Rpc9调控造血干/祖细胞命运维持研究新进展

　　

　脊椎动物造血干细胞在主动脉-性腺-中肾区通过内皮-造血转化过程产生，随后迁移到胎肝（人和小鼠）或尾部造血组织（斑马鱼）进行扩增和定向分化。目前，胚胎期新产生的造血干细胞的维持机制尚不完善，因此，探索这一过程中微环境信号和内源因子的系统调控作用将有助于深入了解造血干细胞发育。

　　中国科学院动物研究所刘峰研究组通过ENU化学诱变筛选，获得一个斑马鱼T淋巴细胞发育缺陷突变体并进行了表型鉴定。应用图位克隆方法，确定该突变体中DNA依赖的RNA聚合酶Ⅲ复合体组分Rpc9 在第二个外显子处发生了T＞A单碱基突变。进一步研究发现，Rpc9缺失会引发过量凋亡从而导致斑马鱼尾部造血组织处造血干/祖细胞减少。抑制p53后，rpc9 斑马鱼突变体中造血干/祖细胞缺陷的表型可以被回救。此外，RNA聚合酶Ⅲ复合体的另外两个组分polr3h 和polr3k 敲低后也会造成斑马鱼胚胎造血干/祖细胞发育缺陷。

　　这项工作证实了RNA聚合酶Ⅲ组分Rpc9 在斑马鱼造血干/祖细胞维持阶段发挥了特异性的正向调控作用。该成果近日在线发表于Development。研究组博士生韦永龙为第一作者，研究员刘峰为通讯作者。该研究得到了香港科技大学教授温子龙和南方医科大学教授张文清的大力支持，由中科院干细胞与再生医学战略性先导科技专项、国家杰出青年科学基金和国家重点基础研究发展计划等资助。

原文摘要：

RNA polymerase III component Rpc9 regulates hematopoietic stem and progenitor cell maintenance in zebrafish

Hematopoietic stem and progenitor cells (HSPCs) are capable of self-renewal and replenishing all lineages of blood cells throughout the lifetime and thus critical for tissue homeostasis. However, the mechanism regulating HSPC development is still incompletely understood. Here, we isolate a zebrafish mutant with defective T lymphopoiesis and positional cloning identifies that Rpc9, a component of DNA-directed RNA polymerase III (Pol III) complex, is responsible for the mutant phenotype. Further analysis shows that rpc9-deficiency leads to the impairment of HSPCs and their derivatives in zebrafish embryos. Excessive apoptosis is observed in the caudal hematopoietic tissue (CHT, the equivalent of fetal liver in mammals) of rpc9−/− embryos and the hematopoietic defects in rpc9−/− embryos can be fully rescued by suppression of p53. Thus, our work illustrate that Rpc9, a component of Pol III, plays an important tissue-specific role in HSPC maintenance during zebrafish embryogenesis and that it might be conserved across vertebrates including mammals.