The role of the microtubule-associated protein Hmmr in forebrain development and Wnt signaling

微管相关蛋白 Hmmr 在前脑发育和 Wnt 信号传导中的作用

• 批准号: 414981996
• 负责人: Dr. Kerstin Feistel
• 金额: --
• 依托单位: Fachgebiet Zoologie (190z)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/414981996?language=en
• 关键词: role; microtubule; associated; protein; Hmmr

Separation of the telencephalon into bilateral hemispheres is a prerequisite for vertebrate forebrain function. This midline separation occurs soon after neural tube closure and is mediated by the floor plate and roof plate, two important brain signaling centers. Functional defects in one of these centers culminate in defective hemisphere separation, termed holoprosencephaly (HPE). The morphogenetic mechanisms underlying HPE development, however, have remained elusive. Our published data show that in Xenopus laevis, the loss of function of Hmmr, a microtubule-associated protein, induces roof plate defects leading to HPE. hmmr mediates the mesenchymal-to-epithelial transition (MET) of neural cells. This function depends on the microtubule binding domain of Hmmr and on cooperation with Wnt / PCP signaling. MET as a morphogenetic mechanism is a prerequisite for anterior neural tube closure as well as roof plate formation and requires switching from canonical to non-canonical Wnt signaling. Our unpublished data show that hmmr attenuates canonical Wnt signaling, while – at the same time – it is required for the non-canonical Wnt pathways. Based on these data, we hypothesize that hmmr functions as a mediator of MET-based morphogenesis by modulating Wnt signaling pathways in a microtubule-dependent manner.The function of hmmr will be investigated in Xenopus laevis as a model organism. Hmmr interaction partners will be identified and functionally tested towards their role in MET and neurulation by gain- and loss-of-function as well as by studying their epistatic relationship with hmmr. Functional domains of Hmmr required for MET will be identified by deletion and mutation analysis. This should result in defective and potentially dominant-negative constructs that will be used as tools for functional analysis in the embryo. A second work package will analyze how hmmr differentially influences canonical vs. non-canonical Wnt signaling in a microtubule-dependent manner and how this mediates MET processes. hmmr-mediated regulation of canonical Wnt signaling will be assessed using the Xenopus double axis assay and luciferase reporter constructs. To identify hmmr’s mode of cooperation with non-canonical signaling, localization and activity of PCP downstream targets will be analyzed. These results will set the ground to establish Xenopus as a model to analyze morphogenetic movements in the emergence of HPE. In vivo imaging using phase contrast X-ray microtomography will be employed to reveal movements of deep tissue contributing to the roof plate. Special focus will be on the analysis of a human de novo mutation in the microtubule-binding region of HMMR, which was identified in a patient with roof plate-derived HPE. This project should reveal a novel role for hmmr in the regulation of Wnt signaling pathways and advance the understanding of hmmr-mediated morphogenetic movements underlying the etiology of HPE.

端脑分离成两侧半球是脊椎动物前脑功能的先决条件。这种中线分离发生在神经管闭合后不久，并由两个重要的大脑信号中心底板和顶板介导。这些中心之一的功能缺陷最终导致有缺陷的半球分离，称为前脑无裂畸形（HPE）。然而，HPE发展的形态发生机制仍然难以捉摸。我们发表的数据表明，在非洲爪蟾，Hmmr，微管相关蛋白的功能丧失，诱导顶板缺陷导致HPE。hmmr介导神经细胞的间质-上皮转化（MET）。该功能依赖于Hmmr的微管结合结构域以及与Wnt / PCP信号传导的合作。MET作为一种形态发生机制是前神经管闭合和顶板形成的先决条件，并且需要从经典Wnt信号传导切换到非经典Wnt信号传导。我们未发表的数据表明，hmmr减弱经典的Wnt信号传导，而-在同一时间-它是所需的非经典的Wnt途径。基于这些数据，我们假设，hmmr的功能作为一个中介的MET为基础的形态发生通过调节Wnt信号通路中的微管依赖martyle-dependent marty.The功能的hmmr将被调查在非洲爪蟾作为一个模式生物。Hmmr相互作用的合作伙伴将被确定和功能测试对他们的作用MET和神经元形成的增益和损失的功能，以及通过研究他们的上位关系与hmmr。将通过缺失和突变分析鉴定MET所需的Hmmr功能结构域。这将导致有缺陷的和潜在的显性负性构建体，这些构建体将用作胚胎中功能分析的工具。第二个工作包将分析hmmr如何以微管依赖性方式差异影响经典与非经典Wnt信号传导，以及这如何介导MET过程。hmmr介导的经典Wnt信号传导的调节将使用爪蟾双轴测定和荧光素酶报告基因构建体来评估。为了鉴定hmmr与非典型信号传导的合作模式，将分析PCP下游靶标的定位和活性。这些结果将奠定基础，建立非洲爪蟾作为一个模型来分析形态发生运动的出现HPE。使用相衬X射线显微断层摄影术的体内成像将用于揭示有助于顶板的深部组织的运动。将特别关注HMMR微管结合区的人类从头突变的分析，该突变在顶板衍生HPE患者中被鉴定。该项目将揭示hmmr在调节Wnt信号通路中的新作用，并促进对HPE病因学的hmmr介导的形态发生运动的理解。