Regulation of hematopoietic stem and progenitor cell fate determination by Dpy30

 描述(申请人提供)：许多血液病是由于染色体异常和基因调控对造血干细胞和祖细胞(HSPC)的维持、增殖和分化的影响。作为哺乳动物体内主要的H3K4甲基化酶，Set1/MLL复合体在发育生物学中占有重要地位，被认为是表观遗传学治疗的潜在药物靶点，因为H3K4甲基化与基因表达密切相关，并且这些复合体中的几个亚单位与包括多发性血癌在内的疾病的广泛关联。然而，目前尚不清楚Set1/MLL复合体的H3K4甲基化活性如何调节正常和异常的造血。我们先前已经证实，Dpy30是Set1/MLL复合体的一个共有的亚基，促进了染色体H3K4的甲基化，并通过促进许多二价标记的发育基因的诱导，对胚胎干细胞的高效分化至关重要。在这个建议中，我们将使用我们最近建立的Dpy30条件基因敲除(KO)小鼠模型来研究Dpy30及其相关的H3K4甲基化在决定HSPC命运中的功能作用。我们已经证明，在Dpy30 KO小鼠中，细胞H3K4甲基化水平显著降低。这些小鼠出现严重的全血细胞减少，在多系造血重建方面存在严重缺陷，但以更多下游造血细胞为代价强烈积累早期表型HSPC，提示造血分化受阻。在竞争性移植系统中的进一步分析也揭示了HSPC命运决定和关键调控基因表达的深刻缺陷。这些结果使我们能够阐明我们在这一建议中的中心假设--Dpy30通过促进关键造血基因的H3K4甲基化，对决定HSPC细胞的命运至关重要。因此，我们提出了两个具体的目标来检验这一假说：(1)：确定Dpy30在HSC维持和HSPC分化中的作用。(2)：剖析Dpy30调控HSPC功能的分子机制。通过揭示Set1/MLL复合体的H3K4甲基化活性在调节HSPC命运决定中先前未知的作用，该项目将对开发针对某些HSPC血液病的治疗策略具有重要意义。

 DESCRIPTION (provided by applicant): Many hematological diseases result from aberrant chromatin and gene regulation of the maintenance, proliferation and differentiation of hematopoietic stem and progenitor cells (HSPCs). As the major H3K4 methylation enzymes in mammals, the Set1/Mll complexes occupy a crucial position in developmental biology, and are considered potential drug targets for epigenetic therapeutics due to the intimate connection of H3K4 methylation with gene expression as well as the extensive association of several subunits in these complexes with diseases, including multiple blood cancers. However, it remains unclear how the H3K4 methylation activity of the Set1/Mll complexes regulates normal and abnormal hematopoiesis. We have previously established that Dpy30, a shared subunit of the Set1/Mll complexes, facilitates chromosomal H3K4 methylation, and is crucial for efficient differentiation of embryonic stem cells by facilitating the induction of many bivalently marked developmental genes. In this proposal, we will study the functional role of Dpy30 and its associated H3K4 methylation in HSPC fate determination using a Dpy30 conditional knockout (KO) mouse model that we recently generated. We have shown that the cellular H3K4 methylation level is markedly reduced in the Dpy30 KO mice. These mice develop severe pancytopenia and have profound defects in multilineage hematopoietic reconstitution, yet strongly accumulate phenotypic early HSPCs at the expense of more downstream hematopoietic cells, suggesting a block in hematopoietic differentiation. Further analyses in a competitive transplantation system also reveal profound defects in HSPC fate determination and in expression of key regulatory genes. These results allowed us to formulate our central hypothesis in this proposal -- Dpy30 is critical for HSPC cell fate determination through facilitating H3K4 methylation of key hematopoietic genes. We thus propose two specific aims to test this hypothesis: (1): To define the role of Dpy30 in HSC maintenance and HSPC differentiation. (2): To dissect the molecular mechanisms by which Dpy30 regulates HSPC function. By revealing a previous unrecognized role of the H3K4 methylation activity of the Set1/Mll complexes in regulating HSPC fate determination, this project will have important implications for developing therapeutic strategies against certain HSPC-based hematological diseases.