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节的上皮细胞增殖和侵袭，但需要更多关于控制这两个关键过程的机制事件的信息。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。虽然先前的研究表明锌指转录因子Ci/Gli家族介导Shh的转录作用，但在肿瘤发生过程中Shh依赖性生长和迁移/侵袭的机制仍然知之甚少。我们已经确定了一个新的Shh通路成员，转移缺失（MIM），其水平在各种上皮癌中发生改变。MIM与Gli癌基因合作，重现sh介导的上皮细胞增殖和侵袭。MIM具有两种可分离的功能：调节Shh靶基因诱导和控制刺激诱导的细胞迁移。MIM通过结合和拮抗Sufu（该通路的中枢负调节因子）来刺激最大程度的Shh靶基因诱导。MIM通过组装控制皮质肌动蛋白丝组装的蛋白复合物来调节细胞迁移。果蝇原始生殖细胞（PGCs）的正常迁移需要精确的细胞骨架响应局部组织迁移信号，包括中胚层来源的hedgehog基因。我们已经证明果蝇MIM （dMIM）突变PGCs不能对这些局部提示作出反应并转移到异位位置。本提案的目标是利用人类和果蝇组织模型解剖这些记录的MIM功能。我们的目标是：1)通过分析Shh通路不同状态下的MIM活性，确定MIM拮抗哪些Sufu活性，并鉴定与MIM相互作用的Sufu蛋白表面，阐明MIM增强Gli转录的机制；2)通过确定MIM的哪些功能促进了sh依赖性的人类癌变，以及MIM如何促进sh依赖性肿瘤的诱导和维持，建立MIM在sh依赖性肿瘤发生的人类模型中的作用；3)通过对dMIM突变体PGCs的细胞骨架变化进行分类，分析dMIM在PGC迁移中的功能，鉴定dMIM与其他细胞骨架调节因子的遗传和生化相互作用，并通过产生额外的dMIM错义等位基因鉴定dMIM的功能域。该提案的资助将导致对Shh信号的上皮生长和侵袭机制的更好理解，并可能导致治疗干预的新靶点。

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.