The ontogeny of tooth succession in Lacerta vivipara Jacquin (1787)

1971 ◽  
Vol 179 (1056) ◽  
pp. 261-289 ◽  
Keyword(s):  
Tooth Development ◽  
Biological Significance ◽  
Tooth Replacement ◽  
Similar Sequence ◽  
Dental Lamina ◽  
Oral Ectoderm ◽  
Three Stages ◽  
Lacerta Vivipara ◽  
Tooth Germs ◽  
Almost All

Edmund (1960) has shown that in the dentitions of almost all non-mammalian vertebrates, teeth are replaced in waves which regularly sweep through alternate tooth positions. He explained the ontogeny of these patterns of tooth replacement in terms of biological units called Zahnreihen whose existence has been accepted by nearly all workers studying tooth replacement. In the present paper it is argued that there is no unequivocal evidence, either during development or in adult animals, that Zahnreihen have any biological significance. Reconstructions were made from serial sections of the developing dentitions in the lower jaws of 15 embryos of Lacerta vivipara . It was evident that Zahnreihen have no significance in this animal. Rudimentary teeth were produced with varying frequency in positions 3, 5, 6, 8, 10 and 13. Contrary to the predictions of all previous theories explaining the ontogeny of tooth development in reptiles it was in these apparently random positions that the first teeth were produced. Furthermore, apart from during the first few days of embryonic dental development, it was clear that the development of a row of alternating teeth was initiated in sequence from the back to the front of the jaw to be followed by a similar sequence of development of the intervening teeth. On the basis of this evidence a new model to explain the sequence of tooth initiation in reptiles is proposed. The following assumptions have been made. (A) Ectomesenchymal cells migrate anteriorly through the developing jaws initiating a reaction from the oral ectoderm. (B) The oral ectoderm develops competence to react to the ectomesenchyme in three stages. First it generates abortive clumps of ectodermal cells; second it becomes capable of inducing the adjacent ectomesenchymal cells to form dentine and third it becomes capable of laying down enamel. (C) At all times the dental lamina has the potential of taking part in tooth development according to the regional competence achieved. (D) Developing tooth germs produce a condition which inhibits tooth development around them. Using these assumptions it is possible to explain all stages in the development of the wave replacement of alternate teeth in L . vivipara . It is also possible to explain previous observations on the ontogeny of reptilian dentitions. The sphere of inhibition which surrounds developing teeth is particularly important because it ensures that developing teeth are evenly spaced through the jaw. It is argued that the wave replacement of alternate teeth is an automatic sequel to this and is of only secondary functional significance.

FGFs and BMP4 induce both Msx1-independent and Msx1-dependent signaling pathways in early tooth development

Development ◽  
1998 ◽  
Vol 125 (21) ◽  
pp. 4325-4333 ◽  
Author(s):  
M. Bei ◽  
R. Maas
Keyword(s):  
Signaling Pathways ◽  
Tooth Development ◽  
Signaling Molecules ◽  
Dependent Manner ◽  
Wild Type ◽  
Independent Manner ◽  
Dental Lamina ◽  
Bmp4 Expression ◽  
Dental Epithelium ◽  
Tooth Germs

During early tooth development, multiple signaling molecules are expressed in the dental lamina epithelium and induce the dental mesenchyme. One signal, BMP4, has been shown to induce morphologic changes in dental mesenchyme and mesenchymal gene expression via Msx1, but BMP4 cannot substitute for all the inductive functions of the dental epithelium. To investigate the role of FGFs during early tooth development, we examined the expression of epithelial and mesenchymal Fgfs in wild-type and Msx1 mutant tooth germs and tested the ability of FGFs to induce Fgf3 and Bmp4 expression in wild-type and Msx1 mutant dental mesenchymal explants. Fgf8 expression is preserved in Msx1 mutant epithelium while that of Fgf3 is not detected in Msx1 mutant dental mesenchyme. Moreover, dental epithelium as well as beads soaked in FGF1, FGF2 or FGF8 induce Fgf3 expression in dental mesenchyme in an Msx1-dependent manner. These results indicate that, like BMP4, FGF8 constitutes an epithelial inductive signal capable of inducing the expression of downstream signaling molecules in dental mesenchyme via Msx1. However, the BMP4 and FGF8 signaling pathways are distinct. BMP4 cannot induce Fgf3 nor can FGFs induce Bmp4 expression in dental mesenchyme, even though both signaling molecules can induce Msx1 and Msx1 is necessary for Fgf3 and Bmp4 expression in dental mesenchyme. In addition, we have investigated the effects of FGFs and BMP4 on the distal-less homeobox genes Dlx1 and Dlx2 and we have clarified the relationship between Msx and Dlx gene function in the developing tooth. Dlx1,Dlx2 double mutants exhibit a lamina stage arrest in maxillary molar tooth development (Thomas B. L., Tucker A. S., Qiu M., Ferguson C. A., Hardcastle Z., Rubenstein J. L. R. and Sharpe P. T. (1997) Development 124, 4811–4818). Although the maintenance of molar mesenchymal Dlx2 expression at the bud stage is Msx1-dependent, both the maintenance of Dlx1 expression and the initial activation of mesenchymal Dlx1 and Dlx2 expression during the lamina stage are not. Moreover, in contrast to the tooth bud stage arrest observed in Msx1 mutants, Msx1,Msx2 double mutants exhibit an earlier phenotype closely resembling the lamina stage arrest observed in Dlx1,Dlx2 double mutants. These results are consistent with functional redundancy between Msx1 and Msx2 in dental mesenchyme and support a model whereby Msx and Dlx genes function in parallel within the dental mesenchyme during tooth initiation. Indeed, as predicted by such a model, BMP4 and FGF8, epithelial signals that induce differential Msx1 and Msx2 expression in dental mesenchyme, also differentially induce Dlx1 and Dlx2 expression, and do so in an Msx1-independent manner. These results integrate Dlx1, Dlx2 and Fgf3 and Fgf8 into the odontogenic regulatory hierarchy along with Msx1, Msx2 and Bmp4, and provide a basis for interpreting tooth induction in terms of transcription factors which, individually, are necessary but not sufficient for the expression of downstream signals and therefore must act in specific combinations.

scholarly journals Early development of rostrum saw-teeth in a fossil ray tests classical theories of the evolution of vertebrate dentitions

2015 ◽  
Vol 282 (1816) ◽  
pp. 20151628 ◽  
Author(s):  
Moya Meredith Smith ◽  
Alex Riley ◽  
Gareth J. Fraser ◽  
Charlie Underwood ◽  
Monique Welten ◽  
...  
Keyword(s):  
Oral Cavity ◽  
Early Development ◽  
Developmental Plasticity ◽  
Tooth Development ◽  
Ct Scanning ◽  
Tooth Size ◽  
Micro Ct ◽  
Tooth Replacement ◽  
Self Renewal ◽  
Dental Lamina

In classical theory, teeth of vertebrate dentitions evolved from co-option of external skin denticles into the oral cavity. This hypothesis predicts that ordered tooth arrangement and regulated replacement in the oral dentition were also derived from skin denticles. The fossil batoid ray Schizorhiza stromeri (Chondrichthyes; Cretaceous) provides a test of this theory. Schizorhiza preserves an extended cartilaginous rostrum with closely spaced, alternating saw-teeth, different from sawfish and sawsharks today. Multiple replacement teeth reveal unique new data from micro-CT scanning, showing how the ‘cone-in-cone’ series of ordered saw-teeth sets arrange themselves developmentally, to become enclosed by the roots of pre-existing saw-teeth. At the rostrum tip, newly developing saw-teeth are present, as mineralized crown tips within a vascular, cartilaginous furrow; these reorient via two 90° rotations then relocate laterally between previously formed roots. Saw-tooth replacement slows mid-rostrum where fewer saw-teeth are regenerated. These exceptional developmental data reveal regulated order for serial self-renewal, maintaining the saw edge with ever-increasing saw-tooth size. This mimics tooth replacement in chondrichthyans, but differs in the crown reorientation and their enclosure directly between roots of predecessor saw-teeth. Schizorhiza saw-tooth development is decoupled from the jaw teeth and their replacement, dependent on a dental lamina. This highly specialized rostral saw, derived from diversification of skin denticles, is distinct from the dentition and demonstrates the potential developmental plasticity of skin denticles.

scholarly journals Anti–USAG-1 therapy for tooth regeneration through enhanced BMP signaling

2021 ◽  
Vol 7 (7) ◽  
pp. eabf1798
Author(s):  
A. Murashima-Suginami ◽  
H. Kiso ◽  
Y. Tokita ◽  
E. Mihara ◽  
Y. Nambu ◽  
...  
Keyword(s):  
Tooth Development ◽  
Bmp Signaling ◽  
Tooth Agenesis ◽  
Tooth Regeneration ◽  
Missing Teeth ◽  
Morphogenetic Protein ◽  
Genetic Abnormalities ◽  
Direct Binding ◽  
Tooth Germs ◽  
Lipoprotein Receptor Related Protein

Uterine sensitization–associated gene-1 (USAG-1) deficiency leads to enhanced bone morphogenetic protein (BMP) signaling, leading to supernumerary teeth formation. Furthermore, antibodies interfering with binding of USAG-1 to BMP, but not lipoprotein receptor–related protein 5/6 (LRP5/6), accelerate tooth development. Since USAG-1 inhibits Wnt and BMP signals, the essential factors for tooth development, via direct binding to BMP and Wnt coreceptor LRP5/6, we hypothesized that USAG-1 plays key regulatory roles in suppressing tooth development. However, the involvement of USAG-1 in various types of congenital tooth agenesis remains unknown. Here, we show that blocking USAG-1 function through USAG-1 knockout or anti–USAG-1 antibody administration relieves congenital tooth agenesis caused by various genetic abnormalities in mice. Our results demonstrate that USAG-1 controls the number of teeth by inhibiting development of potential tooth germs in wild-type or mutant mice missing teeth. Anti–USAG-1 antibody administration is, therefore, a promising approach for tooth regeneration therapy.

Opg, Rank, and Rankl in Tooth Development: Co-ordination of Odontogenesis and Osteogenesis

2004 ◽  
Vol 83 (3) ◽  
pp. 241-244 ◽  
Author(s):  
A. Ohazama ◽  
J.-M. Courtney ◽  
P.T. Sharpe
Keyword(s):  
Tooth Development ◽  
Nuclear Factor Κb ◽  
Cellular Interactions ◽  
Rankl Expression ◽  
Dental Papilla ◽  
Spatiotemporal Expression ◽  
Receptor Activator ◽  
Explant Cultures ◽  
Enamel Epithelium ◽  
Tooth Germs

Osteoprotegerin (OPG), receptor activator of nuclear factor-κB (RANK), and RANK ligand (RANKL) are mediators of various cellular interactions, including bone metabolism. We analyzed expression of these three genes during murine odontogenesis from epithelial thickening to cytodifferentiation stages. Opg showed expression in the thickening and bud epithelium. Expression of Opg and Rank was observed in both the internal and the external enamel epithelium as well as in the dental papilla mesenchyme. Although Rankl expression was not detected in tooth epithelium or mesenchyme, it was expressed in pre-osteogenic mesenchymal cells close to developing tooth germs. All three genes were detected in developing dentary bone at P0. The addition of exogenous OPG to explant cultures of tooth primordia produced a delay in tooth development that resulted in reduced mineralization. We propose that the spatiotemporal expression of these molecules in early tooth and bone primordia cells has a role in co-ordinating bone and tooth development.

Tooth development in the ‘crooked’ mouse

Development ◽  
1977 ◽  
Vol 41 (1) ◽  
pp. 279-287
Author(s):  
J. A. Sofaer
Keyword(s):  
Competitive Inhibition ◽  
Tooth Development ◽  
Tooth Germ ◽  
Axial Skeleton ◽  
Tissue Formation ◽  
Supernumerary Teeth ◽  
Hard Tissue ◽  
Dental Lamina ◽  
Dental Abnormalities ◽  
Rates Of Growth

The semidominant gene ‘crooked’ (Cd) in the mouse produces anomalies of the axial skeleton (resulting in a crooked tail), microphthalmia and dental abnormalities, including small molars with simplified cusp patterns that are equivalent to patterns passed through during normal morphodifferentiation. A series of embryonic litters from Cd/ + × Cd / + matings was used to investigate the embryological basis for the dental abnormalities. Microphthalmic embryos were classed as Cd/Cd, and their most normal litter mates were selected as controls (+ / + or Cd / +). An additional set of control embryos came from the inbred strain CBA/Cam (+ / +). Serial sagittal sections of the heads of these embryos were examined microscopically, and the maximum anteroposterior diameters of the developing upper and lower first molars were measured. Reduction in the rates of growth and morphodifferentiation of Cd/Cd first molars, relative to those of litter mate controls, was associated with the appearance of an adjacent abnormal proliferation of the dental lamina. Some proliferations in older embryos showed signs of early tooth germ formation, but many were seen to have regressed and no examples of supernumerary teeth have been found in Cd/Cd adults. Small size of Cd/Cd molars may therefore result from competitive inhibition of molar growth by a transient abnormal laminal proliferation, and Cd/Cd cusp patterns from the relatively premature onset of hard tissue formation during normal but retarded sequences of morphodifferentiation.

scholarly journals THE BIOLOGICAL SIGNIFICANCE OF SELENIUM AND ITS PLACE IN RNA VIRAL DISEASES

2020 ◽  
Vol 21 (4) ◽  
pp. 21-31
Author(s):  
T.M. Guseynov ◽  
◽  
R.T. Guliyeva ◽  
F.R. Yakhyayeva ◽  
◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Immune Response ◽  
Viral Infections ◽  
Biological Significance ◽  
The Body ◽  
Viral Diseases ◽  
Essential Trace Element ◽  
Regulatory Processes ◽  
P Protein ◽  
Almost All

ABSTRACT. Selenium as an essential trace element takes part in the regulation of many vital processes. This is realized with the help of over 25 selenoproteins that affect oxidative stress, immune response, hormonal metabolism, cognitive function, etc. Recently (in the next 30 - 40 years), there have been reports of the effect on viral infections, which have now become widespread. It turned out that almost all RNA viruses are selenium-dependent objects, that is, their genome contains the codes of the most important selenium containing proteins, including such as glutathione peroxidase, thioredoxinreductase, selenium-P protein, etc. Their synthesis during the development of a viral infection at the expense of the host leads to a weakening of the synthesis of the body's own intracellular selenium proteins, which contributes to the development of oxidative stress and a failure of the immune response. And this leads to the devastation of the selenium depot of the body, intended for the synthesis of its selenium proteins, which participate in vital regulatory processes. This circumstance determines, to replenish the body's resources with selenium, the expediency of using selenium-containing pharmacopoeia preparations as adjuvant in the treatment of RNA viral infections.

scholarly journals PHILOSOPHICAL ATTITUDES OF THE EARLY WORKS OF P. TYCHYNA AS AN OBJECT OF MODERNIST-POSTMODERN MYTH CREATION

2019 ◽  
pp. 5-11
Author(s):  
H. V. Vdovychenko
Keyword(s):  
Cultural Development ◽  
Soviet Period ◽  
The Political ◽  
Political Environment ◽  
Philosophical Foundations ◽  
Early Twenty ◽  
Wide Range ◽  
Three Stages ◽  
Systematic Development ◽  
Almost All

The article classifies and highlights three stages spanning the last hundred years – pre-Soviet, Soviet and post-Soviet, of research and mythol- ogization of the life and creation of P.Tychyna, using the example of studying the philosophical attitudes of his early work in the Ukrainian state, the Ukrainian SSR, Ukraine and abroad. The specifics of the formation of the mentioned stages during 1918 – 2019 were systematically considered on materials, including little-known, studies of more than fifty representatives of domestic and foreing tychynology, as well as a wide range of materi- als of the poetic, prosaic, scientific-journalistic and epistolary heritage of P. Tychyna and his contemporary colleagues. In the context of this review an attempt was made of critical interdisciplinary analysis – cultural and philosophical and literary, of the ideological foundations and the results of the modernist and postmodern mythologization of the early creativity of P. Tychyna as the leading creator and symbol of Ukrainian Modernist and Socialist-Realistic literature and, in general, cultural development. The article identifies three leading aspects of defining and studying the philosophical foundations of P. Tychyna's early work in the twentieth – early twenty first centuries: 1) the absence of the formulation and systematic development of the topic in P. Tychyna studies, except for the initial attempts at each of its stages, so far; 2) the narrow specialty of individual attempts at such research, first of all, almost entirely literary or linguistic, but not professional philosophical and cultural philosophical; 3) the dominant conditionality of the major achievements of almost all of these studies, mainly the Soviet period, the political environment of the development of national humanities and, as a consequence, the consistent isolationist-Soviet-anti-European mythology of P. Tychyna's creative figure and heritage. In view of this, the development of this topic in the context of an interdisciplinary, critically-demythologizing scientific search, formed in the contemporary P. Tychyna studies, has been identified as promising.

scholarly journals Expression, localization and synthesis of small leucine-rich proteoglycans in developing mouse molar tooth germ

2020 ◽  
Vol 64 (1) ◽  
Author(s):  
Angammana Randilini ◽  
Kaoru Fujikawa ◽  
Shunichi Shibata
Keyword(s):  
Organ Culture ◽  
Developmental Stages ◽  
Tooth Development ◽  
Expression Patterns ◽  
Tooth Germ ◽  
Molar Tooth ◽  
Cervical Region ◽  
Metabolic Labeling ◽  
Tooth Formation ◽  
Tooth Germs

The gene expression and protein synthesis of small leucine-rich proteoglycans (SLRPs), including decorin, biglycan, fibromodulin, and lumican, was analyzed in the context of the hypothesis that they are closely related to tooth formation. In situ hybridization, immunohistochemistry, and organ culture with metabolic labeling of [35S] were carried out in mouse first molar tooth germs of different developmental stages using ICR mice at embryonic day (E) 13.5 to postnatal day (P) 7.0. At the bud and cap stage, decorin mRNA was expressed only in the surrounding mesenchyme, but not within the tooth germ. Biglycan mRNA was then expressed in the condensing mesenchyme and the dental papilla of the tooth germ. At the apposition stage (late bell stage), both decorin and biglycan mRNA were expressed in odontoblasts, resulting in a switch of the pattern of expression within the different stages of odontoblast differentiation. Decorin mRNA was expressed earlier in newly differentiating odontoblasts than biglycan. With odontoblast maturation and dentin formation, decorin mRNA expression was diminished and localized to the newly differentiating odontoblasts at the cervical region. Simultaneously, biglycan mRNA took over and extended its expression throughout the new and mature odontoblasts. Both mRNAs were expressed in the dental pulp underlying the respective odontoblasts. At P7.0, both mRNAs were weakly expressed but maintained their spatial expression patterns. Immunostaining showed that biglycan was localized in the dental papillae and pulp. In addition, all four SLRPs showed clear immunostaining in predentin, although the expressions of fibromodulin and lumican mRNAs were not identified in the tooth germs examined. The organ culture data obtained supported the histological findings that biglycan is more predominant than decorin at the apposition stage. These results were used to identify biglycan as the principal molecule among the SLRPs investigated. Our findings indicate that decorin and biglycan show spatial and temporal differential expressions and play their own tissue-specific roles in tooth development.

scholarly journals The Dental Lamina: An Essential Structure for Perpetual Tooth Regeneration in Sharks

2020 ◽  
Vol 60 (3) ◽  
pp. 644-655
Author(s):  
Gareth J Fraser ◽  
Ariane Standing ◽  
Charlie Underwood ◽  
Alexandre P Thiery
Keyword(s):  
Murine Model ◽  
Tooth Development ◽  
Tooth Regeneration ◽  
Regenerative Processes ◽  
Dental Lamina ◽  
Developmental Models ◽  
Nonclassical Models ◽  
Developmental Shift ◽  
Evolutionary Context

Synopsis In recent years, nonclassical models have emerged as mainstays for studies of evolutionary, developmental, and regenerative biology. Genomic advances have promoted the use of alternative taxa for the study of developmental biology, and the shark is one such emerging model vertebrate. Our research utilizes the embryonic shark (Scyliorhinus canicula) to characterize key developmental and regenerative processes that have been overlooked or not possible to study with more classic developmental models. Tooth development is a major event in the construction of the vertebrate body plan, linked in part with the emergence of jaws. Early development of the teeth and morphogenesis is well known from the murine model, but the process of tooth redevelopment and regeneration is less well known. Here we explore the role of the dental lamina in the development of a highly regenerative dentition in sharks. The shark represents a polyphyodont vertebrate with continuously repeated whole tooth regeneration. This is presented as a major developmental shift from the more derived renewal process that the murine model offers, where incisors exhibit continuous renewal and growth of the same tooth. Not only does the shark offer a study system for whole unit dental regeneration, it also represents an important model for understanding the evolutionary context of vertebrate tooth regeneration.

scholarly journals The Effects of Premature Tooth Extraction and Damage on Replacement Timing in the Green Iguana

2020 ◽  
Vol 60 (3) ◽  
pp. 581-593
Author(s):  
Kirstin S Brink ◽  
Ping Wu ◽  
Cheng-Ming Chuong ◽  
Joy M Richman
Keyword(s):  
Tooth Extraction ◽  
Tooth Development ◽  
Tooth Wear ◽  
X Rays ◽  
Tooth Replacement ◽  
Green Iguana ◽  
Dental Tissues ◽  
Functional Tooth ◽  
Green Iguanas ◽  
Replacement Cycle

Synopsis Reptiles with continuous tooth replacement, or polyphyodonty, replace their teeth in predictable, well-timed waves in alternating tooth positions around the mouth. This process is thought to occur irrespective of tooth wear or breakage. In this study, we aimed to determine if damage to teeth and premature tooth extraction affects tooth replacement timing long-term in juvenile green iguanas (Iguana iguana). First, we examined normal tooth development histologically using a BrdU pulse-chase analysis to detect label-retaining cells in replacement teeth and dental tissues. Next, we performed tooth extraction experiments for characterization of dental tissues after functional tooth (FT) extraction, including proliferation and β-Catenin expression, for up to 12 weeks. We then compared these results to a newly analyzed historical dataset of X-rays collected up to 7 months after FT damage and extraction in the green iguana. Results show that proliferation in the dental and successional lamina (SL) does not change after extraction of the FT, and proliferation occurs in the SL only when a tooth differentiates. Damage to an FT crown does not affect the timing of the tooth replacement cycle, however, complete extraction shifts the replacement cycle ahead by 4 weeks by removing the need for resorption of the FT. These results suggest that traumatic FT loss affects the timing of the replacement cycle at that one position, which may have implications for tooth replacement patterning around the entire mouth.

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