scholarly journals The alternative regenerative strategy of bearded dragon unveils the key processes underlying vertebrate tooth renewal

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Lotta Salomies ◽  
Julia Eymann ◽  
Imran Khan ◽  
Nicolas Di-Poï
Keyword(s):  
Deep Understanding ◽  
Functional Specialization ◽  
Tooth Regeneration ◽  
Vertebrate Species ◽  
Directional Growth ◽  
Dental Lamina ◽  
Bearded Dragon ◽  
Conventional Models ◽  
Slow Cycling ◽  
Gene Expression Levels

Deep understanding of tooth regeneration is hampered by the lack of lifelong replacing oral dentition in most conventional models. Here, we show that the bearded dragon, one of the rare vertebrate species with both polyphyodont and monophyodont teeth, constitutes a key model for filling this gap, allowing direct comparison of extreme dentition types. Our developmental and high-throughput transcriptomic data of microdissected dental cells unveils the critical importance of successional dental lamina patterning, in addition to maintenance, for vertebrate tooth renewal. This patterning process happens at various levels, including directional growth but also gene expression levels, dynamics, and regionalization, and involves a large number of yet uncharacterized dental genes. Furthermore, the alternative renewal mechanism of bearded dragon dentition, with dual location of slow-cycling cells, demonstrates the importance of cell migration and functional specialization of putative epithelial stem/progenitor niches in tissue regeneration, while expanding the diversity of dental replacement strategies in vertebrates.

scholarly journals Sox2+ progenitors in sharks link taste development with the evolution of regenerative teeth from denticles

2016 ◽  
Vol 113 (51) ◽  
pp. 14769-14774 ◽  
Author(s):  
Kyle J. Martin ◽  
Liam J. Rasch ◽  
Rory L. Cooper ◽  
Brian D. Metscher ◽  
Zerina Johanson ◽  
...  
Keyword(s):  
Regulatory Networks ◽  
Molecular Mechanisms ◽  
Stem Cell Marker ◽  
Tooth Regeneration ◽  
Dental Lamina ◽  
Shark Teeth ◽  
Regenerative Ability ◽  
Slow Cycling ◽  
Slow Cycling Cell

Teeth and denticles belong to a specialized class of mineralizing epithelial appendages called odontodes. Although homology of oral teeth in jawed vertebrates is well supported, the evolutionary origin of teeth and their relationship with other odontode types is less clear. We compared the cellular and molecular mechanisms directing development of teeth and skin denticles in sharks, where both odontode types are retained. We show that teeth and denticles are deeply homologous developmental modules with equivalent underlying odontode gene regulatory networks (GRNs). Notably, the expression of the epithelial progenitor and stem cell marker sex-determining region Y-related box 2 (sox2) was tooth-specific and this correlates with notable differences in odontode regenerative ability. Whereas shark teeth retain the ancestral gnathostome character of continuous successional regeneration, new denticles arise only asynchronously with growth or after wounding. Sox2+ putative stem cells associated with the shark dental lamina (DL) emerge from a field of epithelial progenitors shared with anteriormost taste buds, before establishing within slow-cycling cell niches at the (i) superficial taste/tooth junction (T/TJ), and (ii) deep successional lamina (SL) where tooth regeneration initiates. Furthermore, during regeneration, cells from the superficial T/TJ migrate into the SL and contribute to new teeth, demonstrating persistent contribution of taste-associated progenitors to tooth regeneration in vivo. This data suggests a trajectory for tooth evolution involving cooption of the odontode GRN from nonregenerating denticles bysox2+ progenitors native to the oral taste epithelium, facilitating the evolution of a novel regenerative module of odontodes in the mouth of early jawed vertebrates: the teeth.

scholarly journals Slow cycling cells in the continuous dental lamina of Scyliorhinus canicula: new evidence for stem cells in sharks

2016 ◽  
Vol 413 (1) ◽  
pp. 39-49 ◽  
Author(s):  
Sam Vandenplas ◽  
Robbe Vandeghinste ◽  
Agnes Boutet ◽  
Sylvie Mazan ◽  
Ann Huysseune
Keyword(s):  
Stem Cells ◽  
Dental Lamina ◽  
Scyliorhinus Canicula ◽  
Slow Cycling ◽  
New Evidence

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 Distinct tooth regeneration systems deploy a conserved battery of genes

EvoDevo ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tyler A. Square ◽  
Shivani Sundaram ◽  
Emma J. Mackey ◽  
Craig T. Miller
Keyword(s):  
Wnt Signaling ◽  
Tooth Regeneration ◽  
Cell Type ◽  
Epithelial Stem Cells ◽  
Dental Lamina ◽  
Dental Tissues ◽  
Wide Range ◽  
Tooth Germs ◽  
Regenerative Systems ◽  
Regeneration Systems

AbstractBackgroundVertebrate teeth exhibit a wide range of regenerative systems. Many species, including most mammals, reptiles, and amphibians, form replacement teeth at a histologically distinct location called the successional dental lamina, while other species do not employ such a system. Notably, a ‘lamina-less’ tooth replacement condition is found in a paraphyletic array of ray-finned fishes, such as stickleback, trout, cod, medaka, and bichir. Furthermore, the position, renewal potential, and latency times appear to vary drastically across different vertebrate tooth regeneration systems. The progenitor cells underlying tooth regeneration thus present highly divergent arrangements and potentials. Given the spectrum of regeneration systems present in vertebrates, it is unclear if morphologically divergent tooth regeneration systems deploy an overlapping battery of genes in their naïve dental tissues.ResultsIn the present work, we aimed to determine whether or not tooth progenitor epithelia could be composed of a conserved cell type between vertebrate dentitions with divergent regeneration systems. To address this question, we compared the pharyngeal tooth regeneration processes in two ray-finned fishes: zebrafish (Danio rerio) and threespine stickleback (Gasterosteus aculeatus). These two teleost species diverged approximately 250 million years ago and demonstrate some stark differences in dental morphology and regeneration. Here, we find that the naïve successional dental lamina in zebrafish expresses a battery of nine genes (bmpr1aa, bmp6, cd34, gli1, igfbp5a, lgr4, lgr6, nfatc1,andpitx2), while active Wnt signaling andLef1expression occur during early morphogenesis stages of tooth development. We also find that, despite the absence of a histologically distinct successional dental lamina in stickleback tooth fields, the same battery of nine genes (Bmpr1a,Bmp6,CD34,Gli1,Igfbp5a,Lgr4,Lgr6,Nfatc1, andPitx2) are expressed in the basalmost endodermal cell layer, which is the region most closely associated with replacement tooth germs. Like zebrafish, stickleback replacement tooth germs additionally expressLef1and exhibit active Wnt signaling. Thus, two fish systems that either have an organized successional dental lamina (zebrafish) or lack a morphologically distinct successional dental lamina (sticklebacks) deploy similar genetic programs during tooth regeneration.ConclusionsWe propose that the expression domains described here delineate a highly conserved “successional dental epithelium” (SDE). Furthermore, a set of orthologous genes is known to mark hair follicle epithelial stem cells in mice, suggesting that regenerative systems in other epithelial appendages may utilize a related epithelial progenitor cell type, despite the highly derived nature of the resulting functional organs.

scholarly journals Developmental dynamics of sex reprogramming by high incubation temperatures in a dragon lizard

2021 ◽  
Author(s):  
Sarah L Whiteley ◽  
Clare E Holleley ◽  
Arthur Georges
Keyword(s):  
Developmental Stages ◽  
Sex Reversal ◽  
Transcriptional Level ◽  
Vertebrate Species ◽  
Gene Environment ◽  
Bearded Dragon ◽  
Pogona Vitticeps ◽  
Incubation Temperatures ◽  
Developmental Dynamics ◽  
Male To Female

In some vertebrate species, gene-environment interactions can determine sex, driving bipotential gonads to differentiate into either ovaries or testes. In the central bearded dragon (Pogona vitticeps), the genetic influence of sex chromosomes (ZZ/ZW) can be overridden by high incubation temperatures, causing ZZ male to female sex reversal. Previous research showed ovotestes, a rare gonadal phenotype with traits of both sexes, develop during sex reversal, leading to the hypothesis that sex reversal relies on high temperature feminisation to outcompete the male genetic cue. To test this, we conducted temperature switching experiments at key developmental stages, and analysed the effect on gonadal phenotypes using histology and transcriptomics. We found sexual fate is more strongly influenced by the ZZ genotype than temperature. Any exposure to low temperatures (28oC) caused testes differentiation, whereas sex reversal required longer exposure to high temperatures. We revealed ovotestes exist along a spectrum of female-ness to male-ness at the transcriptional level. We found inter-individual variation in gene expression changes following temperature switches, suggesting both genetic sensitivity to, and the timing and duration of the temperature cue influences sex reversal. These findings bring new insights to the mechanisms underlying sex reversal, improving our understanding of thermosensitive sex systems in vertebrates.

scholarly journals The abundance of processed pseudogenes derived from glycolytic genes is correlated with their expression level

Genome ◽  
2012 ◽  
Vol 55 (2) ◽  
pp. 147-151 ◽  
Author(s):  
Laura McDonell ◽  
Guy Drouin
Keyword(s):  
Gene Expression ◽  
Reverse Transcriptase ◽  
Age Distribution ◽  
Glycolytic Pathway ◽  
Expression Level ◽  
Vertebrate Species ◽  
Expression Levels ◽  
Processed Pseudogene ◽  
Processed Pseudogenes ◽  
Gene Expression Levels

The abundance of processed pseudogenes in different vertebrate species is known to be proportional to the length of their oogenesis. However, this hypothesis cannot explain why, in a given species, certain genes produce more processed pseudogenes than others. In particular, one would expect that all genes of the glycolytic pathway would generate roughly the same number of processed pseudogenes. However, some glycolitic genes generate more processed pseudogenes than others. Here, we show that there is a positive correlation between the abundance of processed pseudogene generated from glycolytic genes and their level of expression. The variation in expression level of different glycolytic genes likely reflects the fact that some of them, such a GAPDH, have functions other than those they play in glycolysis. Furthermore, the age distribution of GAPDH-processed pseudogenes corresponds to the age distribution of LINE1 elements, which are the source of the reverse transcriptase that generates processed pseudogenes. These results support the hypothesis that gene expression levels affect the level of processed pseudogene production.

scholarly journals Distinct tooth regeneration systems deploy a conserved battery of genes

2020 ◽  
Author(s):  
Tyler A. Square ◽  
Shivani Sundaram ◽  
Emma J. Mackey ◽  
Craig T. Miller
Keyword(s):  
Wnt Signaling ◽  
Gasterosteus Aculeatus ◽  
Tooth Regeneration ◽  
Cell Type ◽  
Epithelial Stem Cells ◽  
Dental Lamina ◽  
Dental Tissues ◽  
Wide Range ◽  
Regenerative Systems ◽  
Regeneration Systems

AbstractBackgroundVertebrate teeth exhibit a wide range of regenerative systems. Many species, including most mammals, reptiles, and amphibians, form replacement teeth at a histologically distinct location called the successional dental lamina, while other species do not employ such a system. Notably, a ‘lamina-less’ tooth replacement condition is found in a paraphyletic array of ray-finned fishes, such as stickleback, trout, cod, medaka, and bichir. Furthermore, the position, renewal potential, and latency times appear to vary drastically across different vertebrate tooth regeneration systems. The progenitor cells underlying tooth regeneration thus present highly divergent arrangements and potentials. Given the spectrum of regeneration systems present in vertebrates, it is unclear if morphologically divergent tooth regeneration systems deploy an overlapping battery of genes in their naïve dental tissues.ResultsIn the present work, we aimed to determine whether or not tooth progenitor epithelia could be composed of a conserved cell type between vertebrate dentitions with divergent regeneration systems. To address this question, we compared the tooth regeneration processes in two ray-finned fishes: zebrafish (Danio rerio) and threespine stickleback (Gasterosteus aculeatus). These two teleost species diverged approximately 250 million years ago, and demonstrate some stark differences in dental morphology and regeneration. Here we find that the successional dental lamina in zebrafish sharply upregulates Wnt signaling and Lef1 expression during early morphogenesis stages of tooth development. Additionally, the naïve zebrafish successional dental lamina expresses a battery of nine genes (Bmpr1a, Bmp6, CD34, Gli1, Igfbp5a, Lgr4, Lgr6, Nfatc1, and Pitx2). We also find that, despite the absence of a histologically distinct successional dental lamina in stickleback tooth fields, new tooth germs also sharply upregulate Wnt signaling and Lef1 expression, and additionally express the same battery of nine genes in the basalmost endodermal cell layer from which replacement tooth epithelia arise. Thus, two fish systems that either have an organized successional dental lamina (zebrafish) or lack a morphologically distinct successional dental lamina (sticklebacks) deploy similar genetic programs during tooth regeneration.ConclusionsWe propose that the expression domains described here delineate a highly conserved “successional dental epithelium” (SDE). Furthermore, a set of orthologous genes is known to mark hair follicle epithelial stem cells in mice, suggesting that regenerative systems in other epithelial appendages may utilize a related epithelial progenitor cell type, despite the highly derived nature of the resulting functional organs.

Cultural Competence Needed to Distinguish Disorder from Difference: Beyond Kumbaya

2015 ◽  
Vol 22 (2) ◽  
pp. 64-76 ◽  
Author(s):  
Catherine J. Crowley ◽  
Kristin Guest ◽  
Kenay Sudler
Keyword(s):  
New York ◽  
New York City ◽  
Public Schools ◽  
Cultural Competence ◽  
York City ◽  
Cultural Sensitivity ◽  
Graduate Program ◽  
Language Disorder ◽  
New York State ◽  
Deep Understanding

What does it mean to have true cultural competence as an speech-language pathologist (SLP)? In some areas of practice it may be enough to develop a perspective that values the expectations and identity of our clients and see them as partners in the therapeutic process. But when clinicians are asked to distinguish a language difference from a language disorder, cultural sensitivity is not enough. Rather, in these cases, cultural competence requires knowledge and skills in gathering data about a student's cultural and linguistic background and analyzing the student's language samples from that perspective. This article describes one American Speech-Language-Hearing Association (ASHA)-accredited graduate program in speech-language pathology and its approach to putting students on the path to becoming culturally competent SLPs, including challenges faced along the way. At Teachers College, Columbia University (TC) the program infuses knowledge of bilingualism and multiculturalism throughout the curriculum and offers bilingual students the opportunity to receive New York State certification as bilingual clinicians. Graduate students must demonstrate a deep understanding of the grammar of Standard American English and other varieties of English particularly those spoken in and around New York City. Two recent graduates of this graduate program contribute their perspectives on continuing to develop cultural competence while working with diverse students in New York City public schools.

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