The Cellular Mechanisms Responsible for AP-2-Dependent Mammalian Morphogenesis

序列特异性DNA结合转录因子是遗传信息的强大调控因子，在胚胎发生过程中负责整合基因表达。对这些蛋白质如何控制细胞命运决定的全面分析将对脊椎动物发育机制产生关键的见解。AP-2蛋白提供了一个特别有吸引力的系统来研究控制发育调节基因表达的各种过程。在胚胎发生过程中，AP-2的表达集中在许多经历复杂形态发生变化的组织中，如发育中的神经嵴、面部、肢体芽、肾脏、乳腺和表皮。此外，AP-2基因的转录受到视黄酸的影响，AP-2可能是这一信号转导途径的重要组成部分。含有AP-2基因纯合子破坏的小鼠会在围产期死亡，并表现出多种严重的发育缺陷。此外，对由野生型细胞和无AP-2细胞组成的嵌合胚胎的初步分析表明，AP-2至少是神经管、面部、眼睛、体壁和四肢形成这五个基本形态发生程序所独立需要的。显然，对AP-2调控的细胞命运决定的透彻理解将产生关于这些正常发育程序的丰富信息。该建议将利用AP-2敲除表型的知识来探索调节哺乳动物形态发生的细胞机制。用lacZ转基因标记的新一代ap -2缺失胚胎干细胞将被建立。这些胚胎干细胞将被用于产生由野生型和无ap -2细胞组成的嵌合胚胎。对这些嵌合动物的分析将提供有关AP-2参与的众多发育程序的细胞基础的详细信息。

Sequence-specific DNA binding transcription factors are powerful regulators of genetic information and are responsible for integrating gene expression during embryogenesis. A comprehensive analysis of how these proteins control cell fate determination will yield critical insight into the mechanisms of vertebrate development. The AP-2 protein presents a particularly attractive system to study the various processes governing developmentally-regulated gene expression. During embryogenesis, AP-2 expression is concentrated in many tissues undergoing complex morphogenic changes - the developing neural crest, face, limb bud, kidney, mammary gland and epidermis. In addition, transcription of the AP-2 gene is influenced by retinoic acid, and AP-2 may act as an integral component of this signal transduction pathway.Mice containing a homozygous disruption of the AP-2 gene die perinatally and exhibit multiple and severe developmental defects. Furthermore, preliminary analysis of chimeric embryos, composed of wild-type and AP-2-null cells, indicates that AP-2 is independently required for at least five fundamental morphogenic programs - formation of the neural tube, face, eye, body-wall and limbs. Clearly, a thorough understanding of the cell fate decisions regulated by AP-2 will yield a wealth of information concerning these normal development programs.This proposal will utilize knowledge of the AP-2 knockout phenotype to probe the cellular mechanisms regulating mammalian morphogenesis. A new generation of AP-2-null embryonic stem cells will be established that are tagged with a lacZ transgene. These ES cells will then be used to generate chimeric embryos composed of wild-type and AP-2-null cells. Analysis of these chimeric animals will provide detailed information concerning the cellular basis of the numerous developmental programs with which AP-2 is involved.