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Eraqi R Khannoon - One of the best experts on this subject based on the ideXlab platform.
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embryonic Skull Development in the gecko tarentola annularis squamata gekkota phyllodactylidae
Journal of Anatomy, 2020Co-Authors: Eraqi R Khannoon, Susan E. EvansAbstract:Tarentola annularis is a climbing gecko with a wide distribution in Africa north of the equator. In the present paper, we describe the Development of the osteocranium of this lizard, from the first appearance of the cranial elements up to the point of hatching. This is based on a combination of histology and cleared and stained specimens. This is the first comprehensive account of gekkotan pre-hatching Skull Development based on a comprehensive series of embryos, rather than a few selected stages. Given that Gekkota is now widely regarded as representing the sister group to other squamates, this account helps to fill a significant gap in the literature. Moreover, as many authors have considered features of the gekkotan Skull and skeleton to be indicative of paedomorphosis, it is important to know whether this hypothesis is supported by delays in the onset of cranial ossification. In fact, we found the sequence of cranial bone ossification to be broadly comparable to that of other squamates studied to date, with no significant lags in Development.
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embryonic Development of Skull bones in the sahara horned viper cerastes cerastes with new insights into structures related to the basicranium and braincase roof
Journal of Anatomy, 2020Co-Authors: Joni Ollonen, Eraqi R Khannoon, Nicolas DipoiAbstract:Ontogenetic studies are crucial for understanding functional morphology, origin and adaptation of Skulls in vertebrates. However, very few studies have so far released complete embryonic series focusing on Skull embryonic Development in species showing diverse and extreme cranial morphologies such as snakes. The wide distribution and unique reproductive and ecological behaviors of venomous vipers, including the heterogeneity in breeding and egg incubation periods in oviparous species, make this group an excellent new model for studying the diversity of Skull Developmental processes in snakes. Here we present the first complete description of osteocranium Development in a viperine snake, Cerastes cerastes, using detailed analysis of the ossification pattern of individual bones across different embryonic stages based on high-resolution micro-computed tomography data. Particularly, we describe in detail the Development of the laterosphenoid from its dorsal and ventral components, dividing the trigeminal foramen into maxillary and mandibular foramina. Furthermore, our data help clarify some controversy concerning the presence and/or origin of structures related to the snake basicranium and braincase roof. For example, our detailed description of supraoccipital Development suggests that this bone derived, at least in part, from the tectum posterius, although the involvement of the tectum synoticum cannot be totally excluded. Similarly, the epiotic centers of supraoccipital ossification are confirmed during braincase Development, and the ancestral lacrimal bone primordium is observed as a ventral element at the early stages of prefrontal Development. Finally, our embryonic C. cerastes data highlight a plausible asymmetry in snake Skull Development, mostly occurring in the basicranium region, but further investigations of embryonic samples and viper species would be required to confirm such phenomenon.
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the Development of the osteocranium in the snake psammophis sibilans serpentes lamprophiidae
Journal of Anatomy, 2020Co-Authors: Ameera Al G A Mohammadi, Eraqi R Khannoon, Susan E. EvansAbstract:Non-avian reptiles are good models to investigate structural and Developmental differences between amniotes. Investigations of craniofacial Development in a complete series of embryos from oviposition up to hatching are still relatively rare. Consideration of a complete series can reveal Developmental events that were previously missed, and thus correct or confirm theories about Developmental events. The Egyptian Sand snake, Psammophis sibilans, has been a key species in descriptions of the snake Skull Development. However, published work was based on a limited sample of specimens collected from the wild. Here, we supplement previous descriptions with an illustrated account of Skull Development in P. sibilans based on a staged series of embryos and histological sections. Our findings largely agree with those of previous authors, although we record differences in Developmental timing, confirming the presence of an egg tooth in this species. We add further observations on the enigmatic fenestra X, showing that it closes rather than merging with the prootic notch. Our observations revealed the likely contribution of the tectum posterius to the occipital roof, the presence of an internal carotid foramen (possibly transitory or variable), and the formation of the initial laterosphenoid pillar.
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RESEARCH ARTICLE The Development of the Skull of the Egyptian Cobra Naja h. haje (Squamata: Serpentes: Elapidae)
2016Co-Authors: Eraqi R Khannoon, Susan E. EvansAbstract:Background The study of craniofacial Development is important in understanding the ontogenetic pro-cesses behind morphological diversity. A complete morphological description of the embry-onic Skull Development of the Egyptian cobra, Naja h. haje, is lacking and there has been little comparative discussion of Skull Development either among elapid snakes or between them and other snakes. Methodology/Principal Findings We present a description of Skull Development through a full sequence of Developmental stages of the Egyptian cobra, and compare it to other snakes. Associated soft tissues of the head are noted where relevant. The first visible ossification centres are in the supra-temporal, prearticular and surangular, with slight ossification visible in parts of the maxilla, prefrontal, and dentary. Epiotic centres of ossification are present in the supraoccipital, and the body of the supraoccipital forms from the tectum posterior not the tectum synoti-cum. The venom glands are visible as distinct bodies as early at stage 5 and enlarge late
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the Development of the Skull of the egyptian cobra naja h haje squamata serpentes elapidae
PLOS ONE, 2015Co-Authors: Eraqi R Khannoon, Susan E. EvansAbstract:Background: The study of craniofacial Development is important in understanding the ontogenetic processes behind morphological diversity. A complete morphological description of the embryonic Skull Development of the Egyptian cobra, Naja h. haje, is lacking and there has been little comparative discussion of Skull Development either among elapid snakes or between them and other snakes. Methodology/Principal Findings: We present a description of Skull Development through a full sequence of Developmental stages of the Egyptian cobra, and compare it to other snakes. Associated soft tissues of the head are noted where relevant. The first visible ossification centres are in the supratemporal, prearticular and surangular, with slight ossification visible in parts of the maxilla, prefrontal, and dentary. Epiotic centres of ossification are present in the supraoccipital, and the body of the supraoccipital forms from the tectum posterior not the tectum synoticum. The venom glands are visible as distinct bodies as early at stage 5 and enlarge later to extend from the otic capsule to the maxilla level with the anterior margin of the eye. The gland becomes more prominent shortly before hatching, concomitant with the Development of the fangs. The tongue shows incipient forking at stage 5, and becomes fully bifid at stage 6. Conclusions/significance: We present the first detailed staging series of cranial Development for the Egyptian cobra, Naja h. haje. This is one of the first studies since the classical works of G. de Beer and W. Parker that provides a detailed description of cranial Development in an advanced snake species. It allows us to correct errors and misinterpretations in previous accounts which were based on a small sample of specimens of uncertain age. Our results highlight potentially significant variation in supraoccipital formation among squamates and the need for further research in this area.
Susan E. Evans - One of the best experts on this subject based on the ideXlab platform.
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embryonic Skull Development in the gecko tarentola annularis squamata gekkota phyllodactylidae
Journal of Anatomy, 2020Co-Authors: Eraqi R Khannoon, Susan E. EvansAbstract:Tarentola annularis is a climbing gecko with a wide distribution in Africa north of the equator. In the present paper, we describe the Development of the osteocranium of this lizard, from the first appearance of the cranial elements up to the point of hatching. This is based on a combination of histology and cleared and stained specimens. This is the first comprehensive account of gekkotan pre-hatching Skull Development based on a comprehensive series of embryos, rather than a few selected stages. Given that Gekkota is now widely regarded as representing the sister group to other squamates, this account helps to fill a significant gap in the literature. Moreover, as many authors have considered features of the gekkotan Skull and skeleton to be indicative of paedomorphosis, it is important to know whether this hypothesis is supported by delays in the onset of cranial ossification. In fact, we found the sequence of cranial bone ossification to be broadly comparable to that of other squamates studied to date, with no significant lags in Development.
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the Development of the osteocranium in the snake psammophis sibilans serpentes lamprophiidae
Journal of Anatomy, 2020Co-Authors: Ameera Al G A Mohammadi, Eraqi R Khannoon, Susan E. EvansAbstract:Non-avian reptiles are good models to investigate structural and Developmental differences between amniotes. Investigations of craniofacial Development in a complete series of embryos from oviposition up to hatching are still relatively rare. Consideration of a complete series can reveal Developmental events that were previously missed, and thus correct or confirm theories about Developmental events. The Egyptian Sand snake, Psammophis sibilans, has been a key species in descriptions of the snake Skull Development. However, published work was based on a limited sample of specimens collected from the wild. Here, we supplement previous descriptions with an illustrated account of Skull Development in P. sibilans based on a staged series of embryos and histological sections. Our findings largely agree with those of previous authors, although we record differences in Developmental timing, confirming the presence of an egg tooth in this species. We add further observations on the enigmatic fenestra X, showing that it closes rather than merging with the prootic notch. Our observations revealed the likely contribution of the tectum posterius to the occipital roof, the presence of an internal carotid foramen (possibly transitory or variable), and the formation of the initial laterosphenoid pillar.
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RESEARCH ARTICLE The Development of the Skull of the Egyptian Cobra Naja h. haje (Squamata: Serpentes: Elapidae)
2016Co-Authors: Eraqi R Khannoon, Susan E. EvansAbstract:Background The study of craniofacial Development is important in understanding the ontogenetic pro-cesses behind morphological diversity. A complete morphological description of the embry-onic Skull Development of the Egyptian cobra, Naja h. haje, is lacking and there has been little comparative discussion of Skull Development either among elapid snakes or between them and other snakes. Methodology/Principal Findings We present a description of Skull Development through a full sequence of Developmental stages of the Egyptian cobra, and compare it to other snakes. Associated soft tissues of the head are noted where relevant. The first visible ossification centres are in the supra-temporal, prearticular and surangular, with slight ossification visible in parts of the maxilla, prefrontal, and dentary. Epiotic centres of ossification are present in the supraoccipital, and the body of the supraoccipital forms from the tectum posterior not the tectum synoti-cum. The venom glands are visible as distinct bodies as early at stage 5 and enlarge late
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the Development of the Skull of the egyptian cobra naja h haje squamata serpentes elapidae
PLOS ONE, 2015Co-Authors: Eraqi R Khannoon, Susan E. EvansAbstract:Background: The study of craniofacial Development is important in understanding the ontogenetic processes behind morphological diversity. A complete morphological description of the embryonic Skull Development of the Egyptian cobra, Naja h. haje, is lacking and there has been little comparative discussion of Skull Development either among elapid snakes or between them and other snakes. Methodology/Principal Findings: We present a description of Skull Development through a full sequence of Developmental stages of the Egyptian cobra, and compare it to other snakes. Associated soft tissues of the head are noted where relevant. The first visible ossification centres are in the supratemporal, prearticular and surangular, with slight ossification visible in parts of the maxilla, prefrontal, and dentary. Epiotic centres of ossification are present in the supraoccipital, and the body of the supraoccipital forms from the tectum posterior not the tectum synoticum. The venom glands are visible as distinct bodies as early at stage 5 and enlarge later to extend from the otic capsule to the maxilla level with the anterior margin of the eye. The gland becomes more prominent shortly before hatching, concomitant with the Development of the fangs. The tongue shows incipient forking at stage 5, and becomes fully bifid at stage 6. Conclusions/significance: We present the first detailed staging series of cranial Development for the Egyptian cobra, Naja h. haje. This is one of the first studies since the classical works of G. de Beer and W. Parker that provides a detailed description of cranial Development in an advanced snake species. It allows us to correct errors and misinterpretations in previous accounts which were based on a small sample of specimens of uncertain age. Our results highlight potentially significant variation in supraoccipital formation among squamates and the need for further research in this area.
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functional relationship between Skull form and feeding mechanics in sphenodon and implications for diapsid Skull Development
PLOS ONE, 2011Co-Authors: Neil Curtis, Marc E H Jones, Susan E. Evans, Paul Ohiggins, Michael J. FaganAbstract:The vertebrate Skull evolved to protect the brain and sense organs, but with the appearance of jaws and associated forces there was a remarkable structural diversification. This suggests that the evolution of Skull form may be linked to these forces, but an important area of debate is whether bone in the Skull is minimised with respect to these forces, or whether Skulls are mechanically “over-designed” and constrained by phylogeny and Development. Mechanical analysis of diapsid reptile Skulls could shed light on this longstanding debate. Compared to those of mammals, the Skulls of many extant and extinct diapsids comprise an open framework of fenestrae (window-like openings) separated by bony struts (e.g., lizards, tuatara, dinosaurs and crocodiles), a cranial form thought to be strongly linked to feeding forces. We investigated this link by utilising the powerful engineering approach of multibody dynamics analysis to predict the physiological forces acting on the Skull of the diapsid reptile Sphenodon. We then ran a series of structural finite element analyses to assess the correlation between bone strain and Skull form. With comprehensive loading we found that the distribution of peak von Mises strains was particularly uniform throughout the Skull, although specific regions were dominated by tensile strains while others were dominated by compressive strains. Our analyses suggest that the frame-like Skulls of diapsid reptiles are probably optimally formed (mechanically ideal: sufficient strength with the minimal amount of bone) with respect to functional forces; they are efficient in terms of having minimal bone volume, minimal weight, and also minimal energy demands in maintenance.
David P Rice - One of the best experts on this subject based on the ideXlab platform.
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rab23 coordinates early osteogenesis by repressing fgf10 perk1 2 and gli1
eLife, 2020Co-Authors: Rakibul Hasan, Maarit Takatalo, Ritva Rice, Tuija Mustonen, David P RiceAbstract:Mutations in the gene encoding Ras-associated binding protein 23 (RAB23) cause Carpenter Syndrome, which is characterized by multiple Developmental abnormalities including polysyndactyly and defects in Skull morphogenesis. To understand how RAB23 regulates Skull Development, we generated Rab23-deficient mice that survive to an age where skeletal Development can be studied. Along with polysyndactyly, these mice exhibit premature fusion of multiple sutures resultant from aberrant osteoprogenitor proliferation and elevated osteogenesis in the suture. FGF10-driven FGFR1 signaling is elevated in Rab23-/-sutures with a consequent imbalance in MAPK, Hedgehog signaling and RUNX2 expression. Inhibition of elevated pERK1/2 signaling results in the normalization of osteoprogenitor proliferation with a concomitant reduction of osteogenic gene expression, and prevention of craniosynostosis. Our results suggest a novel role for RAB23 as an upstream negative regulator of both FGFR and canonical Hh-GLI1 signaling, and additionally in the non-canonical regulation of GLI1 through pERK1/2.
Adriana Jerez - One of the best experts on this subject based on the ideXlab platform.
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embryonic Skull Development in the neotropical viviparous skink mabuya squamata scincidae desarrollo embrionario del craneo en la lagartija vivipara mabuya squamata scincidae
ACTA ZOOLÓGICA MEXICANA (N.S.), 2015Co-Authors: Adriana Jerez, Paola Maria Sanchezmartinez, Ricardo Arturo GuerrafuentesAbstract:ABSTRACT. The systematics of the Americans skinks of the genus Mabuya have been extensively studied , with new arrangements based on molecular analysis. However, the skeletal morphology, their Development and ontogenetic variation have been poorly studied in this genus. We described the embryonic Skull Development of three species of Mabuya and compare it with the African species Trachylepis capensis. We observed that American genus Mabuya presents differences in the Skull Development, including the pila antotica, orbitosphenoid, vomer, and the basicranial fenestra closure. These morphological differences in Mabuya species may be interpreted as putative synapomorphic characters. RESUMEN. La sistematica del genero Mabuya ha sido extensamente estudiada en America y se han propuesto varios arreglos taxonomicos con base en analisis moleculares. Sin embargo, aspectos relacionados con la morfologia del esqueleto, su desarrollo y variacion ontogenetica han sido probrementente estudiados en este genero. En el presente trabajo se describe el desarrollo embrionario del craneo en tres especies del genero Mabuya y se compara con el de la especie africana Trachylepis capensis . Se encontro que el genero Mabuya presenta diferencias en el desarrollo del craneo respecto a la especie africana, incluyendo la pila antotica, el orbitosfenoides, el vomer, y el cierre de la fenestra basicraneal. Estas diferencias en el desarrollo del craneo son importantes, ya que su presencia en todo el genero Mabuya sugiere que se podria tratar de sinapomorfias para este clado.
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embryonic Skull Development in the neotropical viviparous skink mabuya squamata scincidae
Acta Zoológica Mexicana (nueva serie), 2015Co-Authors: Adriana Jerez, Paola Maria Sanchezmartinez, Ricardo Arturo GuerrafuentesAbstract:La sistematica del genero Mabuya ha sido extensamente estudiada en America y se han propuesto varios arreglos taxonomicos con base en analisis moleculares. Sin embargo, aspectos relacionados con la morfologia del esqueleto, su desarrollo y variacion ontogenetica han sido probrementente estudiados en este genero. En el presente trabajo se describe el desarrollo embrionario del craneo en tres especies del genero Mabuya y se compara con el de la especie africana Trachylepis capensis. Se encontro que el genero Mabuya presenta diferencias en el desarrollo del craneo respecto a la especie africana, incluyendo la pila antotica, el orbitosfenoides, el vomer, y el cierre de la fenestra basicraneal. Estas diferencias en el desarrollo del craneo son importantes, ya que su presencia en todo el genero Mabuya sugiere que se podria tratar de sinapomorfias para este clado
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Embryonic Development of the Skull of the Andean lizard Ptychoglossus bicolor (Squamata, Gymnophthalmidae).
Journal of anatomy, 2012Co-Authors: Carlos Hernández-jaimes, Adriana Jerez, Martha Patricia Ramírez-pinillaAbstract:The study of cranial design and Development in Gymnophthalmidae is important to understand the ontogenetic processes behind the morphological diversity of the group and to examine the possible effects of microhabitat use and other ecological parameters, as well as phylogenetic constraints, on Skull anatomy. Complete morphological descriptions of embryonic Skull Development within Gymnophthalmidae are non-existent. Likewise, very little is known about the complete chondrocranium of the family. Herein, the Development of the Skull of the semi-fossorial lizard Ptychoglossus bicolor is described along with an examination of the chondrocranium of other gymnophthalmid taxa and the teiid Cnemidophorus lemniscatus. Cranial chondrification begins with early condensations in the ethmoid, orbitotemporal and occipital regions of the chondrocranium as well as the viscerocranium. Ossification of the Skull starts with elements of the dermatocranium (pterygoid, prefrontal, maxilla and jugal). The orbitosphenoid is the last chondral bone to appear. At birth, the Skull is almost completely ossified and exhibits a large frontoparietal fontanelle. In general terms, the chondrocranium of the gymnophthalmids studied is characteristic of lacertiform terrestrial lizards, in spite of their life habits, and resembles the chondrocranium of C. lemniscatus in many aspects. However, the gymnophthalmids show great variation in the orbitosphenoid and a complex nasal capsule. The latter exhibits greater Development of some nasal cartilages, which make it more complex than in C. lemniscatus. These characteristics might be related to microhabitat use and the well-developed olfactory and vomeronasal systems observed within this clade.
Yang Chai - One of the best experts on this subject based on the ideXlab platform.
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tgf β mediated msx2 expression controls occipital somites derived caudal region of Skull Development
Developmental Biology, 2007Co-Authors: Ryoichi Hosokawa, Mark M Urata, Jun Han, Armen Zehnaly, Pablo Bringas, Kazuaki Nonaka, Yang ChaiAbstract:Craniofacial Development involves cranial neural crest (CNC) and mesoderm-derived cells. TGF-beta signaling plays a critical role in instructing CNC cells to form the craniofacial skeleton. However, it is not known how TGF-beta signaling regulates the fate of mesoderm-derived cells during craniofacial Development. In this study, we show that occipital somites contribute to the caudal region of mammalian Skull Development. Conditional inactivation of Tgfbr2 in mesoderm-derived cells results in defects of the supraoccipital bone with meningoencephalocele and discontinuity of the neural arch of the C1 vertebra. At the cellular level, loss of TGF-beta signaling causes decreased chondrocyte proliferation and premature differentiation of cartilage to bone. Expression of Msx2, a critical factor in the formation of the dorsoventral axis, is diminished in the Tgfbr2 mutant. Significantly, overexpression of Msx2 in Myf5-Cre;Tgfbr2flox/flox mice partially rescues supraoccipital bone Development. These results suggest that the TGF-beta/Msx2 signaling cascade is critical for Development of the caudal region of the Skull.
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conditional inactivation of tgfbr2 in cranial neural crest causes cleft palate and calvaria defects
Development, 2003Co-Authors: Yoshihiro Ito, Jun Han, Pablo Bringas, Jae Yong Yeo, Anna Chytil, Akira Nakajima, Charles F Shuler, Harold L Moses, Yang ChaiAbstract:Cleft palate and Skull malformations represent some of the most frequent congenital birth defects in the human population. Previous studies have shown that TGFβ signaling regulates the fate of the medial edge epithelium during palatal fusion and postnatal cranial suture closure during Skull Development. It is not understood, however, what the functional significance of TGFβ signaling is in regulating the fate of cranial neural crest (CNC) cells during craniofacial Development. We show that mice with Tgfbr2 conditional gene ablation in the CNC have complete cleft secondary palate, calvaria agenesis, and other Skull defects with complete phenotype penetrance. Significantly, disruption of the TGFβ signaling does not adversely affect CNC migration. Cleft palate in Tgfbr2 mutant mice results from a cell proliferation defect within the CNC-derived palatal mesenchyme. The midline epithelium of the mutant palatal shelf remains functionally competent to mediate palatal fusion once the palatal shelves are placed in close contact in vitro. Our data suggests that TGFβ IIR plays a crucial, cell-autonomous role in regulating the fate of CNC cells during palatogenesis. During Skull Development, disruption of TGFβ signaling in the CNC severely impairs cell proliferation in the dura mater, consequently resulting in calvaria agenesis. We provide in vivo evidence that TGFβ signaling within the CNC-derived dura mater provides essential inductive instruction for both the CNC- and mesoderm-derived calvarial bone Development. This study demonstrates that TGFβ IIR plays an essential role in the Development of the CNC and provides a model for the study of abnormal CNC Development.