerate is established and manipulated are areas of intense interest. nutrient signaling plays an important role in pattern formation during regeneration. retinoic acid signaling is the most characterized pathway during this process. exogenous retinoic acid (ra) reprograms the pattern information in regenerating cells to a more posterior, ventral, and proximal ...201830096415
differences in neural stem cell identity and differentiation capacity drive divergent regenerative outcomes in lizards and salamanders.while lizards and salamanders both exhibit the ability to regenerate amputated tails, the outcomes achieved by each are markedly different. salamanders, such as ambystoma mexicanum, regenerate nearly identical copies of original tails. regenerated lizard tails, however, exhibit important morphological differences compared with originals. some of these differences concern dorsoventral patterning of regenerated skeletal and spinal cord tissues; regenerated salamander tail tissues exhibit dorsovent ...201830104374
[biomedical bestiary: the axolotl]. 201930125261
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
the serotonergic somatosensory projection to the tectum of normal and eyeless salamanders.the spinotectal somatosensory projection was compared in normal, genetically eyeless, and embryonically manipulated salamanders. in normal animals, serotonin fluorescence was restricted to the intermediate tectalneuropil. this same region showed both high levels of serotonin uptake and somatosensory single unit electrical activity. in mutant eyeless salamanders and in normal animals enucleated early in development, serotonin fluorescence, serotonin uptake, and somatosensory activity were present ...198130153710
identification of axolotl bh3-only proteins and expression in axolotl organs and apoptotic limb regeneration tissue.like other urodela amphibians, axolotls are able to regenerate lost appendages, even as adults, rendering them unique among higher vertebrates. in reaction to the severe trauma of a lost limb, apoptosis seems to be primarily implicated in the removal of injured cells and tissue homeostasis. little, however, is known about apoptotic pathways and control mechanisms. therefore, here we provide additional information regarding the mechanisms of tissue degradation. expression patterns of bcl-2 family ...201830154109
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
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
using transcriptomics to enable a plethodontid salamander (bolitoglossa ramosi) for limb regeneration research.tissue regeneration is widely distributed across the tree of life. among vertebrates, salamanders possess an exceptional ability to regenerate amputated limbs and other complex structures. thus far, molecular insights about limb regeneration have come from a relatively limited number of species from two closely related salamander families. to gain a broader perspective on the molecular basis of limb regeneration and enhance the molecular toolkit of an emerging plethodontid salamander (bolitoglos ...201830253734
single-cell analysis uncovers convergence of cell identities during axolotl limb regeneration.amputation of the axolotl forelimb results in the formation of a blastema, a transient tissue where progenitor cells accumulate prior to limb regeneration. however, the molecular understanding of blastema formation had previously been hampered by the inability to identify and isolate blastema precursor cells in the adult tissue. we have used a combination of cre-loxp reporter lineage tracking and single-cell messenger rna sequencing (scrna-seq) to molecularly track mature connective tissue (ct) ...201830262634
application and optimization of crispr-cas9-mediated genome engineering in axolotl (ambystoma mexicanum).genomic manipulation is essential to the use of model organisms to understand development, regeneration and adult physiology. the axolotl (ambystoma mexicanum), a type of salamander, exhibits an unparalleled regenerative capability in a spectrum of complex tissues and organs, and therefore serves as a powerful animal model for dissecting mechanisms of regeneration. we describe here an optimized stepwise protocol to create genetically modified axolotls using the crispr-cas9 system. the protocol, ...201830429597
from axolotl to zebrafish: a comparative approach to the study of thyroid involvement in ocular development.while discussion of interactions between the thyroid gland and the eye mostly focus on thyroid eye disease, the involvement of the thyroid and its hormones on development of the eye before birth is also an important perspective that should not be forgotten. experimental models involving amphibians and fish are valuable both because the developing larvae are not constrained within the adult but can be observed and manipulated as they grow autonomously and also because they metamorphose with subst ...201930482907
regenerative models for the integration and regeneration of head skeletal tissues.disease of, or trauma to, the human jaw account for thousands of reconstructive surgeries performed every year. one of the most popular and successful treatment options in this context involves the transplantation of bone tissue from a different anatomical region into the affected jaw. although, this method has been largely successful, the integration of the new bone into the existing bone is often imperfect, and the integration of the host soft tissues with the transplanted bone can be inconsis ...201830486286
transcriptomic landscape of the blastema niche in regenerating adult axolotl limbs at single-cell resolution.regeneration of complex multi-tissue structures, such as limbs, requires the coordinated effort of multiple cell types. in axolotl limb regeneration, the wound epidermis and blastema have been extensively studied via histology, grafting, and bulk-tissue rna-sequencing. however, defining the contributions of these tissues is hindered due to limited information regarding the molecular identity of the cell types in regenerating limbs. here we report unbiased single-cell rna-sequencing on over 25,00 ...201830514844
comparative transcriptomics of rat and axolotl after spinal cord injury dissects differences and similarities in inflammatory and matrix remodeling gene expression patterns.following spinal cord injury in mammals, maladaptive inflammation, and matrix deposition drive tissue scarring and permanent loss of function. in contrast, axolotls regenerate their spinal cord after severe injury fully and without scarring. to explore previously unappreciated molecules and pathways that drive tissue responses after spinal cord injury, we performed a 4-way intersection of rat and axolotl transcriptomics datasets and isolated shared genes with similar or differential expression a ...201830519154
miniscule differences between sex chromosomes in the giant genome of a salamander.in the mexican axolotl (ambystoma mexicanum), sex is determined by a single mendelian factor, yet its sex chromosomes do not exhibit morphological differentiation typical of many vertebrate taxa that possess a single sex-determining locus. as sex chromosomes are theorized to differentiate rapidly, species with undifferentiated sex chromosomes provide the opportunity to reconstruct early events in sex chromosome evolution. whole genome sequencing of 48 salamanders, targeted chromosome sequencing ...201830552368
acquisition and reconstruction of 4d surfaces of axolotl embryos with the flipping stage robotic microscope.we have designed and constructed a flipping stage for a light microscope that can view the whole exterior surface of a 2 mm diameter developing axolotl salamander embryo. it works by rapidly inverting the bottom-heavy embryo, imaging it as it rights itself. the images are then montaged to reconstruct the whole 3d surface versus time, for a full 4d record of the surface. imaging early stage axolotl development will help discover how cell differentiation and movement takes place in the early embry ...201830554603
tracing the origins of axolotl limb regeneration.the mechanisms underlying limb regeneration in axolotl have remained elusive due to limitations in isolating and tracking the cells that replenish lost tissues. in recent work, elly tanaka and barbara treutlein unite their expertise in axolotl limb regeneration and single-cell analysis to reveal cellular mechanisms underpinning regeneration.201830562504
amputation-induced reactive oxygen species signaling is required for axolotl tail regeneration.among vertebrates, salamanders are unparalleled in their ability to regenerate appendages throughput life. however, little is known about early signals that initiate regeneration in salamanders.201930569660
2d and 3d echocardiography in the axolotl (ambystoma mexicanum).cardiac malfunction as a result of ischemic heart disease is a major challenge, and regenerative therapies to the heart are in high demand. a few model species such as zebrafish and salamanders that are capable of intrinsic heart regeneration hold promise for future regenerative therapies for human patients. to evaluate the outcome of cardioregenerative experiments it is imperative that heart function can be monitored. the axolotl salamander (a. mexicanum) represents a well-established model spe ...201830582577
blastemal progenitors modulate immune signaling during early limb regeneration.blastema formation, a hallmark of limb regeneration, requires proliferation and migration of progenitors to the amputation plane. although blastema formation has been well described, the transcriptional programs that drive blastemal progenitors remain unknown. we transcriptionally profiled dividing and non-dividing cells in regenerating stump tissues, as well as the wound epidermis, during early axolotl limb regeneration. our analysis revealed unique transcriptional signatures of early dividing ...201930602532
broad applicability of a streamlined ethyl cinnamate-based clearing procedure.turbidity and opaqueness are inherent properties of tissues that limit the capacity to acquire microscopic images through large tissues. creating a uniform refractive index, known as tissue clearing, overcomes most of these issues. these methods have enabled researchers to image large and complex 3d structures with unprecedented depth and resolution. however, tissue clearing has been adopted to a limited extent due to a combination of cost, time, complexity of existing methods and potential nega ...201930665888
a chromosome-scale assembly of the axolotl genome.the axolotl (ambystoma mexicanum) provides critical models for studying regeneration, evolution, and development. however, its large genome (∼32 gb) presents a formidable barrier to genetic analyses. recent efforts have yielded genome assemblies consisting of thousands of unordered scaffolds that resolve gene structures, but do not yet permit large-scale analyses of genome structure and function. we adapted an established mapping approach to leverage dense snp typing information and for the firs ...201930679309
publisher correction: application and optimization of crispr-cas9-mediated genome engineering in axolotl (ambystoma mexicanum).in the version of this protocol originally published, the recipe for cas9 buffer was incorrectly identified as a recipe for sodium acetate solution, and vice versa. these errors have been corrected in the pdf and html versions of the paper.201930696984
functional properties of axolotl transient receptor potential ankyrin 1 revealed by the heterologous expression system.transient receptor potential ankyrin 1 (trpa1) from tetrapod vertebrates except rodents are activated by high temperature with a relatively clear threshold. our recent investigation suggested that a gradual heat activation without clear threshold might be a common feature for trpa1 of fish. to approach which animal first acquires trpa1 as a threshold detector instead of a gradual heat sensor, here, we focused on trpa1 from axolotls (ambystoma mexicanum). we isolated a full-length cdna of axolotl ...201930702505
epithelial to mesenchymal transition is mediated by both tgf-β canonical and non-canonical signaling during axolotl limb regeneration.axolotls have the amazing ability to regenerate. when compared to humans, axolotls display a very fast wound closure, no scarring and are capable to replace lost appendages perfectly. understanding the signaling mechanism leading to this perfect healing is a key step to help develop regenerative treatments for humans. in this paper, we studied cellular pathways leading to axolotl limb regeneration. we focus on the wound closure phase where keratinocytes migrate to close the lesion site and how e ...201930718780
investigating nrg1 signaling in the regenerating axolotl spinal cord using multiplexed fish.amputation of a salamander tail leads to functional spinal cord regeneration through activation of endogenous stem cells. identifying the signaling pathways that control cell proliferation in these neural stem cells will help elucidate the mechanisms underlying the salamander's regenerative ability. here, we show that neuregulin 1 (nrg1)/erbb2 signaling is an important pathway in the regulation of neural stem cell proliferation in the spinal cord of the axolotl salamander (ambystoma mexicanum). ...201930793850
nerve-mediated expression of histone deacetylases regulates limb regeneration in axolotls.axolotls have amazing abilities to regenerate their lost limbs. nerve and wound epidermis have great impacts on this regeneration. histone deacetylases (hdacs) have been shown to play roles in the regeneration of amphibian tails and limbs. in this study, a bi-phasic up-regulation of hdac1 was noted before early differentiation stage of axolotl limb regeneration. limb regeneration was delayed in larvae incubated with an hdac inhibitor ms-275. local injection of ms-275 or tsa, another hdac inhibit ...201930826398
ap-1cfos/junb/mir-200a regulate the pro-regenerative glial cell response during axolotl spinal cord regeneration.salamanders have the remarkable ability to functionally regenerate after spinal cord transection. in response to injury, gfap+ glial cells in the axolotl spinal cord proliferate and migrate to replace the missing neural tube and create a permissive environment for axon regeneration. molecular pathways that regulate the pro-regenerative axolotl glial cell response are poorly understood. here we show axolotl glial cells up-regulate ap-1cfos/junb after injury, which promotes a pro-regenerative glia ...201930854483
a clinically relevant blunt spinal cord injury model in the regeneration competent axolotl (ambystoma mexicanum) tail.a randomized controlled and blinded animal trial was conducted in the axolotl (ambystoma mexicanum), which has the ability to regenerate from transectional spinal cord injury (sci). the objective of the present study was to investigate the axolotl's ability to regenerate from a blunt spinal cord trauma in a clinical setting. axolotls were block-randomized to the intervention (n=6) or sham group (n=6). a laminectomy of two vertebrae at the level caudal to the hind limbs was performed. to induce a ...201930867717
joints in the appendicular skeleton: developmental mechanisms and evolutionary influences.the joints are a diverse group of skeletal structures, and their genesis, morphogenesis, and acquisition of specialized tissues have intrigued biologists for decades. here we review past and recent studies on important aspects of joint development, including the roles of the interzone and morphogenesis of articular cartilage. studies have documented the requirement of interzone cells in limb joint initiation and formation of most, if not all, joint tissues. we highlight these studies and also re ...201930902250
glycosaminoglycans compositional analysis of urodele axolotl (ambystoma mexicanum) and porcine retina.retinal degenerative diseases, such as age-related macular degeneration (amd) and retinitis pigmentosa (rp), are major causes of blindness worldwide. humans cannot regenerate retina, however, axolotl (ambystoma mexicanum), a laboratory-bred salamander, can regenerate retinal tissue throughout adulthood. classic signaling pathways, including fibroblast growth factor (fgf), are involved in axolotl regeneration. glycosaminoglycan (gag) interaction with fgf is required for signal transduction in thi ...201930963354
opposite t3 response of actg1-fos subnetwork differentiate tailfin fate in xenopus tadpole and post-hatching axolotl.amphibian post-embryonic development and thyroid hormones (th) signaling are deeply and intimately connected. in anuran amphibians, th induce the spectacular and complex process known as metamorphosis. in paedomorphic salamanders, at similar development time, raising levels of th fail to induce proper metamorphosis, as many "larval" tissues (e.g., gills, tailfin) are maintained. why does the same evolutionary conserved signaling pathway leads to alternative phenotypes? we used a combination of d ...201931001200
effect of skeletal paracrine signals on the proliferation of interzone cells.articular cartilage in mammals has limited intrinsic capacity to repair structural defects, a fact that contributes to the chronic and progressive nature of osteoarthritis. in contrast, mexican axolotl salamanders have demonstrated the remarkable ability to spontaneously and completely repair large joint cartilage lesions, a healing process that involves interzone cells in the intraarticular space. furthermore, interzone tissue transplanted into skeletal defects in the axolotl salamander demonst ...201931023058
fgf, bmp, and ra signaling are sufficient for the induction of complete limb regeneration from non-regenerating wounds on ambystoma mexicanum limbs.some organisms, such as the mexican axolotl, have the capacity to regenerate complicated biological structures throughout their lives. which molecular pathways are sufficient to induce a complete endogenous regenerative response in injured tissue is an important question that remains unanswered. using a gain-of-function regeneration assay, known as the accessory limb model (alm), we and others have begun to identify the molecular underpinnings of the three essential requirements for limb regener ...201931026439
rediscovering the axolotl as a model for thyroid hormone dependent development.the mexican axolotl (ambystoma mexicanum) is an important model organism in biomedical research. much current attention is focused on the axolotl's amazing ability to regenerate tissues and whole organs after injury. however, not forgotten is the axolotl's equally amazing ability to thwart aspects of tissue maturation and retain juvenile morphology into the adult phase of life. unlike close tiger salamander relatives that undergo a thyroid hormone regulated metamorphosis, the axolotl does not ty ...201931031711
fgf- and bmp-signaling regulate gill regeneration in ambystoma mexicanum.gill regeneration has not been well studied compared to regeneration of other appendages, such as limb and tail regeneration. here, we focused on axolotl gill regeneration and found that fgf- and bmp-signaling are involved in their gill regeneration mechanism. axolotls have three pairs of gill rami, and each gill ramus has multiple gill filaments. the gills consist of mesenchyme rich in extracellular matrix and epidermis. the gill nerves are supplied from the trigeminal ganglia located in the he ...201931034835
hdac regulates transcription at the outset of axolotl tail regeneration.tissue regeneration is associated with complex changes in gene expression and post-translational modifications of proteins, including transcription factors and histones that comprise chromatin. we tested 172 compounds designed to target epigenetic mechanisms in an axolotl (ambystoma mexicanum) embryo tail regeneration assay. a relatively large number of compounds (n = 55) inhibited tail regeneration, including 18 histone deacetylase inhibitors (hdaci). in particular, romidepsin, an fda-approved ...201931043677
management of multiple protozoan ectoparasites in a research colony of axolotls (ambystoma mexicanum).axolotls (ambystoma mexicanum) from a research colony presented with multifocal, white chalky to gray skin lesions, a diffuse whitish to blue hue to the integument, and friable gill filaments. skin scrapings and wet mounts revealed chilodonella, ichthyobodo, and a trichodinid species. the average overall burden (that is, all 3 species) per axolotl ranged from 0 to 25 parasites per 40 × field (p40f; mean ± 1 sd, 2.6 ± 5.5), with a prevalence of 12%, 60%, and 48%, respectively. concurrent with hus ...201931060645
endoscopic removal of a foreign body in a mexican axolotl (ambystoma mexicanum) with the use of ms222-induced immobilization.this communication briefly describes the use of tricaine methanesulfonate (ms222) to induce chemical restraint/general anesthesia of a mexican axolotl (ambystoma mexicanum) for the endoscopic retrieval of a gastric foreign body. there is very little published scientific literature concerning the anesthesia of mexican axolotls. the anesthesia used in this case was an immersion bath of tricaine methanesulfonate where the concentration of tricaine methanesulfonate was gradually increased to 500 mg/ ...201931120693
longitudinal 16s rrna data derived from limb regenerative tissue samples of axolotl ambystoma mexicanum.the mexican axolotl (ambystoma mexicanum) is a critically endangered species and a fruitful amphibian model for regenerative biology. despite growing body of research on the cellular and molecular biology of axolotl limb regeneration, microbiological aspects of this process remain poorly understood. here, we describe bacterial 16s rrna amplicon dataset derived from axolotl limb tissue samples in the course of limb regeneration. the raw data was obtained by sequencing v3-v4 region of 16s rrna gen ...201931123261
lineage tracing of sclerotome cells in amphibian reveals that multipotent somitic cells originate from lateral somitic frontier.the two somite compartments, dorso-lateral dermomyotome and medio-ventral sclerotome are major vertebrate novelties, but little is known about their evolutionary origin. we determined that sclerotome cells in xenopus come from lateral somitic frontier (lsf) by lineage tracing, ablation experiments and histological analysis. we identified twist1 as marker of migrating sclerotome progenitors in two amphibians, xenopus and axolotl. from these results, three conclusions can be drawn. first, lsf is m ...201931128088
treatment of chytridiomycosis in laboratory axolotls (ambystoma mexicanum) and rough-skinned newts (taricha granulosa).chytridiomycosis is an infectious disease of amphibians caused by the fungal species batrachochytrium dendrobatidis and b. salamandrivorans and has been implicated in the population decline of amphibian species worldwide. this case report describes a successful treatment protocol for chytridiomycosis in laboratory-maintained colonies of axolotls (ambystoma mexicanum) and rough-skinned newts (taricha granulosa). over 12 mo, axolotls (n = 12) in a laboratory-reared colony developed multifocal eryt ...201931142399
deep evolutionary origin of limb and fin regeneration.salamanders and lungfishes are the only sarcopterygians (lobe-finned vertebrates) capable of paired appendage regeneration, regardless of the amputation level. among actinopterygians (ray-finned fishes), regeneration after amputation at the fin endoskeleton has only been demonstrated in polypterid fishes (cladistia). whether this ability evolved independently in sarcopterygians and actinopterygians or has a common origin remains unknown. here we combine fin regeneration assays and comparative rn ...201931270239
inhibiting fibroblast aggregation in skin wounds unlocks developmental pathway to regeneration.salamanders are capable of full-thickness skin regeneration where removal of epidermis, dermis and hypodermis results in scar-free repair. what remains unclear is whether regeneration of these tissues recapitulates the cellular events of skin development or occurs through a process unique to regenerative healing. unfortunately, information on the post-embryonic development of salamander skin is severely lacking, having focused on compartments or cell types, but never on the skin as a complete or ...201931279726
hierarchical pattern formation during amphibian limb regeneration.in 1901 t.h. morgan proposed in "regeneration" that pattern formation in amphibian limb regeneration is a stepwise process. since, biologist have continued to piece together the molecular components of this process to better understand the "patterning code" responsible for regenerate formation. within this context, several different models have been proposed; however, all are based on one of two underlying hypotheses. the first is the "morphogen hypothesis" that dictates that pattern emerges fro ...201931295535
cancer drug repositioning by comparison of gene expression in humans and axolotl (ambystoma mexicanum) during wound healing.urodele amphibians such as the axolotl (ambystoma mexicanum) display a large capacity for tissue regeneration and remarkable resistance to cancer. as a model organism, axolotl thus offers a unique opportunity for cancer research and anticancer drug discovery, not to mention the discerning mechanisms that underpin controlled cellular growth and regeneration versus cancer. to the best of our knowledge, little is known on comparative gene expression changes during regeneration events such as wound ...201931305215
model systems for regeneration: salamanders.salamanders have been hailed as champions of regeneration, exhibiting a remarkable ability to regrow tissues, organs and even whole body parts, e.g. their limbs. as such, salamanders have provided key insights into the mechanisms by which cells, tissues and organs sense and regenerate missing or damaged parts. in this primer, we cover the evolutionary context in which salamanders emerged. we outline the varieties of mechanisms deployed during salamander regeneration, and discuss how these mechan ...201931332037
direct gene knock-out of axolotl spinal cord neural stem cells via electroporation of cas9 protein-grna complexes.the axolotl has the unique ability to fully regenerate its spinal cord. this is largely due to the ependymal cells remaining as neural stem cells (nscs) throughout life, which proliferate to reform the ependymal tube and differentiate into lost neurons after spinal cord injury. deciphering how these nscs retain pluripotency post-development and proliferate upon spinal cord injury to reform the exact pre-injury structure can provide valuable insight into how mammalian spinal cords may regenerate ...201931355781
stability and plasticity of positional memory during limb regeneration in ambystoma mexicanum.urodele amphibians are capable of regenerating their organs after severe damage. during such regeneration, participating cells are given differentiation instructions by the surrounding cells. limb regeneration has been investigated as a representative phenomenon of organ regeneration. cells known as blastema cells are induced after limb amputation. in this process, dermal fibroblasts are dedifferentiated and become undifferentiated similar to limb bud cells. just like limb bud cells, the induced ...202031386776
lissamphibian limbs and the origins of tetrapod hox domains.the expression and function of hox genes have played a key role in the debate on the evolution of limbs from fins. as an early branching tetrapod lineage, lissamphibians may provide information on the origin of the limb's hox domains and particularly how the plesiomorphic tetrapod pattern compares to the hox pattern present in fish fins. here, we comparatively investigated the expression of hox genes in the developing limbs of axolotl and xenopus laevis as well as in the fins of the direct devel ...201931445923
a conserved regulatory program initiates lateral plate mesoderm emergence across chordates.cardiovascular lineages develop together with kidney, smooth muscle, and limb connective tissue progenitors from the lateral plate mesoderm (lpm). how the lpm initially emerges and how its downstream fates are molecularly interconnected remain unknown. here, we isolate a pan-lpm enhancer in the zebrafish-specific draculin (drl) gene that provides specific lpm reporter activity from early gastrulation. in toto live imaging and lineage tracing of drl-based reporters captures the dynamic lpm emerge ...201931451684
label-free imaging of tissue architecture during axolotl peripheral nerve regeneration in comparison to functional recovery.human peripheral nerves hold the potential to regenerate after injuries; however, whether a successful axonal regrowth was achieved can be elucidated only months after injury by assessing function. the axolotl salamander is a regenerative model where nerves always regenerate quickly and fully after all types of injury. here, de- and regeneration of the axolotl sciatic nerve were investigated in a single and double injury model by label-free multiphoton imaging in comparison to functional recover ...201931477751
fgf-signaling is compartmentalized within the mesenchyme and controls proliferation during salamander limb development.although decades of studies have produced a generalized model for tetrapod limb development, urodeles deviate from anurans and amniotes in at least two key respects: their limbs exhibit preaxial skeletal differentiation and do not develop an apical ectodermal ridge (aer). here, we investigated how sonic hedgehog (shh) and fibroblast growth factor (fgf) signaling regulate limb development in the axolotl. we found that shh-expressing cells contributed to the most posterior digit, and that inhibiti ...201931538936
"lost and found": snorna annotation in the xenopus genome and implications for evolutionary studies.small nucleolar rnas (snornas) function primarily as guide rnas for posttranscriptional modification of rrnas and spliceosomal snrnas, both of which are functionally important and evolutionarily conserved molecules. it is commonly believed that snornas and the modifications they mediate are highly conserved across species. however, most relevant data on snorna annotation and rna modification are limited to studies on human and yeast. here, we used rna-sequencing data from the giant oocyte nucleu ...202031553476
total synthesis of griseusins and elucidation of the griseusin mechanism of action.a divergent modular strategy for the enantioselective total synthesis of 12 naturally-occurring griseusin type pyranonaphthoquinones and 8 structurally-similar analogues is described. key synthetic highlights include cu-catalyzed enantioselective boration-hydroxylation and hydroxyl-directed c-h olefination to afford the central pharmacophore followed by epoxidation-cyclization and maturation via diastereoselective reduction and regioselective acetylation. structural revision of griseusin d and a ...201931583069
oled loki as a catalyst for hydroxamate glycosylation.herein we describe the ability of the permissive glycosyltransferase (gt) oled loki to convert a diverse set of >15 histone deacetylase (hdac) inhibitors (hdacis) into their corresponding hydroxamate glycosyl esters. representative glycosyl esters were subsequently evaluated in assays for cancer cell line cytotoxicity, chemical and enzymatic stability, and axolotl embryo tail regeneration. computational substrate docking models were predictive of enzyme-catalyzed turnover and suggest certain hda ...202031621997
analysis of "old" proteins unmasks dynamic gradient of cartilage turnover in human limbs.unlike highly regenerative animals, such as axolotls, humans are believed to be unable to counteract cumulative damage, such as repetitive joint use and injury that lead to the breakdown of cartilage and the development of osteoarthritis. turnover of insoluble collagen has been suggested to be very limited in human adult cartilage. the goal of this study was to explore protein turnover in articular cartilage from human lower limb joints. analyzing molecular clocks in the form of nonenzymatically ...201931633025
contusion spinal cord injury via a microsurgical laminectomy in the regenerative axolotl.the purpose of this study is to establish a standardized and reproducible regenerative blunt spinal cord injury model in the axolotl (ambystoma mexicanum). most clinical spinal cord injuries occur as high energy blunt traumas, inducing contusion injuries. however, most studies in the axolotl spinal cord have been conducted with sharp traumas. hence, this study aims to produce a more clinically relevant regenerative model. due to their impressive ability to regenerate almost any tissue, axolotls ...201931680666
unique high sensitivity to heat of axolotl trpv1 revealed by the heterologous expression system.the thermosensation mechanism plays critical roles in various animals living in different thermal environment. we focused on an axolotl, which is a tailed amphibian originally from lake xochimilco area in the vally of mexico, and examined its behavior response to heat stimulation. mild heat at 33 °c induced noxious locomotive activity to axolotls, but the noxious response of another tailed amphibian, iberian ribbed newt, was not observed at 33 °c. to explore the mechanism for the temperature sen ...202031711646
meningeal foam cells and ependymal cells in axolotl spinal cord regeneration.a previously unreported population of foam cells (foamy macrophages) accumulates in the invasive fibrotic meninges during gap regeneration of transected adult axolotl spinal cord (salamander ambystoma mexicanum) and may act beneficially. multinucleated giant cells (mngcs) also occurred in the fibrotic meninges. actin-label localization and transmission electron microscopy showed characteristic foam cell and mngc podosome and ruffled border-containing sealing ring structures involved in substratu ...201931736973
comparison of protein expression profile of limb regeneration between neotenic and metamorphic axolotl.the axolotl (ambystoma mexicanum) salamander, a urodele amphibian, has an exceptional regenerative capacity to fully restore an amputated limb throughout the life-long lasting neoteny. by contrast, when axolotls are experimentally induced to metamorphosis, attenuation of the limb's regenerative competence is noticeable. here, we sought to discern the proteomic profiles of the early stages of blastema formation of neotenic and metamorphic axolotls after limb amputation by employing lc-ms/ms techn ...202031767146
advancements to the axolotl model for regeneration and aging.loss of regenerative capacity is a normal part of aging. however, some organisms, such as the mexican axolotl, retain striking regenerative capacity throughout their lives. moreover, the development of age-related diseases is rare in this organism. in this review, we will explore how axolotls are used as a model system to study regenerative processes, the exciting new technological advancements now available for this model, and how we can apply the lessons we learn from studying regeneration in ...202031779024
paradoxical changes underscore epigenetic reprogramming during adult zebrafish extraocular muscle regeneration.genomic reprogramming and cellular dedifferentiation are critical to the success of de novo tissue regeneration in lower vertebrates such as zebrafish and axolotl. in tissue regeneration following injury or disease, differentiated cells must retain lineage while assuming a progenitor-like identity in order to repopulate the damaged tissue. understanding the epigenetic regulation of programmed cellular dedifferentiation provides unique insights into the biology of stem cells and cancer and may le ...201931794598
extracting physiological information in experimental biology via eulerian video magnification.videographic material of animals can contain inapparent signals, such as color changes or motion that hold information about physiological functions, such as heart and respiration rate, pulse wave velocity, and vocalization. eulerian video magnification allows the enhancement of such signals to enable their detection. the purpose of this study is to demonstrate how signals relevant to experimental physiology can be extracted from non-contact videographic material of animals.201931831016
structure determination, functional characterization, and biosynthetic implications of nybomycin metabolites from a mining reclamation site-associated streptomyces.we report the isolation and characterization of three new nybomycins (nybomycins b-d, 1-3) and six known compounds (nybomycin, 4; deoxynyboquinone, 5; α-rubromycin, 6; β-rubromycin, 7; γ-rubromycin, 8; and [2α(1e,3e),4β]-2-(1,3-pentadienyl)-4-piperidinol, 9) from the rock creek (mccreary county, ky) underground coal mine acid reclamation site isolate streptomyces sp. ad-3-6. nybomycin d (3) and deoxynyboquinone (5) displayed moderate (3) to potent (5) cancer cell line cytotoxicity and displayed ...201931833370
alginate hydrogel enriched with ambystoma mexicanum epidermal lipoxygenase-loaded pectin nanoparticles for enhanced wound healing. 202031886725
integrative analysis of axolotl gene expression data from regenerative and wound healing limb tissues.axolotl (ambystoma mexicanum) is a urodele amphibian endowed with remarkable regenerative capacities manifested in scarless wound healing and restoration of amputated limbs, which makes it a powerful experimental model for regenerative biology and medicine. previous studies have utilized microarrays and rna-seq technologies for detecting differentially expressed (de) genes in different phases of the axolotl limb regeneration. however, sufficient consistency may be lacking due to statistical limi ...201931889169
normal development in ambystoma mexicanum: a complementary staging table for the skull based on alizarin red s staining.as the role of ambystoma mexicanum, or the mexican axolotl, expands in research applications beyond its traditional use in studies of limb regeneration, a staging table that is more anatomically extensive is required. here, we describe axolotl skull development as it relates to previously established developmental stages that were based on limb development.202031930611
midkine is a dual regulator of wound epidermis development and inflammation during the initiation of limb regeneration.formation of a specialized wound epidermis is required to initiate salamander limb regeneration. yet little is known about the roles of the early wound epidermis during the initiation of regeneration and the mechanisms governing its development into the apical epithelial cap (aec), a signaling structure necessary for outgrowth and patterning of the regenerate. here, we elucidate the functions of the early wound epidermis, and further reveal midkine (mk) as a dual regulator of both aec developmen ...202031934849
operation spinal cord regeneration: patterning information residing in extracellular matrix glycosaminoglycans.spinal cord injuries are devastating, with many complications beyond paralysis and loss of sensory function. although spinal cord regeneration can revolutionize treatment for spinal cord injuries, the goal has not yet been achieved. the regenerative mechanism of axolotls demonstrates that the regeneration is a repeat of developmental process that all animals have all the genes, but axolotls have both the genes and the patterning information to do it at the adult stage.202031944630
lag penalized weighted correlation for time series clustering.the similarity or distance measure used for clustering can generate intuitive and interpretable clusters when it is tailored to the unique characteristics of the data. in time series datasets generated with high-throughput biological assays, measurements such as gene expression levels or protein phosphorylation intensities are collected sequentially over time, and the similarity score should capture this special temporal structure.202031948388
quantitative and qualitative behavioral measurements to assess pain in axolotls (ambystoma mexicanum).effective pain relief in animals relies on the ability to discern pain and assess its severity. however, few objective measures exist to assess the presence and severity of pain in axolotls, and few resources are available regarding drugs and appropriate doses to provide pain relief in this species. this study evaluated behavioral tools for cageside pain assessment and validated a reproducible and reliable quantitative method to evaluate analgesic efficacy in axolotls. animals were divided into ...202031964458
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