GENETIC CONTROL OF CELL FATE DIVERSITY IN DROSOPHILA

这项建议探索了果蝇胚胎表皮中无翼(Wg)信号促进细胞命运决定的机制。WG及其脊椎动物Wnt同源物对于无脊椎动物和脊椎动物胚胎的模式生成都是必不可少的。Wnt信号通路的不适当激活与小鼠的乳腺肿瘤以及人类的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决定，对胎儿和成人的健康问题都是相关的。该项目利用容易得分的幼虫模式作为Wg介导的细胞决策的测试系统。果蝇胚胎分泌一层坚硬的角质层，显示出丰富的结构模式，表明底层表皮中的离散细胞身份。WG信号是产生在野生动物中观察到的不同的角质结构阵列所必需的。这项提案的目标1讨论了突变的Wg分子，它指定了通常在野生型模式中发现的一些但不是全部的细胞命运。这种有限的信号活性的生化基础将从假定的Wg受体分子和已知对Wg功能至关重要的加工步骤方面进行研究。目的2测试Wg信号转导级联的其他组件，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，以确定其合子缺失的微妙影响是由于母亲的贡献，还是反映只参与了Wg介导的细胞反应的一个子集。Aim 3研究了影响Wg活性所指定的细胞命运多样性的其他基因，特别是集中在一个新发现的基因上，该基因特异性地影响由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Wg途径中的一种新功能。目的4描述了这一新基因的分子克隆和随后的基因产物的鉴定计划。

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.