Genetic and Developmental Mechanisms of a Morphogenetic Program

要了解多细胞动物的形态多样性是如何通过基因进化变化的积累而产生的，首先需要了解形态是如何由基因和发育机制指定的。秀丽隐杆线虫（Caenorhabditis elegans）的4细胞尾端正在被研究，作为一种模型，用于阐明产生其形态的基因和发育过程。由于这种结构在相关物种中具有不同的形态，因此尾尖也为形态发生的进化提供了模型。在秀丽隐杆线虫中，成年雌雄同体的尾尖是尖的，而成年雄性的尾尖是钝的。雌雄同体的尖形是由于保留了幼虫的状态，而雄性的钝形是由于细胞融合和细胞大小、形状的变化以及可能的粘附性的变化，这些变化在最后一次幼虫蜕皮之前迅速发生。此外，细胞-细胞信号传导事件可能诱导这些事件的协调表达。为了确定与雄性尾尖形态发生有关的基因，形态学突变体被分离并鉴定。其中一种基因，lep-1，专门控制雄性尾尖细胞的成年命运，目前正在克隆以确定其分子功能和表达模式。已鉴定基因之间的上位相互作用将最终被研究。通过激光微束对多个或单个候选细胞的选择性消融，对诱导尾尖形态发生的假设细胞-细胞相互作用进行了测试。其他可能参与尾端形态发生的细胞过程正在用细胞成分的标记物和抑制剂进行研究。为了给这些遗传和发育分析提供一个精确的微观解剖框架，尾巴尖端的细胞结构正在通过电子显微镜进行详细研究。主要的教育活动以本科和研究生课程（主要是关于进化和进化发育生物学）的形式进行，但参与职前教师教育、本科指导和监督高中、本科和研究生在实验室的研究项目也很重要。在课程和实验中，重点放在以探究为中心的实践学习上。学生们通过基于问题的方法来构建自己的知识和技能。在特别的活动中，鼓励合作学习，以培养沟通技巧和协作能力以及独立工作的能力。在课程作业和评估中，将继续强调语言和解决问题能力的发展。所有这些活动的目标是培养所有参与的学生在生物学知识方面的坚实基础，健康的怀疑主义和创造性的能力，以提出建设性的问题和假设（从而欣赏科学作为一种可接近的，动态的，创造性的人类活动），科学方法作为一般解决问题的工具的实用知识，以及用口头和书面语言有效交流发现和概念的能力。

Fitch, David IBN-9506844 To understand how morphological diversity in multicellular animals has arisen by the accumulation of evolutionary changes in genes, an understanding is first required of how morphology is specified by genes and developmental mechanisms. The 4-celled tail tip of the nematode, Caenorhabditis elegans, is being studied as a model for elucidating the genes and developmental processes involved in producing its morphology. Because this structure adopts different morphologies in related species, the tail tip provides a model for the evolution of morphogenesis as well. In C. elegans, the shape of the tail tip is pointy in adult hermaphrodites and blunt in adult males. The pointy shape in hermaphrodites results from retention of the larval state, whereas the blunt shape in males results from cell fusions and changes in cell size, shape and possible adhesion that occur rapidly, just before the last larval molt. Additionally, a cell-cell signalling event may induce the coordinated expression of these events. To identify genes involved in male tail tip morphogenesis, morphological mutants are being isolated and characterized. One such gene, lep-1, acts specifically to control adult fate in male tail tip cells and is being cloned to determine its molecular function and expression pattern. Epistatic interactions among identified genes will eventually be studied. The hypothesized cell-cell interactions in the induction of tail tip morphogenesis are being tested by selective ablation of multiple or single candidate cells with a laser microbeam. Other cellular processes potentially involved in tail tip morphogenesis are being investigated with markers and inhibitors of cellular components. To provide a precise microanatomical framework for these genetic and developmental analyses, the cellular architecture of the tail tip is being detailed by electron microscopy. The major educational activities take the form of undergraduate and graduate courses (mainly on evolution and evolutionary developmental biology), but participation in pre- service teacher education, undergraduate advising, and supervision of high school, undergraduate and graduate student research projects in the laboratory are also important. In the courses and laboratories, emphasis is placed on inquiry-centered, hands-on learning. Students are guided by question-based approaches to construct their own knowledge and skills. In particular activities, cooperature learning is encouraged to develop communication skills and the ability to work collaboratively as well as independently. A continuing emphasis in both coursework and assessment will be the development of language and problem- solving skills. The objectives of all of these activities are to develop in all of the participating students a solid foundation of knowledge in biology, a hearthy skepticism and creative ability to formulate constructive questions and hypothesis (and thus an appreciation of science as an approachable, dynamic, creative, human activity), a practical knowledge of the scientific method as a general problem-solving tool, and an ability to effectively communicate findings and concepts in both oral and written language.