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Caudal autotomy in rodents is an evolutionarily acquired phenomenon enabling escape from predators, by discarding the tail skin after traumatic injuries. The histological mechanisms underlying caudal autotomy seem to differ among species. Cotton rats ( Sigmodon hispidus ), which are important laboratory rodents for human infectious diseases, possess a fragile tail. In this study, we compared the tail histology of cotton rats with that of laboratory rats ( Rattus norvegicus ), which have no fragility on their tail, to elucidate the process of rodent caudal autotomy. First, the cotton rats developed a false autotomy characterized by loss of the tail sheath with the caudal vertebrae remaining without tail regeneration. Second, we found the fracture plane was continuous from the interscale of the tail epidermis to the dermis, which was lined with an alignment of E-cadherin + cells. Third, we found an obvious cleavage plane between the dermis and subjacent tissues of the cotton-rat tail, where the subcutis was composed of looser, finer, and fragmented collagen fibers compared with those of the rat. Additionally, the cotton-rat tail was easily torn, with minimum bleeding. The median coccygeal artery of the cotton rat had a thick smooth muscle layer, and its lumen was filled with the peeled intima with fibrin coagulation, which might be associated with reduced bleeding following caudal autotomy. Taken together, we reveal the unique histological features of the tail relating to the caudal autotomy process in the cotton rat, and provide novel insights to help clarify the rodent caudal autotomy mechanism., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2021. Published by The Company of Biologists Ltd.)

Seventeen compounds, rather selective, direct or indirect inhibitors and activators of PKA, PKG, and PKC, were analysed for effects on vascular Ca V 1.2 channel current (I Ca1.2 ) by using the patch-clamp technique in single rat tail artery myocytes. The aim was to investigate how PKs regulate I Ca1.2 and disclose any unexpected modulation of Ca V 1.2 channel function by these agents. The cAMP analogues 8-Br-cAMP and 6-Bnz-cAMP partially reduced I Ca1.2 in dialysed cells, while weakly increasing it under the perforated configuration. The β-adrenoceptor agonist isoproterenol and the adenylate cyclase activator forskolin concentration-dependently increased I Ca1.2 ; this effect was reversed by PKA inhibitors H-89 and KT5720, but not by PKI 6-22. The cGMP analogue 8-Br-cGMP, similarly to the NO-donor SNP, moderately reduced I Ca1.2 , this effect being reversed to a slight stimulation under the perforated configuration. Among PKG inhibitors, Rp-8-Br-PET-cGMPS decreased current amplitude in a concentration-dependent manner while Rp-8-Br-cGMPS was ineffective. The non-specific phosphodiesterase inhibitor IBMX increased I Ca1.2 , while H-89, KT5720, and PKI 6-22 antagonized this effect. The PKC activator PMA, but not the diacylglycerol analogue OAG, stimulated I Ca1.2 in a concentration-dependent manner; conversely, the PKCα inhibitor Gö6976 markedly reduced basal I Ca1.2 and, similarly to the PKCδ (rottlerin) and PKCε translocation inhibitors antagonised PMA-induced current stimulation. The ensemble of findings indicates that the stimulation of cAMP/PKA, in spite of the paradoxical effect of both 8-Br-cAMP and 6-Bnz-cAMP, or PKC pathways enhanced, while that of cGMP/PKG weakly inhibited I Ca1.2 in rat tail artery myocytes. Since Rp-8-Br-PET-cGMPS and Gö6976 appeared to block directly Ca V 1.2 channel, their docking to the channel protein was investigated. Both compounds appeared to bind the α 1C subunit in a region involved in Ca V 1.2 channel inactivation, forming an interaction network comparable to that of Ca V 1.2 channel blockers. Therefore, caution should accompany the use of these agents as pharmacological tools to elucidate the mechanism of action of drugs on vascular preparations., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Reptiles are the only amniotes that maintain the capacity to regenerate appendages. This study presents the first anatomical and histological evidence of tail repair with regrowth in an archosaur, the American alligator. The regrown alligator tails constituted approximately 6-18% of the total body length and were morphologically distinct from original tail segments. Gross dissection, radiographs, and magnetic resonance imaging revealed that caudal vertebrae were replaced by a ventrally-positioned, unsegmented endoskeleton. This contrasts with lepidosaurs, where the regenerated tail is radially organized around a central endoskeleton. Furthermore, the regrown alligator tail lacked skeletal muscle and instead consisted of fibrous connective tissue composed of type I and type III collagen fibers. The overproduction of connective tissue shares features with mammalian wound healing or fibrosis. The lack of skeletal muscle contrasts with lizards, but shares similarities with regenerated tails in the tuatara and regenerated limbs in Xenopus adult frogs, which have a cartilaginous endoskeleton surrounded by connective tissue, but lack skeletal muscle. Overall, this study of wild-caught, juvenile American alligator tails identifies a distinct pattern of wound repair in mammals while exhibiting features in common with regeneration in lepidosaurs and amphibia.

Dorsal crest scales and those of the tail spines of the tuatara (Sphenodon punctatus) represent different specializations involved in display and protection. Erection of the dorsal crest occurs in males during combat and courtship, but tail spines are not noticeably involved in these activities. In both scale derivatives corneous beta proteins (CBPs, formerly called beta-keratins) and intermediate filaments keratins (IFKs) were determined by immunolabelling. The dermis is dense with few sparse fibrocytes surrounded by collagen bundles, the latter rather randomly oriented in the crest scales. In the tail ridge scales banded collagen I fibrils form more regular, orthogonally aligned bundles of alternating layers with connections to the basal epidermal membrane. A conglomerate of dermal melanonophores and iridophores is present under the epidermis. The iridophores are the likely origin of the whitish colour of the crest. The epidermis shows a thicker beta-layer with serrated/indented corneocytes in the tail scales while the beta layer is reduced in the crest but contains CBPs. A relatively thick mesos layer is present in both scale derivatives, especially in the crest where its role, aside from limiting transpiration, is not known. The alpha-layer is formed by corneocytes with irregular perimeter and sparse desmosomal remnants. The high labelling intensity for CBPs in the beta-layer disappears in the mesos layer but occurs, albeit strongly reduced, in the alpha-layer as in the other body scales. The take-home message is that the dense dermis and its apical beta-layer strengthen mechanically the ridge spines while the crest is mainly supported by the firm but pliable and less dense or regular dermis., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In amniotes, unlike primary neurulation in the anterior body, secondary neurulation (SN) proceeds along with axial elongation by the mesenchymal-to-epithelial transition of SN precursors in the tail bud. It has been under debate whether the SN is generated by neuromesodermal common progenitor cells (NMPs) or neural restricted lineage. Our direct cell labeling and serial transplantations identify uni-fated (neural) precursors in the early tail bud. The uni-fated SN precursor territory is further divided into two subpopulations, neural-differentiating and self-renewing cells, which are regulated by high- and low levels of Sox2, respectively. Unexpectedly, uni-fated SN precursors change their fate at later stages to produce both SN and mesoderm. Thus, chicken embryos adopt a previously unappreciated prolonged phase with uni-fated SN stem cells in the early tail bud, which is absent or very limited in mouse embryos., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Vertebrate appendage regeneration requires precisely coordinated remodeling of the transcriptional landscape to enable the growth and differentiation of new tissue, a process executed over multiple days and across dozens of cell types. The heterogeneity of tissues and temporally-sensitive fate decisions involved has made it difficult to articulate the gene regulatory programs enabling regeneration of individual cell types. To better understand how a regenerative program is fulfilled by neural progenitor cells (NPCs) of the spinal cord, we analyzed pax6 -expressing NPCs isolated from regenerating Xenopus tropicalis tails. By intersecting chromatin accessibility data with single-cell transcriptomics, we find that NPCs place an early priority on neuronal differentiation. Late in regeneration, the priority returns to proliferation. Our analyses identify Pbx3 and Meis1 as critical regulators of tail regeneration and axon organization. Overall, we use transcriptional regulatory dynamics to present a new model for cell fate decisions and their regulators in NPCs during regeneration., Competing Interests: AK, AC, MW, LS, AW No competing interests declared, (© 2020, Kakebeen et al.)

Tail regeneration in lizards is a unique case of organ regeneration among amniotes. The Review summarizes past and recent studies indicating that tail regeneration utilizes numerous signaling pathways typical for tumor growth. The regenerative blastema-cone contains sparse proliferating cells that utilize coding and noncoding RNAs in an environment rich in water and hyaluronate, as typical for tumor outgrowth. Differently from tumors, the blastema appears as a polarized outgrowth where the distal region contains proliferating cells mainly driven by the up-regulation of Wnt, snoRNAs, and associated onco-genes. The down-regulation of immune-genes coupled with the high production of hyaluronate coating blastema cells likely protect them from attach by immune cells. Immunoevasion of blastema cells allows the proliferation and migration necessary for the morphogenesis of a new tail. Transcriptome and immunolabeling data suggest that gradients for wnts, shh, msx, and signaling receptors are present in the tail blastema. It is hypothesized that cells along these gradients activate different genes, including tumor suppressors that are expressed in more proximal regions where cells stop proliferating and differentiate into tissues of the new tail. The continuous proliferation at the apex of the blastema is turned into a regulated growth in more proximal regions near the original tail. In contrast, it is hypothesized that no or nonresponding gradients of signaling proteins are present in tumor outgrowths so that cell proliferation but no differentiation occurs in expanding tumors. Considering signaling gradients, the lizard model of regeneration can help in understanding the lack of regulation of tumor growth. Anat Rec, 302:1469-1490, 2019. © 2018 American Association for Anatomy., (© 2018 American Association for Anatomy.)

Mesenchymal stem cells (MSCs) have been used in equines as an alternative therapy. A comparative study about the phenotype and in vitro performance of different MSCs tissue sources in adult equines was needed. This study might serve to provide the knowledge to select a valuable harvesting source of MSCs. Bone marrow, synovial and adipose (mesenteric, neck and tail fat) tissues were collected from adult equines. Cell surface markers expression (CD11α/CD18, CD45, CD79α, CD90, CD105 and MHC II) and in vitro differentiation assays were made. In vitro cell migration, cell growth and wound healing capacity tests helped to study their behavior and properties. MSCs phenotype was positively confirmed by the cell surfaces markers and a tri-lineage differentiation profile. Bone marrow cells showed the highest migration capacity, while synovial fluid cells displayed the highest cell growth. Bone marrow cells showed a better wound healing when compared with all the different MSCs. We conclude that bone marrow, synovial and adipose tissue derived from adult equines are a good source for cell therapy but they conserve different functional properties: bone marrow showed an interesting migration and wound healing capacity while synovial fluid cells and their highest cell growth suggest that these MSCs would yield higher cell numbers in a shorter time., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

The vertebrate body forms by continuous generation of new tissue from progenitors at the posterior end of the embryo. The study of these axial progenitors has proved to be challenging in vivo largely because of the lack of unique molecular markers to identify them. Here, we elucidate the expression pattern of the transcription factor Nkx1-2 in the mouse embryo and show that it identifies axial progenitors throughout body axis elongation, including neuromesodermal progenitors and early neural and mesodermal progenitors. We create a tamoxifen-inducible Nkx1-2CreER T2 transgenic mouse and exploit the conditional nature of this line to uncover the lineage contributions of Nkx1-2 -expressing cells at specific stages. We show that early Nkx1-2 -expressing epiblast cells contribute to all three germ layers, mostly neuroectoderm and mesoderm, excluding notochord. Our data are consistent with the presence of some self-renewing axial progenitors that continue to generate neural and mesoderm tissues from the tail bud. This study identifies Nkx1-2 -expressing cells as the source of most trunk and tail tissues in the mouse and provides a useful tool to genetically label and manipulate axial progenitors in vivo ., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)

The formation of the regenerating tail blastema of lizards occurs by the multiplication of stem cells but also some dedifferentiation from adult cells may take place after tail loss by autotomy, as it is suggested in the present study. Using 5BrdU-immunocytochemistry and transmission electron microscopy it is shown that part of the damaged tissues undergo progressive cytological de-differentiation (cell reprogramming). This occurs for muscle, fibrocytes, chondrocytes, adipocytes, and cells derived from the spinal cord during the initial 3-8 days post-autotomy of the tail in the wall lizard Podarcis muralis. Dedifferentiating cells loose most endoplasmic reticulum, sarcomeres in myocells, lipid droplets in adipocytes, extracellular matrix in chondrocytes. Numerous cytoplasmic vesicles are formed, perhaps reflecting an initial sufferance of dedifferentiating cells. These cells are not dying because they incorporate 5BrdU and proliferate. Nuclei of small fibrocytes present in the dermis and inter-muscle connective tissues, initially heterochromatic, become euchromatic and their cytoplasm increases in volume although the endoplasmic reticulum remains limited, as it is typical for mesenchymal cells. The present study, supported by previous transcriptome and 5BrdU-labeling data, and from recent tracing studies, suggests that aside stem cells present in different tissues of the tail, also cell dedifferentiation occurs in the injured tail of lizards. The relative contribution between de-differentiation and stem cells for the formation of the regenerating lizard blastema likely depends from the extension of the trauma., (© 2018 Wiley Periodicals, Inc.)

Ischemic heart disease within developed countries has been associated with high rates of morbidity and mortality. Cell‑based cardiac repair is an emerging therapy for the treatment of cardiac diseases; however, a limited source of the optimal type of donor cell, such as an autologous cardiomyocyte, restricts clinical application. The novel therapeutic use of induced pluripotent stem cells (iPSCs) may serve as a unique and unlimited source of cardiomyocytes; however, iPSC contamination has been associated with teratoma formation following transplantation. The present study investigated whether cardiomyocytes from mouse fibroblasts may be reprogrammed in vitro with four cardiac transcription factors, including GATA binding protein 4, myocyte‑specific enhancer factor 2C, T‑box transcription factor 5, and heart‑ and neural crest derivatives‑expressed protein 2 (GMTH). Cardiac‑specific markers, including α‑myosin heavy chain (α‑MHC), β‑MHC, atrial natriuretic factor, NK2 homeobox 5 and cardiac troponin T were observed within mouse fibroblasts reprogrammed with GMTH, which was reported to be more effective than GMT. In addition, Percoll density centrifugation enriched a population of ~72.4±5.5% α‑MHC+ induced cardiomyocytes, which retained the expression profile of cardiomyocyte markers and were similar to natural neonatal cardiomyocytes in well‑defined sarcomeric structures. The findings of the present study provided a potential solution to myocardial repair via a cell therapy applying tissue engineering with minimized risks of immune rejection and tumor formation.

Unlike mammals, Xenopus laevis tadpoles possess high ability to regenerate their lost organs. In amphibians, the main source of regenerated tissues is lineage-restricted tissue stem cells, but the mechanisms underlying induction, maintenance and differentiation of these stem/progenitor cells in the regenerating organs are poorly understood. We previously reported that interleukin-11 (il-11) is highly expressed in the proliferating cells of regenerating Xenopus tadpole tails. Here, we show that il-11 knockdown (KD) shortens the regenerated tail length, and the phenotype is rescued by forced-il-11-expression in the KD tadpoles. Moreover, marker genes for undifferentiated notochord, muscle, and sensory neurons are downregulated in the KD tadpoles, and the forced-il-11-expression in intact tadpole tails induces expression of these marker genes. Our findings demonstrate that il-11 is necessary for organ regeneration, and suggest that IL-11 plays a key role in the induction and maintenance of undifferentiated progenitors across cell lineages during Xenopus tail regeneration. Xenopus laevis tadpoles have maintained their ability to regenerate various organs. Here, the authors show that interleukin-11 is necessary for organ regeneration, by inducing and maintaining undifferentiated progenitors across cell lineages during Xenopus tail regeneration.

Caudal somites are generated from a pool of progenitor cells located in the tailbud region. These progenitor cells form the presomitic mesoderm that gradually differentiates into somites under the action of the segmentation clock. The signals responsible for tailbud mesoderm progenitor pool maintenance during axial elongation are still elusive. Here, we show that Bmp signaling is sufficient to activate the entire mesoderm progenitor gene signature in primary cultures of caudal mesoderm cells. Bmp signaling acts through the key regulatory genes brachyury ( T ) and Nkx1-2 and contributes to the activation of several other regulators of the mesoderm progenitor gene network. In the absence of Bmp signaling, tailbud mesoderm progenitor cells acquire aberrant gene expression signatures of the heart, blood, muscle and skeletal embryonic lineages. Treatment of embryos with the Bmp inhibitor noggin confirmed the requirement for Bmp signaling for normal T expression and the prevention of abnormal lineage marker activation. Together, these results identify Bmp signaling as a non-cell-autonomous signal necessary for mesoderm progenitor cell homeostasis., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2017. Published by The Company of Biologists Ltd.)

During embryogenesis, the body axis elongates and specializes. In vertebrate groups such as salamanders and lizards, elongation of the posterior body axis (tail) continues throughout life. This phenomenon of post-embryonic tail elongation via addition of vertebrae has remained largely unexplored, and little is known about the underlying developmental mechanisms that promote vertebral addition. Our research investigated tail elongation across life stages in a non-model salamander species, Eurycea cirrigera (Plethodontidae). Post-embryonic addition of segments suggests that the tail tip retains some aspects of embryonic cell/tissue organization and gene expression throughout the life cycle. We describe cell and tissue differentiation and segmentation of the posterior tail using serial histology and expression of the axial tissue markers, MF-20 and Pax6. Embryonic expression patterns of HoxA13 and C13 are shown with in situ hybridization. Tissue sections reveal that the posterior spinal cord forms via cavitation and precedes development of the underlying cartilaginous rod after embryogenesis. Post-embryonic tail elongation occurs in the absence of somites and mesenchymal cells lateral to the midline express MF-20. Pax6 expression was observed only in the spinal cord and some mesenchymal cells of adult Eurycea tails. Distinct temporal and spatial patterns of posterior Hox13 gene expression were observed throughout embryogenesis. Overall, important insights to cell organization, differentiation, and posterior Hox gene expression may be gained from this work. We suggest that further work on gene expression in the elongating adult tail could shed light on mechanisms that link continual axial elongation with regeneration.

Background: In addition to their value as livestock, pigs are susceptible to classical swine fever virus (CSFV) and can serve as reservoirs for CSFV, allowing it to develop into an epizootic. CSFV, a pestivirus of the Flaviviridae family, has a single-stranded RNA genome. Recent research has indicated that the human MxA protein inhibits the life cycles of certain RNA viruses, such as members of the Bunyaviridae family, the Flaviviridae family and others., Results: To produce pigs with antiviral protection against CSFV, transgenic pigs expressing human MxA were generated by nuclear transplantation. Cells from three MxA transgenic piglets were used to investigate in vitro antiviral activity of MxA aganist CSFV, and the results of in vitro indirect immunofluorescence assays, virus titration and real-time PCR indicated that the MxA transgenic pig has an antiviral capacity against CSFV., Conclusions: Transgene with human MxA on pigs is feasible. High levels of MxA expression do inhibit CSFV in vitro at early time points post-infection at 60-96dpi.

Identifying key molecules that launch regeneration has been a long-sought goal. Multiple regenerative animals show an initial wound-associated proliferative response that transits into sustained proliferation if a considerable portion of the body part has been removed. In the axolotl, appendage amputation initiates a round of wound-associated cell cycle induction followed by continued proliferation that is dependent on nerve-derived signals. A wound-associated molecule that triggers the initial proliferative response to launch regeneration has remained obscure. Here, using an expression cloning strategy followed by in vivo gain- and loss-of-function assays, we identified axolotl MARCKS-like protein (MLP) as an extracellularly released factor that induces the initial cell cycle response during axolotl appendage regeneration. The identification of a regeneration-initiating molecule opens the possibility of understanding how to elicit regeneration in other animals.

Vertebrate body axis formation depends on a population of bipotential neuromesodermal cells along the posterior wall of the tailbud that make a germ layer decision after gastrulation to form spinal cord and mesoderm. Despite exhibiting germ layer plasticity, these cells never give rise to midline tissues of the notochord, floor plate and dorsal endoderm, raising the question of whether midline tissues also arise from basal posterior progenitors after gastrulation. We show in zebrafish that local posterior signals specify germ layer fate in two basal tailbud midline progenitor populations. Wnt signaling induces notochord within a population of notochord/floor plate bipotential cells through negative transcriptional regulation of sox2. Notch signaling, required for hypochord induction during gastrulation, continues to act in the tailbud to specify hypochord from a notochord/hypochord bipotential cell population. Our results lend strong support to a continuous allocation model of midline tissue formation in zebrafish, and provide an embryological basis for zebrafish and mouse bifurcated notochord phenotypes as well as the rare human congenital split notochord syndrome. We demonstrate developmental equivalency between the tailbud progenitor cell populations. Midline progenitors can be transfated from notochord to somite fate after gastrulation by ectopic expression of msgn1, a master regulator of paraxial mesoderm fate, or if transplanted into the bipotential progenitors that normally give rise to somites. Our results indicate that the entire non-epidermal posterior body is derived from discrete, basal tailbud cell populations. These cells remain receptive to extracellular cues after gastrulation and continue to make basic germ layer decisions., (© 2016. Published by The Company of Biologists Ltd.)

Primary cells are derived directly from tissue and are thought to be more representative of the physiological state of cells in vivo than established cell lines. However, primary cell cultures usually have a finite life span and need to be frequently re-established. Fibroblasts are an easily accessible source of primary cells. Here, we discuss a simple and quick experimental procedure to establish primary fibroblast cultures from ears and tails of mice. The protocol can be used to establish primary fibroblast cultures from ears stored at RT for up to 10 days. When the protocol is carefully followed, contaminations are unlikely to occur despite the use of non-sterile tissue stored for extended time in some cases. Fibroblasts proliferate rapidly in culture and can be expanded to substantial numbers before undergoing replicative senescence.

Tail biopsy is a common procedure that is performed to obtain genetic material for determining genotype of transgenic mice. The use of anesthetics or analgesics is recommended, although identifying safe and effective drugs for this purpose has been challenging. We evaluated the effects of topical 2.5% lidocaine-2.5% prilocaine cream applied to the distal tail tip at 5 or 60 min before biopsy, immersion of the tail tip for 10 seconds in ice-cold 70% ethanol just prior to biopsy, and immersion of the tail tip in 0.5% bupivacaine for 30 s after biopsy. Mice were 7, 11, or 15 d old at the time of tail biopsy. Acute behavioral responses, plasma corticosterone, and blood glucose were measured after biopsy, and body weight and performance in elevated plus maze and open-field tests after weaning. Ice-cold ethanol prior to biopsy prevented acute behavioral responses to biopsy, and both ice-cold ethanol and bupivacaine prevented elevations in corticosterone and blood glucose after biopsy. Tail biopsy with or without anesthesia did not affect body weight or performance on elevated plus maze or open-field tests. We recommend the use of ice-cold ethanol for topical anesthesia prior to tail biopsy in mice 7 to 15 d old.

Most neurodegenerative diseases are late-onset and aging-related, and no effective treatments have been developed. The successful generation of induced pluripotent stem cells (iPSCs) and the direct conversion of neurons from patients' specific somatic cells have offered cell resources for disease modeling and potential cell transplantation therapy. However, to date, no systematic studies have investigated which approach is more suitable for future cell therapy. In this study, using the two approaches mentioned above in parallel we successfully obtained functional neurons from tail-tip fibroblasts (TTFs) of a 1-year-old mouse, which were characterized by specialized morphologies, neuronal marker expressions, and electrophysiological properties. Genome-wide expression analysis revealed that a set of genes related to the stress response and DNA damage were expressed at a much higher level in iNs than in diNs derived from 1-year-old TTFs. Subsequently, significant decreases in mitochondrial dysfunction and DNA damage were observed in diNs compared with iNs derived from aged TTFs. Moreover, the levels of epigenetic markers such as 5hmC, H3K4me3, H3K9me3, and H3K27me3 in iNs were more similar to those in the old TTFs compared with those in diNs, indicating that the iNs converted directly from TTFs may retain some residual epigenetic memories. By contrast, reprogramming to iPSCs not only rejuvenated the cell stages, but also erased such epigenetic memories obtained along the aging process. Taken together, the results of our study are instructive and meaningful for future clinical applications.

The neural crest is an evolutionary novelty that fostered the emergence of vertebrate anatomical innovations such as the cranium and jaws. During embryonic development, multipotent neural crest cells are specified at the lateral borders of the neural plate before delaminating, migrating and differentiating into various cell types. In invertebrate chordates (cephalochordates and tunicates), neural plate border cells express conserved factors such as Msx, Snail and Pax3/7 and generate melanin-containing pigment cells, a derivative of the neural crest in vertebrates. However, invertebrate neural plate border cells have not been shown to generate homologues of other neural crest derivatives. Thus, proposed models of neural crest evolution postulate vertebrate-specific elaborations on an ancestral neural plate border program, through acquisition of migratory capabilities and the potential to generate several cell types. Here we show that a particular neuronal cell type in the tadpole larva of the tunicate Ciona intestinalis, the bipolar tail neuron, shares a set of features with neural-crest-derived spinal ganglia neurons in vertebrates. Bipolar tail neuron precursors derive from caudal neural plate border cells, delaminate and migrate along the paraxial mesoderm on either side of the neural tube, eventually differentiating into afferent neurons that form synaptic contacts with both epidermal sensory cells and motor neurons. We propose that the neural plate borders of the chordate ancestor already produced migratory peripheral neurons and pigment cells, and that the neural crest evolved through the acquisition of a multipotent progenitor regulatory state upstream of multiple, pre-existing neural plate border cell differentiation programs.

The regeneration of the tail in lizards is likely sustained by stem/progenitor cells located in the stump after amputation of the tail. This microscopic and ultrastructural study shows the localization of 5-bromo-deoxy-uridine (5BrdU)-long retaining labeled cells in different tissues of the tail stump. These putative stem/progenitor cells are sparsely detected in the epidermis of scales, adipose tissue, intermuscle connective septa, myosatellite cells, and perichondrion of the vertebrae. Most of 5BrdU-labeled cells are present in the bone marrow of vertebrae as hemocytoblasts and reticulate cells, whereas more numerous myelocytes and polychromatophilic erythroblasts show a variable level of nuclear labeling. 5BrdU and tritiated-thymidine labeled and unlabeled hemopoietic cells are seen in circulating vessels and in the blastema where their maturation is completed. This observation indicates that the entire differentiation span of both white and red blood cells, at least during tail regeneration, lasts longer than 4 weeks. Labeled polychromatophilic erythroblasts and heterophilic and basophilic myelocytes are present in the synusoidal vessels of the regenerating tail. This study indicates that extravasating blood cells involved in immunity make large part of the forming blastema cell population, but are replaced by mesenchymal cells of different origin. The presence of long retaining labeled cells in tissues of the tail stump is likely connected to the production of blastema mesenchymal cells. Although no direct cell-lineage study has been done, histological, immunocytochemical, and autoradiographic studies have indicated that it is from these tissues that proliferating cells appear mainly localized after tail amputation and blastema formation., (© 2015 Wiley Periodicals, Inc.)

Previous studies showed that Fibroblast Growth Factors (FGF) 1 and 2 are localized in the tissues of the regenerating tail in lizards. In the present immunofluorescence and immunoblotting study we have specifically analyzed the presence and distribution of FGF7 (keratinocyte growth factor) in the regenerating tissues of the tail. FGF7 immunoreactivity is mainly detected in the regenerating epidermis and in sparse fibroblasts of the underlying dermis of the regenerating scales while it is weaker in the other tissues such as the apical ependymal cells and early regenerating muscles. Immunolabeled mesenchymal fibroblasts are frequently present under the epidermis of the forming outer scale surface, a localization that might be connected to beta-cell differentiation in this region of the scale. FGF7 immunolabeling is also seen in differentiating beta-keratinocytes of the beta-layer in the regenerating scales. The present immunofluorescent observations suggest that FGF7 is specifically utilized as a paracrine factor during the process of differentiation of the epidermal layers in the regenerating scales and in particular for beta-cells differentiation., (Copyright © 2015 Elsevier GmbH. All rights reserved.)

The regeneration-competent adult animals have ability to regenerate their lost complex appendages with a near-perfect replica, owing to the positional identity acquired by the progenitor cells in the blastema, i.e. the blastemal cells. CD59, a CD59/Ly6 family member, has been identified as a regulator of positional identity in the tail blastemal cells of Gekko japonicus. To determine whether this function of CD59 is unique to the regenerative amniote(s) and how CD59 mediates PD axis patterning during tail regeneration, we examined its protective role on the complement-mediated cell lysis and intervened CD59 expression in the tail blastemal cells using an in vivo model of adenovirus transfection. Our data revealed that gecko CD59 was able to inhibit complement-mediated cell lysis. Meanwhile, CD59 functioned on positional identity through expression in cartilage precursor cells. Intervening positional identity by overexpression or siRNA knockdown of CD59 resulted in abnormal cartilaginous cone patterning due to the decreased differentiation of blastemal cells to cartilage precursor cells. The cartilage formation-related genes were found to be under the regulation of CD59. These results indicate that CD59, an evolutionarily transitional molecule linking immune and regenerative regulation, affects tail regeneration by mediating cartilage patterning.

Using an antibody against a lizard telomerase-1 component the presence of telomerase has been detected in regenerating lizard tails where numerous cells are proliferating. Immunoblots showed telomerase positive bands at 75-80 kDa in normal tissues and at 50, 75, and 90 kDa in those regenerating. Immunofluorescence and ultrastructural immunolocalization showed telomerase-immunoreactivity in sparCe (few/diluted) mesenchymal cells of the blastema, early regenerating muscles, perichondrium of the cartilaginous tube, ependyma of the spinal cord, and in the regenerating epidermis. Clusters of gold particles were detected in condensing chromosomes of few mesenchymal and epithelial cells in the regenerating tail, but a low to undetectable labeling in interphase cells. Telomerase-immunoreactivity was intense in the nucleus and sparCe (few/diluted) in the cytoplasm of spermatogonia and spermatocytes and drastically decreased in early spermatids where some nuclear labeling remains. Some intense immunoreactivity was seen in few cells near the basal membrane of intestinal enterocytes or in leukocytes (likely lymphocytes) of the intestine mucosa. In spermatogonia, spermatids and in enterocytes part of the nuclear labeling formed cluster of gold particles in dense areas identified as Cajal Bodies, suggesting that telomerase is a marker for these stem cells. This therefore suggests that also the sparCe (few/diluted) telomerase positive cells detected in the regenerating tail may represent sparCe (few/diluted) stem cells localized in regenerating tissues where transit amplifying cells are instead preponderant to allow for tail growth. This observation supports previous studies indicating that few stem cells are present in the stump after tail amputation and give rise to transit amplifying cells for tail regeneration., (© 2015 Wiley Periodicals, Inc.)

This study was aimed at isolation of cells from urine and skin on the ventral part of the tails of healthy adult female buffaloes (Bubalus bubalis), an area rarely exposed to solar radiation, establishment of the cells in culture, and their use as donor cells for production of buffalo embryos by handmade cloning (HMC). The blastocyst rate and total cell number of urine- and tail skin-derived embryos were similar to those of control embryos derived from ear skin cells; however, their apoptotic index was lower (p<0.05) than that of control blastocysts. The global level of histone H3 acetylated at lysine 9 (H3K9ac) was similar in the three types of donor cells and in urine- and tail skin-derived HMC blastocysts and in vitro-fertilized (IVF) blastocysts (controls). The global level of histone H3 trimethylated at lysine 27 (H3K27me3) in the cells was in the order (p<0.05) urine≥tail skin>ear skin-derived cells, whereas in blastocysts, it was higher (p<0.05) in urine- and tail skin-derived HMC blastocysts than that in IVF blastocysts. The expression level of CASPASE3, CASPASE9, P53, DNMT1, DNMT3a, OCT4, and NANOG, which was similar in HMC blastocysts of three the groups, was lower (p<0.05) than that in IVF blastocysts, whereas that of HDAC1 was similar among the four groups. Following transfer of urine-derived embryos (n=10) to five recipients (two embryos/recipient), one of the recipients delivered a normal calf that is now 5 weeks old.

The tail of many species of lizard is used as a site of fat storage, and caudal autotomy is a widespread phenomenon among lizards. This means that caudal fat stores are at risk of being lost if the tail is autotomized. For fat-tailed species, such as the leopard gecko, this may be particularly costly. Previous work has shown that tail regeneration in juveniles of this species is rapid and that it receives priority for energy allocation, even when dietary resources are markedly reduced. We found that the regenerated tails of juvenile leopard geckos are more massive than their original counterparts, regardless of dietary intake, and that they exhibit greater amounts of skeleton, inner fat, muscle and subcutaneous fat than original tails (as assessed through cross-sectional area measurements of positionally equivalent stations along the tail). Autotomy and regeneration result in changes in tail shape, mass and the pattern of tissue distribution within the tail. The regenerated tail exhibits enhanced fat storage capacity, even in the face of a diet that results in significant slowing of body growth. Body growth is thus sacrificed at the expense of rapid tail growth. Fat stores laid down rapidly in the regenerating tail may later be used to fuel body growth or reproductive investment. The regenerated tail thus seems to have adaptive roles of its own, and provides a potential vehicle for studying trade-offs that relate to life history strategy., (Copyright © 2015 Elsevier GmbH. All rights reserved.)

Organ regenerative ability depends on the animal species and the developmental stage. The molecular bases for variable organ regenerative ability, however, remain unknown. Previous studies have identified genes preferentially expressed in the blastema tissues in various animals, but transcriptome analysis of the isolated proliferating blastema cells has not yet been reported. In the present study, we used RNA-sequencing analysis to analyze the gene expression profile of isolated proliferating blastema cells of regenerating Xenopus laevis tadpole tails. We used flow cytometry to isolate proliferating cells, and non-proliferating blastema cells, from regenerating tadpole tails as well as proliferating tail bud cells from tail bud embryos, the latter two of which were used as control cells, based on their DNA content. Among the 28 candidate genes identified by RNA-sequencing analysis, quantitative reverse transcription-polymerase chain reaction identified 10 genes whose expression was enriched in regenerating tadpole tails compared with non-regenerating tadpole tails or tails from the tail bud embryos. Among them, whole mount in situ hybridization revealed that chromosome segregation 1-like and interleukin 11 were expressed in the broad area of the tail blastema, while brevican, lysyl oxidase, and keratin 18 were mainly expressed in the notochord bud in regenerating tails. We further combined whole mount in situ hybridization with immunohistochemistry for the incorporated 5-bromo-2-deoxyuridine to confirm that keratin 18 and interleukin 11 were expressed in the proliferating tail blastema cells. Based on the proposed functions of their homologs in other animal species, these genes might have roles in the extracellular matrix formation in the notochord bud (brevican and lysyl oxidase), cell proliferation (chromosome segregation 1-like and keratin 18), and in the maintenance of the differentiation ability of proliferating blastema cells (interleukin 11) in regenerating tadpole tails.