LIMB REGENERATION IN HIGHER VERTEBRATES

本申请解决了高等脊椎动物（包括人类）组织和器官再生的一般问题。我们的研究是由一般理解指导的，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。本研究以鸡肢芽和小鼠趾为模型，对发育中的肢体组织再生进行了研究 tip.这两种再生模型的不同之处在于，小鼠的先天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鸡肢芽可以被诱导再生。四个具体目标中的两个集中在鸡肢芽中再生反应的诱导上（目标1和2），其余两个目标针对我们继续努力剖析对小鼠中胎儿指再生重要的信号通路（目标3和4）。在aim 1中，我们将测试细胞迁移在招募细胞参与细胞增殖中所起的作用。 再生反应将研究再生反应的诱导在以下方面的作用：1）AER的FGF 4信号传导，2）受损组织维持AER功能的信号传导，以及3）透明质酸产生的要求。在目标2中，我们将进行功能研究，以确定是否涉及Msx 1或ErbB 1的信号传导是诱导再生所必需的。Dealy实验室（项目2）对ErbB 1的初步研究以及最近对小鼠Msxl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，我们将扩展我们先前的研究，表明BMP信号是胎儿趾尖再生所必需的。针对I型Bmp受体，我们将进行 在野生型手指的细胞移植试验中的功能和功能获得研究。这些研究将确定BMP信号是否是细胞参与再生反应所必需的。在目标4中，我们将研究Dlx 5，一个在指尖表达的同源结构域蛋白，在再生反应中发挥的作用。使用Dlx 5突变体和Dlx 5/6双突变体指的再生研究将确定这些Dlx基因是否是再生响应所需的。

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.