The function of Gli proteins in the specification of ossification pathways in pectoral girdle development and evolution

进化生物学中一个长期存在并广泛争论的问题是脊椎动物如何从水中过渡到陆地。这种转变需要骨骼的组成和结构发生巨大变化，以实现陆地进食，呼吸和运动。尽管骨骼变化对脊椎动物进化至关重要，但稀疏的化石记录使其进化轨迹和潜在机制在很大程度上未知。本计画主要探讨鱼类肩胛骨向四足动物肩胛骨转变的遗传机制。我们研究的综合性非常适合桥接多个学科（比较解剖学，遗传学和基因组学）的培训，以创造一个动态的环境，让学生通过动手研究活动和小组讨论学习。为了实现将多学科科学嵌入本科课程的目标，PI在2018年与美国自然历史博物馆（AMNH）建立了一个新的教育计划，探索鱼类到四足动物的过渡。参加本课程的学生将参加罗格斯大学和AMNH的小组讨论，学习如何弥合不同的学科，并解决与鱼类到四足动物过渡相关的问题。总的来说，这个综合性的研究和教育计划将促进对鱼类进化的深入了解，培养本科生和研究生，并告知外行人对“缺失环节”的奥秘的答案，这吸引了我们社会的大量兴趣。这个项目的主要目标是确定在脊椎动物中发现的两种不同类型的骨骼的规格机制，膜内骨和软骨内骨，重点是胸（肩）带。对胸带的关注是基于既定的认识，即在进化成四足动物的过程中，鱼类两种骨骼类型的比例变化使胸带与头骨断开，从而为陆地运动和生活方式铺平了道路。有趣的是，以前的研究表明，gli家族基因gli3调节了肩带发育中膜内和软骨内骨化的平衡。先前的工作也确定了Gli3调节成骨细胞和软骨细胞分化相关的基因。目的1研究Gli家族基因敲除鱼的Gli水平在膜内和软骨内骨化特化中的作用，并对gli家族基因敲除鱼的胚胎和成体表型进行表征。目的2将检验Gli的量调节成骨细胞和软骨细胞分化中涉及的基因组的假设。目标3将使用转基因鱼测试Gli靶基因在指定骨化途径中的功能。这些目标将揭示两种不同类型的骨骼是如何在脊椎动物的胸带中被指定的，并表明这种信号通路的变化可能是从鱼类到四足动物的胸带进化的基础。这个奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

One of the long-standing, and extensively debated, questions in evolutionary biology is how vertebrates transitioned from water to land. The transition required dramatic changes to the composition and architecture of the skeleton to enable terrestrial feeding, respiration, and locomotion. Despite the critical importance of the skeletal changes for vertebrate evolution, the sparse fossil record has rendered its evolutionary trajectory and the underlying mechanisms largely unknown. This project investigates the genetic mechanisms of the skeletal transition of shoulder girdle bones from fish to tetrapods. The integrative nature of our research is well-suited for a training of bridging multiple disciplines (comparative anatomy, genetics, and genomics) to create a dynamic environment where students learn through hands-on research activities and group discussion. Towards the goal of embedding multidisciplinary science into undergraduate curriculum, the PI established a new educational program that explores fish-to-tetrapod transition with the American Museum of Natural History (AMNH) in 2018. Students that take this course will participate in group discussions at Rutgers U and AMNH, learn how to bridge different disciplines, and address questions related to the fish-to-tetrapod transition. Collectively, this integrated research and educational program will reciprocally facilitate the deep understanding of fish evolution, foster undergraduates and graduate students, and inform lay people with the answers to the mysteries of the “missing link” which attracts large amount of interest in our society. The main goal of this project is to identify the specification mechanisms of the two distinct types of bones found in vertebrates, intramembranous and endochondral, focusing on the pectoral (shoulder) girdle. Focus on the pectoral girdle is based on the established appreciation that during the evolution into tetrapods changes in the ratios of two bone types in fish disconnected the pectoral girdle from the skull, thus paving the way to the terrestrial locomotion and way of life. Intriguingly, previous studies showed that one of the gli family gene gli3 regulates a balance of intramembranous and endochondral ossification in pectoral girdle development. Prior work also determined that Gli3 regulates genes involved in osteoblast and chondrocyte differentiation. Objective 1 will identify the roles of the Gli level in the specification of intramembranous and endochondral ossification, and characterize the embryonic and adult phenotypes of gli family gene knockout fish. Objective 2 will test the hypothesis that the amount of Gli regulates the battery of genes involved in osteoblast and chondrocyte differentiation. Objective 3 will test the function of Gli target genes in the specification of ossification pathways using transgenic fish. These objectives will reveal how two distinct types of bones are specified in the vertebrate pectoral girdle and suggest that changes in this signaling pathway could underly the pectoral girdle evolution from fish to tetrapods.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.