Pantalacci Sophie, Prochazka Jan, Martin Arnaud, Rothova Michaela, Lambert Anne, Bernard Laure, Charles Cyril, Viriot Laurent, Peterkova Renata, Laudet Vincent
Molecular Zoology, Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, Université Lyon 1, CNRS, INRA, Ecole Normale Supérieure de Lyon, Lyon, France.
BMC Dev Biol. 2008 Dec 16;8:116. doi: 10.1186/1471-213X-8-116.
The development of the secondary palate has been a main topic in craniofacial research, as its failure results in cleft palate, one of the most common birth defects in human. Nevertheless, palatal rugae (or rugae palatinae), which are transversal ridges developing on the secondary palate, received little attention. However, rugae could be useful as landmarks to monitor anterior/posterior (A/P) palatal growth, and they provide a simple model of mesenchymal-epithelial structures arranged in a serial pattern.
We first determined in which order the nine mouse rugae appear during development. Our results revealed a reiterative process, which is coupled with A/P growth of palatal shelves, and by which rugae 3 to 7b are sequentially interposed, in the increasing distance between the second most anterior ruga, ruga 2, and the two most posterior rugae, rugae 8 and 9. We characterized the steps of ruga interposition in detail, showing that a new ruga forms from an active zone of high proliferation rate, next to the last formed ruga. Then, by analyzing the polymorphism of wild type and Eda(Ta) mutant mice, we suggest that activation-inhibition mechanisms may be involved in positioning new rugae, like for other skin appendages. Finally, we show that the ruga in front of which new rugae form, i.e. ruga 8 in mouse, coincides with an A/P gene expression boundary in the palatal shelves (Shox2/Meox2-Tbx22). This coincidence is significant, since we also found it in hamster, despite differences in the adult ruga pattern of these two species.
We showed that palatal rugae are sequentially added to the growing palate, in an interposition process that appears to be dependent on activation-inhibition mechanisms and reveals a new developmental boundary in the growing palate. Further studies on rugae may help to shed light on both the development and evolution of structures arranged in regular patterns. Moreover, rugae will undoubtedly be powerful tools to further study the anteroposterior regionalization of the growing palate.
继发腭的发育一直是颅面研究的一个主要课题，因为其发育异常会导致腭裂，这是人类最常见的出生缺陷之一。然而，在继发腭上发育形成的腭皱襞（或腭嵴）却很少受到关注。不过，腭皱襞可作为监测腭部前后向（A/P）生长的标志，并且它们提供了一个以系列模式排列的间充质-上皮结构的简单模型。
我们首先确定了九对小鼠腭皱襞在发育过程中出现的顺序。我们的结果揭示了一个反复的过程，该过程与腭突的A/P生长相关，通过这个过程，第3至7b对腭皱襞依次插入到第二靠前的腭皱襞（第2对腭皱襞）与最后两对腭皱襞（第8和9对腭皱襞）之间距离不断增加的区域。我们详细描述了腭皱襞插入的步骤，表明新的腭皱襞从紧邻最后形成的腭皱襞的高增殖率活跃区形成。然后，通过分析野生型和Eda(Ta)突变小鼠的多态性，我们认为激活-抑制机制可能参与新腭皱襞的定位，就像其他皮肤附属器一样。最后，我们表明新腭皱襞形成前方的腭皱襞，即小鼠中的第8对腭皱襞，与腭突中的一个A/P基因表达边界（Shox2/Meox2-Tbx22）相重合。这种重合很重要，因为尽管这两个物种的成年腭皱襞模式存在差异，但我们在仓鼠中也发现了这种情况。
我们表明腭皱襞是在一个似乎依赖于激活-抑制机制的插入过程中依次添加到生长中的腭部的，并且揭示了生长中腭部的一个新的发育边界。对腭皱襞的进一步研究可能有助于阐明以规则模式排列的结构的发育和进化。此外，腭皱襞无疑将成为进一步研究生长中腭部前后区域化的有力工具。
