Karamitros Dimitris, Patmanidi Alexandra L, Kotantaki Panoraia, Potocnik Alexandre J, Bähr-Ivacevic Tomi, Benes Vladimir, Lygerou Zoi, Kioussis Dimitris, Taraviras Stavros
Department of Physiology, Medical School, University of Patras, Rio, Patras 26504, Greece.
Division of Molecular Immunology, MRC/National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK.
Development. 2015 Jan 1;142(1):70-81. doi: 10.1242/dev.109454.
Balancing stem cell self-renewal and initiation of lineage specification programs is essential for the development and homeostasis of the hematopoietic system. We have specifically ablated geminin in the developing murine hematopoietic system and observed profound defects in the generation of mature blood cells, leading to embryonic lethality. Hematopoietic stem cells (HSCs) accumulated in the fetal liver following geminin ablation, while committed progenitors were reduced. Genome-wide transcriptome analysis identified key HSC transcription factors as being upregulated upon geminin deletion, revealing a gene network linked with geminin that controls fetal hematopoiesis. In order to obtain mechanistic insight into the ability of geminin to regulate transcription, we examined Hoxa9 as an example of a key gene in definitive hematopoiesis. We demonstrate that in human K562 cells geminin is associated with HOXA9 regulatory elements and its absence increases HOXA9 transcription similarly to that observed in vivo. Moreover, silencing geminin reduced recruitment of the PRC2 component SUZ12 to the HOXA9 locus and resulted in an increase in RNA polymerase II recruitment and H3K4 trimethylation (H3K4me3), whereas the repressive marks H3K9me3 and H3K27me3 were reduced. The chromatin landscape was also modified at the regulatory regions of HOXA10 and GATA1. K562 cells showed a reduced ability to differentiate to erythrocytes and megakaryocytes upon geminin silencing. Our data suggest that geminin is indispensable for fetal hematopoiesis and regulates the generation of a physiological pool of stem and progenitor cells in the fetal hematopoietic system.
平衡干细胞自我更新与谱系定向程序的启动对于造血系统的发育和稳态至关重要。我们特异性地在发育中的小鼠造血系统中敲除了geminin，并观察到成熟血细胞生成存在严重缺陷，导致胚胎致死。geminin敲除后，造血干细胞（HSCs）在胎肝中积累，而定向祖细胞减少。全基因组转录组分析确定关键的造血干细胞转录因子在geminin缺失时上调，揭示了一个与geminin相关的控制胎儿造血的基因网络。为了深入了解geminin调节转录的机制，我们以Hoxa9为例研究了其在确定性造血中的关键基因。我们证明，在人K562细胞中，geminin与HOXA9调控元件相关，其缺失会增加HOXA9转录，与体内观察到的情况类似。此外，沉默geminin会减少PRC2组分SUZ12募集到HOXA9基因座，并导致RNA聚合酶II募集增加和H3K4三甲基化（H3K4me3）增加，而抑制性标记H3K9me3和H3K27me3减少。HOXA10和GATA1的调控区域的染色质景观也发生了改变。geminin沉默后，K562细胞向红细胞和巨核细胞分化的能力降低。我们的数据表明，geminin对胎儿造血不可或缺，并调节胎儿造血系统中干细胞和祖细胞生理库的生成。
