Tamura Koji, Yonei-Tamura Sayuri, Yano Tohru, Yokoyama Hitoshi, Ide Hiroyuki
Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aobayama, Aoba-ku, Sendai 980-8578, Japan.
Dev Growth Differ. 2008 Jun;50 Suppl 1:S177-87. doi: 10.1111/j.1440-169X.2008.01020.x. Epub 2008 May 6.
The autopod, including the mesopodium and the acropodium, is the most distal part of the tetrapod limb, and developmental mechanisms of autopod formation serve as a model system of pattern formation during development. Cartilage rudiments of the autopod develop after proximal elements have differentiated. The autopod region is marked by a change in the expression of two homeobox genes: future autopod cells are first Hoxa11/Hoxa13-double-positive and then Hoxa13-single-positive. The change in expression of these Hox genes is controlled by upstream mechanisms, including the retinoic acid pathway, and the expression of Hoxa13 is connected to downstream mechanisms, including the autopod-specific cell surface property mediated by molecules, including cadherins and ephrins/Ephs, for cell-to-cell communication and recognition. Comparative analyses of the expression of Hox genes in fish fins and tetrapod limb buds support the notion on the origin of the autopod in vertebrates. This review will focus on the cellular and molecular regulation of the formation of the autopod during development and evolutionary developmental aspects of the origin of the autopod.
自肢体末端，包括中足和远足，是四足动物肢体的最远端部分，自肢体形成的发育机制是发育过程中模式形成的模型系统。近端元件分化后，自肢体的软骨雏形开始发育。自肢体区域以两个同源盒基因表达的变化为标志：未来的自肢体细胞首先是Hoxa11/Hoxa13双阳性，然后是Hoxa13单阳性。这些Hox基因表达的变化由上游机制控制，包括视黄酸途径，而Hoxa13的表达与下游机制相关，包括由钙黏蛋白和 Ephrin/Eph 等分子介导的自肢体特异性细胞表面特性，用于细胞间通讯和识别。对鱼类鳍和四足动物肢体芽中Hox基因表达的比较分析支持了脊椎动物自肢体起源的观点。本综述将重点关注发育过程中自肢体形成的细胞和分子调控以及自肢体起源的进化发育方面。
