Molecular Genetics of Sensory Organ Development

描述（由申请人提供）：神经发生开始于外胚层组织内神经前体细胞命运的模式规范，这一过程由前膜蛋白（基本螺旋-环-螺旋转录激活因子家族）控制。这种前缘因子的作用早在后生动物的进化史中就有，并具有高度的保守性。了解神经前体的决定过程需要鉴定和阐明(1)前神经蛋白直接神经前体特异性基因表达的顺式调控模块，以及(2)前神经基因和蛋白质活性的控制机制。这里提出的研究计划旨在解决这两个基本问题。我们的项目有三个主要目标，都集中在果蝇神经前体细胞命运的转录规范上：研究原基因活性的负调控模式。我们实验室已发表的研究和最近未发表的研究表明，果蝇前体细胞基因achaete和scute受到多种负调控模式的影响。我们将首先完善我们的相关基因基序和蛋白质结构域的定义，然后研究如何这些序列的功能。具体目标2。阐明双顺式调节模块在感觉器官发育中的作用。我们最近的研究表明，在果蝇感觉器官前体细胞中特异性或显性表达的几个基因依赖于至少两个重叠特异性的转录顺式调控模块来指导它们在这些细胞中的活性。我们将在一组选定的神经前体基因中系统地识别这种双增强子，并研究每个模块如何促进相关基因的表达和表型功能。具体目标3。评估一种在神经前体细胞中表达的转录顺式调控代码。我们的实验室已经在多种果蝇基因中鉴定出具有感觉器官前体细胞特异性的转录顺式调控模块。从这些研究中得出的假设是，这些模块的一个关键子集利用特定的顺式调控“代码”（前神经激活剂和基本螺旋-环-螺旋抑制因子结合位点的组合）来赋予神经前体特异性表达。我们将检验这一假设，并研究这些模块如何有助于适当的神经前体规范。具有“神经内分泌”表型的广泛人类肿瘤与前膜基因的强烈过表达相关，包括小细胞肺癌（最致命的肺癌形式）、神经母细胞瘤（一种侵袭性儿童癌症）、甲状腺髓样癌、嗜铬细胞瘤（肾上腺髓质的肿瘤）、前列腺小细胞神经内分泌癌和皮肤默克尔细胞癌。通过阐明通常负调控前叶基因活性的机制，我们的工作可能为这些疾病的发病机制提供重要的见解。

DESCRIPTION (provided by applicant): Neurogenesis begins with the patterned specification of neural precursor cell fates within ectodermal tissue, a process controlled by the proneural proteins, a family of basic helix-loop-helix transcriptional activators. This function of the proneural factors originated deep in metazoan evolutionary history and is highly conserved. Understanding the process of neural precursor determination will require the identification and elucidation of (1) the cis-regulatory modules through which proneural proteins direct neural precursor-specific gene expression, and (2) the mechanisms by which proneural gene and protein activities are controlled. The research program proposed here seeks to address both of these fundamental questions. Our project has three major objectives, all focusing on the transcriptional specification of neural precursor cell fates in Drosophila: Specific Aim 1. Investigate modes of negative regulation of proneural gene activity. Published studies and recent unpublished investigations in our laboratory have demonstrated that the Drosophila proneural genes achaete and scute are subject to multiple modes of negative regulation. We will first refine our definition of the relevant gene motifs and protein domains, and then investigate how each of these sequences functions. Specific Aim 2. Elucidate the roles of dual cis-regulatory modules in sensory organ development. Our recent studies have revealed that several genes expressed specifically or predominantly in sensory organ precursor cells in Drosophila rely on at least two transcriptional cis-regulatory modules of overlapping specificity to direct their activity in these cells. We will identify such dual enhancers systematically in a selected set of neural precursor genes, and investigate how each module contributes to the expression and phenotypic function of the associated gene. Specific Aim 3. Evaluate a proposed transcriptional cis-regulatory code for expression in neural precursor cells. Our laboratory has identified in a variety of Drosophila genes transcriptional cis-regulatory modules with specificity for sensory organ precursor cells. Out of these studies has come the hypothesis that a critical subset of these modules utilize a specific cis-regulatory "code" (a combination of binding sites for proneural activators and basic helix-loop-helix repressors) to confer neural precursor-specific expression. We will test this hypothesis, and investigate how such modules contribute to proper neural precursor specification. A broad spectrum of human tumors with a "neuroendocrine" phenotype are associated with strong overexpression of proneural genes, including small cell lung cancer (the most lethal form of lung cancer), neuroblastoma (an aggressive childhood cancer), medullary thyroid cancer, pheochromocytoma (a tumor of the adrenal medulla), small cell neuroendocrine carcinoma of the prostate, and Merkel cell carcinoma of the skin. By elucidating mechanisms that normally regulate proneural gene activity negatively, our work may offer important insight into the pathogenesis of these diseases.