EGFR/ErbB SIGNALING IN LIMB PATTERNING

这个项目的目标是探索ErbB信号在肢体模式中的作用。ErbB家族由ErbB1(也称为表皮生长因子受体或EGFR)、其他三种受体(ErbB2-4)和11种配体组成。ErbB信号网络被认为是细胞信号反应多样化的范例，因为不同的信号是通过形成ErbB异源二聚体和被多个配体激活而产生的。此外，ErbB信号网络作为多条信号通路的中心汇聚点，整合来自其他受体类的信号，发挥着重要的作用。ErbB1、ErbB4及其配体EGF、TGF-α和Nrg1在雏鸡肢体中以与模式角色一致的方式表达。我们发现，激活的ErbB1的表达会导致包括镜像多指在内的肢体缺陷， 异位的AER、重复的背侧结构和并指，提示ErbB1可能参与AP和DV模式的形成、AER的形成和指间退缩。我们还发现，显性负ErbB的表达抑制了包括ErbB4在内的多个ERBB的信号，而不是ErbB1，会导致肢体缺陷，包括远端结构的丧失，这表明除了ErbB1之外的内源性ErbB对肢体模式是重要的。我们将使用多种功能获得和功能丧失的方法来研究ErbB1、ErbB4及其配体在介导肢体模式事件中的作用，使用在鸡肢体逆转录病毒载体中，以及在小鼠肢体中，肢体组织特异性启动子。我们将探索细胞内信号级联的激活，ErbB异二聚体的形成，以及与其他肢体模式信号的调控关系 如Shh、Fgf、Wnt、BMP和IGF。由于ErbB2和ERBB也在肢体中表达，为了深入了解其他ERBB的作用，并解决ErbB成员之间潜在的功能冗余，我们将同时抑制肢体中的多个ERBB。这些研究应该有助于深入了解ErbB信号网络作为肢体形态发生的关键调节因子之前未被认识到的作用。

The goal of this project is to explore the roles of ErbB signaling in limb patterning. The ErbB family consists of ErbB1 (also known as epidermal growth factor receptor or EGFR); three other receptors (ErbB2-4); and 11 ligands. The ErbB signaling network is considered a paradigm for diversification of cell signal responses, as distinct signals are generated by formation of ErbB heterodimers and activation by multiple ligands. Moreover, the ErbB signaling network plays an important role as a central convergence point for multiple signaling pathways, integrating signals emanating from other receptor classes. ErbB1, ErbB4 and the ligands EGF, TGF-alpha and Nrg1 are expressed in chick limbs in fashions consistent with patterning roles. We have found that expression of activated ErbB1 causes limb defects including mirror-image polydactyly, ectopic AERs, duplicated dorsal structures and syndactyly, suggesting ErbB1 may be involved in AP and DV patterning, AER formation, and interdigital regression. We have also found that expression of a dominant negative ErbB, which inhibits signals from multiple ErbBs including ErbB4 but not ErbB1, causes limb defects including loss of distal structures, indicating that an endogenous ErbB other than ErbB1 is important for limb patterning. We will employ multiple gain and loss of function approaches to investigate the roles of ErbB1, ErbB4 and their ligands in mediating limb patterning events, using in chick limbs retroviral vectors, and in mouse limbs, limb tissue-specific promoters. We will explore the activation of intracellular signaling cascades, formation of ErbB heterodimers, and regulatory relationships with other limb patterning signals such as Shh, FGF, Wnt, BMP, and IGF. Since ErbB2 and ErbBS are also expressed in the limb, to gain insight into roles for other ErbBs, and to address potential functional redundancy among ErbB members, we will inhibit multiple ErbBs simultaneously in the limb. These studies should provide insight into the previously unappreciated role of the ErbB signaling network as a key regulator of limb morphogenesis.