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Malcolm Logan - One of the best experts on this subject based on the ideXlab platform.
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regulatory modulation of the t box gene tbx5 links development evolution and adaptation of the Sternum
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: S. R. B. Bickley, Malcolm LoganAbstract:The Sternum bone lies at the ventral midline of the thorax where it provides a critical attachment for the pectoral muscles that allow the forelimbs to raise the body from the ground. Among tetrapods, Sternum morphology is correlated with the mode of locomotion: Avians that fly have a ventral extension, or keel, on their sterna, which provides an increased area for flight muscle attachment. The Sternum is fused with the ribs attaching on either side; however, unlike the ribs, the sternal precursors do not originate from the somites. Despite the crucial role of the Sternum in tetrapod locomotion, little attention has been given to its acquisition, evolution, and embryological development. We demonstrate an essential role for the T-box transcription factor gene Tbx5 in Sternum and forelimb formation and show that both structures share an embryological origin within the lateral plate mesoderm. Consistent with this shared origin and role of Tbx5, Sternum defects are a characteristic feature of Holt–Oram Syndrome (OMIM 142900) caused by mutations in TBX5. We demonstrate a link between Sternum size and forelimb use across avians and provide evidence that modulation of Tbx5 expression underlies the reduction in Sternum and wing size in a flightless bird, the emu. We demonstrate that Tbx5 is a common node in the genetic pathways regulating forelimb and Sternum development, enabling specific adaptations of these features without affecting other skeletal elements and can also explain the linked adaptation of Sternum and forelimb morphology correlated with mode of locomotion.
Xiaoting Zheng - One of the best experts on this subject based on the ideXlab platform.
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on the absence of sternal elements in anchiornis paraves and sapeornis aves and the complex early evolution of the avian Sternum
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Xiaoting Zheng, Jingmai K Oconnor, Xiaoli Wang, Min Wang, Xiaomei Zhang, Zhonghe ZhouAbstract:Anchiornis (Deinonychosauria: Troodontidae), the earliest known feathered dinosaur, and Sapeornis (Aves: Pygostylia), one of the basalmost Cretaceous birds, are both known from hundreds of specimens, although remarkably not one specimen preserves any sternal ossifications. We use histological analysis to confirm the absence of this element in adult specimens. Furthermore, the excellent preservation of soft-tissue structures in some specimens suggests that no chondrified Sternum was present. Archaeopteryx, the oldest and most basal known bird, is known from only 10 specimens and the presence of a Sternum is controversial; a chondrified Sternum is widely considered to have been present. However, data from Anchiornis and Sapeornis suggest that a Sternum may also have been completely absent in this important taxon, suggesting that the absence of a Sternum could represent the plesiomorphic avian condition. Our discovery reveals an unexpected level of complexity in the early evolution of the avian Sternum; the large amount of observable homoplasy is probably a direct result of the high degree of inherent developmental plasticity of the Sternum compared with observations in other skeletal elements.
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insight into the early evolution of the avian Sternum from juvenile enantiornithines
Nature Communications, 2012Co-Authors: Xiaoting Zheng, Jingmai K Oconnor, Xiaoli Wang, Zhonghe ZhouAbstract:The keeled Sternum is a distinct skeletal element in extant birds. In this study, specimens of juvenile extinct birds—Enantiornithes—from the Early Cretaceous show a unique sequence of development in the Sternum, suggesting differences between living birds and this extinct clade.
Zhonghe Zhou - One of the best experts on this subject based on the ideXlab platform.
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on the absence of sternal elements in anchiornis paraves and sapeornis aves and the complex early evolution of the avian Sternum
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Xiaoting Zheng, Jingmai K Oconnor, Xiaoli Wang, Min Wang, Xiaomei Zhang, Zhonghe ZhouAbstract:Anchiornis (Deinonychosauria: Troodontidae), the earliest known feathered dinosaur, and Sapeornis (Aves: Pygostylia), one of the basalmost Cretaceous birds, are both known from hundreds of specimens, although remarkably not one specimen preserves any sternal ossifications. We use histological analysis to confirm the absence of this element in adult specimens. Furthermore, the excellent preservation of soft-tissue structures in some specimens suggests that no chondrified Sternum was present. Archaeopteryx, the oldest and most basal known bird, is known from only 10 specimens and the presence of a Sternum is controversial; a chondrified Sternum is widely considered to have been present. However, data from Anchiornis and Sapeornis suggest that a Sternum may also have been completely absent in this important taxon, suggesting that the absence of a Sternum could represent the plesiomorphic avian condition. Our discovery reveals an unexpected level of complexity in the early evolution of the avian Sternum; the large amount of observable homoplasy is probably a direct result of the high degree of inherent developmental plasticity of the Sternum compared with observations in other skeletal elements.
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insight into the early evolution of the avian Sternum from juvenile enantiornithines
Nature Communications, 2012Co-Authors: Xiaoting Zheng, Jingmai K Oconnor, Xiaoli Wang, Zhonghe ZhouAbstract:The keeled Sternum is a distinct skeletal element in extant birds. In this study, specimens of juvenile extinct birds—Enantiornithes—from the Early Cretaceous show a unique sequence of development in the Sternum, suggesting differences between living birds and this extinct clade.
S. R. B. Bickley - One of the best experts on this subject based on the ideXlab platform.
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regulatory modulation of the t box gene tbx5 links development evolution and adaptation of the Sternum
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: S. R. B. Bickley, Malcolm LoganAbstract:The Sternum bone lies at the ventral midline of the thorax where it provides a critical attachment for the pectoral muscles that allow the forelimbs to raise the body from the ground. Among tetrapods, Sternum morphology is correlated with the mode of locomotion: Avians that fly have a ventral extension, or keel, on their sterna, which provides an increased area for flight muscle attachment. The Sternum is fused with the ribs attaching on either side; however, unlike the ribs, the sternal precursors do not originate from the somites. Despite the crucial role of the Sternum in tetrapod locomotion, little attention has been given to its acquisition, evolution, and embryological development. We demonstrate an essential role for the T-box transcription factor gene Tbx5 in Sternum and forelimb formation and show that both structures share an embryological origin within the lateral plate mesoderm. Consistent with this shared origin and role of Tbx5, Sternum defects are a characteristic feature of Holt–Oram Syndrome (OMIM 142900) caused by mutations in TBX5. We demonstrate a link between Sternum size and forelimb use across avians and provide evidence that modulation of Tbx5 expression underlies the reduction in Sternum and wing size in a flightless bird, the emu. We demonstrate that Tbx5 is a common node in the genetic pathways regulating forelimb and Sternum development, enabling specific adaptations of these features without affecting other skeletal elements and can also explain the linked adaptation of Sternum and forelimb morphology correlated with mode of locomotion.
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The Gene Tbx5 Links Development, Evolution and Adaptation of the Sternum in Terrestrial Vertebrates
2013Co-Authors: S. R. B. BickleyAbstract:The transition from fins to limbs during the colonisation of land was a key innovation in vertebrate evolution. Changes in the limb and shoulder girdle during this event have been investigated extensively, but little attention has been given to the acquisition of the Sternum, a feature considered characteristic of virtually all terrestrial vertebrates, and which is mandatory for tetrapod locomotion. The Sternum is a thin flat bone lying at the ventral midline of the thorax that provides a crucial attachment site for the pectoral muscles, allowing the forelimbs to raise the body up from the ground. I demonstrate that a Sternum completely fails to form in conditional Tbx5 mutant mouse embryos. Consistent with this, Sternum defects are a characteristic feature of Holt-Oram syndrome, which is caused by mutations in TBX5. While the role of Tbx5 in the development of the heart and forelimbs has been studied extensively, Tbx5 function in Sternum formation is not understood. Using chick and mouse models systems, I set out to investigate the developmental origin of the Sternum, and why it fails to form in the absence of Tbx5. Since the function of the Sternum is to facilitate forelimb movement, I explored the correlation between forelimb use and Sternum morphology by comparing Sternum size across different avian species. I then investigated the genetic adaptations that could explain Sternum and forelimb reduction in flightless birds, using the emu as a model. I suggest that Tbx5 represents a common node in the molecular pathways regulating forelimb and Sternum development.
Hiroshi Iida - One of the best experts on this subject based on the ideXlab platform.
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Surgical repair of pectus excavatum
General Thoracic and Cardiovascular Surgery, 2010Co-Authors: Hiroshi IidaAbstract:Pectus excavatum is the most common chest deformity. Children with severe deformities suffer physical complaints such as frequent respiratory infections and decreased endurance. Patients with even mild deformities may complain of physical and psychological symptoms after puberty. In most patients, cardiac and respiratory function deteriorates, meaning that surgical correction is important for alleviation of symptoms and improving cardiopulmonary function and quality of life. The methods of surgical repair remain controversial. The traditional method, first described by Ravitch, comprises resection of deformed cartilages and correction of the Sternum by wedge osteotomy in the upper sternal cortex. Ravitch’s methods have been modified using autologous or exogenous materials to fix the lower Sternum. Nuss reported a novel method in which neither an anterior wound nor the cutting of cartilage or Sternum is required; instead, a convex metal bar is placed behind the Sternum. We have reported sternocostal elevation, in which a section of costal cartilage is resected, and all of the cartilage stumps are resutured to the Sternum. The secured ribs pull the Sternum bilaterally, such that the resultant force causes the Sternum to rise anteriorly. Because most pectus excavatum patients are young and maintain an acceptable quality of life preoperatively, we believe that the morbidity rate is one of the most important factors in selecting the method for corrective surgery. Repair can be performed safely through the use of skilled techniques and a deep understanding of the anatomy and physiology of the thorax.
