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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

Pax9 expression in coronoid process of guinea pig and opossum. a, b, f Sirius red/alcian blue trichrome staining of parasagittal section through dentary of E32 guinea pig (a, b) and P10 opossum (f). The rudimentary coronoid process of the guinea pig is associated with a small temporalis muscle containing very few fibres (a, b) when compared with the large muscle surrounding the process of the opossum (f). c, g In situ hybridisation shows that Pax9 is expressed around the coronoid process of both the guinea pig (c) and the opossum (g). d, e. Immunofluorescence staining shows that Sox9 is weakly expressed around the coronoid process of the guinea pig (d) compared to the E15.5 mouse (e); temp temporalis muscle; cp coronoid process; Cdy mandibular condyle; Scale bar in a is 1000 µm; Scale in b–f is 100 µm
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Fig3: Pax9 expression in coronoid process of guinea pig and opossum. a, b, f Sirius red/alcian blue trichrome staining of parasagittal section through dentary of E32 guinea pig (a, b) and P10 opossum (f). The rudimentary coronoid process of the guinea pig is associated with a small temporalis muscle containing very few fibres (a, b) when compared with the large muscle surrounding the process of the opossum (f). c, g In situ hybridisation shows that Pax9 is expressed around the coronoid process of both the guinea pig (c) and the opossum (g). d, e. Immunofluorescence staining shows that Sox9 is weakly expressed around the coronoid process of the guinea pig (d) compared to the E15.5 mouse (e); temp temporalis muscle; cp coronoid process; Cdy mandibular condyle; Scale bar in a is 1000 µm; Scale in b–f is 100 µm

Mentions: It is demonstrated above that Pax9 plays a role in establishment of the coronoid process during the ossification of the dentary in the mouse. To investigate whether Pax9 has a conserved role in initiation of the coronoid process we investigated Pax9 expression in different mammalian species, guinea pig (Cavia porcellus), and early postnatal grey short tailed opossum (Monodelphis domestica) (Figs. 1, 3). As a marsupial, opossums are born early compared to placental mammals in their development and the dentary continues to undergo morphogenesis during the first post-natal weeks. Opossum pups do not form a secondary mammalian squamosal-dentary jaw joint, known in humans as the temporomandibular joint (TMJ), until the end of the second postnatal week [24, 25]. This joint is formed in mice by E16.5 [26], thus in this regard opossum pups are equivalent to late stages of embryonic mice. Opossums and guinea pigs were chosen due to the different sizes of their coronoid processes relative to the size of the dentary in the adult, and the fact that they lack of secondary cartilage at the developing coronoid process (Fig. 1), which is similar to the mouse but contrasting to other species such as rats and humas [5].Fig. 3


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

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

Pax9 expression in coronoid process of guinea pig and opossum. a, b, f Sirius red/alcian blue trichrome staining of parasagittal section through dentary of E32 guinea pig (a, b) and P10 opossum (f). The rudimentary coronoid process of the guinea pig is associated with a small temporalis muscle containing very few fibres (a, b) when compared with the large muscle surrounding the process of the opossum (f). c, g In situ hybridisation shows that Pax9 is expressed around the coronoid process of both the guinea pig (c) and the opossum (g). d, e. Immunofluorescence staining shows that Sox9 is weakly expressed around the coronoid process of the guinea pig (d) compared to the E15.5 mouse (e); temp temporalis muscle; cp coronoid process; Cdy mandibular condyle; Scale bar in a is 1000 µm; Scale in b–f is 100 µm
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4644282&req=5

Fig3: Pax9 expression in coronoid process of guinea pig and opossum. a, b, f Sirius red/alcian blue trichrome staining of parasagittal section through dentary of E32 guinea pig (a, b) and P10 opossum (f). The rudimentary coronoid process of the guinea pig is associated with a small temporalis muscle containing very few fibres (a, b) when compared with the large muscle surrounding the process of the opossum (f). c, g In situ hybridisation shows that Pax9 is expressed around the coronoid process of both the guinea pig (c) and the opossum (g). d, e. Immunofluorescence staining shows that Sox9 is weakly expressed around the coronoid process of the guinea pig (d) compared to the E15.5 mouse (e); temp temporalis muscle; cp coronoid process; Cdy mandibular condyle; Scale bar in a is 1000 µm; Scale in b–f is 100 µm
Mentions: It is demonstrated above that Pax9 plays a role in establishment of the coronoid process during the ossification of the dentary in the mouse. To investigate whether Pax9 has a conserved role in initiation of the coronoid process we investigated Pax9 expression in different mammalian species, guinea pig (Cavia porcellus), and early postnatal grey short tailed opossum (Monodelphis domestica) (Figs. 1, 3). As a marsupial, opossums are born early compared to placental mammals in their development and the dentary continues to undergo morphogenesis during the first post-natal weeks. Opossum pups do not form a secondary mammalian squamosal-dentary jaw joint, known in humans as the temporomandibular joint (TMJ), until the end of the second postnatal week [24, 25]. This joint is formed in mice by E16.5 [26], thus in this regard opossum pups are equivalent to late stages of embryonic mice. Opossums and guinea pigs were chosen due to the different sizes of their coronoid processes relative to the size of the dentary in the adult, and the fact that they lack of secondary cartilage at the developing coronoid process (Fig. 1), which is similar to the mouse but contrasting to other species such as rats and humas [5].Fig. 3

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