乳腺癌扩增序列BCAS2通过调控wnt/β-catenin信号通路促进脊椎动物胚胎初级造血的研究

Hematopoiesis occurs in two successive waves, primitive and definitive hematopoiesis during vertebrate embryonic development. Primitive hematopoietic progenitors, which function in the rapid production of large numbers of erythroid cells that support the growth and survival of the embryo, are the first cell type specified from the mesoderm late in gastrulation. Wnt/β-catenin signaling is highly activited and required for primitive hematopoiesis, but the regulation of this pathway remains to investigate. During the screen for Wnt/β-catenin signaling pathway modulators, we identified BCAS2 (Breast cancer amplified sequence 2), the core component of CDC5L/PRP19 complex, could promote Wnt signaling transduction. Preliminary data showed that Zebrafish bcas2 is specifically expressed in primitive hematopoietic tissues and is essencial for blood cell formation. The depletion of BCAS2 in mouse MEF cells led to total loss of Wnt activition induced-nuclear accumulation of β-catenin. Our study also indicates that BCAS2 may increase Wnt signalling through preventing the degradation and also the nuclear export of β-catenin in the nucleus. In this proposal, we plan using zebrafish and mouse embryo as model systems to explore the fuction and molecular mechanisms of BCAS2 during primitive hematopoiesis. Given the potential importance of β-catenin degradation in the nucleus, our study will make conceptual breakthrough in the regulation of Wnt/β-catenin signaling.

初级造血前体细胞来源于原肠晚期中胚层，可以产生的大量血细胞为胚胎细胞存活和快速增殖提供氧气。Wnt/β-catenin信号是初级造血发育所必需的，然而其在初级造血发育过程中的调控机制目前所知甚少。我们发现PRP19/CDC5L复合体成员BCAS2可以促进Wnt/β-catenin信号传导。初步的研究结果表明，斑马鱼bcas2在初级造血组织有特异表达，在初级造血发育过程中有重要作用。敲除BCAS2的小鼠MEF细胞核中几乎检测不到Wnt激活引起的β-catenin在核内的积聚。进一步的研究揭示，BCAS2可能通过两种方式调控Wnt/β-catenin信号通路：抑制细胞核β-catenin降解及阻止β-catenin出核。本项目将深入研究BCAS2在初级造血发育中的功能和分子机制。鉴于核内β-catenin蛋白降解的重要性，我们相信本项目的实施会取得重要的的概念性突性突破和原创性成果。

初级造血前体细胞来源于原肠晚期中胚层，可以产生的大量血细胞为胚胎细胞存活和快速增殖提供氧气。Wnt/β-catenin信号是初级造血发育所必需的，然而其在初级造血发育过程中的调控机制目前所知甚少。我们发现PRP19/CDC5L复合体成员BCAS2可以促进Wnt/β-catenin信号传导。有意思的是，斑马鱼bcas2在初级造血组织有特异表达。通过CRISPR/Cas9技术，我们制备了bcas2斑马鱼突变体。bcas2斑马鱼突变体呈现严重的初级造血缺陷，红系细胞数目明显减少。经过基因互做分析和大量生化实验检测，我们发现bcas2可以与β-catenin直接结合，抑制其出核，从而造成β-catenin在核内积聚，促进Wnt信号和初级造血发生。我们的研究第一次揭示了bcas2通过促进Wnt信号参与初级造血的功能机制，对于了解血液系统发育过程提供了新的理解。这些研究结果正在整理成文，准备投稿。另外，在本项目的资助下，我们还进行了一系列的研究工作，发表在Nature Communications、Cell Research、PLOS Biology 和Science Advances等著名的国际期刊。

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