Ectopic expression of Msx-2 in posterior limb bud mesoderm impairs limb morphogenesis while inducing BIMP-4 expression, inhibiting cell proliferation, and promoting apoptosis
Ectopic expression of Msx-2 in posterior limb bud mesoderm impairs limb morphogenesis while inducing BIMP-4 expression, inhibiting cell proliferation, and promoting apoptosis
复制标题
DOI：
10.1006/dbio.1998.8880
复制
发表时间：
1998-05-01
影响因子：
2.7
通讯作者：
Kosher, RA
中科院分区：
文献类型：
--
作者：
Ferrari, D;Lichtler, AC;Kosher, RA
在雏鸡肢体发育的早期阶段，含有同源盒的基因 Msx-2 在肢芽前缘的中胚层和中近后缘的一组离散中胚层细胞中表达。 Msx-2 表达的这些域大致划分了进展区的前边界和后边界，进展区是顶端外胚层脊 (AER) 下方高度增殖的后中胚层细胞，产生肢体的骨骼元件和相关结构。在发育后期，随着 AER 失去活性，Msx-2 表达扩展到远端中胚层，随后扩展到界定发育中手指的指间充质。 Msx-2表达的区域表现出比进展区细胞明显更少的增殖，并且还涵盖程序性细胞死亡的几个区域，包括前部和后部坏死区以及指间充质。因此，我们认为Msx-2可能处于一个调节网络中，该网络通过抑制其高度表达的肢体中胚层区域的形态发生来界定进展区。在本研究中，我们表明，从肢芽最初形成时起，Msx-2 通过逆转录病毒表达载体在进展区后中胚层中异位表达，严重损害了肢体形态发生。 Msx-2感染的肢体通常沿前后轴火热狭窄，偶尔被截断，并表现出骨骼成分形成模式的改变，表明由于异位Msx-2表达，后中胚层大部分的形态发生受到抑制。我们进一步表明，Msx-2通过减少其所在后中胚层区域的细胞增殖和促进细胞凋亡来损害肢体形态发生。异位表达。后中胚层中异位 Msx-2 表达的区域也表现出 BMP-4 的异位表达，BMP-4 是一种分泌的信号分子，在正常肢体发育过程中，在前肢中胚层、后坏死区和指间充质中与 Msx-2 共表达。这表明Msx-2调节BMP-4表达并且Msx-2对肢体形态发生的抑制作用可能部分由BMP-4介导。这些研究表明，在正常肢体发育过程中，Msx-2是调节网络的关键组成部分，该网络通过抑制其高度表达的肢体中胚层区域的形态发生来界定进展区的边界，从而限制骨骼元件和相关结构在进展区的生长和形成。我们还报告说，在我们检查的正常肢体发育的所有阶段，整个 AER 中都存在相当大量的凋亡细胞和增殖细胞，这表明猿 AER 的许多细胞不断经历程序性细胞死亡，同时细胞增殖产生新的 AER 细胞。因此，细胞增殖和程序性细胞死亡之间的平衡可能在维持 AER 活性方面发挥非常重要的作用。 (C) 1998 年学术出版社。
During early stages of chick limb development, the homeobox-containing gene Msx-2 is expressed in the mesoderm at the anterior margin of the limb bud and in a discrete group of mesodermal cells at the midproximal posterior margin. These domains of Msx-2 expression roughly demarcate the anterior and posterior boundaries of the progress zone, the highly proliferating posterior mesodermal cells underneath the apical ectodermal ridge (AER) that give rise to the skeletal elements of the limb and associated structures. Later in development as the AER loses its activity, Msx-2 expression expands into the distal mesoderm and subsequently into the interdigital mesenchyme which demarcates the developing digits. The domains of Msx-2 expression exhibit considerably less proliferation than the cells of the progress zone and also encompass several regions of programmed cell death including the anterior and posterior necrotic zones and interdigital mesenchyme. We have thus suggested that Msx-2 may be in a regulatory network that delimits the progress zone by suppressing the morphogenesis of the regions of the limb mesoderm in which it is highly expressed. In the present study we show that ectopic expression of Msx-2 via a retroviral expression vector in the posterior mesoderm of the progress zone from the time of initial formation of the limb bud severely impairs Limb morphogenesis. Msx-2-infected limbs are typically Fiery narrow along the anteroposterior axis, are occasionally truncated, and exhibit alterations in the pattern of formation of skeletal elements, indicating that as a consequence of ectopic Msx-2 expression the morphogenesis of large portions of the posterior mesoderm has been suppressed We further show that Msx-2 impairs limb morphogenesis by reducing cell proliferation and promoting apoptosis in the regions of the posterior mesoderm in which it is ectopically expressed. The domains of ectopic Msx-2 expression in the posterior mesoderm also exhibit ectopic expression of BMP-4, a secreted signaling molecule that is coexpressed with Msx-2 during normal limb development in the anterior limb mesoderm, the posterior necrotic zone, and interdigital mesenchyme. This Indicates that Msx-2 regulates BMP-4 expression and that the suppressive effects of Msx-2 on limb morphogenesis might be mediated in part by BMP-4. These studies indicate that during normal limb development Msx-2 is a key component of a regulatory network that delimits the boundaries of the progress zone by suppressing the morphogenesis of the regions of the limb mesoderm in which it is highly expressed, thus restricting the outgrowth and formation of skeletal elements rand associated structures to the progress zone. We also report that rather large numbers of apoptotic cells as well as proliferating cells are present throughout the AER during all stages of normal limb development we have examined, indicating that many of the cells of the AER ape continuously undergoing programmed cell death at the same time that new AER cells are being generated by cell proliferation. Thus, a balance between cell proliferation and programmed cell death may play a very important role in maintaining the activity of the AER. (C) 1998 Academic Press.