• MeSH
• Ambystoma embryology   physiology   MeSH
• Metamorphosis, Biological drug effects   MeSH
• Thyroid Hormones pharmacology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Thyroid Hormones MeSH

BACKGROUND: During amphibian metamorphosis, the crucial moment lies in the rearrangement of the heart, reflecting the changes in circulatory demands. However, little is known about the exact shifts linked with this rearrangement. Here, we demonstrate such myocardial changes in axolotl (Ambystoma mexicanum) from the morphological and physiological point of view. RESULTS: Micro-CT and histological analysis showed changes in ventricular trabeculae organization, completion of the atrial septum and its connection to the atrioventricular valve. Based on Myosin Heavy Chain and Smooth Muscle Actin expression we distinguished metamorphosis-induced changes in myocardial differentiation at the ventricular trabeculae and atrioventricular canal. Using optical mapping, faster speed of conduction through the atrioventricular canal was demonstrated in metamorphic animals. No differences between the groups were observed in the heart rates, ventricular activation times, and activation patterns. CONCLUSIONS: Transition from aquatic to terrestrial life-style is reflected in the heart morphology and function. Rebuilding of the axolotl heart during metamorphosis was connected with reorganization of ventricular trabeculae, completion of the atrial septum and its connection to the atrioventricular valve, and acceleration of AV conduction.

• Keywords
• atrial septation, metamorphosis, micro-CT, optical mapping, trabeculae, ventricular septation,
• MeSH
• Ambystoma mexicanum * physiology   MeSH
• Biological Evolution MeSH
• Metamorphosis, Biological physiology   MeSH
• Myocardium MeSH
• Heart * MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

• MeSH
• Ambystoma anatomy & histology   MeSH
• Microscopy, Electron MeSH
• Muscles ultrastructure   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH

Vertebrate dentitions arise at various places within the oropharyngeal cavity including the jaws, the palate, or the pharynx. These dentitions develop in a highly organized way, where new tooth germs are progressively added adjacent to the initiator center, the first tooth. At the same time, the places where dentitions develop house the contact zones between the outer ectoderm and the inner endoderm, and this colocalization has instigated various suggestions on the roles of germ layers for tooth initiation and development. Here, we study development of the axolotl dentition, which is a complex of five pairs of tooth fields arranged into the typically tetrapod outer and inner dental arcades. By tracking the expression patterns of odontogenic genes, we reason that teeth of both dental arcades originate from common tooth-competent zones, one present on the mouth roof and one on the mouth floor. Progressive compartmentalization of these zones and a simultaneous addition of new tooth germs distinct for each prospective tooth field subsequently control the final shape and composition of the axolotl dentition. Interestingly, by following the fate of the GFP-labeled oral ectoderm, we further show that, in three out of five tooth field pairs, the first tooth develops right at the ecto-endodermal boundary. Our results thus indicate that a single tooth-competent zone gives rise to both dental arcades of a complex tetrapod dentition. Further, we propose that the ecto-endodermal boundary running through this zone should be accounted for as a potential source of instruction factors instigating the onset of the odontogenic program.

• Keywords
• axolotl, dental arcades, ectoderm, endoderm, initiation, patterning, tooth development,
• Publication type
• Journal Article MeSH

• MeSH
• Ambystoma growth & development   MeSH
• Metamorphosis, Biological * MeSH
• History, 20th Century MeSH
• Animals MeSH
• Check Tag
• History, 20th Century MeSH
• Animals MeSH
• Publication type
• Biography MeSH
• Journal Article MeSH
• Historical Article MeSH
• Geographicals
• Czechoslovakia MeSH

• About
• Laufberger, V

The asymmetric localization of biomolecules is critical for body plan development. One of the most popular model organisms for early embryogenesis studies is Xenopus laevis but there is a lack of information in other animal species. Here, we compared the early development of two amphibian species-the frog X. laevis and the axolotl Ambystoma mexicanum. This study aimed to identify asymmetrically localized RNAs along the animal-vegetal axis during the early development of A. mexicanum. For that purpose, we performed spatial transcriptome-wide analysis at low resolution, which revealed dynamic changes along the animal-vegetal axis classified into the following categories: profile alteration, de novo synthesis and degradation. Surprisingly, our results showed that many of the vegetally localized genes, which are important for germ cell development, are degraded during early development. Furthermore, we assessed the motif presence in UTRs of degraded mRNAs and revealed the enrichment of several motifs in RNAs of germ cell markers. Our results suggest novel reorganization of the transcriptome during embryogenesis of A. mexicanum to converge to the similar developmental pattern as the X. laevis.

• Keywords
• Ambystoma mexicanum, RNA localization, TOMO-seq, animal-vegetal axis, early development,
• Publication type
• Journal Article MeSH

The oral cavity of vertebrates is generally thought to arise as an ectodermal invagination. Consistent with this, oral teeth are proposed to arise exclusively from ectoderm, contributing to tooth enamel epithelium, and from neural crest derived mesenchyme, contributing to dentin and pulp. Yet in many vertebrate groups, teeth are not restricted only to the oral cavity, but extend posteriorly as pharyngeal teeth that could be derived either directly from the endodermal epithelium, or from the ectodermal epithelium that reached this location through the mouth or through the pharyngeal slits. However, when the oropharyngeal membrane, which forms a sharp ecto/endodermal border, is broken, the fate of these cells is poorly known. Here, using transgenic axolotls with a combination of fate-mapping approaches, we present reliable evidence of oral teeth derived from both the ectoderm and endoderm and, moreover, demonstrate teeth with a mixed ecto/endodermal origin. Despite the enamel epithelia having a different embryonic source, oral teeth in the axolotl display striking developmental uniformities and are otherwise identical. This suggests a dominant role for the neural crest mesenchyme over epithelia in tooth initiation and, from an evolutionary point of view, that an essential factor in teeth evolution was the odontogenic capacity of neural crest cells, regardless of possible 'outside-in' or 'inside-out' influx of the epithelium.

• MeSH
• Ambystoma mexicanum embryology   MeSH
• Ectoderm cytology   embryology   MeSH
• Endoderm cytology   embryology   MeSH
• Epithelium embryology   MeSH
• Animals, Genetically Modified MeSH
• Morphogenesis MeSH
• Tooth cytology   embryology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

BACKGROUND: Previous studies have reported that periderm (the outer ectodermal layer) in zebrafish partially expands into the mouth and pharyngeal pouches, but does not reach the medial endoderm, where the pharyngeal teeth develop. Instead, periderm-like cells, arising independently from the outer periderm, cover prospective tooth-forming epithelia and are crucial for tooth germ initiation. Here we test the hypothesis that restricted expansion of periderm is a teleost-specific character possibly related to the derived way of early embryonic development. To this end, we performed lineage tracing of the periderm in a non-teleost actinopterygian species possessing pharyngeal teeth, the sterlet sturgeon (Acipenser ruthenus), and a sarcopterygian species lacking pharyngeal teeth, the axolotl (Ambystoma mexicanum). RESULTS: In sturgeon, a stratified ectoderm is firmly established at the end of gastrulation, with minimally a basal ectodermal layer and a surface layer that can be homologized to a periderm. Periderm expands to a limited extent into the mouth and remains restricted to the distal parts of the pouches. It does not reach the medial pharyngeal endoderm, where pharyngeal teeth are located. Thus, periderm in sturgeon covers prospective odontogenic epithelium in the jaw region (oral teeth) but not in the pharyngeal region. In axolotl, like in sturgeon, periderm expansion in the oropharynx is restricted to the distal parts of the opening pouches. Oral teeth in axolotl develop long before mouth opening and possible expansion of the periderm into the mouth cavity. CONCLUSIONS: Restricted periderm expansion into the oropharynx appears to be an ancestral feature for osteichthyans, as it is found in sturgeon, zebrafish and axolotl. Periderm behavior does not correlate with presence or absence of oral or pharyngeal teeth, whose induction may depend on 'ectodermalized' endoderm. It is proposed that periderm assists in lumenization of the pouches to create an open gill slit. Comparison of basal and advanced actinopterygians with sarcopterygians (axolotl) shows that different trajectories of embryonic development converge on similar dynamics of the periderm: a restricted expansion into the mouth and prospective gill slits.

• Keywords
• Axolotl, Ectoderm, Gill slits, Mouth, Oropharynx, Periderm, Pharyngeal pouches, Sturgeon, Teeth,
• Publication type
• Journal Article MeSH

A combined alkaline phosphatase (AP) and dipeptidlypeptidase IV (DPP IV) staining reaction has demonstrated enzymatic heterogeneity of the arterial and venous segments of capillaries in rat skeletal muscle. This study compared the staining reactions of skeletal muscles in many commonly used laboratory animals, including the axolotl, chick, quail, Monodelphys, rat, mouse, hamster, guinea pig, rabbit, dog, monkey, and human. DPP IV activity was found in the venous ends of the capillaries and in the endothelium of some larger veins in many of the species but was never demonstrated in the arterial side of the circulation. AP was found in the arterial ends of capillaries in all species except the axolotl, and it was also found in the endothelium of larger arteries of most species. AP activity was absent in venous endothelium of all species except for birds and Monodelphys. DPP IV activity was found in the perineurium of intramuscular nerves of most species, and AP activity was commonly seen in tendons and intramuscular connective tissue. The interspecies variability found in this study shows that care must be taken in comparing experimental data involving this technique from one species to another, but within a species the technique allows a fine level of discrimination between functionally distinct compounds of skeletal muscle tissue.

• MeSH
• Alkaline Phosphatase analysis   MeSH
• Ambystoma mexicanum MeSH
• Staining and Labeling * MeSH
• Endothelium, Vascular enzymology   MeSH
• Coturnix MeSH
• Dipeptidyl Peptidase 4 MeSH
• Dipeptidyl-Peptidases and Tripeptidyl-Peptidases analysis   MeSH
• Haplorhini MeSH
• Capillaries enzymology   MeSH
• Rabbits MeSH
• Cricetinae MeSH
• Rats MeSH
• Chickens MeSH
• Humans MeSH
• Guinea Pigs MeSH
• Mice MeSH
• Connective Tissue enzymology   MeSH
• Tendons enzymology   MeSH
• Muscles blood supply   enzymology   innervation   MeSH
• Opossums MeSH
• Veins enzymology   MeSH
• Animals MeSH
• Check Tag
• Rabbits MeSH
• Cricetinae MeSH
• Rats MeSH
• Humans MeSH
• Guinea Pigs MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH
• Comparative Study MeSH
• Names of Substances
• Alkaline Phosphatase MeSH
• Dipeptidyl Peptidase 4 MeSH
• Dipeptidyl-Peptidases and Tripeptidyl-Peptidases MeSH

Cartilage of the vertebrate jaw is derived from cranial neural crest cells that migrate to the first pharyngeal arch and form a dorsal "maxillary" and a ventral "mandibular" condensation. It has been assumed that the former gives rise to palatoquadrate and the latter to Meckel's (mandibular) cartilage. In anamniotes, these condensations were thought to form the framework for the bones of the adult jaw and, in amniotes, appear to prefigure the maxillary and mandibular facial prominences. Here, we directly test the contributions of these neural crest condensations in axolotl and chick embryos, as representatives of anamniote and amniote vertebrate groups, using molecular and morphological markers in combination with vital dye labeling of late-migrating cranial neural crest cells. Surprisingly, we find that both palatoquadrate and Meckel's cartilage derive solely from the ventral "mandibular" condensation. In contrast, the dorsal "maxillary" condensation contributes to trabecular cartilage of the neurocranium and forms part of the frontonasal process but does not contribute to jaw joints as previously assumed. These studies reveal the morphogenetic processes by which cranial neural crest cells within the first arch build the primordia for jaw cartilages and anterior cranium.

• Keywords
• NASA Discipline Evolutionary Biology, Non-NASA Center,
• MeSH
• Ambystoma embryology   MeSH
• Staining and Labeling MeSH
• Coloring Agents MeSH
• Biological Evolution * MeSH
• Models, Biological MeSH
• Cartilage embryology   ultrastructure   MeSH
• Neural Crest cytology   MeSH
• Embryo, Nonmammalian MeSH
• Fluorescein-5-isothiocyanate MeSH
• In Situ Hybridization MeSH
• Chick Embryo MeSH
• Mandible embryology   growth & development   MeSH
• Maxilla embryology   growth & development   MeSH
• Morphogenesis MeSH
• Body Patterning MeSH
• Green Fluorescent Proteins MeSH
• Animals MeSH
• Check Tag
• Chick Embryo MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH
• Names of Substances
• Coloring Agents MeSH
• Fluorescein-5-isothiocyanate MeSH
• Green Fluorescent Proteins MeSH