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由基因进化变化的积累而产生的，首先需要理解形态是如何由基因和发育机制指定的。人们正在研究秀丽线虫的4细胞尾端，以此作为阐明产生其形态所涉及的基因和发育过程的模型。由于这种结构在近缘物种中采用不同的形态，尾端也为形态发生的进化提供了一种模式。在线虫中，尾尖的形状在成年两性动物中是尖的，在成年雄性动物中是钝的。两性的尖形是由于幼虫状态的保留，而雄性的钝形是由于细胞融合和细胞大小、形状和可能的粘连的变化，这些变化在最后一次幼虫蜕皮之前发生得很快。此外，细胞-细胞信号事件可以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，形态突变体正在被分离和鉴定。其中一个基因lep-1，在雄性尾尖细胞中专门控制成虫的命运，目前正在被克隆，以确定其分子功能和表达模式。最终将研究已识别基因之间的上位性相互作用。通过用激光微束选择性地消融多个或单个候选细胞来检验在诱导尾尖形态发生中假设的细胞与细胞之间的相互作用。其他可能涉及尾尖形态发生的细胞过程正在用细胞成分的标记和抑制物进行研究。为了为这些遗传和发育分析提供一个精确的显微解剖框架，尾尖的细胞结构正在通过电子显微镜进行详细的研究。主要的教育活动采取本科生和研究生课程的形式(主要是进化论和进化发育生物学)，但参与职前教师教育、本科生指导以及在实验室监督高中、本科生和研究生的研究项目也很重要。在课程和实验室中，重点是以探究为中心的动手学习。学生在基于问题的方法指导下构建自己的知识和技能。特别是鼓励合作学习，以发展沟通技巧和合作及独立工作的能力。课程和评估将继续强调语言和解决问题的技能的发展。所有这些活动的目标都是培养所有参与的学生扎实的生物学知识基础，对提出建设性问题和假设的充分怀疑和创造性能力(从而认识到科学是一种可接近的、动态的、创造性的人类活动)，作为解决问题的一般工具的科学方法的实用知识，以及有效地用口头和书面语言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.