CAREER: Forces Underlying Germ Band Retraction in Drosophila Embryogenesis

智力优势尽管发育中的胚胎的身体形态最终是由其遗传程序决定的，但形态发生的直接原因是细胞间力量的产生和调节。研究发育的遗传方法已经取得了巨大的成功，特别是在决定细胞命运模式的基因方面。然而，额外的基因决定了细胞命运决定的机械后果。为了从突变的形态表型中明确地确定这些基因的作用，定量地了解形态发生的力量是至关重要的。本着这种精神，本项目包括实验和计算调查，研究果蝇（Drosophila melanogaster）胚带收缩的形态发生事件背后的力量。通过激光显微外科手术和计算建模，对细菌带内收的工作模型进行了实验挑战。工作模型基于三种组织的不同作用。这些作用体现在以下假设中：(i)胚带收缩是由空间和时间调节的羊膜收缩驱动的；（ii）胚带本身被动地对羊膜中的张力作出反应；(3)羊膜张力的分布是由羊膜与卵黄囊的接触决定的。根据这些假设，本项目的具体目标是：1。描述羊膜在胚带回缩（GBR）中的物理作用，包括这一作用的空间和时间限制。以确定是否有活性成分的细胞形状的变化观察到收缩的胚芽带。以高空间和时间分辨率定量绘制和模拟GBR背后的力量。将突变的gbr失败表型与潜在力量中的缺陷联系起来。注意，这些目标补充了果蝇胚胎发生的传统遗传方法。通过专注于一种模式生物，大量的遗传技术是可用的，这项研究的结果将提供急需的杠杆作用，使现在和未来的研究能够更好地将形态发生与发育的遗传程序联系起来。更广泛的影响作为上述研究目标成功的组成部分，PI的教育计划将使并鼓励物理学和生物学的学生跨越学科鸿沟。该计划的四个主要重点是：(i)通过实施物理教育研究的最佳实践来改善生命科学本科专业的物理教育；（ii）为本科生提供跨学科的研究机会；（iii）通过与当地HBCU菲斯克大学（Fisk University）的合作，招募未被充分代表的少数民族参与生物物理研究；（iv）为物理科学家开发跨学科研究生课程，强调跨学科交流复杂思想的能力。这些综合教育活动的主要更广泛的影响将是加强跨学科研究，通过培养学生跨越物理学/生物学界面的工作，并通过增加对物理学和生物学主流中的生物物理学的欣赏。此外，该研究项目为一个研究得非常充分的系统提供了一个新的视角。通过定义果蝇胚胎发生的一个重要步骤的机械方面，这项研究将建立新的智力基础设施。它将使大量研究这个问题的研究人员能够提出一套全新的问题。此外，本项目开发的软件工具（用于图像处理和使用激光钻孔技术分析内力）将广泛传播到果蝇研究界。

INTELLECTUAL MERITAlthough the body plan of a developing embryo is ultimately determined by its genetic program, the proximate cause of morphogenesis is the generation and regulation of intercellular forces. Genetic approaches to development have been hugely successful, particularly in regard to the genes that determine patterns of cell-fate determination. However, additional genes then determine the mechanical consequences of cell-fate decisions. To unambiguously determine the role of these genes from mutant morphological phenotypes, it is crucial to quantitatively understand the forces underlying morphogenesis. In that spirit, this project involves experimental and computational investigations of the forces underlying the morphogenetic event of germ-band retraction in the fruit fly, Drosophila melanogaster. A working model for germ-band retraction will be experimentally challenged through laser-microsurgery and computational modeling. The working model is based on distinct roles for each of three tissues. These roles are embodied in the following hypotheses: (i) germ-band retraction is driven by spatially and temporally regulated contraction of the amnioserosa; (ii) the germ band itself responds passively to tension in the amnioserosa; and (iii) the distribution of tension in the amnioserosa is determined by contact between the amnioserosa and yolk sac. In light of these hypotheses, the specific goals of this project are:1. To delineate the physical role of the amnioserosa in germ-band retraction (GBR), including the spatial and temporal limitations of this role.2. To determine if there is an active component to the cell shape changes observed in the retracting germ band.3. To quantitatively map and model the forces underlying GBR with high spatial and temporal resolution.4. To link mutant GBR-failure phenotypes to defects in the underlying forces.Note that these goals complement traditional genetic approaches to Drosophila embryogenesis. By focusing on a model organism for which a vast array of genetic techniques are available, the results of this research will provide much-needed leverage, enabling this and future investigations to better connect morphogenesis to the genetic program of development.BROADER IMPACTSIntegral to success in the research goals stated above, the PI's educational plan will enable and encourage students from both physics and biology to work across the disciplinary divide. The four main thrusts of this plan are: (i) to improve the physics education of undergraduate life-science majors by implementing best practices from physics-education research; (ii) to provide interdisciplinary research opportunities for undergraduates; (iii) to recruit under-represented minorities into biophysical research through a partnership with Fisk University, a local HBCU, and (iv) to develop an interdisciplinary graduate course for physical scientists that stresses the ability to communicate complex ideas across disciplinary lines. The major broader impact of these integrated educational activities will be to strengthen interdisciplinary research, both by preparing students to work across the physics/biology interface and by increasing the appreciation of biophysics within the physics and biology mainstreams. Furthermore, the research project provides a new perspective on an exceedingly well-studied system. By defining the mechanical aspects of a major step in Drosophila embryogenesis, this research will build new intellectual infrastructure. It will enable the large community of researchers working on this problem to ask an entirely new set of questions. In addition, the software tools developed in this project (both for image processing and for analyzing the intrinsic forces using laser hole-drilling techniques) will be disseminated broadly to the Drosophila research community.