An epidermal mechanism for digit separation

项目摘要/摘要 对鸟类和哺乳动物手指形成的发育生物学研究的长期历史已经定义了 数字分离过程的细胞和分子基础。在细胞水平上，细胞的凋亡 指间间充质，以及指间和指间的差异生长，中介指间分离。这个 指间细胞凋亡是通过减少覆盖的表皮中FGF8的表达来启动的，这触发了一种 指间充质中分子的级联变化，最终导致细胞凋亡和退化 指间组织。这一过程的失败被认为是许多先天畸形的基础 人类患有手指融合，每10000名新生儿中就有3-10人出现这种情况。通过我们在Grh13上的工作-/- 在老鼠身上，我们发现了一种全新的基于上皮的手指分离机制。我们的数据表明 虽然指间细胞凋亡是数字分离所必需的，但这是不够的。我们发现了一种 近端小的多层上皮舌结构(称为指间上皮舌；IET) 分开的数字连接点。为了正常的手指形成，这个结构中的上皮细胞需要经历 分叉伴随着指间充质细胞死亡。本申请中的假设为：1) 当指间连接上皮向近端移动并从背侧和腹侧表面移动时， 对指间充质细胞死亡的反应，在其前缘形成多层上皮舌结构 以及2)指间上皮舌的分叉需要GRHL3控制的通路 允许数字分隔。我们提出了两个目的来检验这些假说。在目标1中，我们将描述 指间上皮舌运动和分叉的细胞机制。在目标2中，我们 将定义一条GRHL3调控的分子通路，负责指间上皮的分叉 舌头。这些研究具有重要意义和创新性，因为它们定义了一种以前未被识别的细胞 和正常数字分离所需的分子途径。

PROJECT SUMMARY/ABSTRACT A long history of developmental biology research into avian and mammalian digit formation has defined the cellular and molecular underpinnings of the digit separation process. At a cellular level, apoptosis of the interdigital mesenchyme, as well as differential digit and interdigital growth, mediate digit separation. The interdigital apoptosis is initiated by decreasing FGF8 expression in the overlying epidermis which triggers a cascade of molecular changes in the interdigital mesenchyme, ultimately resulting in apoptosis and regression of the interdigital tissue. A failure of this process is thought to underlie a number of congenital abnormalities in humans with fused digits, a condition observed in 3-10 per 10 thousand births. Through our work on Grhl3-/- mice, we discovered an entirely new epithelial-based mechanism for digit separation. Our data suggest that while interdigital apoptosis is required for digit separation it is not sufficient. We identified the formation of a small multilayered epithelial tongue structure (referred to as the interdigital epithelial tongue; IET) proximally at the separating digit junctions. For normal digit formation, the epithelia within this structure needs to undergo bifurcation concomitant with the interdigital mesenchymal cell death. The hypotheses in this application are: 1) that as the interdigital juncture epithelium moves proximally and from the dorsal and ventral surfaces in response to interdigital mesenchyme cell death, a multilayered epithelial tongue structure forms at its leading edge; and 2) that a GRHL3-controlled pathway is required for bifurcation of the interdigital epithelial tongue to allow digit separation. We propose two Aims to test these hypotheses. In Aim 1, we will characterize the cellular mechanisms responsible for movement and bifurcation of the interdigital epithelial tongue. In Aim 2, we will define a GRHL3-regulated molecular pathway responsible for bifurcation of the interdigital epithelial tongue. These studies are significant and innovative because they define a previously unrecognized cellular and molecular pathway required for normal digit separation.