Ikuta Tetsuro, Saiga Hidetoshi
Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, Hachiohji, Tokyo, Japan.
Dev Dyn. 2005 Jun;233(2):382-9. doi: 10.1002/dvdy.20374.
Hox genes have been regarded to play a central role in anterior-posterior patterning of the animal body. Variations of Hox genes among animal species in the number, order on a chromosome, and the developmental expression pattern may reflect an evolutionary history. Therefore, it is definitely necessary to characterize Hox genes of wide variety of animal species, especially the species occupying key positions in the animal phylogeny. Ascidians, belonging to the subphylum Urochordata, are one of the sister groups of vertebrates in the phylum Chordata. Recent studies have shown that nine Hox genes of Ciona intestinalis, an ascidian species, are present on two chromosomes in the genome. In this review, we discuss the present state of Hox genes in ascidians, focusing on their novel chromosomal organization and expression pattern with unique features and how the novel organization has evolved in relation to the unique body plan of ascidians.
Hox基因被认为在动物身体的前后模式形成中起着核心作用。动物物种之间Hox基因在数量、染色体上的排列顺序以及发育表达模式上的差异可能反映了进化历史。因此，明确各种动物物种的Hox基因特征，尤其是在动物系统发育中占据关键位置的物种，绝对是必要的。海鞘属于尾索动物亚门，是脊索动物门中脊椎动物的姐妹类群之一。最近的研究表明，海鞘物种玻璃海鞘的九个Hox基因存在于基因组的两条染色体上。在这篇综述中，我们讨论了海鞘中Hox基因的现状，重点关注它们独特的染色体组织和具有独特特征的表达模式，以及这种新的组织是如何与海鞘独特的身体结构相关联而进化的。
