Identification of target genes for the Xenopus Hes-related protein XHR1, a prepattern factor specifying the midbrain-hindbrain boundary
Identification of target genes for the Xenopus Hes-related protein XHR1, a prepattern factor specifying the midbrain-hindbrain boundary
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DOI：
10.1016/j.ydbio.2005.04.020
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发表时间：
2005-07-01
影响因子：
2.7
通讯作者：
Taira, M
中科院分区：
文献类型：
--
作者：
Takada, H;Hattori, D;Taira, M
中脑-后脑边界（MHB）是脊椎动物中枢神经系统发育的局部组织者。以前，我们确定了MHB特异性bHLH-WRPW转录抑制基因，非洲爪蟾Hes相关1（XHR 1），这是最初表达的推定MHB（前MHB）地区在早期原肠胚阶段。为了更好地了解参与MHB形成的基因级联，我们使用非洲爪蟾cDNA宏阵列和地塞米松（DEX）诱导的XHR 1（XHR 1-VP 16-GR）的显性负转录激活因子构建体，通过差异筛选研究了XHR 1下游的基因。在新鉴定的XHR 1的候选靶基因中，有分裂相关基因增强子（ESR 1、ESR 3/7和ESR 9）和非洲爪蟾卵裂2（XCL 2）。XHR 1-VP 16-GR诱导ESR基因和UCL 2以及Xdelta 1，Xngnr 1和XHR 1本身在DEX存在下的表达，即使在用蛋白质合成抑制剂放线菌酮预处理后。这表明这些基因是XHR 1的直接靶点。反义吗啉寡核苷酸和野生型XHR 1异位表达的XHR 1敲低实验表明，XHR 1是必要的，足以抑制ESR基因在前MHB区域。前MHB区域中ESR基因的错误表达抑制了MHB标记基因Pax 2，这表明XHR 1对ESR基因的抑制至少部分是前MHB早期发育所需的。我们的数据还表明，XHR 1不被Notch信号激活，与ESR基因不同。综上所述，我们提出了一个模型，其中XHR 1通过抑制那些可能的直接靶基因将前MHB区域定义为前模式基因。(C)2005年爱思唯尔公司All rights reserved.
The midbrain-hindbrain boundary (MHB) acts as a local organizer in the development of the CNS in vertebrates. Previously, we identified an MHB-specific bHLH-WRPW transcriptional repressor gene, Xenopus Hes-related 1 (XHR1), which is initially expressed in the presumptive MHB (pre-MHB) region at the early gastrula stage. To better understand the gene cascades involved in MHB formation, we investigated the genes downstream from XHR1 by differential screening using a Xenopus cDNA macroarray and a dexamethasone (DEX)inducible, dominant-negative transcriptional activator construct of XHR1 (XHR1-VP16-GR). Among the newly identified candidate target genes of XHR1 were Enhancer of split-related genes (ESR1, ESR3/7, and ESR9) and Xenopus laevis cleavage 2 (XCL2). XHR1-VP16-GR induced the expression of the ESR genes and UCL2 as well as Xdelta1, Xngnr1, and XHR1 itself in the presence of DEX even after pretreatment with the protein synthesis inhibitor, cycloheximide. This suggests that these genes are direct targets of XHR1. XHR1-knockdown experiments with antisense morpholino oligos and ectopic expression of wild-type XHR1 revealed that XHR1 is necessary and sufficient to repress ESR genes in the pre-MHB region. Misexpression of the ESR genes in the pre-MHB region repressed the MHB marker gene, Pax2, suggesting that the repression of the ESR genes by XHR1 is at least partly required for the early development of the pre-MHB. Our data also show that XHR1 is not activated by Notch signaling, differing from ESR genes. Taken together, we propose a model in which XHR1 defines the pre-MHB region as a prepattern gene by repressing those possible direct target genes. (C) 2005 Elsevier Inc. All rights reserved.