BEG4/MIM Function in Epithelial Neoplasia

描述(由申请人提供)：虽然已知癌变源于不受调控的上皮细胞增殖和侵袭，但还需要关于控制这两个关键过程的机制事件的更多信息。不受控制的Shh靶基因诱导可促进高达25%的人类癌症的生长和侵袭。虽然以前的研究表明锌指转录因子Ci/Gli家族介导Shh的转录效应，但肿瘤发生过程中Shh依赖的生长和迁移/侵袭的机制仍不清楚。我们已经发现了一个新的Shh通路成员，在转移中缺失(MIM)，它的水平在各种上皮性癌症中发生变化。MIM与Gli癌基因协同作用，重述Shh介导的上皮细胞增殖和侵袭。MIM有两个可分离的功能：调节Shh靶基因的诱导和控制刺激诱导的细胞迁移。MIM通过结合并拮抗该途径的中央负调控因子Sufu来刺激最大限度的Shh靶基因的诱导。MIM通过组装控制皮质肌动蛋白细丝组装的蛋白质复合体来调节细胞迁移。果蝇原始生殖细胞(PgCs)的正常迁移需要细胞骨架对包括中胚层来源的刺猬在内的局部组织迁移线索的准确反应。我们已经证明，果蝇MIM(DMIM)突变的PGCs不能对这些局部提示做出反应，并转移到异位位置。这项提议的目标是使用人类和果蝇组织模型来剖析这些有文献记载的MIM功能。我们的目标是：1)通过分析MIM在Shh途径不同状态下的活性，阐明MIM增强Gli转录的机制，确定哪些Sufu活性与MIM相互作用的Sufu蛋白表面；2)通过确定哪些MIM功能参与Shh依赖的人类肿瘤的发生，以及MIM如何促进Shh依赖的肿瘤的诱导和维持，确定MIM在Shh依赖的肿瘤发生中的作用；3)通过对dMIM突变的PGC中细胞骨架的变化进行分类，分析dMIM在PGC迁移中的作用，确定dMIM与其他细胞骨架调控因子的遗传和生化相互作用，并通过产生额外的dMIM错义等位基因来确定dMIM的功能结构域。这一建议的资助将使人们更好地了解Shh信号在上皮细胞生长和侵袭中的作用机制，并可能为治疗干预带来新的靶点。

DESCRIPTION (provided by applicant): While it is known that carcinogenesis stems from unregulated epithelial proliferation and invasion, additional information is needed about the mechanistic events controlling these two critical processes. Uncontrolled Shh target gene induction promotes growth and invasion of up to 25% of human cancers. While previous studies indicate that the Ci/Gli family of zinc finger transcription factors mediates the transcriptional effects of Shh, the mechanisms for Shh-dependent growth and migration/invasion during tumorigenesis remain poorly understood. We have identified a novel Shh pathway member, Missing in Metastasis (MIM), whose levels are altered in a variety of epithelial cancers. MIM cooperates with the Gli oncogene to recapitulate Shh-mediated epithelial proliferation and invasion. MIM has two separable functions: regulation of Shh target gene induction, and control of stimuli-induced cellular migration. MIM stimulates maximal Shh target gene induction by binding to and antagonizing Sufu, the central negative regulator of the pathway. MIM regulates cellular migration by assembling protein complexes that control cortical actin filament assembly. Normal migration of Drosophila primordial germ cells (PGCs) requires precise cytoskeletal response to local tissue migratory cues that include mesoderm-derived hedgehog. We have shown that Drosophila MIM (dMIM) mutant PGCs fail to respond to these local cues and metastasize to ectopic locations. The goal of this proposal is to dissect these documented MIM functions using human and Drosophila tissue models. We aim to 1) elucidate the mechanism of MIM potentiation of Gli transcription by assaying MIM activity in different states of the Shh pathway, determine which Sufu activity MIM antagonizes and identify the Sufu protein surface with which MIM interacts; 2) establish the role of MIM in a human model of Shh-dependent tumorigenesis by determining which MIM function contributes to Shh-dependent human carcinogenesis, and how MIM contributes to Shh-dependent tumor induction and maintenance; 3) analyze dMIM function in PGC migration by categorizing cytoskeletal changes in dMIM mutant PGCs, identify the genetic and biochemical interactions of dMIM with other cytoskeletal regulators, and identify dMIM functional domains through the generation of additional dMIM missense alleles. The funding of this proposal will lead to a greater understanding of the mechanisms of epithelial growth and invasion by Shh signaling and may lead to new targets for therapeutic intervention.