Znf521调节FoxM1和c-Kit在造血干细胞静息状态中的作用及分子机制

It’s an important scientific issue to understand how Znf521 regulates FoxM1 and c-Kit in maintaining the quiescence of hematopoietic stem cells. We generated the Znf521 conditional knockout mice, and investigated it’s function in the hematopoietic stem cells. we found that deletion of Znf521 result in a decrease in the proportion of quiescent cells in LSK population, and also a decrease in the number of hematopoietic stem/progenitor cells. Based on the comparison of gene expression profile between Znf521-deficient HSCs and the wildtype control HSCs, two genes (FoxM1 and c-Kit) stand out due to their significant down-regulation in Znf521-deficient HSCs. And further studies demonstrated that the transcription activity of FoxM1 and c-Kit are regulated by Znf521。Our previous studies illuminate that FoxM1 is an essential intrinsic factor for maintaining the quiescence of hematopoietic stem cells, and published papers also show that c-Kit functions in maintaining the quiescence of HSCs as the receptor of extrinsic factor Scf. We hypothesis that Znf521 maintaining the quiescence of hematopoietic stem cells by orchestrating the roles of intrinsic factor FoxM1 and extricsin factor c-Kit. This project will elucidate how Znf521 regulates FoxM1 and c-Kit in maintaining the quiescence of hematopoietic stem cells in molecular level and animal model level. Our research results will definitely improve our understanding about the molecular networks which controling the quiescence of hematopoietic stem cells.

Znf521如何调控FoxM1及c-Kit影响造血干细胞静息状态是重要的科学问题。我们利用Znf521条件敲除小鼠模型研究Znf521基因在造血干细胞中的功能时发现：Znf521敲除导致静息状态造血干细胞比例明显降低，并伴造血干细胞与前体细胞数量减少。利用Micro-array比较Znf521缺失与正常造血干细胞基因表达变化，发现FoxM1与c-Kit基因被显著下调，实验表明FoxM1与c-Kit启动子受到Znf521调控。我们曾报道FoxM1是造血干细胞静息状态重要内在调控因素，而c-Kit是外在调控因素Scf的受体。我们提出Znf521通过干预干细胞内在因素相关基因FoxM1及外在因素相关基因c-Kit，实现对造血干细胞静息状态的调控。本课题拟从分子及动物模型水平阐明Znf521协调FoxM1与c-Kit调控造血干细胞静息状态。研究结果对理解造血干细胞静息状态分子调控网络具有重要意义。

Zfp521 是锌指蛋白转录因子家族成员之一，高表达于静息态的HSC中，对于胎肝造血干细胞的自我更新和分化有重要的作用。然而，其在成体造血的功能尚未阐明。为了探究Zfp521在成体造血中的功能，我们构建了血液系统特异性敲除Zfp521 的小鼠模型。我们发现在稳态情况下，Zfp521的缺失并不影响成体造血，相反，由Zfp521缺失骨髓细胞重建的Zfp521 缺失嵌合体小鼠的造血干祖细胞数目降低，且静息状态的细胞数目减少并伴有凋亡增加。竞争性骨髓移植实验结果表明在细胞再生压力条件下，Zfp521对于调节造血干细胞的自我更新和分化有重要的作用。我们进一步探究了Zfp521调节造血干细胞的自我更新和分化的分子机制。我们发现Zfp521 可以直接结合在 NF-κB信号通路的重要调节子Rela的启动子上，并抑制其转录活性。Zfp521的结合可以上调Rela启动子上H3K9me3 修饰水平，同时降低H3K9ac 修饰水平。在Zfp521缺失的嵌合体小鼠中，敲低Rela的表达可以抑制过度活化的NF-κB信号通路，并且可以逆转Zfp521缺失引起的造血干细胞静息态水平降低的表型。因此，我们的结果表明在成体造血过程中Zfp521至少部分通过调控Rela的表达，影响NF-κB信号通路，调节造血干细胞自我更新和静息态维持。