Regulation of hematopoietic stem and progenitor cell fate determination by Dpy30

 描述（由申请人提供）：许多血液病是由造血干细胞和祖细胞（HSPC）的维持、增殖和分化的异常染色质和基因调控引起的。作为哺乳动物中主要的H3 K4甲基化酶，Set 1/M11复合物在发育生物学中占据关键地位，并且由于H3 K4甲基化与基因表达的密切联系以及这些复合物中的几个亚基与疾病（包括多种血液癌症）的广泛关联而被认为是表观遗传疗法的潜在药物靶标。然而，仍不清楚Set 1/Mll复合物的H3 K4甲基化活性如何调节正常和异常的造血。我们先前已经确定，Dpy 30，Set 1/M11复合物的共享亚基，促进染色体H3 K4甲基化，并且通过促进许多双链标记的发育基因的诱导而对胚胎干细胞的有效分化至关重要。在本提案中，我们将使用我们最近产生的Dpy 30条件性敲除（KO）小鼠模型研究Dpy 30及其相关H3 K4甲基化在HSPC命运决定中的功能作用。我们已经表明，细胞H3 K4甲基化水平在Dpy 30 KO小鼠中显著降低。这些小鼠发生严重的全血细胞减少症，并且在多谱系造血重建中具有严重缺陷，但以更多下游造血细胞为代价强烈积累表型早期HSPC，表明造血分化受阻。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制定我们的中心假设在这个建议-Dpy 30是至关重要的HSPC细胞命运的决定，通过促进H3 K4甲基化的关键造血基因。因此，我们提出了两个具体的目的来验证这一假设：（1）：确定Dpy 30在HSC维持和HSPC分化中的作用。(2)目的：探讨Dpy 30调控HSPC功能的分子机制。通过揭示Set 1/Mll复合物的H3 K4甲基化活性在调节HSPC命运决定中的先前未被认识的作用，该项目将对开发针对某些基于HSPC的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.