【作者】 李响；

【导师】 孟安明；

【作者基本信息】 清华大学 ， 生物学， 2010， 博士

【摘要】 脊椎动物的初级造血作用能够产生各种原始血细胞,为胚胎中各个组织和器官的发育提供养分。整个过程是在复杂而精密的信号网络调节下进行的,任何调控失衡都会导致严重的发育缺陷或者重大的疾病。通过对造血过程中关键调节因子的研究有利于揭示造血作用的分子机制,完善调控网络,为相关疾病的治疗提供理论基础。NuRD去乙酰基化复合体对于成红细胞、淋巴细胞等各种血细胞的分化具有关键作用,但是它在初级造血中的作用却从未有过报道。本文以斑马鱼作为模式动物,从NuRD复合体中决定其特异性的重要组分Mta3入手,研究Mta3/NuRD复合体在初级造血过程中的作用。本研究发现,在斑马鱼胚胎中敲低mta3基因的表达会特异性地导致初级造血标记基因gata1、hbbe3的表达缺失,红细胞生成减少,初级造血出现严重缺陷。而过量表达mta3基因则能够促进初级造血作用,并且可以挽救mta3下调造成的造血缺陷。进一步对其机制的研究表明,下调或上调mta3表达并不影响血细胞的增殖和凋亡,而是特异性的作用于scl/lmo2等早期造血关键基因的上游,影响血祖细胞向造血前体细胞的分化。Mta3对于造血过程的调控依赖于NuRD复合体的去乙酰基化活性。用去乙酰基化酶抑制剂VPA处理斑马鱼胚胎,可以阻断mta3过量表达对于造血的促进作用;而过量表达NuRD复合体中其它组份HDAC1、MBD3则与过表达mta3一样能够促进初级造血标记基因的表达。利用VPA、TSA抑制胚胎中的去乙酰基化酶活性与mta3基因的敲低一样,可以抑制决定造血前体细胞特化的关键基因scl等的表达,表明Mta3/NuRD复合体作为一个整体调控斑马鱼的初级造血作用,并且位于造血调节网络的顶部。本研究首次证明了Mta3/NuRD复合体是斑马鱼初级造血过程所必须的,它通过调控scl的表达起始来影响造血前体细胞命运的决定,位于造血调控网络的顶部。这一发现为脊椎动物初级造血调控提供了新的机制,丰富了初级造血的调节网络。更多还原

【Abstract】 Through vertebrate primitive hematopoiesis, precursor cells give rise to all kinds of primitive blood cells, which provide nutritional factors for embryonic organs and tissues. The whole process of primitive hematopoiesis is under complicated and precise control, and any improper control will cause severe defects of development or malignant diseases. Identification of key regulators in hematopoiesis will help figure out molecular mechanisms underlying each process, build up an entire network, and provide appropriate candidates for clinical treatments. The NuRD deacetylation complex plays important roles in differentiation of erythrocytes and lymphocytes, but its role in primitive hematopoiesis has not been reported before. In this study, using zebrafish as a model system, the potential role of the Mta3/NuRD complex in primitive hematopoiesis has been investigated with a focus on its component Mta3.In our study, it is demonstrated that knockdown of mta3 inhibits the expression of primitive hematopoietic markers gata1 and hbbe3, reduces the number of red blood cells and causes severe defects in primitive hematopoiesis. Overexpression of mta3 mRNA promotes hematopoiesis and rescues blood defects caused by mta3 knockdown. However, down- or up-regulation of mta3 expression has no effect on apoptosis or proliferation of hematopoietic cells. Indeed, mta3 acts upstream of Scl/Lmo2 to specify hematopoietic precursors from hemangioblasts. Treatment with the histone deacetylases inhibitor VPA blocks the promoting effect of mta3 overexpression on primitive hematopoiesis, whereas overexpressions of HDAC1 or MBD3, two other components of NuRD complex, enhances the expression of hematopoietic markers in a way similar to mta3 overexpression. Furthermore, inhibition of histone deacetylase activity by VPA or TSA treatment affects the expression of early hematopoietic master gene scl, which is identical to mta3 knockdown effect. These results suggest that the Mta3/NuRD complex regulates zebrafish primitive hematopoiesis and acts at the top of the regulatory hierarchy of primitive hematopoiesis.In conclusion, this study demonstrates for the first time that, the Mta3/NuRD complex is essential for zebrafish primitive hematopoiesis. The complex regulates the specification of hematopoietic precursors by controlling the initiation of scl expression and acts at the top of the regulatory hierarchy of primitive hematopoiesis. These findings provide new insight into the regulation of vertebrate primitive hematopoiesis, and enrich the regulatory network.更多还原