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Species-specific modifications of mandible shape reveal independent mechanisms for growth and initiation of the coronoid.

Anthwal N, Peters H, Tucker AS - Evodevo (2015)

Bottom Line: We also demonstrate that Sox9 plays a role independent of chondrogenesis in the growth of the coronoid process in response to muscle interaction.The mandibular coronoid process is initiated by intrinsic factors, but later growth is dependent on extrinsic signals from the muscle.These extrinsic influences are hypothesised to be the basis of the variation in coronoid length seen across the mammalian lineage.

View Article: PubMed Central - PubMed

Affiliation: Department of Craniofacial Development and Stem Cell Biology, Dental Institute, King's College London, London, SE1 9RT UK.

ABSTRACT

Background: The variation in mandibular morphology of mammals reflects specialisations for different diets. Omnivorous and carnivorous mammals posses large mandibular coronoid processes, while herbivorous mammals have proportionally smaller or absent coronoids. This is correlated with the relative size of the temporalis muscle that forms an attachment to the coronoid process. The role of this muscle attachment in the development of the variation of the coronoid is unclear.

Results: By comparative developmental biology and mouse knockout studies, we demonstrate here that the initiation and growth of the coronoid are two independent processes, with initiation being intrinsic to the ossifying bone and growth dependent upon the extrinsic effect of muscle attachment. A necessary component of the intrinsic patterning is identified as the paired domain transcription factor Pax9. We also demonstrate that Sox9 plays a role independent of chondrogenesis in the growth of the coronoid process in response to muscle interaction.

Conclusions: The mandibular coronoid process is initiated by intrinsic factors, but later growth is dependent on extrinsic signals from the muscle. These extrinsic influences are hypothesised to be the basis of the variation in coronoid length seen across the mammalian lineage.

No MeSH data available.


Related in: MedlinePlus

Alizarin red/Alcian blue staining of guinea pig, mouse and opossums mandibles. a–c The coronoid process is a distinct part of the dentary in mammals such as the mouse (Mus musculus) and opossum (Mondelphis domestica) during development and in the adult (a, b), whereas the guinea pig (Caviaporcellus) displays a coronoid process comparable with the mouse in embryonic stages (E37 presented in c), but only has a rudimentary process in adults. d Conditional deletion of Pax9 in neural crest lineage cells results in a loss of the coronoid process [8]; Arrowheads: location of coronoid process; asterisk location of condylar process, double dagger location of absent coronoid process
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Fig1: Alizarin red/Alcian blue staining of guinea pig, mouse and opossums mandibles. a–c The coronoid process is a distinct part of the dentary in mammals such as the mouse (Mus musculus) and opossum (Mondelphis domestica) during development and in the adult (a, b), whereas the guinea pig (Caviaporcellus) displays a coronoid process comparable with the mouse in embryonic stages (E37 presented in c), but only has a rudimentary process in adults. d Conditional deletion of Pax9 in neural crest lineage cells results in a loss of the coronoid process [8]; Arrowheads: location of coronoid process; asterisk location of condylar process, double dagger location of absent coronoid process

Mentions: Mammals have adapted to a range of different ecological niches, including a wide variety of diets from the purely carnivorous to exclusively herbivorous. To adapt to these various lifestyles, the skeletal elements associated with feeding have changed in size and shape during evolution. Many of these elements, such at the teeth and skeleton of the jaws are among the defining characteristic of mammals [1]. In contrast to other gnathostomes, the mammalian mandible comprises a single bone (the dentary) that has undergone an increase in complexity and modularity during evolution [2]. The coronoid process, which is the site of attachment of the temporalis muscle, is one of the morphological units of the dentary that offers insight into the adaptations that have occurred during mammalian evolution. Following the late cretaceous angiosperm radiation (100.5 million years ago), an increased number of plant and fruit based dietary niches were made available to early mammals. Adaptation to a more herbivorous diet resulted in changes in the size and shape of the mandible bone such that extant carnivorous, omnivorous, and insectivorous mammals, including mice and Didelphidae opossums (Fig. 1a, b) have a large coronoid process, reflecting the basal mammalian form, while herbivores have a reduced process [3]. Extreme versions of this form can be observed in grass- and leaf-eating mammals such as guinea pigs, where bite force is lower compared with other rodents [4] and the coronoid process is relatively small in size such that it appears absent in many adults (Fig. 1c) [5].Fig. 1


Species-specific modifications of mandible shape reveal independent mechanisms for growth and initiation of the coronoid.

Anthwal N, Peters H, Tucker AS - Evodevo (2015)

Alizarin red/Alcian blue staining of guinea pig, mouse and opossums mandibles. a–c The coronoid process is a distinct part of the dentary in mammals such as the mouse (Mus musculus) and opossum (Mondelphis domestica) during development and in the adult (a, b), whereas the guinea pig (Caviaporcellus) displays a coronoid process comparable with the mouse in embryonic stages (E37 presented in c), but only has a rudimentary process in adults. d Conditional deletion of Pax9 in neural crest lineage cells results in a loss of the coronoid process [8]; Arrowheads: location of coronoid process; asterisk location of condylar process, double dagger location of absent coronoid process
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4644282&req=5

Fig1: Alizarin red/Alcian blue staining of guinea pig, mouse and opossums mandibles. a–c The coronoid process is a distinct part of the dentary in mammals such as the mouse (Mus musculus) and opossum (Mondelphis domestica) during development and in the adult (a, b), whereas the guinea pig (Caviaporcellus) displays a coronoid process comparable with the mouse in embryonic stages (E37 presented in c), but only has a rudimentary process in adults. d Conditional deletion of Pax9 in neural crest lineage cells results in a loss of the coronoid process [8]; Arrowheads: location of coronoid process; asterisk location of condylar process, double dagger location of absent coronoid process
Mentions: Mammals have adapted to a range of different ecological niches, including a wide variety of diets from the purely carnivorous to exclusively herbivorous. To adapt to these various lifestyles, the skeletal elements associated with feeding have changed in size and shape during evolution. Many of these elements, such at the teeth and skeleton of the jaws are among the defining characteristic of mammals [1]. In contrast to other gnathostomes, the mammalian mandible comprises a single bone (the dentary) that has undergone an increase in complexity and modularity during evolution [2]. The coronoid process, which is the site of attachment of the temporalis muscle, is one of the morphological units of the dentary that offers insight into the adaptations that have occurred during mammalian evolution. Following the late cretaceous angiosperm radiation (100.5 million years ago), an increased number of plant and fruit based dietary niches were made available to early mammals. Adaptation to a more herbivorous diet resulted in changes in the size and shape of the mandible bone such that extant carnivorous, omnivorous, and insectivorous mammals, including mice and Didelphidae opossums (Fig. 1a, b) have a large coronoid process, reflecting the basal mammalian form, while herbivores have a reduced process [3]. Extreme versions of this form can be observed in grass- and leaf-eating mammals such as guinea pigs, where bite force is lower compared with other rodents [4] and the coronoid process is relatively small in size such that it appears absent in many adults (Fig. 1c) [5].Fig. 1

Bottom Line: We also demonstrate that Sox9 plays a role independent of chondrogenesis in the growth of the coronoid process in response to muscle interaction.The mandibular coronoid process is initiated by intrinsic factors, but later growth is dependent on extrinsic signals from the muscle.These extrinsic influences are hypothesised to be the basis of the variation in coronoid length seen across the mammalian lineage.

View Article: PubMed Central - PubMed

Affiliation: Department of Craniofacial Development and Stem Cell Biology, Dental Institute, King's College London, London, SE1 9RT UK.

ABSTRACT

Background: The variation in mandibular morphology of mammals reflects specialisations for different diets. Omnivorous and carnivorous mammals posses large mandibular coronoid processes, while herbivorous mammals have proportionally smaller or absent coronoids. This is correlated with the relative size of the temporalis muscle that forms an attachment to the coronoid process. The role of this muscle attachment in the development of the variation of the coronoid is unclear.

Results: By comparative developmental biology and mouse knockout studies, we demonstrate here that the initiation and growth of the coronoid are two independent processes, with initiation being intrinsic to the ossifying bone and growth dependent upon the extrinsic effect of muscle attachment. A necessary component of the intrinsic patterning is identified as the paired domain transcription factor Pax9. We also demonstrate that Sox9 plays a role independent of chondrogenesis in the growth of the coronoid process in response to muscle interaction.

Conclusions: The mandibular coronoid process is initiated by intrinsic factors, but later growth is dependent on extrinsic signals from the muscle. These extrinsic influences are hypothesised to be the basis of the variation in coronoid length seen across the mammalian lineage.

No MeSH data available.


Related in: MedlinePlus