ORGANOGENESIS OF THE PHARYNX IN C ELEGANS

驱动前肠发育的基因和机制主要是 未知，代表着发育生物学的一个新领域。我们是 通过研究儿童咽部的形成来研究前肠发育 线虫。此前，我们确定了一个基因座， PHA-4，它是建立咽和直肠原基所必需的： 携带PhA-4基因突变的动物作为没有咽喉和 直肠。我们最近克隆了PHA-4，并表明它编码一种 果蝇基因叉头的同源物。这一结果，加上我们的 表型分析表明，前肠(咽)和后肠(直肠) 发育在蠕虫和苍蝇之间保存了500多年 一百万年。令人惊讶的是，闭锁的肛门和食道 闭锁是一种常见的人类先天缺陷，这表明 人类体内可能存在发育途径。 这项建议将把我们对咽形成的研究扩展到三年 方式。 目的1.咽部发育依赖于不同细胞系的细胞 组装成一个完整的器官。PHA-4基因标志着 这些不同的细胞谱系在表型(即 来自所有细胞谱系的咽细胞在pha-4突变体中丢失)，并通过 表达(即PhA-4：：GFP报告基因在咽部细胞中表达 来自所有血统)。要了解多个单元的融合如何 血统形成一个器官的原基是如何实现的，我们将分析 PHA-4在咽部细胞中得到表达。我们将使用 缺失分析、报告构建、不同突变体的组合 背景和流动性变化分析，以解决这一问题。 目的2.我们将研究PHA-4是否直接激活了两个 用于区分两种PhA-4模型的候选咽部基因 功能：1)PHA-4可以提前启动下游的层级结构 调节剂-4可能是许多人或所有人的必备辅助因素 咽部基因，早期和晚期。 目的3.目前已鉴定的咽部发育所需基因很少。 为了发现形成咽部所必需的新基因座，我们将 表现出移除基因的纯合缺陷的表型特征 是咽部发育所必需的。这些可分为三种表型 类别：i)分叉咽ii)小咽iii)咽阻滞 原基植物。在我们初步调查的基础上，我们将选择最 有希望进行进一步分析的候选人。

The genes and mechanisms that drive foregut development are largely unknown and represent a new area of developmental biology. We are studying foregut development by investigating pharynx formation in the nematode Caenorhabditis elegans. Previously, we identified a locus, pha-4, that is required to establish the pharynx and rectum primordia: animals bearing pha-4 mutations arrest as larvae that lack a pharynx and a rectum. We have recently cloned pha-4 and shown that it encodes a homolog of the Drosophila gene fork head. This result, coupled with our phenotypic analyses, suggest that foregut (pharynx) and hindgut (rectum) development have been conserved between worms and flies for over 500 million years. Strikingly, imperforate anus coupled with esophageal atresia is a common human birth defect, suggesting that similar developmental pathways may exist in humans. This proposal will extend our studies of pharynx formation in three ways. Aim 1. Pharynx development depends on cells from different cell lineages assembling into an integrated organ. The pha-4 gene marks the convergence of these different cell lineages both by phenotype (i.e. pharynx cells from all cell lineages are lost in pha-4 mutants) and by expression (i.e. a pha-4::GFP reporter is expressed in pharynx cells from all lineages). To understand how the convergence of multiple cell lineages into one organ primordium is achieved, we will analyze how pha-4 expression is established in pharynx cells. We will use a combination of deletion analysis, reporter constructs, different mutant backgrounds, and mobility shift assays to address this issue. Aim 2. We will investigate whether PHA-4 directly activates two candidate pharynx genes to distinguish between two models of pha-4 function: 1) pha-4 could act early to initiate a hierarchy of downstream regulators 2) pha-4 could be an obligate co-factor for many or all pharynx genes, early and late. Aim 3. Few genes required for pharynx development have been identified. To discover new loci that are necessary to form the pharynx, we will phenotypically characterize homozygous deficiencies that remove genes needed for pharynx development. These fall into three phenotypic classes: i) bifurcated pharynx ii) small pharynx iii) arrested pharynx primordium. On the basis of our initial survey, we will choose the most promising candidates for further analysis.