LIMB REGENERATION IN HIGHER VERTEBRATES

这项应用解决了包括人类在内的高等脊椎动物组织和器官再生的一般问题。我们的研究是基于这样一个普遍的理解，即再生和发育具有相似的机制，再生能力在胚胎中增强，并随着发育年龄的增长而下降。我们的研究集中在以鸡的肢芽和小鼠的手指为模型的发育中的肢体组织的再生 小费。这两种再生模式的不同之处在于，小鼠天生的再生反应有助于分子遗传学研究，以揭示必要的信号通路，而缺乏任何再生能力的小鸡肢芽可以被诱导再生。四个特定目标中的两个专注于在鸡肢芽中诱导再生反应(目标1和2)，其余两个目标旨在继续努力剖析对小鼠胎儿手指再生至关重要的信号通路(目标3和4)。在目标1中，我们将测试细胞迁移在招募细胞参与 再生反应。再生反应的诱导将从以下几个方面进行研究：1)AER的FGF4信号，2)损伤组织维持AER功能的信号，以及3)产生透明质酸的要求。在目标2中，我们将进行功能研究，以确定诱导再生是否需要涉及Msx1或ErbB1的信号。Dealy实验室(项目2)对ErbB 1的初步研究以及最近对小鼠Msx1突变体的研究表明，这些信号通路将在再生反应中发挥重要作用。在目标3中，我们将扩展我们之前的研究，表明BMP信号是胎儿指尖再生所必需的。我们将以I型BMP受体为靶点进行丢失 野生型数字在细胞移植检测中的功能和功能研究进展。这些研究将确定BMP信号是否对细胞参与再生反应至关重要。在目标4中，我们将研究Dlx5，一种在指尖表达的同源结构域蛋白，在再生反应中扮演的角色。使用Dlx5突变体和Dlx5/6双突变数字进行的再生研究将确定这些DLX基因是否是再生反应所必需的。

This application addresses the general problem of tissue and organ regeneration in higher vertebrates, including man. Our studies are guided by the general understanding that regeneration and development share similar mechanisms, and that regenerative ability is enhanced in the embryo and declines with developmental age. Our studies focus on regeneration of developing limb tissues using as models the chick limb bud and the mouse digit tip. These two regeneration models are distinct in that an innate regeneration response in the mouse lends itself to molecular genetic studies to uncover essential signaling pathways, whereas the chick limb bud, which lacks any regenerative ability whatsoever, can be induced to regenerate. Two of the four specific aims focus on the induction of a regeneration response in the chick limb bud (Aims 1 and 2), and the remaining two aims target our continuing effort to dissect signaling pathways important for fetal digit regeneration in the mouse (Aims 3 and 4). In aim 1 we will test the role that cell migration plays in the recruitment of cells to participate in the regeneration response. The induction of a regeneration response will be studied with respect to the role of 1) FGF4 signaling by the AER, 2) signaling by injured tissue to maintain AER function, and 3) a requirement of hyaluronan production. In aim 2 we will carry out functional studies to determine whether signaling involving Msx1 or ErbB1 is required for induced regeneration. Preliminary studies from the Dealy lab (Project 2) on ErbB 1, and recent studies with the mouse Msxl mutant suggest that these signaling pathways will play important roles in the regeneration response. In aim 3 we will extend our previous studies showing that BMP signaling is required for fetal digit tip regeneration. Targeting the type I Bmp receptors we will carry out loss of function and gain of function studies in cell transplantation assays in wildtype digits. These studies will determine whether BMP signaling essential for cells to participate in a regeneration response. In aim 4 we will investigate the role that Dlx5, a homeodomain protein expressed in the digit tip, plays in the regeneration response. Regeneration studies using the Dlx5 mutant and the Dlx5/6 double mutant digit will determine whether these Dlx genes are required for a regeneration response.