MADS AND VERTEBRATE LIMB DEVELOPMENT

Mad（母亲反对十肢瘫痪）基因家族被认为 在细胞质信号转导中起关键作用， 转化生长因子β（TGF-β）配体家族。 骨 形态发生蛋白（BMP）是TGF-β型配体，涉及 发育过程，包括模式化和分化， 脊椎动物的肢体 本研究将探讨在此过程中， Mad蛋白在发育中的鸡肢中的作用， 人的异位表达（通过逆转录病毒介导的基因转移） Mad蛋白Smad 1、Smad 5和DPC 4。 负显性和 还将测试这些蛋白质的组成型活化形式。 的 Mad蛋白在BMP信号转导通路中的位置将被 通过测定野生型和突变型Mads抑制 BMP的激活和显性负性版本的影响 受体的 最后，分析了内生性Mads在发展中的作用， 鸡胚肢将通过克隆得到确认， Chick Mads的特点。 这一特性将包括在现场 杂交分析以及在胚胎肢中的过表达， 证实了先前用人Mads获得的表型。 TGF- β配体家族与细胞生长的控制有关， Mad基因DPC 4和MADR 2的缺失与 某些癌症 因此，研究Mad在生物学中的功能， 正如本提案所概述的那样， 了解细胞生长和发育的控制， 肿瘤发生的过程。

The Mad (Mothers against decapentaplegic) gene family is thought to play a key role in the cytoplasmic transduction of signals from the transforming growth factor beta (TGF-beta) family of ligands. The bone morphogenetic proteins (BMPs) are TGF-beta type ligands implicated in developmental processes which include patterning and differentiation of the vertebrate limb. This research proposed here will address the role of Mad proteins in the developing chick limb by examining the effect ectopic expression (by retroviral mediated gene transfer) of the human Mad proteins Smad1, Smad5, and DPC4. Dominant negative and constitutively activated forms of these proteins will also be tested. The position of Mad proteins in the BMP signal transduction pathway will be tested by assaying the ability of wild-type and mutant Mads to suppress the effects of activated and dominant negative versions of the BMP receptor. Finally, the role of endogenous Mads in the development of the chick embryonic limb will be confirmed by the cloning and characterization of chick Mads. This characterization will include in situ hybridization analysis as well as overexpression in the embryonic limb to confirm the phenotypes previously obtained with human Mads. The TGF- beta family of ligands have been implicated in the control of cell growth, and loss of the Mad genes DPC4 and MADR2 has been associated with certain carcinomas. Therefore the study of Mad function in a biological context, as outlined in this proposal, will lead to a greater understanding of the control of cell growth and development, critical processes in the genesis of tumors.