Aulehla A, Johnson R L
Department of Biochemistry and Molecular Biology, University of Texas, M.D. Anderson Cancer Center, Houston, Texas, 77030, USA.
Dev Biol. 1999 Mar 1;207(1):49-61. doi: 10.1006/dbio.1998.9164.
The metameric organization of the vertebrate trunk is a characteristic feature of all members of this phylum. The origin of this metamerism can be traced to the division of paraxial mesoderm into individual units, termed somites, during embryonic development. Despite the identification of somites as the first overt sign of segmentation in vertebrates well over 100 years ago, the mechanism(s) underlying somite formation remain poorly understood. Recently, however, several genes have been identified which play prominent roles in orchestrating segmentation, including the novel secreted factor lunatic fringe. To gain further insight into the mechanism by which lunatic fringe controls somite development, we have conducted a thorough analysis of lunatic fringe expression in the unsegmented paraxial mesoderm of chick embryos. Here we report that lunatic fringe is expressed predominantly in somite -II, where somite I corresponds to the most recently formed somite and somite -I corresponds to the group of cells which will form the next somite. In addition, we show that lunatic fringe is expressed in a highly dynamic manner in the chick segmental plate prior to somite formation and that lunatic fringe expression cycles autonomously with a periodicity of somite formation. Moreover, the murine ortholog of lunatic fringe undergoes a similar cycling expression pattern in the presomitic mesoderm of somite stage mouse embryos. The demonstration of a dynamic periodic expression pattern suggests that lunatic fringe may function to integrate notch signaling to a cellular oscillator controlling somite segmentation.
脊椎动物躯干的分节组织是该门所有成员的一个特征。这种分节现象的起源可以追溯到胚胎发育过程中轴旁中胚层分裂为单个单元，即体节。尽管早在100多年前就已确定体节是脊椎动物中分割的首个明显迹象，但体节形成的潜在机制仍知之甚少。然而，最近已鉴定出几个在协调分割过程中起重要作用的基因，包括新发现的分泌因子lunatic fringe。为了进一步深入了解lunatic fringe控制体节发育的机制，我们对鸡胚未分节的轴旁中胚层中lunatic fringe的表达进行了全面分析。在此我们报告，lunatic fringe主要在体节-II中表达，其中体节I对应于最近形成的体节，体节-I对应于将形成下一个体节的细胞群。此外，我们表明，在体节形成之前，lunatic fringe在鸡的体节板中以高度动态的方式表达，并且lunatic fringe的表达以体节形成的周期自主循环。此外，lunatic fringe的小鼠直系同源物在体节期小鼠胚胎的前体节中胚层中经历类似的循环表达模式。动态周期性表达模式的证明表明，lunatic fringe可能起到将Notch信号整合到控制体节分割的细胞振荡器中的作用。
