RUI: Roles of Paracrine Factors in Formation of the Turtle Shell

RUI：旁分泌因子在龟壳形成中的作用

• 批准号: 0316025
• 负责人: Scott Gilbert
• 金额: $ 36.55万
• 依托单位: Swarthmore College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2007-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0316025&HistoricalAwards=false
• 关键词: RUI; Roles; Paracrine; Factors; Formation

0316025GilbertThe turtle shell is a remarkable evolutionary novelty. No other extant vertebrate has a casing made almost exclusively of bone, and no other vertebrate has its limbs forming within its ribs. The turtle shell is composed of two main parts, the dorsal carapace and the ventral plastron. Between them, on the lateral sides, is a bridge. The carapace contains fifty bones and is supported by the ribs, which grow dorsolaterally rather than ventrally. The major effort of this project will expand earlier studies of carapace development. These earlier studies found (1) that the costal bones that form the bony plate of the carapace grow out from the ribs in both directions, (2) that the costal bones begin to form after the endochondral ossification front of the rib has passed that region of the dermis, and (3) that the bones around the anterior ribs form earlier than those of the posterior ribs. The current project seeks to test whether the ribs induce the ossification of the carapacial dermis and the formation of the bony plate of the carapace. Specifically, it tests the hypothesis that the ossification of the turtle dermis is a by-product of paracrine factors secreted by the ribs as they undergo endochondral ossification. The first part of this developmental scenario contends that as the ribs undergo their normal endochondral ossification, the Indian hedgehog that they secrete during this process would induce the dermal cells around them to express and secrete BMP2/4/7. The second part of this scheme is that the Bone Morphogenetic Proteins would act in both paracrine and autocrine fashions to ossify the dermis, causing a progressive front of intramembranous ossification in the dorsal dermis of the developing turtle. To test this, the turtle homologues for the msx2, ihh, bmp2, bmp4, bmp7, fgf8, and noggin genes would be cloned and their expression analyzed by in situ hybridization. Second, beads or cells secreting the BMP-inhibitory protein, Noggin, would be implanted into hatchling carapaces to see if this inhibition would prevent turtle shell formation. Conversely, BMP-containing beads would be implanted into the dorsal dermis to see if they could induce precocious bone development in other parts of the carapacial dermis. If this hypothesis is validated, this research has wide-ranging implications. First, it would go very far to explaining the "age-old" question of "how the turtle got its shell." Second, this research would show that the developmental program used to form the turtle carapace is a consequence of putting rib cartilage into new positions in the body. Third, the results of this research will aid in the reconstruction of the phylogenetic path leading to the "sudden" emergence of turtles in the late Triassic. The data would provide a mechanism for the rapid development of the carapace (as inferred by the fossil record). Pedagogically, if this hypothesis were correct, this research would provide an excellent and readily understood example of developmental co-option in vertebrates. This work is especially relevant for the training of biology students and the integration of teaching and research. During the past two years, the project has benefited from the talents of ten undergraduates, one graduate student, and three postdoctoral fellows. These have included several women, as well as persons from disabled and under-represented minority groups. The first year of this program will be undertaken at the Thomas Jefferson University School of Medicine, where the Orthopedics Research group is studying the role of hedgehog and BMPs in jaw development. During the second two years this research will be performed at Swarthmore College (during the academic year) and Thomas Jefferson University (during the summers). .

[03:16025]吉尔伯特龟壳是一种非凡的进化新事物。没有其他现存的脊椎动物有几乎完全由骨头构成的肠衣，也没有其他脊椎动物的四肢是在肋骨内形成的。龟壳由两个主要部分组成，背甲壳和腹板。在它们之间的两侧，有一座桥。甲壳包含50块骨头，由肋骨支撑，这些肋骨是背外侧而不是腹侧生长的。这个项目的主要努力将扩展早期对甲壳发育的研究。这些早期的研究发现：(1)形成甲骨板的肋骨从肋骨两个方向长出来，(2)肋骨在肋骨前部的软骨内成骨通过真皮区域后开始形成，(3)前肋骨周围的骨比后肋骨形成得早。目前的项目旨在测试肋骨是否诱导了甲壳真皮的骨化和甲壳骨板的形成。具体来说，它验证了海龟真皮的骨化是肋骨在软骨内骨化过程中分泌的旁分泌因子的副产品的假设。这一发育假说的第一部分认为，当肋骨经历正常的软骨内成骨时，它们在此过程中分泌的印度hedgehog基因会诱导周围的真皮细胞表达和分泌BMP2/4/7。该方案的第二部分是，骨形态发生蛋白会以旁分泌和自分泌的方式作用于真皮的骨化，导致发育中的海龟背真皮的膜内骨化的进展前沿。为了验证这一点，我们克隆了海龟的msx2、ihh、bmp2、bmp4、bmp7、fgf8和noggin基因的同源物，并通过原位杂交分析了它们的表达。第二，将分泌bmp抑制蛋白Noggin的珠粒或细胞植入孵化的甲壳中，观察这种抑制是否会阻止龟壳的形成。相反，含有bmp的小珠子将被植入背侧真皮，以观察它们是否能在甲壳真皮的其他部位诱发骨质早熟。如果这一假设得到证实，这项研究将产生广泛的影响。首先，它将在很大程度上解释“海龟是如何得到壳的”这个“古老”的问题。其次，这项研究将表明，用于形成甲壳的发育程序是将肋骨软骨置于身体新位置的结果。第三，本研究结果将有助于重建导致晚三叠世龟“突然”出现的系统发育路径。这些数据将为甲壳的快速发育提供一种机制（根据化石记录推断）。在教学上，如果这个假设是正确的，这项研究将为脊椎动物的发展选择提供一个很好的和容易理解的例子。这项工作对培养生物学专业的学生和实现教学与科研的结合具有重要意义。在过去的两年中，该项目受益于10名本科生，1名研究生和3名博士后。其中包括几名妇女，以及残疾人和代表性不足的少数群体的人。该项目的第一年将在托马斯·杰斐逊大学医学院进行，那里的骨科研究小组正在研究刺猬蛋白和bmp在颌骨发育中的作用。在接下来的两年里，这项研究将在斯沃斯莫尔学院（在学年期间）和托马斯杰斐逊大学（在夏季期间）进行。