Global analysis of RAR-responsive genes in the Xenopus neurula. Xenopus laevis

Retinoid signaling is important for patterning the vertebrate hindbrain and midaxial regions. We recently showed that signaling through retinoic acid receptors (RARs) is essential for anteroposterior patterning along the entire body axis. To further investigate the mechanisms through which RARs act, we employed microarray analysis to investigate the effects of modulating RAR activity on target gene expression. We identified 334 upregulated genes (92% of which were validated) including known RA responsive genes, known genes that have never been proposed as RA targets and many hypothetical and unidentified genes (n = 166). 67 validated downregulated genes were identified including known RA responsive genes and anterior marker genes. The expression patterns of selected upregulated genes (n = 45) were examined at neurula stages using whole mount in situ hybridization. We found that most of these genes were expressed in the neural tube and many were expressed in anterior tissues such as neural crest, brain, eye anlagen, and cement gland. Some were expressed in tissues such as notochord, somites, pronephros and blood islands, where retinoic acid (RA) plays established roles in organogenesis. Members of this set of newly identified RAR target genes are likely to play important roles in neural patterning and organogenesis under the control of RAR signaling pathways and their further characterization will expand our understanding of RA signaling during development. Keywords = retinoid Keywords = microarray Keywords = RAR Keywords = neurula Keywords = anteroposterior patterning Keywords = and organogenesis Keywords: repeat sample

类视黄醇（retinoid）信号通路对脊椎动物后脑及中轴区域的模式建成至关重要。我们此前的研究证实，维甲酸受体（retinoic acid receptors, RAR）介导的信号通路对整个体轴的前后轴模式建成具有关键作用。为进一步解析RAR发挥作用的分子机制，我们采用微阵列（microarray）分析技术，探究了调控RAR活性对靶基因表达的影响。我们共鉴定得到334个上调基因（其中92%已完成验证），涵盖已知的维甲酸（retinoic acid, RA）应答基因、此前未被认定为RA靶标的已知基因，以及166个假想基因与未鉴定基因。同时鉴定得到67个经验证的下调基因，涵盖已知的RA应答基因与前部标记基因。我们采用整体原位杂交（whole mount in situ hybridization）技术，在神经胚（neurula）阶段检测了45个筛选得到的上调基因的表达模式。研究发现，多数此类基因在神经管中表达，且众多基因在前部组织中存在表达，包括神经嵴、脑、眼原基及粘腺。部分基因则在脊索、体节、前肾及血岛等组织中表达——维甲酸（RA）在这些组织的器官发生过程中已被证实发挥关键作用。本研究中新鉴定得到的RAR靶基因集合，极有可能在RAR信号通路调控的神经模式建成与器官发生过程中发挥重要功能；对这些基因的进一步解析，将加深我们对发育过程中RA信号通路的认知。关键词：类视黄醇、微阵列、维甲酸受体（RAR）、神经胚、前后轴模式建成、器官发生、重复样本