GENETIC CONTROL OF CELL FATE DIVERSITY IN DROSOPHILA

本研究探讨了果蝇胚胎表皮中无翼信号通路促进细胞命运决定的机制。在无脊椎动物和脊椎动物胚胎中，Wnt及其同系物是产生模式的关键。Wnt信号通路的不适当激活与小鼠乳腺肿瘤以及人类黑色素瘤和结肠癌有关。因此，了解这些分子如何影响细胞命运的决定与胎儿和成人的健康问题有关。该项目利用易于评分的幼虫模式作为检测系统，用于wg介导的细胞决策。果蝇胚胎分泌坚韧的角质层，显示出丰富的结构模式，表明在下面的表皮中有独立的细胞身份。在野生型动物中观察到的各种角质层结构的产生需要Wg信号。本提案的目标1讨论了一个突变的Wg分子，它指定了一些，但不是全部，通常在野生型模式中发现的细胞命运。这种有限的信号活动的生化基础将根据假定的Wg受体分子和已知的Wg功能所必需的加工步骤进行检查。目的2测试了Wg信号转导级联的其他成分，以确定它们在不同Wg介导的细胞命运决定中的确切作用。将对最近发现的转录因子dTCF进行生殖系克隆分析，以确定其合子丢失的微妙影响是由于母体的贡献，还是仅反映了wg介导的细胞反应的一部分。目的3研究影响Wg活性指定的细胞命运多样性的其他基因，特别关注一个新发现的基因，该基因专门影响Aim 1中描述的突变Wg分子产生的多样性。这种特异性可能表明在Wg通路中有一种新的功能。目标4描述了该新基因的分子克隆计划及其基因产物的后续表征。

This proposal explores the mechanisms by which Wingless (Wg) signaling promotes cell fate decisions in the Drosophila embryonic epidermis. Wg and its vertebrate Wnt homologues are essential for generating pattern in both invertebrate and vertebrate embryos. Inappropriate activation of the Wnt signaling pathway has been implicated in mammary tumors in mice, and melanomas and colon carcinomas in humans. Therefore, understanding how these molecules influence cell fate decisions is relevant to both fetal and adult human health issues. The project utilizes the easily scored larval pattern as an assay system for Wg-mediated cellular decisions. Drosophila embryos secrete a tough cuticular layer that displays a rich pattern of structures, indicative of discrete cell identities in the underlying epidermis. Wg signaling is required for generating the diverse array of cuticular structures observed in the wild- type animal. Aim 1 of this proposal discusses a mutant Wg molecule that specifies some, but not all, of the cell fates normally found in wild-type pattern. The biochemical basis for this limited signaling activity will be examined with respect to putative Wg receptor molecules and processing steps known to be essential for Wg function. Aim 2 tests other components of the Wg signal transduction cascade to determine their precise roles in the distinct Wg-mediated cell fate decisions. Germ line clone analysis of the recently identified transcription factor, dTCF, will be undertaken to determine whether the subtle effects of its zygotic loss are due to maternal contribution, or reflect participation in only a subset of the Wg-mediated cellular responses. Aim 3 examines other genes that influence the diversity of cell fates specified by Wg activity, particularly concentrating on a newly identified gene that specifically influences the diversity generated by the mutant Wg molecule described in Aim 1. This specificity may indicate a novel function in the Wg pathway. Aim 4 describes a plan for the molecular cloning of this new gene and for the subsequent characterization of its gene product.