Molecular control of cranial placode progenitor formation

 描述（由申请人提供）：颅基板是胚胎头部外胚层的增厚，产生感觉器官（视透镜、嗅上皮和内耳）、腺垂体和颅神经节的一个子集的细胞。颅基板发育缺陷导致了一系列广泛的人类先天性疾病，包括失明、耳聋、嗅觉丧失、激素失衡和口面感觉缺陷。因此，确定调节颅基板祖细胞出现的分子机制对于理解这些条件至关重要。虽然它们产生非常多样的细胞类型，如感觉神经元、透镜纤维和激素分泌细胞，但所有基板祖细胞都来自共同的前体区域，该前体区域与称为基板前区（PPR）的前神经板相邻。PPR最终分离成不同的域，其中细胞将采用每个感觉基板的命运特征。我们以前已经表明，转录因子Zic 1是必要的，足以促进颅基板的命运。在设计用于鉴定爪蟾胚胎基板特化过程中由Zic 1激活的基因的微阵列筛选中，我们回收了几种参与视黄酸（RA）代谢和功能的因子，包括脂质运载蛋白型前列腺素D2合酶（LPGDS），视黄酸载体，视黄醇脱氢酶2（RALDH 2），负责从其前体视黄醇合成视黄酸的酶，视黄酸代谢酶Cyp26c和细胞视黄酸结合蛋白2（CRABP 2），表明视黄酸信号在Zic 1下游基板形成中的重要性。提出的实验是精心设计的，以测试Zic 1控制基板祖细胞形成非细胞自主调节视黄酸的生产，运输和降解在前神经板的假设。我们设计了三个具体目标来具体解决这个问题。(1)我们将描述Zic 1通过激活LPGDS、RALDH 2和Cyp26c以非细胞自主方式建立PPR的分子机制。(2)我们将分析在外植体试验中响应Zic1产生的基板祖细胞的命运，并确定与RA信号传导合作以产生基板衍生物的全谱的因素。(3)我们将表征在颅基板祖细胞形成过程中介导Zic1激活的RA信号传导的核受体。拟议的实验将建立RA在基板命运的调节中的作用，并更广泛地定义RA信号在颅面发育中的重要性。

 DESCRIPTION (provided by applicant): Cranial placodes are thickenings of the embryonic head ectoderm that give rise to cells of the sensory organs (the optic lens, the olfactory epithelium and the inner ear), the adenohypophysis, and a subset of cranial ganglia. Defects in cranial placodes development cause a wide array of human congenital diseases ranging from blindness, deafness and anosmia, to hormone imbalance and orofacial sensory deficits. Therefore, defining the molecular mechanisms regulating the emergence of cranial placode progenitor is critical to understand these conditions. While they produce very diverse cell types such as sensory neurons, lens fibers and hormone secreting cells, all placode progenitors arise from a common precursor field that borders the anterior neural plate known as the pre-placodal region (PPR). The PPR eventually segregates into distinct domains in which cells will adopt fate characteristic for each sensory placode. We have previously shown that the transcription factor Zic1 is necessary and sufficient to promote cranial placodes fate. In a microarray screen designed to identify genes activated by Zic1 during placode specification in Xenopus embryos, we recovered several factors involved in retinoic acid (RA) metabolism and function, including lipocalin type prostaglandin D2 synthase (LPGDS), a retinoic acid carrier, retinaldehyde dehydrogenase 2 (RALDH2), the enzyme responsible for the synthesis of retinoic acid from its precursor retinal, a retinoic acid metabolizing enzyme, Cyp26c, and the cellular retinoic acid binding protein 2 (CRABP2), signifying the importance of retinoic acid signaling in placode formation downstream of Zic1. The proposed experiments are crafted to test the hypothesis that Zic1 controls placode progenitor formation non-cell autonomously by regulating retinoic acid production, transport and degradation at the anterior neural plate. We have designed three specific aims to specifically address this question. (1) We will delineate the molecular mechanisms by which Zic1 establishes the PPR in a non-cell autonomous manner though the activation of LPGDS, RALDH2 and Cyp26c. (2) We will analyze the fate of the placode progenitors generated in response to Zic1 in an explant assay, and identify the factors that cooperate with RA signaling to generate the full spectrum of placode derivatives. (3) We will characterize the nuclear receptors mediating Zic1-activated RA signaling during cranial placode progenitor formation. The proposed experiments will establish the role of RA in the regulation of placode fate, and more broadly define the importance of RA signaling in craniofacial development.