Dissertation Research: Developmental Maintenance of Evolutionary Conservatism: A Comparative and Experimental Analysis of Sphenoid Skeletogenesis in Birds and Mammals

史密斯9701104形态守恒的基本机制还不是很清楚。虽然一些解剖区域经历了重大的进化转变，但另一些区域对变化持抵制态度。在五亿年的进化过程中，尽管头骨的其他部分发生了许多变化，但椎骨头部的一个部分--蝶骨区域--的结构之间的关系一直保持不变。经典比较解剖学和现代分子和细胞方法相结合，研究蝶骨骨架的形态发生过程，并表征可能使这一区域在脊椎动物中进化保护的发育特性。本文提出了两项补充研究。第一个确定了在形成蝶骨图案中重要的特定元素。以前进行的实验，如基因敲除、外科手术和致畸治疗，被分析以产生数据，关于神经管、脊索、三叉神经和脑下垂体的扰动如何影响蝶骨拥有内在的模式信息。这涉及到神经脊和中胚层细胞的新的实验性移植。这一研究1)提供和理解了形态发生事件如何影响骨骼模式，2)对复杂的颅骨结构的整合提供了新的见解，3)为形态进化中的发育相互作用的研究提供了重要的范例。

Smith 9701104 Basic mechanisms underlying morphological conservation are not well understood. While some anatomical regions undergo major evolutionary transformations, others are resistant to change. The relations among structures in one part of the vertebrae head, the sphenoid region, have remained constant during five hundred million years of evolution despite numerous modifications in other parts of the skull. Classical comparative anatomy and contemporary molecular and cellular approaches are combined to investigate morphogenetic processes involved in pattering the sphenoid skeleton and t characterize developmental properties that may enable evolutionary conservation of this region across vertebrates. Two complementary studies are proposed. The first identifies specific elements that are important in pattering the sphenoid skeleton. Previously performed experiments such as gene knockouts, surgical manipulations, and teratogen treatments are analyzed to generate data on how perturbations to the neural tube, notochord, trigeminal nerve, and pituitary gland affect the sphenoid skeleton possess intrinsic patterning information. This involves new experimental transplantations of neural crest and mesodermal cells. This investigation 1) provides and understanding of how morphogenetic events affect skeletal patterning, 2) gives new insights on the integration of complex cranial structures, and 3) contributes important examples to the study of developmental interactions in morphological evolution.