Fish Dentitions as Paradigms for Odontogenic Questions

Huysseune, Ann; heyden, Christine Van der; Verreijdt, L.; Wautier, Kristel; Damme, Nele Van

doi:10.1080/03008200290000808

Cited by 13 publications

(6 citation statements)

References 33 publications

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“…Also, ' in strong contrast to the foregut endoderm, neither the ectoderm, nor the mesoderm display patterning properties that lead to skeletogenesis of the facial bones'. Similar positional information could organise the pattern of pharyngeal denticles, teeth and membrane bone of the splanchnocranium, but needs to be established experimentally in fish (see Huysseune et al, 2002 for a review of endodermal participation in odontogenesis in fish). In zebrafish mutants, the initial iterative pattern in the pharyngeal region is dependent on endodermal signalling, and is also required to make the separate cartilages in the branchial arches (Piotrowski & Nüsslein-Volhard, 2000).…”

Section: A Developmental Model From Phylogenetic Patternmentioning

confidence: 98%

“…There can be little doubt that in both the developmental and functional senses, true teeth form in pharyngognaths despite their location on the fifth branchial arch. Importantly, they are truly a part of the splanchnoskeleton and under the putative inductive influence of endoderm lining the pharyngeal cavity (Huysseune et al, 2002 ;Section IV.1).…”

Section: Arthrodiramentioning

confidence: 99%

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Origin and evolution of gnathostome dentitions: a question of teeth and pharyngeal denticles in placoderms

Johanson¹,

Smith

2005

Biol. Rev.

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The fossil group Placodermi is the most phylogenetically basal of the clade of jawed vertebrates but lacks a marginal dentition comparable to that of the dentate Chondrichthyes, Acanthodii and Osteichthyes (crown-group Gnathostomata). The teeth of crown-group gnathostomes are part of an ordered dentition replaced from, and patterned by, a dental lamina, exemplified by the elasmobranch model. A dentition recognised by these criteria has been previously judged absent in placoderms, based on structural evidence such as absence of tooth whorls and typical vertebrate dentine. However, evidence for regulated tooth addition in a precise spatiotemporal order can be observed in placoderms, but significantly, only within the group Arthrodira. In these fossils, as in other jawed vertebrates with statodont, non-replacing dentitions, new teeth are added at the ends of rows below the bite, but in line with biting edges of the dentition. The pattern is different on each gnathal bone and probably arises from single odontogenic primordia on each, but tooth rows are arranged in a distinctive placoderm pattern. New teeth are made of regular dentine comparable to that of crown-gnathostomes, formed from a pulp cavity. This differs from semidentine previously described for placoderm gnathalia, a type present in the external dermal tubercles. The Arthrodira is a derived taxon within the Placodermi, hence origin of teeth in placoderms occurs late in the phylogeny and teeth are convergently derived, relative to those of other jawed vertebrates. More basal placoderm taxa adopted other strategies for providing biting surfaces and these vary substantially, but include addition of denticles to the growing gnathal plates, at the margins of pre-existing denticle patches. These alternative strategies and apparent absence of regular dentine have led to previous interpretations that teeth were entirely absent from the placoderm dentition. A consensus view emerged that a dentition, as developed within a dental lamina, is a synapomorphy characterising the clade of crown-group gnathostomes. Recent comparisons between sets of denticle whorls in the pharyngeal region of the jawless fish Loganellia scotica (Thelodonti) and those in sharks suggest homology of these denticle sets on gill arches. Although the placoderm pharyngeal region appears to lack denticles (placoderm gill arches are poorly known), the posterior wall of the pharyngeal cavity, formed by a bony flange termed the postbranchial lamina, is covered in rows of patterned denticle arrays. These arrays differ significantly, both in morphology and arrangement, from those of the denticles located externally on the head and trunkshield plates. Denticles in these arrays are homologous to denticles associated with the gill arches in other crown-gnathostomes, with pattern similarities for order and position of pharyngeal denticles. From their location in the pharynx these are inferred to be under the influence of a cell lineage from endoderm, rather than ectoderm. Tooth sets and tooth whorls in crow...

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Section: A Developmental Model From Phylogenetic Patternmentioning

confidence: 98%

Section: Arthrodiramentioning

confidence: 99%

Origin and evolution of gnathostome dentitions: a question of teeth and pharyngeal denticles in placoderms

Johanson¹,

Smith

2005

Biol. Rev.

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“…The dental patterns of polyphyodont vertebrates are remarkably diverse and have been extensively studied [30]. Several models have been proposed to explain the successive appearance of teeth in these animals [4].…”

Section: (A) a Model Of Dental Patterningmentioning

confidence: 99%

The first formed tooth serves as a signalling centre to induce the formation of the dental row in zebrafish

Gibert¹,

Samarut

Ellis³

et al. 2019

Proc. R. Soc. B.

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The diversity of teeth patterns in actinopterygians is impressive with tooth rows in many locations in the oral and pharyngeal regions. The first-formed tooth has been hypothesized to serve as an initiator controlling the formation of the subsequent teeth. In zebrafish, the existence of the first tooth (named 4 V 1 ) is puzzling as its replacement is induced before the opening of the mouth. Functionally, it has been shown that 4 V 1 formation requires fibroblast growth factor (FGF) and retinoic acid (RA) signalling. Here, we show that the ablation of 4 V 1 prevents the development of the dental row demonstrating its dependency over it. If endogenous levels of FGF and RA are restored after 4 V 1 ablation, embryonic dentition starts again by de novo formation of a first tooth, followed by the dental row. Similarly, induction of anterior ectopic teeth induces subsequent tooth formation, demonstrating that the initiator tooth is necessary and sufficient for dental row formation, probably via FGF ligands released by 4 V 1 to induce the formation of subsequent teeth. Our results show that by modifying the formation of the initiator tooth it is possible to control the formation of a dental row. This could help to explain the diversity of tooth patterns observed in actinopterygians and more broadly, how diverse traits evolved through molecular fine-tuning.

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“…In zebrafish, an animal with no oral but only pharyngeal teeth that are considered to develop from endoderm epithelia (e.g. [62, 63]), some have speculated that the dentition might be derived from endoderm with some pharyngeal ectoderm epithelial cells in close proximity [38]. According to available data, vertebrate teeth can be derived equally from ectoderm as well as endoderm cells.…”

Section: New Perspectivesmentioning

confidence: 99%

The odontode explosion: The origin of tooth‐like structures in vertebrates

et al. 2010

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We integrate recent data to shed new light on the thorny controversy of how teeth arose in evolution. Essentially we show (a) how teeth can form equally from any epithelium, be it endoderm, ectoderm or a combination of the two and (b) that the gene expression programs of oral vs. pharyngeal teeth are remarkably similar. Classic theories suggest that (i) skin denticles evolved first and odontode-inductive surface ectoderm merged inside the oral cavity to form teeth (the 'outside-in' hypothesis) or that (ii) patterned odontodes evolved first from endoderm deep inside the pharyngeal cavity (the 'inside-out' hypothesis). We propose a new perspective that views odontodes as structures sharing a deep molecular homology, united by sets of co-expressed genes defining a competent thickened epithelium and a collaborative neural crest derived ectomesenchyme. Simply put, odontodes develop 'inside and out,' wherever and whenever these co-expressed gene sets signal to one another. Our perspective complements the classic theories and highlights an agenda for specific experimental manipulations in model and non-model organisms.

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Fish Dentitions as Paradigms for Odontogenic Questions

Cited by 13 publications

References 33 publications

Origin and evolution of gnathostome dentitions: a question of teeth and pharyngeal denticles in placoderms

Origin and evolution of gnathostome dentitions: a question of teeth and pharyngeal denticles in placoderms

The first formed tooth serves as a signalling centre to induce the formation of the dental row in zebrafish

The odontode explosion: The origin of tooth‐like structures in vertebrates

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