Growth/Differentiation Factors in Organogenesis

器官发生中的生长/分化因素

• 批准号: 6558874
• 负责人: ALAN PERANTONI
• 金额: --
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6558874
• 关键词: Wilms' tumor; biological signal transduction; carcinogenesis; cell differentiation; cell growth regulation; developmental genetics; growth factor; growth factor receptors; histogenesis; kidney; kidney neoplasms; tissue /cell culture

Morphogenesis in the differentiating metanephros is regulated by reciprocal interactions between ureteric bud epithelia and the metanephric mesenchyme. The ureteric bud invades the overlying metanephric mesenchyme and induces conversion of the mesenchyme into stromal and epithelial elements, which form the nephron. Concurrently, the mesenchyme stimulates the ureteric bud to grow, branch, and eventually form the collecting duct system of the adult kidney. The Differentiation and Neoplasia Section has focused on the elucidation of mechanisms of inductive signaling in metanephric development, seeking (1) the ligands responsible for nephronic differentiation, (2) other non-inductive regulatory factors of nephrogenesis, and (3) the molecular targets of induction. 1) Previously, we reported the establishment of a cell line from the renal inductor, ureteric bud, and have now purified two soluble secreted inductive factors from medium conditioned by these bud cells. We have determined that they are leukemia inhibitory factor (LIF) and transforming growth factor-b2 (TGFb2), that they can function independently of each other to induce tubular differentiation, and that in combination with FGF2, they accelerate this process to yield tubules with kinetics comparable to those in vivo. We have also found that signaling by these inductive cytokines correlates with activation of the Wnt pathway, which plays a central role in metanephric morphogenesis. 2) We have also analyzed the developmental regulatory effects of two members of the secreted Frizzled-related protein (sFRP) family which are normally expressed in the metanephros. These soluble receptors for Wnts can modulate Wnt protein interaction with and activation of membrane-bound Frizzled receptors. In studies of metanephric development, we reported that sFRP-1 is a potent inhibitor of Wnt signaling and tubulogenesis, while sFRP-2 can partially block the inhibitory activity of sFRP-1. 3) Finally, in our search for molecular targets of induction, we have identified some 72 sequences, of which 36 are novel, by differential display. One of the cDNA sequences that is down-regulated with tubule formation, i.e., CITED1/melanocyte-specific gene 1, seems to play a pivotal role in specification of metanephric mesenchyme. Its expression is localized to mesenchymal blastemal populations of the metanephros and nephroblastoma but not in differentiated epithelia, and it appears to block tubulogenesis through modulation of Wnt signaling. This would suggest that it functions as a gatekeeper for metanephric blastemal cell differentiation. These findings provide insight into the dynamics and complex interactions that modulate stem cell commitment in the kidney, and perturbations of these dynamics, at least in part, may explain the accumulation of blastemal populations in neoplasms such as the nephroblastoma, which often manifests a grossly expanded blastemal component.

分化后肾的形态发生受输尿管芽上皮和后肾间质之间相互作用的调节。输尿管芽侵入上面的后肾间质并诱导间质转化为基质和上皮成分，形成肾单位。同时，间充质刺激输尿管芽生长、分支，并最终形成成人肾脏的集合管系统。分化和肿瘤部分专注于阐明后肾发育中诱导信号传导的机制，寻找（1）负责肾分化的配体，（2）肾发生的其他非诱导性调节因子，以及（3）诱导的分子靶点。 1）之前，我们报道了从肾诱导物、输尿管芽建立的细胞系，并且现在已经从这些芽细胞条件的培养基中纯化了两种可溶性分泌诱导因子。我们已经确定它们是白血病抑制因子（LIF）和转化生长因子-b2（TGFb2），它们可以彼此独立地发挥作用，诱导肾小管分化，并且与FGF2结合，它们加速这一过程，产生动力学与体内相当的肾小管。我们还发现这些诱导性细胞因子的信号传导与 Wnt 通路的激活相关，而 Wnt 通路在后肾形态发生中发挥着核心作用。 2）我们还分析了通常在后肾表达的分泌型卷曲相关蛋白（sFRP）家族的两个成员的发育调节作用。这些 Wnt 的可溶性受体可以调节 Wnt 蛋白与膜结合卷曲受体的相互作用并激活膜结合卷曲受体。在后肾发育的研究中，我们报道 sFRP-1 是 Wnt 信号传导和肾小管发生的有效抑制剂，而 sFRP-2 可以部分阻断 sFRP-1 的抑制活性。 3）最后，在我们寻找诱导分子靶标的过程中，我们通过差异显示鉴定了大约 72 个序列，其中 36 个是新的。随着肾小管形成而下调的 cDNA 序列之一，即 CITED1/黑素细胞特异性基因 1，似乎在后肾间充质的规范中发挥着关键作用。它的表达局限于后肾和肾母细胞瘤的间充质胚细胞群，但不在分化的上皮细胞中表达，并且它似乎通过调节 Wnt 信号传导来阻断肾小管发生。这表明它充当后肾胚细胞分化的看门人。这些发现提供了对调节肾脏中干细胞定向的动态和复杂相互作用的深入了解，并且这些动态的扰动至少部分地可以解释肾母细胞瘤等肿瘤中胚基群体的积累，肾母细胞瘤通常表现为胚基成分严重扩张。