Characterization of an amphioxus paired box gene, AmphiPax2/5/8: developmental expression patterns in optic support cells, nephridium, thyroid-like structures and pharyngeal gill slits, but not in the midbrain-hindbrain boundary region.
Characterization of an amphioxus paired box gene, AmphiPax2/5/8: developmental expression patterns in optic support cells, nephridium, thyroid-like structures and pharyngeal gill slits, but not in the midbrain-hindbrain boundary region.
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发表时间：
1999-03
期刊：
影响因子：
4.6
通讯作者：
Z. Kozmík;N. Holland;A. Kalousová;J. Pačes;M. Schubert;L. Holland
中科院分区：
文献类型：
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作者：
Z. Kozmík;N. Holland;A. Kalousová;J. Pačes;M. Schubert;L. Holland
在发育基因表达的基础上，脊椎动物中枢神经系统包括：前脑+前中脑、具有组织特性的中脑-后脑边界区（MHB）和菱形脊髓结构域。脊椎动物MHB的特点是位置、组织者特性和作为Wnt1和嵌入基因以及Pax2/5/8亚家族基因的早期作用位点。Wada等人（Wada， H., Saiga， H., Satoh， N.和Holland， P. W. H. (1998) Development 125, 1113-1122）根据海鞘动物Pax258的表达，认为海鞘动物具有类似脊椎动物的MHB。在另一种无脊椎脊索动物文昌鱼中，缺乏类似脊椎动物MHB的基因表达证据。因此，我们分离并鉴定了文昌鱼中该亚家族的唯一成员AmphiPax2/5/8。AmphiPax2/5/8最初在菱形脊髓结构域表达良好，而不是在MHB预期的位置。相比之下，AmphiPax2/5/8的其他表达域大多与脊椎动物Pax2、Pax5和Pax8的结构域相对应，这些结构域可能是同源的——眼睛、肾、甲状腺样结构和咽鳃缝的支持细胞；尽管AmphiPax2/5/8没有转录到任何可以解释为脊椎动物耳基板或耳囊同源物的结构中。综上所述，AmphiPax2/5/8的发育表达表明文昌鱼中枢神经系统缺乏类似脊椎动物峡区的MHB。关于海鞘和文昌鱼神经系统发育的其他基因表达数据将有助于确定MHB是否是文昌鱼继发性丢失的基础脊索动物特征。另一种说法是，MHB是脊椎动物的创新。
On the basis of developmental gene expression, the vertebrate central nervous system comprises: a forebrain plus anterior midbrain, a midbrain-hindbrain boundary region (MHB) having organizer properties, and a rhombospinal domain. The vertebrate MHB is characterized by position, by organizer properties and by being the early site of action of Wnt1 and engrailed genes, and of genes of the Pax2/5/8 subfamily. Wada and others (Wada, H., Saiga, H., Satoh, N. and Holland, P. W. H. (1998) Development 125, 1113-1122) suggested that ascidian tunicates have a vertebrate-like MHB on the basis of ascidian Pax258 expression there. In another invertebrate chordate, amphioxus, comparable gene expression evidence for a vertebrate-like MHB is lacking. We, therefore, isolated and characterized AmphiPax2/5/8, the sole member of this subfamily in amphioxus. AmphiPax2/5/8 is initially expressed well back in the rhombospinal domain and not where a MHB would be expected. In contrast, most of the other expression domains of AmphiPax2/5/8 correspond to expression domains of vertebrate Pax2, Pax5 and Pax8 in structures that are probably homologous - support cells of the eye, nephridium, thyroid-like structures and pharyngeal gill slits; although AmphiPax2/5/8 is not transcribed in any structures that could be interpreted as homologues of vertebrate otic placodes or otic vesicles. In sum, the developmental expression of AmphiPax2/5/8 indicates that the amphioxus central nervous system lacks a MHB resembling the vertebrate isthmic region. Additional gene expression data for the developing ascidian and amphioxus nervous systems would help determine whether a MHB is a basal chordate character secondarily lost in amphioxus. The alternative is that the MHB is a vertebrate innovation.