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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
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
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
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
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
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
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
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
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
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
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
[prolactin enhancement of absorption of sodium ions in isolated gills from larva of ambystoma mexicanum]. 20144120136
[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
[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
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
comparison of the effects of vitamin a on limb development and regeneration in the axolotl, ambystoma mexicanum.the objective of this investigation was to compare the effect of vitamin a on limb development and limb regeneration in the same animal, at the same time, thus eliminating the possibility that species differences or different rates of uptake between animals would influence the results. axolotl larvae had both right limbs amputated and then were treated with retinol palmitate by immersion at 60 or 300 mg l-1 for 4 or 10 days. intact left developing limbs at the cone, two-digit, or four-digit stag ...20133711785
genomics of a metamorphic timing qtl: met1 maps to a unique genomic position and regulates morph and species-specific patterns of brain transcription.very little is known about genetic factors that regulate life history transitions during ontogeny. closely related tiger salamanders (ambystoma species complex) show extreme variation in metamorphic timing, with some species foregoing metamorphosis altogether, an adaptive trait called paedomorphosis. previous studies identified a major effect quantitative trait locus (met1) for metamorphic timing and expression of paedomorphosis in hybrid crosses between the biphasic eastern tiger salamander (am ...201323946331
role of bilateral zones of ingressing superficial cells during gastrulation of ambystoma mexicanum.vital dye staining and cell lineage tracers were used to mark superficial cells of early ambystoma mexicanum gastrulae. superficial marks placed between the equator and the blastopore, on the dorsal midline, stained notochord, whereas marks or injections made at similar animal-vegetal levels but 90 degrees to either side of the dorsal midline were later found in somitic mesoderm. notochord marks remained on the dorsal surface of the archenteron throughout gastrulation, though they became elongat ...20133794603
the pigmentary system of developing axolotls. iv. an analysis of the axanthic phenotype.the axanthic mutant in the mexican axolotl (ambystoma mexicanum) was analysed with respect to the differentiation of pigment cells. transmission electron micrographs revealed the presence of melanophores and cells that are described as unpigmented xanthophores in axanthic skin. iridophores apparently failed to differentiate in axanthic axolotls (a pattern similar to that observed in melanoid axolotls). chromatographic analyses of skin extracts confirmed that there are no pteridines (xanthophore ...20133794587
changes in patterns of protein synthesis in axolotl oocytes during progesterone-induced maturation.patterns of protein phosphorylation and synthesis during axolotl (ambystoma mexicanum) oocyte maturation were studied by incorporation of [32p]orthophosphate and [35s]methionine into polypeptides, followed by two-dimensional gel electrophoresis. various alterations were observed after progesterone treatment: de novo appearance of [35s]methionine-labelled polypeptides, a quantitative increase in previously synthesized proteins and a quantitative decrease in or disappearance of other previously sy ...20133723056
spatial distribution of prominin-1 (cd133)-positive cells within germinative zones of the vertebrate brain.in mammals, embryonic neural progenitors as well as adult neural stem cells can be prospectively isolated based on the cell surface expression of prominin-1 (cd133), a plasma membrane glycoprotein. in contrast, characterization of neural progenitors in non-mammalian vertebrates endowed with significant constitutive neurogenesis and inherent self-repair ability is hampered by the lack of suitable cell surface markers. here, we have investigated whether prominin-1-orthologues of the major non-mamm ...201323723983
prominent role of prominin in the retina.prominin molecules represent a new family of pentaspan membrane glycoproteins expressed throughout the animal kingdom. the name originates from its localization on membrane protrusion, such as microvilli, filopodia, lamellipodia, and microspikes. following the original description in mouse and human, representative prominin members were found in fish (e.g., danio rerio), amphibian (ambystoma mexicanum, xenopus laevis), worm (caenorhabditis elegans), and flies (drosophila melanogaster). mammalian ...201323161075
cranial muscles in amphibians: development, novelties and the role of cranial neural crest cells.our research on the evolution of the vertebrate head focuses on understanding the developmental origins of morphological novelties. using a broad comparative approach in amphibians, and comparisons with the well-studied quail-chicken system, we investigate how evolutionarily conserved or variable different aspects of head development are. here we review research on the often overlooked development of cranial muscles, and on its dependence on cranial cartilage development. in general, cranial mus ...201322780231
profiling neurotransmitter receptor expression in the ambystoma mexicanum brain.ability to regenerate limbs and central nervous system (cns) is unique to few vertebrates, most notably the axolotl (ambystoma sp.). however, despite the fact the neurotransmitter receptors are involved in axonal regeneration, little is known regarding its expression profile. in this project, rt-pcr and qpcr were performed to gain insight into the neurotransmitter receptors present in ambystoma. its functional ability was studied by expressing axolotl receptors in xenopus laevis oocytes by eithe ...201323353105
de novo transcriptome sequencing of axolotl blastema for identification of differentially expressed genes during limb regeneration.salamanders are unique among vertebrates in their ability to completely regenerate amputated limbs through the mediation of blastema cells located at the stump ends. this regeneration is nerve-dependent because blastema formation and regeneration does not occur after limb denervation. to obtain the genomic information of blastema tissues, de novo transcriptomes from both blastema tissues and denervated stump ends of ambystoma mexicanum (axolotls) 14 days post-amputation were sequenced and compar ...201323815514
foamy virus for efficient gene transfer in regeneration studies.molecular studies of appendage regeneration have been hindered by the lack of a stable and efficient means of transferring exogenous genes. we therefore sought an efficient integrating virus system that could be used to study limb and tail regeneration in salamanders.201323641815
lmx-1b and wnt-7a expression in axolotl limb during development and regeneration.axolotls (ambystoma mexicanum) have the ability to regenerate amputated limbs throughout their life span. during limb regeneration as well as development, undifferentiated cells in the blastema acquire positional information to reproduce the original pattern along three cardinal limb axes: anteroposterior, proximodistal and dorsoventral. in the present study, we attempted to understand the molecular mechanism involved in patterning of axolotl limb development and regeneration along the dorsovent ...201323614984
positional information is reprogrammed in blastema cells of the regenerating limb of the axolotl (ambystoma mexicanum).the regenerating region of an amputated salamander limb, known as the blastema, has the amazing capacity to replace exactly the missing structures. by grafting cells from different stages and regions of blastemas induced to form on donor animals expressing green fluorescent protein (gfp), to non-gfp host animals, we have determined that the cells from early stage blastemas, as well as cells at the tip of late stage blastemas are developmentally labile such that their positional identity is repro ...201324086768
germline transgenic methods for tracking cells and testing gene function during regeneration in the axolotl.the salamander is the only tetrapod that regenerates complex body structures throughout life. deciphering the underlying molecular processes of regeneration is fundamental for regenerative medicine and developmental biology, but the model organism had limited tools for molecular analysis. we describe a comprehensive set of germline transgenic strains in the laboratory-bred salamander ambystoma mexicanum (axolotl) that open up the cellular and molecular genetic dissection of regeneration. we demo ...201324052945
molecular cloning, sequence analysis and phylogeny of first caudata g-type lysozyme in axolotl (ambystoma mexicanum).lysozymes are key proteins that play important roles in innate immune defense in many animal phyla by breaking down the bacterial cell-walls. in this study, we report the molecular cloning, sequence analysis and phylogeny of the first caudate amphibian g-lysozyme: a full-length spleen cdna library from axolotl (ambystoma mexicanum). a goose-type (g-lysozyme) est was identified and the full-length cdna was obtained using race-pcr. the axolotl g-lysozyme sequence represents an open reading frame f ...201324199859
pseudotyped retroviruses for infecting axolotl in vivo and in vitro.axolotls are poised to become the premiere model system for studying vertebrate appendage regeneration. however, very few molecular tools exist for studying crucial cell lineage relationships over regeneration or for robust and sustained misexpression of genetic elements to test their function. furthermore, targeting specific cell types will be necessary to understand how regeneration of the diverse tissues within the limb is accomplished. we report that pseudotyped, replication-incompetent retr ...201323344705
comparative pelvic development of the axolotl (ambystoma mexicanum) and the australian lungfish (neoceratodus forsteri): conservation and innovation across the fish-tetrapod transition.the fish-tetrapod transition was one of the major events in vertebrate evolution and was enabled by many morphological changes. although the transformation of paired fish fins into tetrapod limbs has been a major topic of study in recent years, both from paleontological and comparative developmental perspectives, the interest has focused almost exclusively on the distal part of the appendage and in particular the origin of digits. relatively little attention has been paid to the transformation o ...201323342976
revisiting the relationship between regenerative ability and aging.contrary to the longstanding view that newts (notophthalamus viridescens), but not axolotls (ambystoma mexicanum), can regenerate a lens, a recent report in bmc biology by panagiotis tsonis and colleagues shows axolotls indeed possess this ability during early larval stages. in contrast, they show that zebrafish never posses this ability, even as embryos. this underscores the importance of comparing regenerative ability across species and reinforces the need to consider organ regeneration in the ...201323336699
proliferation zones in the axolotl brain and regeneration of the telencephalon.although the brains of lower vertebrates are known to exhibit somewhat limited regeneration after incisional or stab wounds, the urodele brain exhibits extensive regeneration after massive tissue removal. discovering whether and how neural progenitor cells that reside in the ventricular zones of urodeles proliferate to mediate tissue repair in response to injury may produce novel leads for regenerative strategies. here we show that endogenous neural progenitor cells resident to the ventricular z ...201323327114
progressive specification rather than intercalation of segments during limb regeneration.an amputated salamander limb regenerates the correct number of segments. models explaining limb regeneration were largely distinct from those for limb development, despite the presence of common patterning molecules. intercalation has been an important concept to explain salamander limb regeneration, but clear evidence supporting or refuting this model was lacking. in the intercalation model, the first blastema cells acquire fingertip identity, creating a gap in positional identity that triggers ...201324337297
expression of tropomyosin in relation to myofibrillogenesis in axolotl hearts.the anatomy, function and embryonic development of the heart have been of interest to clinicians and researchers alike for centuries. a beating heart is one of the key criteria in defining life or death in humans. an understanding of the multitude of genetic and functional elements that interplay to form such a complex organ is slowly evolving with new genetic, molecular and experimental techniques. despite the need for ever more complex molecular techniques some of our biggest leaps in knowledg ...201325984327
molecular cloning, sequence analysis and homology modeling of the first caudata amphibian antifreeze-like protein in axolotl (ambystoma mexicanum).antifreeze proteins (afps) refer to a class of polypeptides that are produced by certain vertebrates, plants, fungi, and bacteria and which permit their survival in subzero environments. in this study, we report the molecular cloning, sequence analysis and three-dimensional structure of the axolotl antifreeze-like protein (aflp) by homology modeling of the first caudate amphibian aflp. we constructed a full-length spleen cdna library of axolotl (ambystoma mexicanum). an est having highest simila ...201323915159
variation in salamander tail regeneration is associated with genetic factors that determine tail morphology.very little is known about the factors that cause variation in regenerative potential within and between species. here, we used a genetic approach to identify heritable genetic factors that explain variation in tail regenerative outgrowth. a hybrid ambystomatid salamander (ambystoma mexicanum x a. andersoni) was crossed to an a. mexicanum and 217 offspring were induced to undergo metamorphosis and attain terrestrial adult morphology using thyroid hormone. following metamorphosis, each salamander ...201323843997
body wall development in lamprey and a new perspective on the origin of vertebrate paired fins.classical hypotheses regarding the evolutionary origin of paired appendages propose transformation of precursor structures (gill arches and lateral fin folds) into paired fins. during development, gnathostome paired appendages form as outgrowths of body wall somatopleure, a tissue composed of somatic lateral plate mesoderm (lpm) and overlying ectoderm. in amniotes, lpm contributes connective tissue to abaxial musculature and forms ventrolateral dermis of the interlimb body wall. the phylogenetic ...201323818600
nerve independent limb induction in axolotls.urodele amphibians can regenerate their limbs. during limb regeneration, dermal fibroblasts are transformed into undifferentiated cells called blastema cells. these dermis-blastema cells show multipotency. such so-called endogenous reprogramming of cell differentiation is one of the main targets of amphibian limb regeneration studies. it is well recognized that nerve presence controls the initiation of limb regeneration. accordingly, nerve factors have been sought in amphibian limb regeneration. ...201323769980
macrophages are required for adult salamander limb regeneration.the failure to replace damaged body parts in adult mammals results from a muted growth response and fibrotic scarring. although infiltrating immune cells play a major role in determining the variable outcome of mammalian wound repair, little is known about the modulation of immune cell signaling in efficiently regenerating species such as the salamander, which can regrow complete body structures as adults. here we present a comprehensive analysis of immune signaling during limb regeneration in a ...201323690624
complement-triggered pathways orchestrate regenerative responses throughout phylogenesis.adult tissue plasticity, cell reprogramming, and organ regeneration are major challenges in the field of modern regenerative medicine. devising strategies to increase the regenerative capacity of tissues holds great promise for dealing with donor organ shortages and low transplantation outcomes and also provides essential impetus to tissue bioengineering approaches for organ repair and replacement. the inherent ability of cells to reprogram their fate by switching into an embryonic-like, pluripo ...201323684626
comparative transcriptional profiling of the axolotl limb identifies a tripartite regeneration-specific gene program.understanding how the limb blastema is established after the initial wound healing response is an important aspect of regeneration research. here we performed parallel expression profile time courses of healing lateral wounds versus amputated limbs in axolotl. this comparison between wound healing and regeneration allowed us to identify amputation-specific genes. by clustering the expression profiles of these samples, we could detect three distinguishable phases of gene expression - early wound ...201323658691
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
axolotl as a model to study scarless wound healing in vertebrates: role of the transforming growth factor beta signaling pathway.the skin is our largest organ, with the primary role of protection against assaults from the outside world. it also suffers frequent damage, from minor scrapes to, more rarely, complete destruction such as in third-degree burns. it is therefore, by its nature, an organ that would benefit tremendously from being able to regenerate itself.201324527347
gain-of-function assays in the axolotl (ambystoma mexicanum) to identify signaling pathways that induce and regulate limb regeneration.the adult salamander has been studied as a model for regeneration of complex tissues for many decades. only recently with the development of gain-of-function assays for regeneration, has it been possible to screen for and assay the function of the multitude of signaling factors that have been identified in studies of embryonic development and tumorigenesis. given the conservation of function of these regulatory pathways controlling growth and pattern formation, it is now possible to use the func ...201324029949
muscle and connective tissue progenitor populations show distinct twist1 and twist3 expression profiles during axolotl limb regeneration.limb regeneration involves re-establishing a limb development program from cells within adult tissues. identifying molecular handles that provide insight into the relationship between cell differentiation status and cell lineage is an important step to study limb blastema cell formation. here, using single cell pcr, focusing on newly isolated twist1 sequences, we molecularly profile axolotl limb blastema cells using several progenitor cell markers. we link their molecular expression profile to t ...201323103585
connective tissue cells, but not muscle cells, are involved in establishing the proximo-distal outcome of limb regeneration in the axolotl.during salamander limb regeneration, only the structures distal to the amputation plane are regenerated, a property known as the rule of distal transformation. multiple cell types are involved in limb regeneration; therefore, determining which cell types participate in distal transformation is important for understanding how the proximo-distal outcome of regeneration is achieved. we show that connective tissue-derived blastema cells obey the rule of distal transformation. they also have nuclear ...201323293283
dual embryonic origin of the hyobranchial apparatus in the mexican axolotl (ambystoma mexicanum).traditionally, the cartilaginous viscerocranium of vertebrates is considered as neural crest (nc)-derived. morphological work carried out on amphibian embryos in the first half of the xx century suggested potentially mesodermal origin for some hyobranchial elements. since then, the embryonic sources of the hyobranchial apparatus in amphibians has not been investigated due to lack of an appropriate long-term labelling system. we performed homotopic transplantations of neural folds along with the ...201324623073
wound healing in mammals and amphibians: toward limb regeneration in mammals.mammalian fetal skin regenerates perfectly, but adult skin repairs by the formation of scar tissue. the cause of this imperfect repair by adult skin is not understood. in contrast, wounded adult amphibian (urodeles and anurans) skin is like mammalian fetal skin in that it repairs by regeneration, not scarring. scar-free wound repair in adult xenopus is associated with expression of the paired homeobox transcription factor prx1 by mesenchymal cells of the wound, a feature shared by mesenchymal ce ...201323263248
cell cycle regulation and regeneration.regeneration of ear punch holes in the mrl mouse and amputated limbs of the axolotl show a number of similarities. a large proportion of the fibroblasts of the uninjured mrl mouse ear are arrested in g2 of the cell cycle, and enter nerve-dependent mitosis after injury to form a ring-shaped blastema that regenerates the ear tissue. multiple cell types contribute to the establishment of the regeneration blastema of the urodele limb by dedifferentiation, and there is substantial reason to believe t ...201323263201
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
[effect of gamma-butyric acid and picrotoxin on reaction potentials of the tegmentum of the midbrain in frogs and axolotls]. 201314165640
lens regeneration in axolotl: new evidence of developmental plasticity.among vertebrates lens regeneration is most pronounced in newts, which have the ability to regenerate the entire lens throughout their lives. regeneration occurs from the dorsal iris by transdifferentiation of the pigment epithelial cells. interestingly, the ventral iris never contributes to regeneration. frogs have limited lens regeneration capacity elicited from the cornea during pre-metamorphic stages. the axolotl is another salamander which, like the newt, regenerates its limbs or its tail w ...201223244204
reprogramming to pluripotency is an ancient trait of vertebrate oct4 and pou2 proteins.the evolutionary origins of the gene network underlying cellular pluripotency, a central theme in developmental biology, have yet to be elucidated. in mammals, oct4 is a factor crucial in the reprogramming of differentiated cells into induced pluripotent stem cells. the oct4 and pou2 genes evolved from a pou class v gene ancestor, but it is unknown whether pluripotency induced by oct4 gene activity is a feature specific to mammals or was already present in ancestral vertebrates. here we report t ...201223232409
gene expression patterns specific to the regenerating limb of the mexican axolotl.salamander limb regeneration is dependent upon tissue interactions that are local to the amputation site. communication among limb epidermis, peripheral nerves, and mesenchyme coordinate cell migration, cell proliferation, and tissue patterning to generate a blastema, which will form missing limb structures. an outstanding question is how cross-talk between these tissues gives rise to the regeneration blastema. to identify genes associated with epidermis-nerve-mesenchymal interactions during lim ...201223213371
regeneration of limb joints in the axolotl (ambystoma mexicanum).in spite of numerous investigations of regenerating salamander limbs, little attention has been paid to the details of how joints are reformed. an understanding of the process and mechanisms of joint regeneration in this model system for tetrapod limb regeneration would provide insights into developing novel therapies for inducing joint regeneration in humans. to this end, we have used the axolotl (mexican salamander) model of limb regeneration to describe the morphology and the expression patte ...201223185640
association of modified cytosines and the methylated dna-binding protein mecp2 with distinctive structural domains of lampbrush chromatin.we have investigated the association of dna methylation and proteins interpreting methylation state with the distinctive closed and open chromatin structural domains that are directly observable in the lampbrush chromosomes (lbcs) of amphibian oocytes. to establish the distribution in lbcs of mecp2, one of the key proteins binding 5-methylcytosine-modified dna (5mc), we expressed ha-tagged mecp2 constructs in xenopus laevis oocytes. full-length mecp2 was predominantly targeted to the closed, tra ...201223149574
a galvanotaxis assay for analysis of neural precursor cell migration kinetics in an externally applied direct current electric field.the discovery of neural stem and progenitor cells (collectively termed neural precursor cells) (npcs) in the adult mammalian brain has led to a body of research aimed at utilizing the multipotent and proliferative properties of these cells for the development of neuroregenerative strategies. a critical step for the success of such strategies is the mobilization of npcs toward a lesion site following exogenous transplantation or to enhance the response of the endogenous precursors that are found ...201223093363
microarray analysis of microrna expression during axolotl limb regeneration.among vertebrates, salamanders stand out for their remarkable capacity to quickly regrow a myriad of tissues and organs after injury or amputation. the limb regeneration process in axolotls (ambystoma mexicanum) has been well studied for decades at the cell-tissue level. while several developmental genes are known to be reactivated during this epimorphic process, less is known about the role of micrornas in urodele amphibian limb regeneration. given the compelling evidence that many micrornas ti ...201223028429
neuropeptide y enhances olfactory mucosa responses to odorant in hungry rats.neuropeptide y (npy) plays an important role in regulating appetite and hunger in vertebrates. in the hypothalamus, npy stimulates food intake under the control of the nutritional status. previous studies have shown the presence of npy and receptors in rodent olfactory system, and suggested a neuroproliferative role. interestingly, npy was also shown to directly modulate olfactory responses evoked by a food-related odorant in hungry axolotls. we have recently demonstrated that another nutritiona ...201223024812
early regulation of axolotl limb regeneration.amphibian limb regeneration has been studied for a long time. in amphibian limb regeneration, an undifferentiated blastema is formed around the region damaged by amputation. the induction process of blastema formation has remained largely unknown because it is difficult to study the induction of limb regeneration. the recently developed accessory limb model (alm) allows the investigation of limb induction and reveals early events of amphibian limb regeneration. the interaction between nerves and ...201222933482
reconstitution of the central nervous system during salamander tail regeneration from the implanted neurospheres.urodele amphibians such as axolotl are well known for their regenerative potential of the damaged central nervous system structures. upon tail amputation, neural stem cells behind the amputation plane undergo self-renewing divisions and contribute to the functional spinal cord in the newly formed regenerate. the neural stem cells, harboring this potential, can be isolated from the animal and cultured under the suspension conditions. after 2-3 weeks in vitro they will proliferate and form the flo ...201222914942
retrotransposon long interspersed nucleotide element-1 (line-1) is activated during salamander limb regeneration.salamanders possess an extraordinary capacity for tissue and organ regeneration when compared to mammals. in our effort to characterize the unique transcriptional fingerprint emerging during the early phase of salamander limb regeneration, we identified transcriptional activation of some germline-specific genes within the mexican axolotl (ambystoma mexicanum) that is indicative of cellular reprogramming of differentiated cells into a germline-like state. in this work, we focus on one of these ge ...201222913491
activation of germline-specific genes is required for limb regeneration in the mexican axolotl.the capacity for tissue and organ regeneration in humans is dwarfed by comparison to that of salamanders. emerging evidence suggests that mechanisms learned from the early phase of salamander limb regeneration-wound healing, cellular dedifferentiation and blastemal formation-will reveal therapeutic approaches for tissue regeneration in humans. here we describe a unique transcriptional fingerprint of regenerating limb tissue in the mexican axolotl (ambystoma mexicanum) that is indicative of cellu ...201222841627
spatiotemporal regulation of keratin 5 and 17 in the axolotl limb.amphibians have greater regeneration capability than higher vertebrates. they can regenerate their limbs after an amputation. as a limb is regenerated, a regeneration-specific epithelium called the apical epithelial cap (aec) is induced. the aec is an essential structure for limb regeneration. despite the importance of the aec, molecular marker genes have not been well studied at the molecular level.201222836940
reconstitution of the central and peripheral nervous system during salamander tail regeneration.we show that after tail amputation in ambystoma mexicanum (axolotl) the correct number and spacing of dorsal root ganglia are regenerated. by transplantation of spinal cord tissue and nonclonal neurospheres, we show that the central spinal cord represents a source of peripheral nervous system cells. interestingly, melanophores migrate from preexisting precursors in the skin. finally, we demonstrate that implantation of a clonally derived spinal cord neurosphere can result in reconstitution of al ...201222829665
structural and functional analysis of intra-articular interzone tissue in axolotl salamanders.knowledge of mechanisms directing diarthrodial joint development may be useful in understanding joint pathologies and identifying new therapies. we have previously established that axolotl salamanders can fully repair large articular cartilage lesions, which may be due to the presence of an interzone-like tissue in the intra-articular space. study objectives were to further characterize axolotl diarthrodial joint structure and determine the differentiation potential of interzone-like tissue in a ...201222800772
visualization of retinoic acid signaling in transgenic axolotls during limb development and regeneration.retinoic acid (ra) plays a necessary role in limb development and regeneration, but the precise mechanism by which it acts during these processes is unclear. the role of ra in limb regeneration was first highlighted by the remarkable effect that it has on respecifying the proximodistal axis of the regenerating limb so that serially repeated limbs are produced. to facilitate the study of ra signaling during development and then during regeneration of the same structure we have turned to the axolo ...201222627291
nerve signaling regulates basal keratinocyte proliferation in the blastema apical epithelial cap in the axolotl (ambystoma mexicanum).the ability of adult vertebrates to repair tissue damage is widespread and impressive; however, the ability to regenerate structurally complex organs such as the limb is limited largely to the salamanders. the fact that most of the tissues of the limb can regenerate has led investigators to question and identify the barriers to organ regeneration. from studies in the salamander, it is known that one of the earliest steps required for successful regeneration involves signaling between nerves and ...201222537500
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