Control of Neuroblast Proliferation in Drosophila

描述（由申请人提供）：本项目的长期目标是阐明控制干细胞增殖的分子机制，以响应发育线索。干细胞是独特的前体，可以自我更新并产生各种细胞类型。干细胞分裂不足会导致出生缺陷，而不受控制的分裂会导致许多类型的癌症。因此，干细胞对所有生物体的健康、活力和维持具有巨大影响。在果蝇中，神经元干细胞或神经母细胞的亚群在幼虫孵化后处于静止状态，并在特定的发育阶段恢复细胞分裂;增殖的时间受到trol突变的影响。Trol激活静止神经母细胞的分裂。我们已经表明，trol编码的同源哺乳动物串珠素，生长因子的共受体。我们的遗传和生物化学分析表明，由两种生长因子Bnl（果蝇FGF）和Hh激活的信号通路驱动受调节细胞的分裂起始。通过这些途径的信号传导由Trol调节。我们已经开始生产融合蛋白和产生域特异性抗体。两种类型的试剂将用于探测突变Trol蛋白的结构以及Trol-FGF和Trol-Hh结合的特异性。我们将使用抗体和trol-GAL 4转基因来跟踪trol表达。我们将研究每种途径如何协同或独立地影响特定的神经母细胞或神经母细胞亚群的分裂，通过改变配体和其他成分的水平，表征途径蛋白的表达模式，并阻断FGF途径的激活。为了阐明信号特异性是如何实现的，我们将检测trol和bnl或hh之间的等位基因特异性相互作用，确定过表达trol结构域在弱配体突变体中的作用，研究同时改变Bnl和Hh水平的后果，并确定糖部分在信号特异性中的作用。这些研究将为干细胞分裂受发育线索控制的机制提供重要的见解-这是一个在所有动物（包括人类）中具有根本重要性的过程。

DESCRIPTION (provided by applicant): The long-term goal of this project is to elucidate the molecular mechanism(s) controlling stem cell proliferation in response to developmental cues. Stem cells are unique precursors that are self-renewing and give rise to various cell types. Insufficient stem cell division leads to birth defects, while uncontrolled division leads to many types of cancer. Thus, stem ceils have an enormous impact on the health, viability and maintenance of all organisms. In Drosophila, subsets of neuronal stem cells, or neuroblasts, are quiescent upon larval hatching and resume cell division at specific developmental stages; the timing of proliferation is affected by mutations in trol. Trol activates division in quiescent neuroblasts. We have shown that trol encodes a homolog of mammalian Perlecan, a co-receptor for growth factors. Our genetic and biochemical analyses suggest that the signaling pathways activated by two growth factors, Bnl (the Drosophila FGF) and Hh, drive initiation of division in the regulated cells. Signaling by these pathways is modulated by Trol. We have begun to produce fusion proteins and generate domain-specific antibodies. Both types of reagents will be used to probe the structure of mutant Trol proteins and the specificity of Trol-FGF and Trol-Hh binding. We will use the antibodies and a trol-GAL4 transgene to follow trol expression. We will examine how each pathway acts in concert or independently to affect division of specific neuroblasts or neuroblast subsets by altering the levels of ligands and other components, characterizing the expression pattern of pathway proteins, and blocking activation of the FGF pathway. To elucidate how signaling specificity is attained, we will assay for allele-specific interactions between trol and bnl or hh, ascertain the effect of over-expressing trol domains in weak ligand mutants, study the consequences of simultaneously changing levels of both Bnl and Hh, and determine the role of sugar moieties in signaling specificity. These studies will provide important insights into the mechanism(s) by which stem cell division is controlled by developmental cues--a process of fundamental importance in all animals, including humans.