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Kyomen S, Murillo-Rincón AP, Kaucká M. Evolutionary mechanisms modulating the mammalian skull development. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220080. [PMID: 37183900 PMCID: PMC10184257 DOI: 10.1098/rstb.2022.0080] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023] Open
Abstract
Mammals possess impressive craniofacial variation that mirrors their adaptation to diverse ecological niches, feeding behaviour, physiology and overall lifestyle. The spectrum of craniofacial geometries is established mainly during embryonic development. The formation of the head represents a sequence of events regulated on genomic, molecular, cellular and tissue level, with each step taking place under tight spatio-temporal control. Even minor variations in timing, position or concentration of the molecular drivers and the resulting events can affect the final shape, size and position of the skeletal elements and the geometry of the head. Our knowledge of craniofacial development increased substantially in the last decades, mainly due to research using conventional vertebrate model organisms. However, how developmental differences in head formation arise specifically within mammals remains largely unexplored. This review highlights three evolutionary mechanisms acknowledged to modify ontogenesis: heterochrony, heterotopy and heterometry. We present recent research that links changes in developmental timing, spatial organization or gene expression levels to the acquisition of species-specific skull morphologies. We highlight how these evolutionary modifications occur on the level of the genes, molecules and cellular processes, and alter conserved developmental programmes to generate a broad spectrum of skull shapes characteristic of the class Mammalia. This article is part of the theme issue 'The mammalian skull: development, structure and function'.
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Affiliation(s)
- Stella Kyomen
- Max Planck Institute for Evolutionary Biology, August-Thienemann-Strasse 2, Plön 24306, Germany
| | - Andrea P Murillo-Rincón
- Max Planck Institute for Evolutionary Biology, August-Thienemann-Strasse 2, Plön 24306, Germany
| | - Markéta Kaucká
- Max Planck Institute for Evolutionary Biology, August-Thienemann-Strasse 2, Plön 24306, Germany
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Sharp AC, Dutel H, Watson PJ, Gröning F, Crumpton N, Fagan MJ, Evans SE. Assessment of the mechanical role of cranial sutures in the mammalian skull: Computational biomechanical modelling of the rat skull. J Morphol 2023; 284:e21555. [PMID: 36630615 PMCID: PMC10107956 DOI: 10.1002/jmor.21555] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 01/03/2023] [Accepted: 01/05/2023] [Indexed: 01/13/2023]
Abstract
Cranial sutures are fibrocellular joints between the skull bones that are progressively replaced with bone throughout ontogeny, facilitating growth and cranial shape change. This transition from soft tissue to bone is reflected in the biomechanical properties of the craniofacial complex. However, the mechanical significance of cranial sutures has only been explored at a few localised areas within the mammalian skull, and as such our understanding of suture function in overall skull biomechanics is still limited. Here, we sought to determine how the overall strain environment is affected by the complex network of cranial sutures in the mammal skull. We combined two computational biomechanical methods, multibody dynamics analysis and finite element analysis, to simulate biting in a rat skull and compared models with and without cranial sutures. Our results show that including complex sutures in the rat model does not substantially change overall strain gradients across the cranium, particularly strain magnitudes in the bones overlying the brain. However, local variations in strain magnitudes and patterns can be observed in areas close to the sutures. These results show that, during feeding, sutures may be more important in some regions than others. Sutures should therefore be included in models that require accurate local strain magnitudes and patterns of cranial strain, particularly if models are developed for analysis of specific regions, such as the temporomandibular joint or zygomatic arch. Our results suggest that, for mammalian skulls, cranial sutures might be more important for allowing brain expansion during growth than redistributing biting loads across the cranium in adults.
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Affiliation(s)
- Alana C Sharp
- Department of Musculoskeletal and Ageing Sciences, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK.,Department of Cell and Developmental Biology, University College London, London, UK
| | - Hugo Dutel
- Department of Engineering, University of Hull, Hull, UK.,Faculty of Science, School of Earth Sciences, University of Bristol, Bristol, UK
| | | | - Flora Gröning
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen, UK
| | - Nick Crumpton
- Department of Cell and Developmental Biology, University College London, London, UK
| | | | - Susan E Evans
- Department of Cell and Developmental Biology, University College London, London, UK
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White HE, Goswami A, Tucker AS. The Intertwined Evolution and Development of Sutures and Cranial Morphology. Front Cell Dev Biol 2021; 9:653579. [PMID: 33842480 PMCID: PMC8033035 DOI: 10.3389/fcell.2021.653579] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Accepted: 03/08/2021] [Indexed: 12/21/2022] Open
Abstract
Phenotypic variation across mammals is extensive and reflects their ecological diversification into a remarkable range of habitats on every continent and in every ocean. The skull performs many functions to enable each species to thrive within its unique ecological niche, from prey acquisition, feeding, sensory capture (supporting vision and hearing) to brain protection. Diversity of skull function is reflected by its complex and highly variable morphology. Cranial morphology can be quantified using geometric morphometric techniques to offer invaluable insights into evolutionary patterns, ecomorphology, development, taxonomy, and phylogenetics. Therefore, the skull is one of the best suited skeletal elements for developmental and evolutionary analyses. In contrast, less attention is dedicated to the fibrous sutural joints separating the cranial bones. Throughout postnatal craniofacial development, sutures function as sites of bone growth, accommodating expansion of a growing brain. As growth frontiers, cranial sutures are actively responsible for the size and shape of the cranial bones, with overall skull shape being altered by changes to both the level and time period of activity of a given cranial suture. In keeping with this, pathological premature closure of sutures postnatally causes profound misshaping of the skull (craniosynostosis). Beyond this crucial role, sutures also function postnatally to provide locomotive shock absorption, allow joint mobility during feeding, and, in later postnatal stages, suture fusion acts to protect the developed brain. All these sutural functions have a clear impact on overall cranial function, development and morphology, and highlight the importance that patterns of suture development have in shaping the diversity of cranial morphology across taxa. Here we focus on the mammalian cranial system and review the intrinsic relationship between suture development and morphology and cranial shape from an evolutionary developmental biology perspective, with a view to understanding the influence of sutures on evolutionary diversity. Future work integrating suture development into a comparative evolutionary framework will be instrumental to understanding how developmental mechanisms shaping sutures ultimately influence evolutionary diversity.
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Affiliation(s)
- Heather E White
- Department of Life Sciences, Natural History Museum, London, United Kingdom.,Centre for Craniofacial and Regenerative Biology, King's College London, London, United Kingdom.,Division of Biosciences, University College London, London, United Kingdom
| | - Anjali Goswami
- Department of Life Sciences, Natural History Museum, London, United Kingdom.,Division of Biosciences, University College London, London, United Kingdom
| | - Abigail S Tucker
- Centre for Craniofacial and Regenerative Biology, King's College London, London, United Kingdom
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White HE, Clavel J, Tucker AS, Goswami A. A comparison of metrics for quantifying cranial suture complexity. J R Soc Interface 2020; 17:20200476. [PMID: 33023399 PMCID: PMC7653371 DOI: 10.1098/rsif.2020.0476] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 09/08/2020] [Indexed: 01/20/2023] Open
Abstract
Cranial sutures play critical roles in facilitating postnatal skull development and function. The diversity of function is reflected in the highly variable suture morphology and complexity. Suture complexity has seldom been studied, resulting in little consensus on the most appropriate approach for comparative, quantitative analyses. Here, we provide the first comprehensive comparison of current approaches for quantifying suture morphology, using a wide range of two-dimensional suture outlines across extinct and extant mammals (n = 79). Five complexity metrics (sinuosity index (SI), suture complexity index (SCI), fractal dimension (FD) box counting, FD madogram and a windowed short-time Fourier transform with power spectrum density (PSD) calculation) were compared with each other and with the shape variation in the dataset. Analyses of suture shape demonstrate that the primary axis of variation captured attributes other than complexity, supporting the use of a complexity metric over raw shape data for sutural complexity analyses. Each approach captured different aspects of complexity. PSD successfully discriminates different sutural features, such as looping patterns and interdigitation amplitude and number, while SCI best-captured variation in interdigitation number alone. Therefore, future studies should consider the relevant attributes for their question when selecting a metric for comparative analysis of suture variation, function and evolution.
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Affiliation(s)
- Heather E. White
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
- Centre for Craniofacial and Regenerative Biology, King's College LondonSE1 9RT, UK
- Division of Biosciences, University College LondonWC1E 6DE, UK
| | - Julien Clavel
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France
| | - Abigail S. Tucker
- Centre for Craniofacial and Regenerative Biology, King's College LondonSE1 9RT, UK
| | - Anjali Goswami
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
- Division of Biosciences, University College LondonWC1E 6DE, UK
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Byron C, Segreti M, Hawkinson K, Herman K, Patel S. Dietary material properties shape cranial suture morphology in the mouse calvarium. J Anat 2018; 233:807-813. [PMID: 30298923 DOI: 10.1111/joa.12888] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/22/2018] [Indexed: 11/29/2022] Open
Abstract
Cranial sutures are fibrous connective tissue articulations found between intramembranous bones of the vertebrate cranium. Growth and remodeling of these tissues is partially regulated by biomechanical loading patterns that include stresses related to chewing. Advances in oral processing structure and function of the cranium that enabled mammalian-style chewing is commonly tied to the origins and evolution of this group. To what degree masticatory overuse or underuse shapes the complexity and ossification around these articulations can be predicted based on prior experimental and comparative work. Here, we report on a mouse model system that has been used to experimentally manipulate dietary material properties in order to investigate cranial suture morphology. Experimental groups were fed diets of contrasting material properties. A masticatory overuse group was fed pelleted rodent chow, nuts with shells, and given access to cotton bedding squares. An underuse group was deprived of cotton bedding as well as diverse textured food, and instead received gelatinized food continuously. Animals were raised from weaning to adulthood on these diets, and sagittal, coronal and lambdoid suture morphology was compared between groups. Predicted intergroup variation was observed in mandibular corpus size and calvarial suture morphology, suggesting that masticatory overuse is associated with jaw and suture growth. The anterior region of the sagittal suture where it intersects with the coronal suture (bregma) showed no effect from the experiment. The posterior sagittal suture where it intersects with the lambdoid sutures (lambda) was more complex in the overuse group. In other words, the posterior calvarium was responsive to dietary material property demands while the anterior calvarium was not. This probably resulted from the different strain magnitudes and/or strain frequencies that occurred during overuse diets with diverse material properties as compared with underuse diets deprived of such enrichment. This work highlights the contrasting pattern of the sutural response to loading differences within the calvarium as a result of diet.
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Affiliation(s)
- Craig Byron
- Department of Biology, Mercer University, Macon, GA, USA
| | - Meghan Segreti
- Department of Biology, Mercer University, Macon, GA, USA
| | | | - Katelyn Herman
- Department of Biology, Mercer University, Macon, GA, USA
| | - Shivam Patel
- Department of Biology, Mercer University, Macon, GA, USA
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