Control by tra-1 of sexual differentiation in C. elegans

两性二态性是几乎所有动物发育的基本特征，并影响体内许多组织和细胞类型。在秀丽隐杆线虫（Caenorhabditis elegans）中，单个基因tra-1的活性对决定整个身体发育为雄性还是雌性是必要和充分的。如果tra-1是活跃的，所有组织分化为雌性，而如果tra-1是不活跃的，所有组织分化为雄性。因此，tra-1是研究性别分化的理想候选者。此外，秀丽隐杆线虫是进行此类研究的理想生物，因为两性差异很大，发育可以在单细胞水平上进行分析，并且存在强大的分子和遗传工具。在这个项目中，我想回答两个基本问题：第一，由tra-1调节的基因mab-3如何调节男性的性发育和行为；第二，tra-1在性腺和性别特异性肌肉中控制哪些基因。tra-1的活性如何直接影响性别分化？为了找到答案，我建议用两种方法研究受tra-1调节的基因。首先是检查mab-3，这是我们之前发现的一种tra-1靶基因，它控制着男性感觉器官的发育，也是男性行为所必需的。Mab-3与昆虫和脊椎动物的性调节有关，这表明在远亲动物中，性发育以类似的机制发生。DMRT1是一种与mab-3相关的基因，与人类睾丸发育和性逆转综合征有关。我们将使用基因筛选来鉴定受mab-3调控的基因，这些基因对感觉器官的发育很重要。我们还将研究哪些感觉神经元需要mab-3来控制男性行为。第二种方法是鉴定受tra-1控制的新基因。为了找到这些基因，我们将使用DNA微阵列，这使我们能够快速识别来自两性的性别特异性mrna。我们将使用RNA干扰（RNAi）来测试性别特异性基因的功能，并将研究感兴趣的基因的表达。从这一筛选中，我们将选择少量基因进行进一步研究，重点关注那些似乎直接受tra-1调控的基因，并在发育早期对性腺和肌肉组织的特异性性别分化起作用。这些实验将最终揭示tra-1如何控制性别分化的分子细节。

Sexual dimorphism is a fundamental feature of development in virtually all animals, and affects many tissues and cell types in the body. In the nematode Caenorhabditis elegans, the activity of a single gene, tra-1, is necessary and sufficient to dictate whether the entire body develops as male or female. If tra-1 is active, all tissues differentiate as female, whereas if tra-1 is inactive, all tissues differentiate as male. Thus tra-1 is an ideal candidate with which to study sexual differentiation. In addition, C. elegans is an ideal organism in which to perform such studies because the two sexes differ extensively, development can be analyzed at the single cell level, and powerful molecular and genetic tools exist. In this project I want to answer two basic questions: first, how does mab-3, a gene regulated by tra-1, regulate male sexual development and behavior, and second, what genes does tra-1 control in the gonad and in sex-specific muscles. How does the activity of tra-1 direct sexual differentiation? To find out, I propose to study genes that are regulated by tra-1, using two approaches. The first is to examine mab-3, a tra-1 target gene we identified previously that controls male development of sense organs and also is required for male behavior. mab-3 is related to sexual regulators in insects and vertebrates, suggesting that sexual development occurs by similar mechanisms in distantly related animals. DMRT1, a gene related to mab-3, is implicated in human testis development and sex reversal syndromes. We will use genetic screens to identify genes regulated by mab-3 that are important for sense organ development. We also will study which sensory neurons require mab-3 for male behavior. The second approach is to identify new genes that are controlled by tra-1. To find these genes we will use DNA microarrays, which allow us to rapidly identify sex- specific mRNAs from the two sexes. We will use RNA interference (RNAi) to test the functions of sex-specific genes and will study the expression of those of interest. From this screen, we will select a small number of genes for further study, concentrating on those that appear to be directly regulated by tra-1 and act early in development to specific sex-specific differentiation of the gonad and musculature. These experiments will ultimately reveal in molecular detail how tra-1 controls sexual differentiation.