Department of Biological Sciences, University of Alberta, Edmonton, Canada.
Dev Biol. 2010 Apr 15;340(2):306-17. doi: 10.1016/j.ydbio.2010.01.033. Epub 2010 Feb 1.
During vertebrate development, the initial wave of hematopoiesis produces cells that help to shape the developing circulatory system and oxygenate the early embryo. The differentiation of primitive erythroid and myeloid cells occurs within a short transitory period, and is subject to precise molecular regulation by a hierarchical cascade of transcription factors. The TALE-class homeodomain transcription factors Meis and Pbx function to regulate embryonic hematopoiesis, but it is not known where Meis and Pbx proteins participate in the hematopoietic transcription factor cascade. To address these questions, we have ablated Meis1 and Pbx proteins in zebrafish, and characterized their molecular effects on known markers of primitive hematopoiesis. Embryos lacking Meis1 and Pbx exhibit a severe reduction in the expression of gata1, the earliest marker of erythroid cell fate, and fail to produce visible circulating blood cells. Concomitant with a loss of gata1, Meis1- and Pbx-depleted embryos exhibit downregulated embryonic hemoglobin (hbae3) expression, and possess increased numbers of pu.1-positive myeloid cells. gata1-overexpression rescues hbae3 expression in Pbx-depleted; meis1-morphant embryos, placing Pbx and Meis1 upstream of gata1 in the erythropoietic transcription factor hierarchy. Our study conclusively demonstrates that Meis1 and Pbx act to specify the erythropoietic cell lineage and inhibit myelopoiesis.
在脊椎动物发育过程中，最初的造血过程产生的细胞有助于塑造正在发育的循环系统，并为早期胚胎供氧。原始红细胞和髓样细胞的分化发生在一个短暂的过渡时期，受到转录因子层次级联的精确分子调控。TALE 类同源域转录因子 Meis 和 Pbx 有助于调节胚胎造血，但尚不清楚 Meis 和 Pbx 蛋白在造血转录因子级联中的参与位置。为了解决这些问题，我们在斑马鱼中敲除了 Meis1 和 Pbx 蛋白，并对其对原始造血的已知标志物的分子影响进行了特征分析。缺乏 Meis1 和 Pbx 的胚胎中 gata1 的表达严重减少，gata1 是红细胞命运的最早标志物，且无法产生可见的循环血细胞。与 gata1 的缺失同时发生的是，Meis1 和 Pbx 耗竭的胚胎中胚胎血红蛋白（hbae3）的表达下调，并且 pu.1 阳性的髓样细胞数量增加。gata1 的过表达挽救了 Pbx 耗竭的；meis1 突变胚胎中的 hbae3 表达，将 Pbx 和 Meis1 置于红细胞生成转录因子级联中的 gata1 上游。我们的研究结论性地表明，Meis1 和 Pbx 作用于指定红细胞谱系并抑制髓样细胞生成。
