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Kenessey DE, Stojanowski CM, Paul KS. Evaluating predictions of the patterning cascade model of crown morphogenesis in the human lower mixed and permanent dentition. PLoS One 2024; 19:e0304455. [PMID: 38935640 PMCID: PMC11210800 DOI: 10.1371/journal.pone.0304455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 05/13/2024] [Indexed: 06/29/2024] Open
Abstract
OBJECTIVE The patterning cascade model of crown morphogenesis has been studied extensively in a variety of organisms to elucidate the evolutionary history surrounding postcanine tooth form. The current research is the first to use a large modern human sample to examine whether the crown configuration of lower deciduous and permanent molars aligns with expectations derived from the model. This study has two main goals: 1) to determine if metameric and antimeric pairs significantly differ in size, accessory trait expression, and relative intercusp spacing, and 2) assess whether the relative distance among early-forming cusps accounts for observed variation in accessory cusp expression. METHODS Tooth size, intercusp distance, and morphological trait expression data were collected from 3D scans of mandibular dental casts representing participants of the Harvard Solomon Islands Project. Paired tests were utilized to compare tooth size, accessory trait expression, and relative intercusp distance between diphyodont metameres and permanent antimeres. Proportional odds logistic regression was implemented to investigate how the odds of greater accessory cusp expression vary as a function of the distance between early-developing cusps. RESULTS/SIGNIFICANCE Comparing paired molars, significant differences were identified for tooth size and cusp 5 expression. Several relative intercusp distances emerged as important predictors of cusp 6 expression, however, results for cusp 5 and cusp 7 did not match expected patterns. These findings support previous quantitative genetic results and suggest the development of neighboring crown structures represents a zero-sum partitioning of cellular territory and resources. As such, this study contributes to a better understanding of the foundations of deciduous and permanent molar crown variation in humans.
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Affiliation(s)
- Dori E. Kenessey
- Department of Anthropology, U niversity of Nevada, Reno, Nevada, United States of America
| | - Christopher M. Stojanowski
- Center for Bioarchaeological Research, School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, United States of America
| | - Kathleen S. Paul
- Department of Anthropology, University of Arkansas, Fayetteville, Arkansas, United States of America
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2
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Blankenship-Sefczek EC, Goodman AH, Hubbe M, Hunter JP, Guatelli-Steinberg D. Nutritional supplementation, tooth crown size, and trait expression in individuals from Tezonteopan, Mexico. PLoS One 2024; 19:e0305123. [PMID: 38843220 PMCID: PMC11156277 DOI: 10.1371/journal.pone.0305123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 05/23/2024] [Indexed: 06/09/2024] Open
Abstract
Understanding how epigenetic factors impact dental phenotypes can help refine the use of teeth for elucidating biological relationships among human populations. We explored relationships among crown size, principal cusp spacing, and accessory cusp expression in maxillary dental casts of nutritionally supplemented (n = 34) and non-supplemented (n = 39) individuals from Tezonteopan, Mexico. We hypothesized that the non-supplemented group would exhibit smaller molar crowns and reduced intercusp spacing. Since intercusp spacing is thought to be more sensitive to epigenetic influences than crown size, we predicted that the supplemented and non-supplemented groups would differ more in the former than the latter. Previous work suggests that molar accessory cusp expression may be elevated under conditions of stress. We therefore expected evidence of greater Carabelli and Cusp 5 trait expression in the non-supplemented group. We further hypothesized that anterior teeth would be affected by nutritional stress during development, with the non-supplemented group having smaller anterior tooth crowns and therefore limited space to form the tuberculum dentale. Finally, we tested whether the presence of molar accessory traits followed predictions of the Patterning Cascade Model of tooth morphogenesis in the entire sample. Our results supported the expectation that cusp spacing would differ more than molar crown size between the two groups. Carabelli trait showed little evidence of frequency differences between groups, but some evidence of greater trait scores in the non-supplemented group. The non-supplemented group also showed evidence of greater Cusp 5 frequency and expression. In the central incisors and canines, there was strong evidence for smaller crown sizes and reduced tuberculum dentale frequency in the non-supplemented group. With both groups pooled together, there was strong evidence of closer mesiodistal distances among principal cusps in molars with accessory cusps, a finding that is consistent with the PCM. Overall, our findings suggest that nutritional stress may affect accessory cusp expression.
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Affiliation(s)
- Erin C. Blankenship-Sefczek
- Department of Oral Biology, School of Dentistry, Creighton University, Omaha, Nebraska, United States of America
- Department of Anthropology, The Ohio State University, Columbus, Ohio, United States of America
| | - Alan H. Goodman
- School of Natural Sciences, Hampshire College, Amherst, Massachusetts, United States of America
| | - Mark Hubbe
- Department of Anthropology, The Ohio State University, Columbus, Ohio, United States of America
| | - John P. Hunter
- Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Newark, Ohio, United States of America
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3
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Miyazaki J, Kondo S, Tanijiri T, Negishi S. Morphological differences between the first and second maxillary premolar crowns: A three-dimensional surface homologous modeling analysis. J Oral Biosci 2024; 66:20-25. [PMID: 38280717 DOI: 10.1016/j.job.2024.01.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 01/21/2024] [Accepted: 01/22/2024] [Indexed: 01/29/2024]
Abstract
OBJECTIVES The current study used a three-dimensional (3D) surface homologous modeling to analyze the structure of maxillary first premolar (P1) and second premolar (P2) crowns, to identify any morphological differences between them, particularly in their cuspal structures. METHODS The study sample comprised 27 male elementary and junior high school students from Chiba Prefecture, Japan. Plaster casts were collected and the 3D coordinates were used to measure the crown structures. Thereafter, principal component (PC) analysis was carried out using the 3D coordinates of the homologous models, containing 4498 anatomical data points, including 9 landmarks. RESULTS The findings indicated that P1 was significantly larger than P2, despite both teeth exhibiting similar intercuspal distances. The homologous model analysis revealed that 61.5 % of the total variance could be explained up to the fourth PC. Overall size and shape in the mesiodistal and buccolingual directions were estimated using PC1 and PC2, respectively. Both components highlighted a shape factor, indicating that the buccal cusp was more well-developed than the lingual cusp in P1 compared to P2. CONCLUSIONS The variations in the size of the mesial and distal premolar teeth and the relationships between the cusps in the completed tooth crowns can be explained using molecular biology developmental models.
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Affiliation(s)
- Julie Miyazaki
- Department of Orthodontics, School of Dentistry at Matsudo, Nihon University, Chiba, Japan
| | - Shintaro Kondo
- Research Institute of Oral Science, School of Dentistry at Matsudo, Nihon University, Chiba, Japan.
| | | | - Shinichi Negishi
- Department of Orthodontics, School of Dentistry at Matsudo, Nihon University, Chiba, Japan
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4
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Miyazaki J, Kondo S, Negishi S. Sexual dimorphism in the three-dimensional detailed crown structure of maxillary first premolars. J Oral Biosci 2024; 66:13-19. [PMID: 38097173 DOI: 10.1016/j.job.2023.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/06/2023] [Accepted: 12/08/2023] [Indexed: 03/08/2024]
Abstract
OBJECTIVES Maxillary first premolars have a unique shape because of their curvature features, positional relationship of the cusps, and most prominent points, making them different from other teeth. This study aimed to quantitatively analyze the detailed three-dimensional morphometric structure of maxillary first premolars and sexual dimorphism. METHODS The study participants were 60 elementary and junior high school students (30 boys and 30 girls) in Japan. The distance between landmarks was measured using the three-dimensional coordinates of plaster casts, and the data collected was statistically analyzed. RESULTS Sexual dimorphism was greater in the lingual cusp, showing greater variation in size than the buccal cusp. Boys exhibited significantly larger relative distances in the mesiodistal and buccolingual directions than girls; particularly, regarding mesiodistal diameter of the central groove, mesial slope of the buccal cusp, and distal slope of the lingual cusp. These results may be due to a slight difference in the timing of secondary enamel knots between boys and girls during the developmental stage, which was reflected in the sexual dimorphism of the completed teeth. Curvature features, cusp positions, and most prominent points were considered individual traits because they were not interrelated. CONCLUSIONS Subtle differences during the developmental stage may lead to sexual dimorphism of the completed crown. Furthermore, the morphological characteristics of the maxillary first premolars may be related to their location in the dental arch.
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Affiliation(s)
- Julie Miyazaki
- Department of Orthodontics, School of Dentistry at Matsudo, Nihon University, Chiba, Japan
| | - Shintaro Kondo
- Research Institute of Oral Science, School of Dentistry at Matsudo, Nihon University, Chiba, Japan.
| | - Shinichi Negishi
- Department of Orthodontics, School of Dentistry at Matsudo, Nihon University, Chiba, Japan
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5
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Selig KR. Hypoconulid loss in cercopithecins: Functional and developmental considerations. J Hum Evol 2024; 187:103479. [PMID: 38181576 DOI: 10.1016/j.jhevol.2023.103479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 11/28/2023] [Accepted: 11/28/2023] [Indexed: 01/07/2024]
Abstract
Cercopithecins differ from papionins in lacking a M3 hypoconulid. Although this loss may be related to dietary differences, the functional and developmental ramifications of hypoconulid loss are currently unclear. The following makes use of dental topographic analysis to quantify shape variation in a sample of cercopithecin M3s, as well as in a sample of Macaca, which has a hypoconulid. To help understand the consequences of hypoconulid loss, Macaca M3s were virtually cropped to remove the hypoconulid and were also subjected to dental topographic analysis. The patterning cascade model and the inhibitory cascade model attempt to explain variation in cusp pattern and molar proportions, respectively. These models have both previously been used to explain patterns of variation in cercopithecines, but have not been examined in the context of hypoconulid loss. For example, previous work suggests that earlier developing cusps impact the development of later developing cusps (i.e., the hypoconulid) and that cercopithecines do not conform to the predictions of the inhibitory cascade model in that the size of the molars is not linear moving distally. Results of the current study suggest that the loss of the hypoconulid is associated with a reduction in dental topography among cercopithecins, which is potentially related to diet, although the connection to diet is not necessarily clear. Results also suggest that the loss of the hypoconulid can be explained by the patterning cascade model, and that hypoconulid loss explains the apparent lack of support for the inhibitory cascade model among cercopithecines. These findings highlight the importance of a holistic approach to studying variation in molar proportions and developmental models.
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Affiliation(s)
- Keegan R Selig
- Department of Evolutionary Anthropology, Duke University, Biological Sciences Building, 130 Science Drive, Durham, NC, 27708, USA.
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6
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Nadolski EM, Moczek AP. Promises and limits of an agency perspective in evolutionary developmental biology. Evol Dev 2023; 25:371-392. [PMID: 37038309 DOI: 10.1111/ede.12432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 01/23/2023] [Accepted: 03/02/2023] [Indexed: 04/12/2023]
Abstract
An agent-based perspective in the study of complex systems is well established in diverse disciplines, yet is only beginning to be applied to evolutionary developmental biology. In this essay, we begin by defining agency and associated terminology formally. We then explore the assumptions and predictions of an agency perspective, apply these to select processes and key concept areas relevant to practitioners of evolutionary developmental biology, and consider the potential epistemic roles that an agency perspective might play in evo devo. Throughout, we discuss evidence supportive of agential dynamics in biological systems relevant to evo devo and explore where agency thinking may enrich the explanatory reach of research efforts in evolutionary developmental biology.
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Affiliation(s)
- Erica M Nadolski
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - Armin P Moczek
- Department of Biology, Indiana University, Bloomington, Indiana, USA
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Chapple SA, Skinner MM. A tooth crown morphology framework for interpreting the diversity of primate dentitions. Evol Anthropol 2023; 32:240-255. [PMID: 37486115 DOI: 10.1002/evan.21994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 03/25/2023] [Accepted: 06/19/2023] [Indexed: 07/25/2023]
Abstract
Variation in tooth crown morphology plays a crucial role in species diagnoses, phylogenetic inference, and the reconstruction of the evolutionary history of the primate clade. While a growing number of studies have identified developmental mechanisms linked to tooth size and cusp patterning in mammalian crown morphology, it is unclear (1) to what degree these are applicable across primates and (2) which additional developmental mechanisms should be recognized as playing important roles in odontogenesis. From detailed observations of lower molar enamel-dentine junction morphology from taxa representing the major primate clades, we outline multiple phylogenetic and developmental components responsible for crown patterning, and formulate a tooth crown morphology framework for the holistic interpretation of primate crown morphology. We suggest that adopting this framework is crucial for the characterization of tooth morphology in studies of dental development, discrete trait analysis, and systematics.
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Affiliation(s)
- Simon A Chapple
- School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Matthew M Skinner
- School of Anthropology and Conservation, University of Kent, Canterbury, UK
- Department of Human Origins, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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A Mutation in CACNA1S Is Associated with Multiple Supernumerary Cusps and Root Maldevelopment. Diagnostics (Basel) 2023; 13:diagnostics13050895. [PMID: 36900039 PMCID: PMC10000453 DOI: 10.3390/diagnostics13050895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 02/21/2023] [Accepted: 02/23/2023] [Indexed: 03/03/2023] Open
Abstract
BACKGROUND Enamel knots and Hertwig epithelial root sheath (HERS) regulate the growth and folding of the dental epithelium, which subsequently determines the final form of tooth crown and roots. We would like to investigate the genetic etiology of seven patients affected with unique clinical manifestations, including multiple supernumerary cusps, single prominent premolars, and single-rooted molars. METHODS Oral and radiographic examination and whole-exome or Sanger sequencing were performed in seven patients. Immunohistochemical study during early tooth development in mice was performed. RESULTS A heterozygous variant (c. 865A>G; p.Ile289Val) in CACNA1S was identified in all the patients, but not in an unaffected family member and control. Immunohistochemical study showed high expression of Cacna1s in the secondary enamel knot. CONCLUSIONS This CACNA1S variant seemed to cause impaired dental epithelial folding; too much folding in the molars and less folding in the premolars; and delayed folding (invagination) of HERS, which resulted in single-rooted molars or taurodontism. Our observation suggests that the mutation in CACNA1S might disrupt calcium influx, resulting in impaired dental epithelium folding, and subsequent abnormal crown and root morphology.
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9
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Chapple SA, Skinner MM. Primate tooth crown nomenclature revisited. PeerJ 2023; 11:e14523. [PMID: 36650833 PMCID: PMC9840859 DOI: 10.7717/peerj.14523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 11/15/2022] [Indexed: 01/15/2023] Open
Abstract
Cusp patterning on living and extinct primate molar teeth plays a crucial role in species diagnoses, phylogenetic inference, and the reconstruction of the evolutionary history of the primate clade. These studies rely on a system of nomenclature that can accurately identify and distinguish between the various structures of the crown surface. However, studies at the enamel-dentine junction (EDJ) of some primate taxa have demonstrated a greater degree of cusp variation and expression at the crown surface than current systems of nomenclature allow. In this study, we review the current nomenclature and its applicability across all the major primate clades based on investigations of mandibular crown morphology at the enamel-dentine junction revealed through microtomography. From these observations, we reveal numerous new patterns of lower molar accessory cusp expression in primates. We highlight numerous discrepancies between the expected patterns of variation inferred from the current academic literature, and the new patterns of expected variation seen in this study. Based on the current issues associated with the crown nomenclature, and an incomplete understanding of the precise developmental processes associated with each individual crown feature, we introduce these structures within a conservative, non-homologous naming scheme that focuses on simple location-based categorisations. Until there is a better insight into the developmental and phylogenetic origin of these crown features, these categorisations are the most practical way of addressing these structures. Until then, we also suggest the cautious use of accessory cusps for studies of taxonomy and phylogeny.
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Affiliation(s)
- Simon A. Chapple
- School of Anthropology and Conservation, University of Kent at Canterbury, Canterbury, Kent, United Kingdom
| | - Matthew M. Skinner
- School of Anthropology and Conservation, University of Kent at Canterbury, Canterbury, Kent, United Kingdom,Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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10
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Harano T, Asahara M. The anteriorization of tooth position underlies the atavism of tooth morphology: Insights into the morphogenesis of mammalian molars. Evolution 2022; 76:2986-3000. [PMID: 36200621 DOI: 10.1111/evo.14637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 08/29/2022] [Accepted: 09/15/2022] [Indexed: 01/22/2023]
Abstract
The evolution and development of complex molars as a key innovation in mammals have long been of interest yet remain poorly understood. With reference to century-old theories and modern findings, we focused on the teeth of pinnipeds (Carnivora) and cetaceans (Cetartiodactyla), which are morphologically simple compared with those of other mammals, and thus can be considered a reversal toward the ancestral state of nonmammalian synapsids. By reconstructing the evolutionary history of tooth complexity for the phylogenies of Carnivora and Cetartiodactyla, we established that a secondary evolution of simple teeth from more complex molars has occurred independently multiple times. Our phylogenetic comparative analyses showed that a simplification in tooth morphology was correlated with a more anterior dentition position relative to the component bones of the upper jaw in both Carnivora and Cetartiodactyla. These results suggest that the anterior shift of tooth position relative to the morphogenetic fields present in the jaw contributed to the evolutionary simplification in molar morphology. Our findings provide insights into the developmental basis of complex mammalian dentition.
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Affiliation(s)
- Tomohiro Harano
- Division of Liberal Arts and Sciences, Aichi Gakuin University, Nisshin, 470-0195, Japan
| | - Masakazu Asahara
- Division of Liberal Arts and Sciences, Aichi Gakuin University, Nisshin, 470-0195, Japan
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11
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Measuring Molarization: Change Through Time in Premolar Function in An Extinct Stem Primate Lineage. J MAMM EVOL 2022. [DOI: 10.1007/s10914-022-09623-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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12
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Brun-Usan M, Zimm R, Uller T. Beyond genotype-phenotype maps: Toward a phenotype-centered perspective on evolution. Bioessays 2022; 44:e2100225. [PMID: 35863907 DOI: 10.1002/bies.202100225] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 06/30/2022] [Accepted: 07/04/2022] [Indexed: 11/08/2022]
Abstract
Evolutionary biology is paying increasing attention to the mechanisms that enable phenotypic plasticity, evolvability, and extra-genetic inheritance. Yet, there is a concern that these phenomena remain insufficiently integrated within evolutionary theory. Understanding their evolutionary implications would require focusing on phenotypes and their variation, but this does not always fit well with the prevalent genetic representation of evolution that screens off developmental mechanisms. Here, we instead use development as a starting point, and represent it in a way that allows genetic, environmental and epigenetic sources of phenotypic variation to be independent. We show why this representation helps to understand the evolutionary consequences of both genetic and non-genetic phenotype determinants, and discuss how this approach can instigate future areas of empirical and theoretical research.
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Affiliation(s)
- Miguel Brun-Usan
- Department of Biology, Lund University, 22362, Lund, Sweden.,Institute for Life Sciences/Electronics and Computer Science, University of Southampton, SO17 1BJ, Southampton, UK
| | - Roland Zimm
- Ecole Normale Supérieure de Lyon, Institute de Génomique Fonctionnelle de Lyon, Lyon, France
| | - Tobias Uller
- Institute for Life Sciences/Electronics and Computer Science, University of Southampton, SO17 1BJ, Southampton, UK
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Abstract
AbstractEvolvability is best addressed from a multi-level, macroevolutionary perspective through a comparative approach that tests for among-clade differences in phenotypic diversification in response to an opportunity, such as encountered after a mass extinction, entering a new adaptive zone, or entering a new geographic area. Analyzing the dynamics of clades under similar environmental conditions can (partially) factor out shared external drivers to recognize intrinsic differences in evolvability, aiming for a macroevolutionary analog of a common-garden experiment. Analyses will be most powerful when integrating neontological and paleontological data: determining differences among extant populations that can be hypothesized to generate large-scale, long-term contrasts in evolvability among clades; or observing large-scale differences among clade histories that can by hypothesized to reflect contrasts in genetics and development observed directly in extant populations. However, many comparative analyses can be informative on their own, as explored in this overview. Differences in clade-level evolvability can be visualized in diversity-disparity plots, which can quantify positive and negative departures of phenotypic productivity from stochastic expectations scaled to taxonomic diversification. Factors that evidently can promote evolvability include modularity—when selection aligns with modular structure or with morphological integration patterns; pronounced ontogenetic changes in morphology, as in allometry or multiphase life cycles; genome size; and a variety of evolutionary novelties, which can also be evaluated using macroevolutionary lags between the acquisition of a trait and phenotypic diversification, and dead-clade-walking patterns that may signal a loss of evolvability when extrinsic factors can be excluded. High speciation rates may indirectly foster phenotypic evolvability, and vice versa. Mechanisms are controversial, but clade evolvability may be higher in the Cambrian, and possibly early in the history of clades at other times; in the tropics; and, for marine organisms, in shallow-water disturbed habitats.
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Morita W, Morimoto N, Otsu K, Miura T. Stripe and spot selection in cusp patterning of mammalian molar formation. Sci Rep 2022; 12:9149. [PMID: 35701484 PMCID: PMC9197828 DOI: 10.1038/s41598-022-13539-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 05/25/2022] [Indexed: 11/09/2022] Open
Abstract
Tooth development is governed largely by epithelial-mesenchymal interactions and is mediated by numerous signaling pathways. This type of morphogenetic processes has been explained by reaction-diffusion systems, especially in the framework of a Turing model. Here we focus on morphological and developmental differences between upper and lower molars in mice by modeling 2D pattern formation in a Turing system. Stripe vs. spot patterns are the primary types of variation in a Turing model. We show that the complexity of the cusp cross-sections can distinguish between stripe vs. spot patterns, and mice have stripe-like upper and spot-like lower molar morphologies. Additionally, our computational modeling that incorporates empirical data on tooth germ growth traces the order of cusp formation and relative position of the cusps in upper and lower molars in mice. We further propose a hypothetical framework of developmental mechanism that could help us understand the evolution of the highly variable nature of mammalian molars associated with the acquisition of the hypocone and the increase of lophedness.
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Affiliation(s)
- Wataru Morita
- Department of Anthropology, National Museum of Nature and Science, Ibaraki, Japan.
| | - Naoki Morimoto
- Laboratory of Physical Anthropology, Department of Zoology, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Keishi Otsu
- Division of Developmental Biology and Regenerative Medicine, Department of Anatomy, Iwate Medical University, Iwate, Japan
| | - Takashi Miura
- Department of Anatomy and Cell Biology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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15
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Paul KS, Stojanowski CM, Hughes T, Brook AH, Townsend GC. Genetic Correlation, Pleiotropy, and Molar Morphology in a Longitudinal Sample of Australian Twins and Families. Genes (Basel) 2022; 13:genes13060996. [PMID: 35741762 PMCID: PMC9222655 DOI: 10.3390/genes13060996] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 05/24/2022] [Accepted: 05/25/2022] [Indexed: 01/01/2023] Open
Abstract
This study aims to expand our understanding of the genetic architecture of crown morphology in the human diphyodont dentition. Here, we present bivariate genetic correlation estimates for deciduous and permanent molar traits and evaluate the patterns of pleiotropy within (e.g., m1–m2) and between (e.g., m2–M1) dentitions. Morphology was observed and scored from dental models representing participants of an Australian twin and family study (deciduous n = 290, permanent n = 339). Data collection followed Arizona State University Dental Anthropology System standards. Genetic correlation estimates were generated using maximum likelihood variance components analysis in SOLAR v.8.1.1. Approximately 23% of deciduous variance components models and 30% of permanent variance components models yielded significant genetic correlation estimates. By comparison, over half (56%) of deciduous–permanent homologues (e.g., m2 hypocone–M1 hypocone) were significantly genetically correlated. It is generally assumed that the deciduous and permanent molars represent members of a meristic molar field emerging from the primary dental lamina. However, stronger genetic integration among m2–M1/M2 homologues than among paired deciduous traits suggests the m2 represents the anterior-most member of a “true” molar field. The results indicate genetic factors act at distinct points throughout development to generate homologous molar form, starting with the m2, which is later replaced by a permanent premolariform crown.
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Affiliation(s)
- Kathleen S. Paul
- Department of Anthropology, University of Arkansas, Fayetteville, AR 72701, USA
- Correspondence: ; Tel.: +1-479-718-1352
| | - Christopher M. Stojanowski
- Center for Bioarchaeological Research, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, USA;
| | - Toby Hughes
- Adelaide Dental School, The University of Adelaide, Adelaide, SA 5005, Australia; (T.H.); (A.H.B.)
| | - Alan H. Brook
- Adelaide Dental School, The University of Adelaide, Adelaide, SA 5005, Australia; (T.H.); (A.H.B.)
- Barts and the London Dental Institute, Queen Mary University of London, London EC1M 6AX, UK
| | - Grant C. Townsend
- Adelaide Dental School, The University of Adelaide, Adelaide, SA 5005, Australia; (T.H.); (A.H.B.)
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Bermúdez de Castro JM, García-Campos C, Sarmiento S, Martinón-Torres M. The protoconid: a key cusp in lower molars. Evidence from a recent modern human population. Ann Hum Biol 2022; 49:145-151. [PMID: 35521995 DOI: 10.1080/03014460.2022.2074539] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
BACKGROUND The molar (M) size sequence in the genus Homo is decreasing and the general pattern in Homo sapiens is M1 > M2 > M3. AIM To gain a better understanding of the reduction patterns of molar components (cusps), we aim to assess the area of the protoconid, the phylogenetically oldest cusp of the lower molars. SUBJECT AND METHODS We measured the protoconid and the total crown area in the scaled photographs of a recent modern human sample of lower molars (76 males and 39 females). The values were statistically analysed. RESULTS The absolute size of the protoconid increases significantly between M1 and M2/M3, whereas the relative size of this cusp increases significantly from M1 to M3. In the latter, reduction or disappearance of the cusps of the talonid is common. CONCLUSIONS The results can be explained in the framework of the patterning cascade model. As the first cusp to appear developmentally, the protoconid forms in response to signals from the primary enamel knot, likely contributing to its stability. Inhibitory signals emitted during the protoconid formation may lead to the reduction or disappearance of the talonid cusps, if these do not have enough time to form before the end of the molar morphogenetic process.
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Affiliation(s)
- José María Bermúdez de Castro
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH). Paseo de la Sierra de Atapuerca 3, 09002, Burgos, Spain.,Anthropology Department, University College London, London, UK
| | - Cecilia García-Campos
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH). Paseo de la Sierra de Atapuerca 3, 09002, Burgos, Spain
| | - Susana Sarmiento
- Universidad Isabel I, Calle de Fernán González, 76, 09003 Burgos, Spain
| | - María Martinón-Torres
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH). Paseo de la Sierra de Atapuerca 3, 09002, Burgos, Spain.,Anthropology Department, University College London, London, UK
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17
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The biological significance of tooth identification based on developmental and evolutional viewpoints. J Oral Biosci 2022; 64:287-302. [DOI: 10.1016/j.job.2022.05.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Revised: 05/11/2022] [Accepted: 05/13/2022] [Indexed: 11/22/2022]
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18
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Riederer JM, Tiso S, van Eldijk TJ, Weissing FJ. Capturing the facets of evolvability in a mechanistic framework. Trends Ecol Evol 2022; 37:430-439. [DOI: 10.1016/j.tree.2022.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 01/13/2022] [Accepted: 01/18/2022] [Indexed: 10/19/2022]
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19
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Phenotyping in the era of genomics: MaTrics—a digital character matrix to document mammalian phenotypic traits. Mamm Biol 2021. [DOI: 10.1007/s42991-021-00192-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
AbstractA new and uniquely structured matrix of mammalian phenotypes, MaTrics (Mammalian Traits for Comparative Genomics) in a digital form is presented. By focussing on mammalian species for which genome assemblies are available, MaTrics provides an interface between mammalogy and comparative genomics.MaTrics was developed within a project aimed to find genetic causes of phenotypic traits of mammals using Forward Genomics. This approach requires genomes and comprehensive and recorded information on homologous phenotypes that are coded as discrete categories in a matrix. MaTrics is an evolving online resource providing information on phenotypic traits in numeric code; traits are coded either as absent/present or with several states as multistate. The state record for each species is linked to at least one reference (e.g., literature, photographs, histological sections, CT scans, or museum specimens) and so MaTrics contributes to digitalization of museum collections. Currently, MaTrics covers 147 mammalian species and includes 231 characters related to structure, morphology, physiology, ecology, and ethology and available in a machine actionable NEXUS-format*. Filling MaTrics revealed substantial knowledge gaps, highlighting the need for phenotyping efforts. Studies based on selected data from MaTrics and using Forward Genomics identified associations between genes and certain phenotypes ranging from lifestyles (e.g., aquatic) to dietary specializations (e.g., herbivory, carnivory). These findings motivate the expansion of phenotyping in MaTrics by filling research gaps and by adding taxa and traits. Only databases like MaTrics will provide machine actionable information on phenotypic traits, an important limitation to genomics. MaTrics is available within the data repository Morph·D·Base (www.morphdbase.de).
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20
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Lafuma F, Corfe IJ, Clavel J, Di-Poï N. Multiple evolutionary origins and losses of tooth complexity in squamates. Nat Commun 2021; 12:6001. [PMID: 34650041 PMCID: PMC8516937 DOI: 10.1038/s41467-021-26285-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 09/27/2021] [Indexed: 11/21/2022] Open
Abstract
Teeth act as tools for acquiring and processing food, thus holding a prominent role in vertebrate evolution. In mammals, dental-dietary adaptations rely on tooth complexity variations controlled by cusp number and pattern. Complexity increase through cusp addition has dominated the diversification of mammals. However, studies of Mammalia alone cannot reveal patterns of tooth complexity conserved throughout vertebrate evolution. Here, we use morphometric and phylogenetic comparative methods across fossil and extant squamates to show they also repeatedly evolved increasingly complex teeth, but with more flexibility than mammals. Since the Late Jurassic, multiple-cusped teeth evolved over 20 times independently from a single-cusped common ancestor. Squamates frequently lost cusps and evolved varied multiple-cusped morphologies at heterogeneous rates. Tooth complexity evolved in correlation with changes in plant consumption, resulting in several major increases in speciation. Complex teeth played a critical role in vertebrate evolution outside Mammalia, with squamates exemplifying a more labile system of dental-dietary evolution.
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Affiliation(s)
- Fabien Lafuma
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, FI-00014, Helsinki, Finland.
| | - Ian J Corfe
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, FI-00014, Helsinki, Finland.
- Geological Survey of Finland, FI-02150, Espoo, Finland.
| | - Julien Clavel
- Department of Life Sciences, The Natural History Museum, London, SW7 5BD, UK
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France
| | - Nicolas Di-Poï
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, FI-00014, Helsinki, Finland.
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21
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Paul KS, Stojanowski CM, Hughes T, Brook A, Townsend GC. The genetic architecture of anterior tooth morphology in a longitudinal sample of Australian twins and families. Arch Oral Biol 2021; 129:105168. [PMID: 34174590 DOI: 10.1016/j.archoralbio.2021.105168] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 05/24/2021] [Accepted: 05/25/2021] [Indexed: 12/21/2022]
Abstract
OBJECTIVE This study presents a quantitative genetic analysis of human anterior dental morphology in a longitudinal sample of known genealogy. The primary aim of this work is to generate a suite of genetic correlations within and between deciduous and permanent characters to access patterns of integration across the diphyodont dental complex. DESIGN Data were recorded from casted tooth crowns representing participants of a long-term Australian twin and family study (deciduous n = 290, permanent n = 339). Morphological trait expression was observed and scored following Arizona State University Dental Anthropology System standards. Bivariate genetic correlations were estimated using maximum likelihood variance decomposition models in SOLAR v.8.1.1. RESULTS Genetic correlation estimates indicate high levels of integration between antimeres but low to moderate levels among traits within a tooth row. Only 9% of deciduous model comparisons were significant, while pleiotropy was indicated for one third of permanent trait pairs. Canine characters stood out as strongly integrated, especially in the deciduous dentition. For homologous characters across dentitions (e.g., deciduous i1 shoveling and permanent I1 shoveling), ∼70% of model comparisons yielded significant genetic correlations. CONCLUSIONS Patterns of genetic correlation suggest a morphological canine module that spans the primary and secondary dentition. Results also point to the existence of a genetic mechanism conserving morphology across the diphyodont dental complex, such that paired deciduous and permanent traits are more strongly integrated than characters within individual tooth rows/teeth.
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Affiliation(s)
- Kathleen S Paul
- Department of Anthropology, University of Arkansas, Fayetteville, AR 72701, United States.
| | - Christopher M Stojanowski
- Center for Bioarchaeological Research, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, United States
| | - Toby Hughes
- Adelaide Dental School, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Alan Brook
- Adelaide Dental School, The University of Adelaide, Adelaide, SA 5005, Australia; Barts and the London Dental Institute, Queen Mary University of London, London, E1, UK
| | - Grant C Townsend
- Adelaide Dental School, The University of Adelaide, Adelaide, SA 5005, Australia
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22
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Developmental influence on evolutionary rates and the origin of placental mammal tooth complexity. Proc Natl Acad Sci U S A 2021; 118:2019294118. [PMID: 34083433 PMCID: PMC8202019 DOI: 10.1073/pnas.2019294118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Interactions during development among genes, cells, and tissues can favor the more frequent generation of some trait variants compared with others. This developmental bias has often been considered to constrain adaptation, but its exact influence on evolution is poorly understood. Using computer simulations of development, we provide evidence that molecules promoting the formation of mammalian tooth cusps could help accelerate tooth complexity evolution. Only relatively small developmental changes were needed to derive the more complex, rectangular upper molar typical of early placental mammals from the simpler triangular ancestral pattern. Development may therefore have enabled the relatively fast divergence of the early placental molar dentition. Development has often been viewed as a constraining force on morphological adaptation, but its precise influence, especially on evolutionary rates, is poorly understood. Placental mammals provide a classic example of adaptive radiation, but the debate around rate and drivers of early placental evolution remains contentious. A hallmark of early dental evolution in many placental lineages was a transition from a triangular upper molar to a more complex upper molar with a rectangular cusp pattern better specialized for crushing. To examine how development influenced this transition, we simulated dental evolution on “landscapes” built from different parameters of a computational model of tooth morphogenesis. Among the parameters examined, we find that increases in the number of enamel knots, the developmental precursors of the tooth cusps, were primarily influenced by increased self-regulation of the molecular activator (activation), whereas the pattern of knots resulted from changes in both activation and biases in tooth bud growth. In simulations, increased activation facilitated accelerated evolutionary increases in knot number, creating a lateral knot arrangement that evolved at least ten times on placental upper molars. Relatively small increases in activation, superimposed on an ancestral tritubercular molar growth pattern, could recreate key changes leading to a rectangular upper molar cusp pattern. Tinkering with tooth bud geometry varied the way cusps initiated along the posterolingual molar margin, suggesting that small spatial variations in ancestral molar growth may have influenced how placental lineages acquired a hypocone cusp. We suggest that development could have enabled relatively fast higher-level divergence of the placental molar dentition.
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23
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Correlation structure of the cheek teeth enamel crown patterns in the genus Equus (Mammalia: Equidae): an analysis by geometric morphometrics with outline points. RUSSIAN JOURNAL OF THERIOLOGY 2021. [DOI: 10.15298/rusjtheriol.20.1.08] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Saeki N, Inui-Yamamoto C, Kuraki M, Itoh S, Inubushi T, Okamoto M, Akiyama S, Wakisaka S, Abe M. Senescence-accelerated mouse prone 8 (SAMP8) mice exhibit reduced entoconid in the lower second molar. Arch Oral Biol 2021; 128:105172. [PMID: 34058725 DOI: 10.1016/j.archoralbio.2021.105172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 05/18/2021] [Accepted: 05/24/2021] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The position and size of the major cusps in mammalian molars are arranged in a characteristic pattern that depends on taxonomy. In humans, the cusp which locates distally within each molar is smaller than the mesially located cusp, which is referred to as "distal reduction". Although this concept has been well-recognized, it is still unclear how this reduction occurs. Current study examined whether senescence-accelerating mouse prone 8 (SAMP8) mice could be a possible animal model for studying how the mammalian molar cusp size is determined. DESIGN SAMP8 mice were compared with parental control (SAMR1) mice. Microcomputed tomography images of young and aged mice were captured to observe molar cusp morphologies. Cusp height from cement-enamel junction and mesio-distal length of molars were measured. The statistical comparison of the measurements was performed by Mann-Whitney U test. RESULTS SAMP8 mice showed reduced development of the disto-lingual cusp (entoconid) of lower second molar when compared with SAMR1 mice. The enamel thickness and structure was disturbed at entoconid, and aged SAMP8 mice displayed severe wear of the entoconid in lower second molar. These phenotypes were observed on both sides of the lower second molar. CONCLUSIONS In addition to the general senescence phenotype observed in SAMP8 mice, this strain may genetically possess molar cusp phenotypes which is determined prenatally. Further, SAMP8 mice would be a potential model strain to study the genetic causes of the distal reduction of molar cusp size.
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Affiliation(s)
- Naoya Saeki
- Department of Oral Anatomy and Developmental Biology, Osaka University Graduate School of Dentistry, Yamada-oka 1-8, Suita, Osaka, Japan; Division of Special Care Dentistry, Osaka University Dental Hospital, Osaka, Japan
| | - Chizuko Inui-Yamamoto
- Department of Oral Anatomy and Developmental Biology, Osaka University Graduate School of Dentistry, Yamada-oka 1-8, Suita, Osaka, Japan
| | - Moe Kuraki
- Department of Oral Anatomy and Developmental Biology, Osaka University Graduate School of Dentistry, Yamada-oka 1-8, Suita, Osaka, Japan
| | - Shousaku Itoh
- Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Osaka, Japan
| | - Toshihiro Inubushi
- Department of Orthodontics and Dentofacial Orthopedics, Osaka University Graduate School of Dentistry, Osaka, Japan
| | - Motoki Okamoto
- Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Osaka, Japan
| | - Shigehisa Akiyama
- Division of Special Care Dentistry, Osaka University Dental Hospital, Osaka, Japan
| | - Satoshi Wakisaka
- Department of Oral Anatomy and Developmental Biology, Osaka University Graduate School of Dentistry, Yamada-oka 1-8, Suita, Osaka, Japan
| | - Makoto Abe
- Department of Oral Anatomy and Developmental Biology, Osaka University Graduate School of Dentistry, Yamada-oka 1-8, Suita, Osaka, Japan.
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25
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Davies TW, Alemseged Z, Gidna A, Hublin JJ, Kimbel WH, Kullmer O, Spoor F, Zanolli C, Skinner MM. Accessory cusp expression at the enamel-dentine junction of hominin mandibular molars. PeerJ 2021; 9:e11415. [PMID: 34055484 PMCID: PMC8141287 DOI: 10.7717/peerj.11415] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 04/16/2021] [Indexed: 11/20/2022] Open
Abstract
Studies of hominin dental morphology frequently consider accessory cusps on the lower molars, in particular those on the distal margin of the tooth (C6 or distal accessory cusp) and the lingual margin of the tooth (C7 or lingual accessory cusp). They are often utilized in studies of hominin systematics, where their presence or absence is assessed at the outer enamel surface (OES). However, studies of the enamel-dentine junction (EDJ) suggest these traits may be more variable in development, morphology and position than previously thought. Building on these studies, we outline a scoring procedure for the EDJ expression of these accessory cusps that considers the relationship between these accessory cusps and the surrounding primary cusps. We apply this scoring system to a sample of Plio-Pleistocene hominin mandibular molars of Paranthropus robustus, Paranthropus boisei, Australopithecus afarensis, Australopithecus africanus, Homo sp., Homo habilis and Homo erectus from Africa and Asia (n = 132). We find that there are taxon-specific patterns in accessory cusp expression at the EDJ that are consistent with previous findings at the OES. For example, P. robustus M1s and M2s very often have a distal accessory cusp but no lingual accessory cusp, while H. habilis M1s and M2s show the opposite pattern. The EDJ also reveals a number of complicating factors; some apparent accessory cusps at the enamel surface are represented at the EDJ only by shouldering on the ridges associated with the main cusps, while other accessory cusps appear to have little or no EDJ expression at all. We also discuss the presence of double and triple accessory cusps, including the presence of a double lingual accessory cusp on the distal ridge of the metaconid in the type specimen of H. habilis (OH 7–M1) that is not clear at the OES due to occlusal wear. Overall, our observations, as well as our understanding of the developmental underpinnings of cusp patterning, suggest that we should be cautious in our comparisons of accessory cusps for taxonomic interpretations.
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Affiliation(s)
- Thomas W Davies
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Zeresenay Alemseged
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois, United States
| | - Agness Gidna
- Paleontology Unit, National Museum of Tanzania, Dar es Salaam, Tanzania
| | - Jean-Jacques Hublin
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.,Collège de France, Paris, France
| | - William H Kimbel
- Institute of Human Origins, and School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, United States
| | - Ottmar Kullmer
- Department of Paleobiology and Environment, Institute of Ecology, Evolution, and Diversity, Goethe University, Frankfurt, Germany.,Department of Palaeoanthropology, Senckenberg Research Institute and Natural History Museum Frankfurt, Frankfurt am Main, Germany
| | - Fred Spoor
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.,Centre for Human Evolution Research, Department of Earth Sciences, Natural History Museum, London, United Kingdom.,Department of Anthropology, University College London, London, United Kingdom
| | - Clément Zanolli
- Univ. Bordeaux, CNRS, MCC, PACEA, UMR 5199, F-33600 Pessac, France
| | - Matthew M Skinner
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.,School of Anthropology and Conservation, University of Kent, Canterbury, United Kingdom.,Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
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26
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Evans AR, Pollock TI, Cleuren SGC, Parker WMG, Richards HL, Garland KLS, Fitzgerald EMG, Wilson TE, Hocking DP, Adams JW. A universal power law for modelling the growth and form of teeth, claws, horns, thorns, beaks, and shells. BMC Biol 2021; 19:58. [PMID: 33781258 PMCID: PMC8008625 DOI: 10.1186/s12915-021-00990-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 02/22/2021] [Indexed: 11/29/2022] Open
Abstract
Background A major goal of evolutionary developmental biology is to discover general models and mechanisms that create the phenotypes of organisms. However, universal models of such fundamental growth and form are rare, presumably due to the limited number of physical laws and biological processes that influence growth. One such model is the logarithmic spiral, which has been purported to explain the growth of biological structures such as teeth, claws, horns, and beaks. However, the logarithmic spiral only describes the path of the structure through space, and cannot generate these shapes. Results Here we show a new universal model based on a power law between the radius of the structure and its length, which generates a shape called a ‘power cone’. We describe the underlying ‘power cascade’ model that explains the extreme diversity of tooth shapes in vertebrates, including humans, mammoths, sabre-toothed cats, tyrannosaurs and giant megalodon sharks. This model can be used to predict the age of mammals with ever-growing teeth, including elephants and rodents. We view this as the third general model of tooth development, along with the patterning cascade model for cusp number and spacing, and the inhibitory cascade model that predicts relative tooth size. Beyond the dentition, this new model also describes the growth of claws, horns, antlers and beaks of vertebrates, as well as the fangs and shells of invertebrates, and thorns and prickles of plants. Conclusions The power cone is generated when the radial power growth rate is unequal to the length power growth rate. The power cascade model operates independently of the logarithmic spiral and is present throughout diverse biological systems. The power cascade provides a mechanistic basis for the generation of these pointed structures across the tree of life. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-00990-w.
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Affiliation(s)
- Alistair R Evans
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia. .,Geosciences, Museums Victoria, Melbourne, Victoria, 3001, Australia.
| | - Tahlia I Pollock
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - Silke G C Cleuren
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - William M G Parker
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - Hazel L Richards
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - Kathleen L S Garland
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - Erich M G Fitzgerald
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia.,Geosciences, Museums Victoria, Melbourne, Victoria, 3001, Australia
| | - Tim E Wilson
- School of Mathematical Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - David P Hocking
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia.,Geosciences, Museums Victoria, Melbourne, Victoria, 3001, Australia
| | - Justin W Adams
- Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, 3800, Australia
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27
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Laiolo P, Pato J, Illera JC, Obeso JR. Selection for functional performance in the evolution of cuticle hardening mechanisms in insects. Evolution 2021; 75:1132-1142. [PMID: 33634481 DOI: 10.1111/evo.14201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 02/15/2021] [Accepted: 02/17/2021] [Indexed: 11/29/2022]
Abstract
Calcified tissues have repeatedly evolved in many animal lineages and show a tremendous diversity of forms and functions. The cuticle of many insects is enriched with elements other than Calcium, a strategy of hardening that is taxonomically widespread but apparently poorly variable among clades. Here, we investigate the evolutionary potential of the enrichment with metals in insect cuticle at different biological levels. We combined experimental evidence of Zinc content variation in the mandibles of a target species (Chorthippus cazurroi [Bolívar]) with phylogenetic comparative analyses among grasshopper species. We found that mandibular Zinc content was repeatable among related individuals and was associated with an indicator of fitness, so there was potential for adaptive variation. Among species, Zinc enrichment evolved as a consequence of environmental and dietary influences on the physical function of the jaw (cutting and chewing), suggesting a role of natural selection in environmental fit. However, there were also important within and transgenerational environmental sources of similarity among individuals. These environmental influences, along with the tight relationship with biomechanics, may limit the potential for diversification of this hardening mechanism. This work provides novel insights into the diversification of biological structures and the link between evolutionary capacity and intra- and interspecific variation.
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Affiliation(s)
- Paola Laiolo
- Research Unit of Biodiversity (UO, CSIC, PA), Oviedo University, Mieres, 33600, Spain
| | - Joaquina Pato
- Research Unit of Biodiversity (UO, CSIC, PA), Oviedo University, Mieres, 33600, Spain
| | - Juan Carlos Illera
- Research Unit of Biodiversity (UO, CSIC, PA), Oviedo University, Mieres, 33600, Spain
| | - José Ramón Obeso
- Research Unit of Biodiversity (UO, CSIC, PA), Oviedo University, Mieres, 33600, Spain
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28
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Abstract
Identifying developmental explanations for the evolution of complex structures like mammalian molars is fundamental to studying phenotypic variation. Previous study showed that a "morphogenetic gradient" of molar proportions was explained by a balance between inhibiting/activating activity from earlier developing molars, termed the inhibitory cascade model (ICM). Although this model provides an explanation for variation in molar proportions, what remains poorly understood is if molar shape, or specifically complexity (i.e., the number of cusps, crests), can be explained by the same developmental model. Here, we show that molar complexity conforms to the ICM, following a linear, morphogenetic gradient along the molar row. Moreover, differing levels of inhibiting/activating activity produce contrasting patterns of molar complexity depending on diet. This study corroborates a model for the evolution of molar complexity that is developmentally simple, where only small-scale developmental changes need to occur to produce change across the entire molar row, with this process being mediated by an animal's ecology. The ICM therefore provides a developmental framework for explaining variation in molar complexity and a means for testing developmental hypotheses in the broader context of mammalian evolution.
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29
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Gomes Rodrigues H, Lihoreau F, Orliac M, Boisserie JR. Characters from the deciduous dentition and its interest for phylogenetic reconstruction in Hippopotamoidea (Cetartiodactyla: Mammalia). Zool J Linn Soc 2020. [DOI: 10.1093/zoolinnean/zlaa147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Teeth are frequently used in phylogeny in order to better characterize the evolution of extinct mammal species. While most studies have focused on the adult dentition, the consideration of characters from the deciduous dentition could also contribute to reinforce phylogenetic assumptions or disentangle phylogenetic issues. We chose to investigate the characters of the deciduous dentition in cetartiodactyl taxa in relation to the disputed relationships within hippopotamoids, especially the position of Hippopotamidae. We describe the deciduous dentition of 51 species, among a dataset of 70 cetartiodactyls. We noticed that second and third deciduous premolars have a much lower degree of molarization, and are more suitable for coding than fourth deciduous premolars. Thirty-nine resulting characters were thus added to a previously published matrix, and parsimony and maximum-likelihood analyses were performed. Both analyses provided a better resolved topology for most taxa than without these characters, and with better support for most nodes in the parsimony analysis. Moreover, this analysis provides additional characters supporting the hypothesis of an emergence of hippopotamids within bothriodontine anthracotheres from the Palaeogene of Africa. The promising use of characters from the deciduous dentition in phylogeny should allow discussion of the underlying ontogenetic mechanisms at the origin of dental homology.
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Affiliation(s)
- Helder Gomes Rodrigues
- Institut des Sciences de l’Evolution de Montpellier (ISEM), Univ Montpellier, CNRS, IRD, Montpellier, France
- Centre de Recherche en Paléontologie - Paris (CR2P), UMR CNRS 7207, CP38, Muséum national d’Histoire naturelle, Sorbonne Université, Paris, France
| | - Fabrice Lihoreau
- Institut des Sciences de l’Evolution de Montpellier (ISEM), Univ Montpellier, CNRS, IRD, Montpellier, France
| | - Maëva Orliac
- Institut des Sciences de l’Evolution de Montpellier (ISEM), Univ Montpellier, CNRS, IRD, Montpellier, France
| | - Jean-Renaud Boisserie
- Laboratoire Paléontologie Evolution Paléoécosystèmes Paléoprimatologie, CNRS, Université de Poitiers - UFR SFA, Poitiers Cedex, France
- Centre Français des Études Éthiopiennes, CNRS, Ministère de l’Europe et des affaires étrangères - Addis Abeba, Éthiopie
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30
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Berio F, Evin A, Goudemand N, Debiais‐Thibaud M. The intraspecific diversity of tooth morphology in the large-spotted catshark Scyliorhinus stellaris: insights into the ontogenetic cues driving sexual dimorphism. J Anat 2020; 237:960-978. [PMID: 32667054 PMCID: PMC7542197 DOI: 10.1111/joa.13257] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 05/02/2020] [Accepted: 05/26/2020] [Indexed: 02/06/2023] Open
Abstract
Teeth in sharks are shed and replaced throughout their lifetime. Morphological dental changes through ontogeny have been identified in several species and have been correlated with shifts in diet and the acquisition of sexual maturity. However, these changes were rarely quantified in detail along multiple ontogenetic stages, which makes it difficult to infer the developmental processes responsible for the observed plasticity. In this work, we use micro-computed tomography and 3D geometric morphometrics to describe and analyze the tooth size and shape diversity across three ontogenetic stages (hatchling, juvenile, and sexually mature) in the large-spotted catshark Scyliorhinus stellaris (Linnaeus, 1758). We first describe the intra-individual variation of tooth form for each sex at each ontogenetic stage. We provide a tooth morphospace for palatoquadrate and Meckelian teeth and identify dental features, such as relative size and number of cusps, involved in the range of variation of the observed morphologies. We then use these shape data to draw developmental trajectories between ontogenetic stages and for each tooth position within the jaw to characterize ontogenetic patterns of sexual dimorphism. We highlight the emergence of gynandric heterodonty between the juvenile and mature ontogenetic stages, with mature females having tooth morphologies more similar to juveniles' than mature males that display regression in the number of accessory cusps. From these data, we speculate on the developmental processes that could account for such developmental plasticity in S. stellaris.
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Affiliation(s)
- Fidji Berio
- CNRS, IRD, EPHEUMR5554Institut des Sciences de l’Évolution de Montpellier, ISEMUniversité de MontpellierMontpellierFrance
- Centre National de la Recherche ScientifiqueÉcole Normale Supérieure de LyonInstitut de Génomique Fonctionnelle de LyonUMR 5242Université Claude Bernard Lyon 1Univ. LyonLyonFrance
| | - Allowen Evin
- CNRS, IRD, EPHEUMR5554Institut des Sciences de l’Évolution de Montpellier, ISEMUniversité de MontpellierMontpellierFrance
| | - Nicolas Goudemand
- Centre National de la Recherche ScientifiqueÉcole Normale Supérieure de LyonInstitut de Génomique Fonctionnelle de LyonUMR 5242Université Claude Bernard Lyon 1Univ. LyonLyonFrance
| | - Mélanie Debiais‐Thibaud
- CNRS, IRD, EPHEUMR5554Institut des Sciences de l’Évolution de Montpellier, ISEMUniversité de MontpellierMontpellierFrance
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Fung S, Lee J, Yong R, Ranjitkar S, Kaidonis J, Pilbrow V, Panagiotopoulou O, Fiorenza L. A functional analysis of Carabelli trait in Australian aboriginal dentition. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 174:375-383. [PMID: 32779189 DOI: 10.1002/ajpa.24120] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 06/16/2020] [Accepted: 07/08/2020] [Indexed: 12/24/2022]
Abstract
OBJECTIVES Carabelli is a nonmetric dental trait variably expressed as a small pit to a prominent cusp in the maxillary molars of modern humans. Investigations on the occurrence and expression rates of this trait have been conducted extensively, tracing its origin to genetic sources. However, there remains a lack of understanding about its potential role in chewing. In this study, we examine molar macrowear with the aim of reconstructing Carabelli trait occlusal dynamics occurring during chewing. METHODS We have examined 96 deciduous and permanent maxillary molars of children and young adults from Yuendumu, an Australian Aboriginal population that was at an early stage of transition from a nomadic and hunter-gatherer way of life to a more settled existence. We apply a well-established method, called Occlusal Fingerprint Analysis, which is a digital approach for analyzing dental macrowear allowing the reconstruction of jaw movements required to produce wear pattern specific to each tooth. RESULTS Carabelli trait slightly enlarges the surface functional area, especially in those molars where this feature is expressed in its cuspal form and it is closer to the occlusal plane. Moreover, the highly steep contact planes would also indicate that Carabelli wear areas contribute to increasing the shearing abilities of the occluded teeth, which are particularly important when processing fibrous and tough foods. CONCLUSIONS The macrowear analysis suggests that Carabelli trait in the Aboriginal people from Yuendumu slightly enhanced occlusion and probably played some functional role during mastication. Future biomechanical and microwear analyses could provide additional information on the mechanical adaptation of Carabelli trait in modern human dentition.
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Affiliation(s)
- Sarah Fung
- Monash Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia
| | - Jinyoung Lee
- Monash Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia
| | - Robin Yong
- Adelaide Dental School, University of Adelaide, Adelaide, South Australia, Australia
| | - Sarbin Ranjitkar
- Adelaide Dental School, University of Adelaide, Adelaide, South Australia, Australia
| | - John Kaidonis
- Adelaide Dental School, University of Adelaide, Adelaide, South Australia, Australia
| | - Varsha Pilbrow
- Australian Institute of Archaeology, La Trobe University, Melbourne, Victoria, Australia
| | - Olga Panagiotopoulou
- Monash Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia
| | - Luca Fiorenza
- Monash Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia.,Earth Sciences, University of New England, Armidale, New South Wales, Australia
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32
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Malik Z, Roth DM, Eaton F, Theodor JM, Graf D. Mesenchymal Bmp7 Controls Onset of Tooth Mineralization: A Novel Way to Regulate Molar Cusp Shape. Front Physiol 2020; 11:698. [PMID: 32719613 PMCID: PMC7350786 DOI: 10.3389/fphys.2020.00698] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 05/28/2020] [Indexed: 01/14/2023] Open
Abstract
Investigating the molecular basis for tooth shape variation provides an important glimpse into the evolution of tooth function. We recently showed that loss of mesenchymal BMP7 is sufficient to alter morphology and function of the toothrow. Here we report on the underlying mechanism. Expression of mesenchymal Bmp7 is observed at sites where mineralization is initiated, in tooth cusps of developing molars. Neural crest-specific deletion of Bmp7 (Bmp7ncko) resulted in a complete lack of dentin/enamel formation at birth, the time when mineralization is normally initiated in the upper molars, similar to what was observed in Bmp2ncko mice. Unlike loss of Bmp2, loss of Bmp7 did not affect odontoblast polarization and did not significantly alter the levels of pSmad1/5/8, but almost completely abolished canonical Wnt signaling in (pre)-ameloblasts. Tooth mineralization resumed with a 48-h delay allowing for additional mesenchymal proliferation. Enamel volume was still reduced at P4 and P8, but was comparable in erupted teeth, which were broader and had altered cusp shapes. Tooth eruption was also delayed. Overall, enamel appeared inconspicuous, although some structural changes along with reduced mineral density could be observed. Loss of Bmp7 led to an increase in mesenchymal Bmp6 suggesting an interplay between Bmp6 and Bmp7 in the regulation of mineralization initiation. Our findings show that regulation of the onset of tooth mineralization is a hitherto unsuspected mechanism controlling tooth shape variation. Initiation of tooth mineralization is regulated by a complex epithelial-mesenchymal Bmp/Wnt-signaling network to which Bmp7 contributes. This network is separate and independent of the Bmp2-signaling network regulating odontoblast cell polarization. From an evolutionary perspective, addition of Bmp7 as initiator of tooth mineralization might be akin to an upgrade of an existing computer operating system. While not essential, it provides obviously sufficient advantage warranting its evolutionary incorporation.
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Affiliation(s)
- Zeba Malik
- School of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Daniela M Roth
- School of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Farah Eaton
- School of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Jessica M Theodor
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Daniel Graf
- School of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.,Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
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Fiorenza L, Menter CG, Fung S, Lee J, Kaidonis J, Moggi-Cecchi J, Townsend G, Kullmer O. The functional role of the Carabelli trait in early and late hominins. J Hum Evol 2020; 145:102816. [PMID: 32580080 DOI: 10.1016/j.jhevol.2020.102816] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 04/17/2020] [Accepted: 04/17/2020] [Indexed: 01/04/2023]
Abstract
The Carabelli trait is a dental feature that forms along the lingual margin of the protocone of deciduous and permanent maxillary molars. It is variably expressed, ranging from a small pit or furrow to a large cusp, and its development seems to be associated with crown size and molar cusp spatial configuration. The degree of expression of the Carabelli trait differs systematically between hominin taxa, and for this reason, it has been used extensively in the reconstruction of their phylogeny. However, the functional implications of having a large Carabelli trait remain unclear. In this study, we analyze the macrowear pattern of maxillary molars of early and late hominins using the occlusal fingerprint analysis method, an approach based on digital models of teeth that helps in reconstructing occlusal dynamics occurring during mastication. Tooth crowns with a small Carabelli cusp generally exhibit larger wear contact areas that extended cervically, while two additional new occlusal contact areas are common in teeth characterized by a large Carabelli cusp. These wear areas are created at the beginning of the chewing cycle, when occluding with the slopes of the lingual groove of the lower molars, between the metaconid and entoconid cusps. Advancing tooth wear leads to a slight enlargement of Carabelli occlusal contacts increasing their functional area. A steep inclination could be mechanically important in food reduction and in balancing the functional load distribution during mastication contacts. Steep wear areas are particularly developed in primates that process foods characterized by tough and fibrous textural properties. Future biomechanical and microwear texture analyses could provide additional information on the mechanical adaptation of this dental trait.
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Affiliation(s)
- Luca Fiorenza
- Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, 3800, Australia; Earth Sciences, University of New England, Armidale, NSW, 2351, Australia.
| | - Colin G Menter
- Department of Biology, University of Florence, 50122, Firenze, Italy
| | - Sarah Fung
- Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, 3800, Australia
| | - Jinyoung Lee
- Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, 3800, Australia
| | - John Kaidonis
- Adelaide Dental School, University of Adelaide, Adelaide, SA, 5005, Australia
| | | | - Grant Townsend
- Adelaide Dental School, University of Adelaide, Adelaide, SA, 5005, Australia
| | - Ottmar Kullmer
- Department of Paleoanthropology, Senckenberg Research Institute and Natural History Museum Frankfurt, Senckenberganlage 25, 60325 Frankfurt a. M., Germany; Department of Paleobiology and Environment, Institute of Ecology, Evolution, and Diversity, Johann Wolfgang Goethe University, Max-von-Laue-Str. 13, 60438, Frankfurt, Germany
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Laakkonen J, Jernvall J. Muscles of Mastication and the Temporo-Mandibular Joint of the Saimaa (Pusa hispida saimensis) and Baltic (Pusa hispida botnica) Ringed Seals. ANN ZOOL FENN 2020. [DOI: 10.5735/086.057.0103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Juha Laakkonen
- Division of Veterinary Anatomy and Developmental Biology, Department of Veterinary Biosciences, Faculty of Veterinary Medicine, P.O. Box 66, FI-00014 University of Helsinki, Finland
| | - Jukka Jernvall
- Institute of Biotechnology, P.O. Box 56, FI-00014 University of Helsinki, Finland
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35
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Morita W, Morimoto N, Kono RT, Suwa G. Metameric variation of upper molars in hominoids and its implications for the diversification of molar morphogenesis. J Hum Evol 2019; 138:102706. [PMID: 31785453 DOI: 10.1016/j.jhevol.2019.102706] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 10/20/2019] [Accepted: 10/20/2019] [Indexed: 11/18/2022]
Abstract
Metameric variation of molar size is in part associated with the dietary adaptations of mammals and results from slight alterations of developmental processes. Humans and great apes exhibit conspicuous variation in tooth morphology both between taxa and across tooth types. However, the manner in which metameric variation in molars emerged among apes and humans via evolutionary alterations in developmental processes remains largely unknown. In this study, we compare the enamel-dentine junction of the upper molars of humans-which closely correlates with morphology of the outer enamel surface and is less affected by wear-with that of the other extant hominoids: chimpanzees, bonobos, gorillas, orangutans, and gibbons. We used the morphometric mapping method to quantify and visualize three-dimensional morphological variation, and applied multivariate statistical analyses. Results revealed the following: 1) extant hominoids other than humans share a common pattern of metameric variation characterized by a largely linear change in morphospace; this indicates a relatively simple graded change in metameric molar shape; 2) intertaxon morphological differences become less distinct from the mesial to distal molars; and 3) humans diverge from the extant ape pattern in exhibiting a distinct metameric shape change trajectory in the morphospace. The graded shape change and lower intertaxon resolution from the mesial to distal molars are consistent with the concept of a 'key' tooth. The common metameric pattern observed among the extant nonhuman hominoids indicates that developmental patterns underlying metameric variation were largely conserved during ape evolution. Furthermore, the human-specific metameric pattern suggests considerable developmental modifications in the human lineage.
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Affiliation(s)
- Wataru Morita
- Developmental Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland; Department of Oral Functional Anatomy, Faculty of Dental Medicine, Hokkaido University, Hokkaido, Japan.
| | - Naoki Morimoto
- Laboratory of Physical Anthropology, Department of Zoology, Graduate School of Science, Kyoto University, Kyoto, Japan.
| | - Reiko T Kono
- Faculty of Letters, Keio University, Kanagawa, Japan
| | - Gen Suwa
- The University Museum, The University of Tokyo, Tokyo, Japan
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36
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Bailey SE, Brophy JK, Moggi-Cecchi J, Delezene LK. The deciduous dentition of Homo naledi: A comparative study. J Hum Evol 2019; 136:102655. [DOI: 10.1016/j.jhevol.2019.102655] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 08/06/2019] [Accepted: 08/08/2019] [Indexed: 12/23/2022]
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37
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Davies TW, Delezene LK, Gunz P, Hublin JJ, Skinner MM. Endostructural morphology in hominoid mandibular third premolars: Discrete traits at the enamel-dentine junction. J Hum Evol 2019; 136:102670. [DOI: 10.1016/j.jhevol.2019.102670] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 09/06/2019] [Accepted: 09/06/2019] [Indexed: 12/20/2022]
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38
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Affiliation(s)
- David Jablonski
- Department of Geophysical Sciences University of Chicago Chicago Illinois
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39
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Barbière F, Ronez C, Ortiz PE, Martin RA, Pardiñas UFJ. A new nomenclatural system for the study of sigmodontine rodent molars: first step towards an integrative phylogeny of fossil and living cricetids. Biol J Linn Soc Lond 2019. [DOI: 10.1093/biolinnean/blz021] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Franck Barbière
- Instituto Superior de Correlación Geológica (INSUGEO), Yerba Buena, Tucumán, Argentina
| | - Christophe Ronez
- Instituto de Diversidad y Evolución Austral (IDEAus-CONICET), Puerto Madryn, Chubut, Argentina
| | - Pablo E Ortiz
- Instituto Superior de Correlación Geológica (INSUGEO), Yerba Buena, Tucumán, Argentina
- Cátedra de Paleontología, Facultad de Ciencias Naturales e Instituto Miguel Lillo, San Miguel de Tucumán, Argentina
| | - Robert A Martin
- Department of Biological Sciences, Murray State University, Murray, KT, USA
| | - Ulyses F J Pardiñas
- Instituto de Diversidad y Evolución Austral (IDEAus-CONICET), Puerto Madryn, Chubut, Argentina
- Instituto Nacional de Biodiversidad (INABIO), Quito, Ecuador
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40
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Stojanowski CM, Paul KS, Seidel AC, Duncan WN, Guatelli‐Steinberg D. Quantitative genetic analyses of postcanine morphological crown variation. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2019; 168:606-631. [DOI: 10.1002/ajpa.23778] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 11/20/2018] [Accepted: 12/26/2018] [Indexed: 01/05/2023]
Affiliation(s)
- Christopher M. Stojanowski
- Center for Bioarchaeological Research School of Human Evolution and Social Change, Arizona State University Tempe Arizona
| | - Kathleen S. Paul
- Center for Bioarchaeological Research School of Human Evolution and Social Change, Arizona State University Tempe Arizona
| | - Andrew C. Seidel
- Center for Bioarchaeological Research School of Human Evolution and Social Change, Arizona State University Tempe Arizona
| | - William N. Duncan
- Department of Sociology and Anthropology East Tennessee State University Johnson City Tennessee
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Xiao H, Lei L, Peng J, Yang D, Zeng Q, Zheng J, Zhou Z. Research of the role of microstructure in the wear mechanism of canine and bovine enamel. J Mech Behav Biomed Mater 2019; 92:33-39. [PMID: 30654218 DOI: 10.1016/j.jmbbm.2018.12.036] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 12/26/2018] [Accepted: 12/27/2018] [Indexed: 10/27/2022]
Abstract
The relationship between the microstructure and tribological behavior of mammalian tooth enamel has not been fully understood. In this paper, the microstructure, mechanical properties, and tribological behavior of canine (carnivore) and bovine (herbivore) enamel are studied using scanning electronic microscopy and nano-indentation/scratch technique, aiming to reveal the contribution of enamel microstructure to its mechanical and tribological properties. Canine enamel has a microstructure of hard keyhole-like rods embedded in soft inter-rod enamel, and its surface exhibits high resistance against both micro-crack initiation and crack-induced delamination during friction and wear process. Bovine enamel with the microstructure consisting of the hydroxyapatite (HAP) nano-fibers in decussation has higher surface hardness and better capabilities of resisting wear and encumbering crack propagation, as compared to canine enamel. In sum, the soft inter-rod enamel in the canine enamel contributes to high load tolerance and then protects enamel surface from brittle damage, while the staggered arrangement of HAP nano-fibers benefits hard bovine enamel in crack propagation resistance and then help resist wear and fatigue. The findings suggest that there exists a self-adaptation in enamel microstructure and tribological performance of mammals with their feeding habits, which will promote and assist the bionic design of high-performance materials.
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Affiliation(s)
- Heng Xiao
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
| | - Lei Lei
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
| | - Jiapin Peng
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
| | - Dan Yang
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
| | - Qihang Zeng
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
| | - Jing Zheng
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China.
| | - Zhongrong Zhou
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
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42
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Dimensionality Reduction Techniques for Visualizing Morphometric Data: Comparing Principal Component Analysis to Nonlinear Methods. Evol Biol 2018. [DOI: 10.1007/s11692-018-9464-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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43
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Lanzetti A, Berta A, Ekdale EG. Prenatal Development of the Humpback Whale: Growth Rate, Tooth Loss and Skull Shape Changes in an Evolutionary Framework. Anat Rec (Hoboken) 2018; 303:180-204. [DOI: 10.1002/ar.23990] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 01/15/2018] [Accepted: 01/24/2018] [Indexed: 01/01/2023]
Affiliation(s)
- Agnese Lanzetti
- Department of BiologySan Diego State University San Diego California
| | - Annalisa Berta
- Department of BiologySan Diego State University San Diego California
| | - Eric G. Ekdale
- Department of BiologySan Diego State University San Diego California
- San Diego Natural History Museum San Diego California
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Nakayama M, Kondo O, Pesonen P, Alvesalo L, Lähdesmäki R. Influence of long and short arms of X chromosome on maxillary molar crown morphology. PLoS One 2018; 13:e0207070. [PMID: 30439977 PMCID: PMC6237344 DOI: 10.1371/journal.pone.0207070] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Accepted: 10/24/2018] [Indexed: 12/03/2022] Open
Abstract
Although genes on the human X chromosome reportedly influence tooth crown morphology, little is known about X chromosome activation or inactivation systems relevant to morphological variations. We assessed the relationships between tooth crown size and crown morphological traits in females with Turner syndrome, the variants of which include complete absence of one X chromosome, lack of the short arm (Xp), or duplication of the long arms (Xq), and then estimated the functions of Xp and Xq in the process of unilateral X chromosome inactivation during tooth crown development. The mesiodistal and buccolingual diameters in the maxillary first (M1) and second (M2) permanent molars were compared among X chromosome karyotypes by multiple regression analyses, and their relationships with the development of Carabelli’s cusp and the distolingual cusp were analyzed using logistic regression analysis. The crown sizes increased in the order of the 46,X,i(Xq) karyotype, 45,X and 45,X/46,XX karyotypes, and control group. A lower frequency of Carabelli’s cusp and higher frequency of a reduced distolingual cusp in M1 were characteristics of Turner syndrome. The overall M1 and M2 crown sizes differed among the X chromosome karyotypes, whereas a smaller crown size was associated with a reduced distolingual cusp but not with Carabelli’s cusp. Considering the differences in chromosome arrangement among females with Turner syndrome and the process of unilateral X chromosome inactivation, the observed results can be considered in terms of quantity or number of promoters/inhibitors during tooth crown development. The X chromosome karyotypes have a strong influence on the overall crown sizes of the M1 and M2 molars because those karyotypes with variable numbers of active gene regions directly influence tooth germ development in an early stage of human odontogenesis. The later forming cusps, such as the distolingual cusp and Carabelli’s cusp, may be affected by this developmental prerequisite.
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Affiliation(s)
- Mitsuko Nakayama
- Oral Development and Orthodontics, Research Unit of Oral Health Sciences, Medical Faculty, University of Oulu, Oulu, Finland
- Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland
- Department of Anatomy I, Nihon University, School of Dentistry at Matsudo, Matsudo, Japan
- * E-mail:
| | - Osamu Kondo
- Department of Biological Science, Graduate School of Science, University of Tokyo, Tokyo, Japan
| | - Paula Pesonen
- Northern Finland Birth Cohorts, Faculty of Medicine, University of Oulu, Oulu, Finland
| | - Lassi Alvesalo
- Oral Development and Orthodontics, Research Unit of Oral Health Sciences, Medical Faculty, University of Oulu, Oulu, Finland
| | - Raija Lähdesmäki
- Oral Development and Orthodontics, Research Unit of Oral Health Sciences, Medical Faculty, University of Oulu, Oulu, Finland
- Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland
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45
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Savriama Y, Valtonen M, Kammonen JI, Rastas P, Smolander OP, Lyyski A, Häkkinen TJ, Corfe IJ, Gerber S, Salazar-Ciudad I, Paulin L, Holm L, Löytynoja A, Auvinen P, Jernvall J. Bracketing phenogenotypic limits of mammalian hybridization. ROYAL SOCIETY OPEN SCIENCE 2018; 5:180903. [PMID: 30564397 PMCID: PMC6281900 DOI: 10.1098/rsos.180903] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 10/29/2018] [Indexed: 05/09/2023]
Abstract
An increasing number of mammalian species have been shown to have a history of hybridization and introgression based on genetic analyses. Only relatively few fossils, however, preserve genetic material, and morphology must be used to identify the species and determine whether morphologically intermediate fossils could represent hybrids. Because dental and cranial fossils are typically the key body parts studied in mammalian palaeontology, here we bracket the potential for phenotypically extreme hybridizations by examining uniquely preserved cranio-dental material of a captive hybrid between grey and ringed seals. We analysed how distinct these species are genetically and morphologically, how easy it is to identify the hybrids using morphology and whether comparable hybridizations happen in the wild. We show that the genetic distance between these species is more than twice the modern human-Neanderthal distance, but still within that of morphologically similar species pairs known to hybridize. By contrast, morphological and developmental analyses show grey and ringed seals to be highly disparate, and that the hybrid is a predictable intermediate. Genetic analyses of the parent populations reveal introgression in the wild, suggesting that grey-ringed seal hybridization is not limited to captivity. Taken together, we postulate that there is considerable potential for mammalian hybridization between phenotypically disparate taxa.
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Affiliation(s)
- Yoland Savriama
- Developmental Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
| | - Mia Valtonen
- Developmental Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Juhana I. Kammonen
- Genome Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
| | - Pasi Rastas
- Genome Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
| | - Olli-Pekka Smolander
- Genome Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
| | - Annina Lyyski
- Genome Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
| | - Teemu J. Häkkinen
- Developmental Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
| | - Ian J. Corfe
- Developmental Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
| | - Sylvain Gerber
- Institut Systématique Evolution Biodiversité (ISYEB), Muséum national d'Histoire naturelle, CNRS, Sorbonne Université, EPHE, 45 rue Buffon, CP 50, 75005 Paris, France
| | - Isaac Salazar-Ciudad
- Developmental Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
- Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
| | - Lars Paulin
- Genome Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
| | - Liisa Holm
- Genome Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
- Faculty of Biological and Environmental Sciences, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
| | - Ari Löytynoja
- Genome Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
- Authors for correspondence: Ari Löytynoja e-mail:
| | - Petri Auvinen
- Genome Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
- Authors for correspondence: Petri Auvinen e-mail:
| | - Jukka Jernvall
- Developmental Biology Program, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland
- Authors for correspondence: Jukka Jernvall e-mail:
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Billet G, Bardin J. Serial Homology and Correlated Characters in Morphological Phylogenetics: Modeling the Evolution of Dental Crests in Placentals. Syst Biol 2018; 68:267-280. [DOI: 10.1093/sysbio/syy071] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 10/22/2018] [Indexed: 01/24/2023] Open
Affiliation(s)
- Guillaume Billet
- CR2P, UMR 7207, Muséum national d’Histoire naturelle, CNRS, Sorbonne Université, 8 rue Buffon 75005 Paris, France
| | - Jérémie Bardin
- CR2P, UMR 7207, Sorbonne Université, MNHN, CNRS, T.46-56, E.5, case 104, 4 place Jussieu, 75252 Paris cedex 05, France
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47
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Laugel-Haushalter V, Morkmued S, Stoetzel C, Geoffroy V, Muller J, Boland A, Deleuze JF, Chennen K, Pitiphat W, Dollfus H, Niederreither K, Bloch-Zupan A, Pungchanchaikul P. Genetic Evidence Supporting the Role of the Calcium Channel, CACNA1S, in Tooth Cusp and Root Patterning. Front Physiol 2018; 9:1329. [PMID: 30319441 PMCID: PMC6170876 DOI: 10.3389/fphys.2018.01329] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 09/03/2018] [Indexed: 01/08/2023] Open
Abstract
In this study, we report a unique dominantly inherited disorganized supernumerary cusp and single root phenotype presented by 11 affected individuals belonging to 5 north-eastern Thai families. Using whole exome sequencing (WES) we identified a common single missense mutation that segregates with the phenotype in exon 6 of CACNA1S (Cav1.1) (NM_000069.2: c.[865A > G];[=] p.[Ile289Val];[=]), the Calcium Channel, Voltage-Dependent, L Type, Alpha-1s Subunit, OMIM ∗ 114208), affecting a highly conserved amino-acid isoleucine residue within the pore forming subdomain of CACNA1S protein. This is a strong genetic evidence that a voltage-dependent calcium ion channel is likely to play a role in influencing tooth morphogenesis and patterning.
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Affiliation(s)
- Virginie Laugel-Haushalter
- Laboratoire de Génétique Médicale, UMR_S INSERM U1112, IGMA, Faculté de Médecine, FMTS, Université de Strasbourg, Strasbourg, France
| | - Supawich Morkmued
- Biofilm Research Group, Department of Pediatric Dentistry, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand.,Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CERBM, INSERM U 1258, CNRS- UMR 7104, Université de Strasbourg, Strasbourg, France
| | - Corinne Stoetzel
- Laboratoire de Génétique Médicale, UMR_S INSERM U1112, IGMA, Faculté de Médecine, FMTS, Université de Strasbourg, Strasbourg, France
| | - Véronique Geoffroy
- Laboratoire de Génétique Médicale, UMR_S INSERM U1112, IGMA, Faculté de Médecine, FMTS, Université de Strasbourg, Strasbourg, France
| | - Jean Muller
- Laboratoire de Génétique Médicale, UMR_S INSERM U1112, IGMA, Faculté de Médecine, FMTS, Université de Strasbourg, Strasbourg, France.,Laboratoires de Diagnostic Génétique, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - Anne Boland
- Centre National de Recherche en Génomique Humaine (CNRGH), Institut de Biologie François Jacob, Direction de la Recherche Fondamentale, Commissariat à l'Energie Atomique et aux Energies Alternatives, Paris, France
| | - Jean-François Deleuze
- Centre National de Recherche en Génomique Humaine (CNRGH), Institut de Biologie François Jacob, Direction de la Recherche Fondamentale, Commissariat à l'Energie Atomique et aux Energies Alternatives, Paris, France
| | - Kirsley Chennen
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CERBM, INSERM U 1258, CNRS- UMR 7104, Université de Strasbourg, Strasbourg, France.,Department of Computer Science, ICube, CNRS - UMR 7357, Fédération de Médecine Translationnelle de Strasbourg, Université de Strasbourg, Strasbourg, France
| | - Waranuch Pitiphat
- Department of Community Dentistry, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand
| | - Hélène Dollfus
- Laboratoire de Génétique Médicale, UMR_S INSERM U1112, IGMA, Faculté de Médecine, FMTS, Université de Strasbourg, Strasbourg, France.,Centre de Référence pour les Affections Rares en Génétique Ophtalmologique, Filière SENSGENE, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - Karen Niederreither
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CERBM, INSERM U 1258, CNRS- UMR 7104, Université de Strasbourg, Strasbourg, France.,Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
| | - Agnès Bloch-Zupan
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CERBM, INSERM U 1258, CNRS- UMR 7104, Université de Strasbourg, Strasbourg, France.,Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France.,Hôpitaux Universitaires de Strasbourg (HUS), Pôle de Médecine et Chirurgie Bucco-Dentaires Hôpital Civil, Centre de Référence des Maladies Rares Orales et Dentaires, O-Rares, Filière Santé Maladies Rares TETE COU, European Reference Network ERN CRANIO, Strasbourg, France
| | - Patimaporn Pungchanchaikul
- Biofilm Research Group, Department of Pediatric Dentistry, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand
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48
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Renaud S, Ledevin R, Souquet L, Gomes Rodrigues H, Ginot S, Agret S, Claude J, Herrel A, Hautier L. Evolving Teeth Within a Stable Masticatory Apparatus in Orkney Mice. Evol Biol 2018. [DOI: 10.1007/s11692-018-9459-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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49
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Losada JM, Leslie AB. Why are the seed cones of conifers so diverse at pollination? ANNALS OF BOTANY 2018; 121:1319-1331. [PMID: 29528365 PMCID: PMC6007286 DOI: 10.1093/aob/mcy029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 02/16/2018] [Indexed: 05/24/2023]
Abstract
BACKGROUND AND AIMS Form and function relationships in plant reproductive structures have long fascinated biologists. Although the intricate associations between specific pollinators and reproductive morphology have been widely explored among animal-pollinated plants, the evolutionary processes underlying the diverse morphologies of wind-pollinated plants remain less well understood. Here we study how this diversity may have arisen by focusing on two conifer species in the pine family that have divergent reproductive cone morphologies at pollination. METHODS Standard histology methods, artificial wind pollination assays and phylogenetic analyses were used in this study. KEY RESULTS A detailed study of cone ontogeny in these species reveals that variation in the rate at which their cone scales mature means that pollination occurs at different stages in their development, and thus in association with different specific morphologies. Pollination experiments nevertheless indicate that both species effectively capture pollen. CONCLUSIONS In wind-pollinated plants, morphological diversity may result from simple variation in development among lineages rather than selective pressures for any major differences in function or performance. This work also illustrates the broader importance of developmental context in understanding plant form and function relationships; because plant reproductive structures perform many different functions over their lifetime, subtle differences in development may dramatically alter the specific morphologies that they use to meet these demands.
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Affiliation(s)
- Juan M Losada
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA
- Arnold Arboretum of Harvard University, Boston, MA, USA
| | - Andrew B Leslie
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA
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50
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Ortiz A, Bailey SE, Schwartz GT, Hublin JJ, Skinner MM. Evo-devo models of tooth development and the origin of hominoid molar diversity. SCIENCE ADVANCES 2018; 4:eaar2334. [PMID: 29651459 PMCID: PMC5895448 DOI: 10.1126/sciadv.aar2334] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 02/28/2018] [Indexed: 06/08/2023]
Abstract
The detailed anatomical features that characterize fossil hominin molars figure prominently in the reconstruction of their taxonomy, phylogeny, and paleobiology. Despite the prominence of molar form in human origins research, the underlying developmental mechanisms generating the diversity of tooth crown features remain poorly understood. A model of tooth morphogenesis-the patterning cascade model (PCM)-provides a developmental framework to explore how and why the varying molar morphologies arose throughout human evolution. We generated virtual maps of the inner enamel epithelium-an indelibly preserved record of enamel knot arrangement-in 17 living and fossil hominoid species to investigate whether the PCM explains the expression of all major accessory cusps. We found that most of the variation and evolutionary changes in hominoid molar morphology followed the general developmental rule shared by all mammals, outlined by the PCM. Our results have implications for the accurate interpretation of molar crown configuration in hominoid systematics.
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Affiliation(s)
- Alejandra Ortiz
- Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, USA
| | - Shara E. Bailey
- Center for the Study of Human Origins, Department of Anthropology, New York University, New York, NY 10003, USA
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany
| | - Gary T. Schwartz
- Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, USA
| | - Jean-Jacques Hublin
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany
| | - Matthew M. Skinner
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany
- School of Anthropology and Conservation, University of Kent, Canterbury CT2 7NR, UK
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