GENETIC CONTROL OF CELL FATE DIVERSITY IN DROSOPHILA

本研究探讨了果蝇胚胎表皮中无翅（Wg）信号促进细胞命运决定的机制。 Wg及其脊椎动物Wnt同源物是无脊椎动物和脊椎动物胚胎中产生模式所必需的。 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的决定是有关胎儿和成人的健康问题。该项目利用易于评分的幼虫模式作为Wg介导的细胞决定的测定系统。 果蝇胚胎分泌一个坚韧的表皮层，显示出丰富的结构模式，表明在下面的表皮离散细胞身份。 Wg信号传导是产生在野生型动物中观察到的多种表皮结构阵列所必需的。 本提案的目的1讨论了一种突变型Wg分子，其指定了通常在野生型模式中发现的一些但不是全部细胞命运。 这种有限的信号传导活性的生化基础将检查相对于推定的Wg受体分子和加工步骤已知是必不可少的Wg功能。 目的2测试Wg信号转导级联的其他组分，以确定它们在不同的Wg介导的细胞命运决定中的确切作用。 将对最近鉴定的转录因子dTCF进行生殖系克隆分析，以确定其合子丢失的微妙影响是否是由于母体贡献，或反映仅参与Wg介导的细胞应答的一个子集。 目的3检查影响由Wg活性指定的细胞命运多样性的其他基因，特别是集中于新鉴定的基因，其特异性影响由目的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途径中的新功能。 目的4描述了这个新基因的分子克隆和随后的基因产物表征的计划。

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.