Kalev-Zylinska Maggie L, Horsfield Julia A, Flores Maria Vega C, Postlethwait John H, Vitas Maria R, Baas Andrea M, Crosier Philip S, Crosier Kathryn E
Division of Molecular Medicine, The University of Auckland, Auckland, New Zealand.
Development. 2002 Apr;129(8):2015-30. doi: 10.1242/dev.129.8.2015.
RUNX1/AML1/CBFA2 is essential for definitive hematopoiesis, and chromosomal translocations affecting RUNX1 are frequently involved in human leukemias. Consequently, the normal function of RUNX1 and its involvement in leukemogenesis remain subject to intensive research. To further elucidate the role of RUNX1 in hematopoiesis, we cloned the zebrafish ortholog (runx1) and analyzed its function using this model system. Zebrafish runx1 is expressed in hematopoietic and neuronal cells during early embryogenesis. runx1 expression in the lateral plate mesoderm co-localizes with the hematopoietic transcription factor scl, and expression of runx1 is markedly reduced in the zebrafish mutants spadetail and cloche. Transient expression of runx1 in cloche embryos resulted in partial rescue of the hematopoietic defect. Depletion of Runx1 with antisense morpholino oligonucleotides abrogated the development of both blood and vessels, as demonstrated by loss of circulation, incomplete development of vasculature and the accumulation of immature hematopoietic precursors. The block in definitive hematopoiesis is similar to that observed in Runx1 knockout mice, implying that zebrafish Runx1 has a function equivalent to that in mammals. Our data suggest that zebrafish Runx1 functions in both blood and vessel development at the hemangioblast level, and contributes to both primitive and definitive hematopoiesis. Depletion of Runx1 also caused aberrant axonogenesis and abnormal distribution of Rohon-Beard cells, providing the first functional evidence of a role for vertebrate Runx1 in neuropoiesis. To provide a base for examining the role of Runx1 in leukemogenesis, we investigated the effects of transient expression of a human RUNX1-CBF2T1 transgene [product of the t(8;21) translocation in acute myeloid leukemia] in zebrafish embryos. Expression of RUNX1-CBF2T1 caused disruption of normal hematopoiesis, aberrant circulation, internal hemorrhages and cellular dysplasia. These defects reproduce those observed in Runx1-depleted zebrafish embryos and RUNX1-CBF2T1 knock-in mice. The phenotype obtained with transient expression of RUNX1-CBF2T1 validates the zebrafish as a model system to study t(8;21)-mediated leukemogenesis.
RUNX1/AML1/CBFA2对于定向造血至关重要，影响RUNX1的染色体易位常与人类白血病相关。因此，RUNX1的正常功能及其在白血病发生中的作用仍在深入研究中。为进一步阐明RUNX1在造血中的作用，我们克隆了斑马鱼同源基因（runx1），并使用该模型系统分析其功能。斑马鱼runx1在胚胎早期发育过程中在造血细胞和神经细胞中表达。侧板中胚层中runx1的表达与造血转录因子scl共定位，并且在斑马鱼突变体spadetail和cloche中runx1的表达明显降低。在cloche胚胎中瞬时表达runx1导致造血缺陷部分得到挽救。用反义吗啉代寡核苷酸耗尽Runx1消除了血液和血管的发育，这通过循环丧失、血管系统发育不完全以及未成熟造血前体细胞的积累得以证明。定向造血的阻滞类似于在Runx1基因敲除小鼠中观察到的情况，这意味着斑马鱼Runx1具有与哺乳动物中相当的功能。我们的数据表明，斑马鱼Runx1在成血管细胞水平上在血液和血管发育中均发挥作用，并有助于原始造血和定向造血。耗尽Runx1还导致异常的轴突发生和罗霍恩 - 比尔细胞的异常分布，这为脊椎动物Runx1在神经发生中的作用提供了首个功能证据。为了为研究Runx1在白血病发生中的作用提供基础，我们研究了人RUNX1 - CBF2T1转基因[急性髓性白血病中t(8;21)易位的产物]在斑马鱼胚胎中的瞬时表达效应。RUNX1 - CBF2T1的表达导致正常造血破坏、异常循环、内出血和细胞发育异常。这些缺陷重现了在耗尽Runx1的斑马鱼胚胎和RUNX1 - CBF2T1基因敲入小鼠中观察到的值。RUNX1 - CBF2T1瞬时表达获得的表型验证了斑马鱼作为研究t(8;21)介导的白血病发生的模型系统。
