Surface ectodermal mechanism and maternal intervention of neural tube defects

项目摘要/摘要 我们研究的长期目标是揭示哺乳动物的细胞和分子机制。 神经管闭合缺陷。了解神经管关闭的基本机制可能会 转化为预防神经管闭合缺陷的应用，包括脑外畸形和无脑畸形 在颅区和脊柱裂在脊椎尾部区域。颅裂，最严重但罕见的 在平面细胞动物模型中发现了大脑和脊柱完全开放的神经管闭合缺陷 极性(PCP)信号突变体。Wnt/？-catenin信号通路与Wnt/？catenin信号通路有几个共同的成分 PCP信号通路，在广泛的发育过程和相关过程中发挥关键作用 精神错乱。然而，Wnt/B-catenin信号在神经管闭合和相关的结构性出生中的作用 人们对缺陷仍然知之甚少。LRP6是Wnt/？-catenin信号通路的辅助受体，也是 参与PCP信号通路，机制不明。LRP6基因的自发性点突变 在小鼠模型中，基因导致颅神经管或脊髓神经管闭合缺陷，并与 患有神经管闭合缺陷的人类。补充叶酸可能不会阻止神经管关闭 LRP6突变体的缺陷。为了解决LRP6介导的信号级联在神经管关闭中的作用，我们 已经产生了一个有条件的LRP6基因打靶小鼠品系。使用各种CRE鼠标线，我们有 初步发现LRP6在神经管闭合中起着细胞谱系和区域特异性的作用。另一方面 另一方面，LRP6可能与另一个辅助受体LRP5在介导？连环蛋白信号传导中存在功能冗余。 神经管关闭。我们最近已经证明，有条件地消融 神经外胚层谱系细胞引起的脊柱裂类似于，但比 神经外胚层LRP6突变体，提示LRP5可能补偿了LRP6部分功能的丧失 介导Wnt/？-catenin信号转导。许多研究都集中在神经外胚层或神经上皮细胞。 在神经管关闭时神经板折叠或弯曲过程中可能起重要作用的细胞。然而，它的作用是 神经管闭合过程中邻近的非神经表面外胚层细胞仍然知之甚少。基座 根据我们的初步发现，我们认为LRP5/6介导的Wnt/？catenin信号调节一个独特的 细胞过程中的非神经面外胚层细胞沿整个神经管直接闭合 肩尾体轴，以及非神经表面Wnt/？-catenin信号级联中断 外胚层细胞会导致各种类型的严重神经管闭合缺陷。我们还建议 Wnt/？-catenin信号关键下游效应因子的基因激活可防止神经管闭合 外胚层突变体表面的缺陷。为了解决这些假设，我们将进行条件基因- 目标分析与各种强大和创新的研究方法相结合，以检查 在这些新的突变小鼠模型中神经管关闭缺陷的细胞和分子机制。我们 还将探讨LRP5/6介导的Wnt/？连环蛋白的区域特异性和基因剂量依赖的作用 神经管关闭过程中的信号通路。我们将通过以下方法测试神经管闭合缺陷的遗传挽救 有条件地激活关键候选下游效应器。这项研究可能会揭示出重要的线索 在人类新生儿中预防叶酸无法治疗的神经管闭合缺陷。

PROJECT SUMMARY/ABSTRACT The long-term goal of our research is to uncover the cellular and molecular mechanisms of mammalian neural tube closure defects. Understanding the basic mechanisms underlying neural tube closure may translate into applications for preventing neural tube closure defects, including exencephaly and anencephaly at the cranial region and spina bifida at the caudal spinal region. Craniorachischisis, the severest but rare neural tube closure defect with entirely open brain and spine, has been found in the animal model of planar cell polarity (PCP) signaling mutants. The Wnt/ß-catenin signaling pathway shares several components with the PCP signaling pathway, and plays crucial roles in a wide range of developmental processes and related disorders. However, the role of Wnt/ß-catenin signaling in neural tube closure and related structural birth defects remains poorly understood. Lrp6 is a coreceptor in the Wnt/ß-catenin signaling pathway and is also involved in the PCP signaling pathway with unknown mechanisms. Spontaneous point mutations in the Lrp6 gene give rise to either cranial or spinal neural tube closure defects in the mouse model, and are associated with neural tube closure defects in humans. Folate supplementation may not prevent neural tube closure defects in Lrp6 mutants. To address the role of Lrp6-mediated signaling cascades in neural tube closure, we have generated a conditional gene-targeting mouse line of Lrp6. Using various Cre mouse lines, we have preliminarily found that Lrp6 plays cell lineage- and region-specific roles in neural tube closure. On the other hand, Lrp6 may have functional redundancy with another coreceptor, Lrp5, in mediating ß-catenin signaling in neural tube closure. We have recently demonstrated that conditional ablation of ß-catenin in the neuroectodermal lineage cells causes spina bifida that is similar to, but severer than those seen in the neuroectodermal Lrp6 mutants, suggesting that Lrp5 may compensate for a partial loss-of-function of Lrp6 to mediate Wnt/ß-catenin signaling. Numerous studies have been focused on neuroectodermal or neuroepithelial cells that maybe important in neural plate folding or bending during neural tube closure. However, the role of the adjacent non-neural surface ectodermal cells during neural tube closure remains poorly understood. Based on our preliminary findings, we propose that Lrp5/6-mediated Wnt/ß-catenin signaling regulates a unique cellular process in the non-neural surface ectodermal cells to direct neural tube closure along the entire rostrocaudal body axis, and that disruption of the Wnt/ß-catenin signaling cascade in the non-neural surface ectodermal cells will cause a spectrum of all types of severe neural tube closure defects. We also propose that genetic activation of the key downstream effectors of Wnt/ß-catenin signaling can prevent neural tube closure defects in the surface ectodermal mutants. To address these hypotheses, we will conduct conditional gene- targeting analyses in combination with various powerful and innovative research approaches to examine the cellular and molecular mechanisms of neural tube closure defects in these novel mutant mouse models. We will also address the region-specific and gene-dosage-dependent roles of the Lrp5/6-mediated Wnt/ß-catenin signaling pathway during neural tube closure. We will test the genetic rescue of neural tube closure defects by conditional activation of the key candidate downstream effectors. This study may reveal significant clues towards preventing folate-untreatable neural tube closure defects in human newborns.