Takahashi Noriyuki, Tochimoto Naoko, Ohmori Shin-Ya, Mamada Hiroshi, Itoh Mari, Inamori Masako, Shinga Jun, Osada Shin-Ichi, Taira Masanori
Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan.
Int J Dev Biol. 2005;49(8):939-51. doi: 10.1387/ijdb.052083nt.
A cDNA library derived from the anterior neuroectoderm (ANE) of Xenopus late-gastrula embryos was systematically screened to isolate novel developmental regulatory genes involved in early brain development. We isolated 1,706 5 expressed sequence tags (ESTs), which were subdivided into 1,383 clusters and categorized into 19 classes based on predicted functions according to their similarities to other known genes. Of these, 757 clusters that were considered possible novel regulatory genes or unknown genes were subjected to expression pattern analysis using whole-mount in situ hybridization. Genes from 69 clusters (9%) were expressed in the ANE region. Based on their expression patterns and predicted amino acid sequences, 25 genes were selected for further analysis as novel Xenopus genes expressed broadly or region-specifically in the ANE. Eighteen genes were expressed in postulated patterning centers in the neuroectoderm, including the anterior (four genes) and lateral (nine genes) neural ridges, the midbrain-hindbrain boundary region (one gene) and the midline region of the neural plate (two genes), whereas 13 genes were expressed in the eye anlagen. Therefore, early regionalization of the neuroectoderm appears to occur mainly in those neural patterning centers and the eye anlagen. We determined the entire coding regions of p54nrb, Semaphorin 6D and a novel gene designated scribble-related protein 1 (SCRP1). Interestingly, Semaphorin 6D is expressed in the mesoderm with a dorsoventral gradient, as well as in the ectoderm at the gastrula stage, implying a new role for this protein in development other than in axon guidance.
为了分离出参与早期脑发育的新型发育调控基因，我们系统地筛选了来自非洲爪蟾晚期原肠胚前神经外胚层（ANE）的cDNA文库。我们分离出了1706个表达序列标签（EST），这些EST被细分为1383个簇，并根据与其他已知基因的相似性，按照预测功能分为19类。其中，757个被认为可能是新型调控基因或未知基因的簇，通过全胚胎原位杂交进行表达模式分析。69个簇（9%）的基因在ANE区域表达。根据它们的表达模式和预测的氨基酸序列，选择了25个基因作为在ANE中广泛或区域特异性表达的新型非洲爪蟾基因进行进一步分析。18个基因在神经外胚层假定的模式形成中心表达，包括前神经嵴（4个基因）和侧神经嵴（9个基因）、中脑-后脑边界区域（1个基因）以及神经板的中线区域（2个基因），而13个基因在眼原基中表达。因此，神经外胚层的早期区域化似乎主要发生在那些神经模式形成中心和眼原基中。我们确定了p54nrb、Semaphorin 6D和一个名为scribble相关蛋白1（SCRP1）的新型基因的完整编码区。有趣的是，Semaphorin 6D在中胚层中呈背腹梯度表达，在原肠胚阶段的外胚层中也有表达，这意味着该蛋白在发育中除了轴突导向之外还有新的作用。
