Shoguchi E, Harada Y, Numakunai T, Satoh N
Department of Zoology, Graduate School of Science, Kyoto University, Kyoto, Japan.
Genesis. 2000 Jun;27(2):58-63. doi: 10.1002/1526-968x(200006)27:2<58::aid-gene20>3.0.co;2-8.
The Otx gene encodes a homeodomain transcription factor that has a highly conserved role in brain formation of both flies and vertebrates. To deduce evolutionary relationship of the chordate central nervous system to the larval or adult nervous system of nonchordate deuterostomes, we characterized the expression of the Otx gene (Sj-Otx) throughout the entire embryonic and larval development of the sea cucumber Stichopus japonicus. Sj-Otx transcripts were detected in fertilized eggs and in the posterior part of the archenteron of gastrulae. However, the expression was downregulated as embryos developed into auricularia larvae. Sj-Otx was expressed again in the ciliary bands of late auricularia larvae, just before metamorphosis to doliolaria larvae. The expression domain corresponded to the domains moving to the mouth during metamorphosis and sinking into the buccal cavity, but not to the five transverse ciliary bands of the doliolaria. The expression gradually disappeared during further development and was not detected in juveniles. These results indicate that the gene responsible for chordate brain formation is expressed in the ciliary bands of auricularia larvae.
Otx基因编码一种同源结构域转录因子，在果蝇和脊椎动物的大脑形成过程中发挥着高度保守的作用。为了推断脊索动物中枢神经系统与非脊索动物后口动物幼虫或成体神经系统的进化关系，我们对日本刺参整个胚胎和幼虫发育过程中Otx基因（Sj - Otx）的表达进行了特征分析。在受精卵和原肠胚原肠的后部检测到了Sj - Otx转录本。然而，随着胚胎发育成耳状幼虫，该表达下调。就在变态为桶状幼虫之前，Sj - Otx在晚期耳状幼虫的纤毛带中再次表达。该表达区域对应于变态过程中向口部移动并沉入口腔的区域，但与桶状幼虫的五条横向纤毛带不对应。在进一步发育过程中，该表达逐渐消失，在幼体中未检测到。这些结果表明，负责脊索动物大脑形成的基因在耳状幼虫的纤毛带中表达。
