McReynolds Lisa J, Tucker Jennifer, Mullins Mary C, Evans Todd
Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Exp Hematol. 2008 Dec;36(12):1604-1615. doi: 10.1016/j.exphem.2008.08.005. Epub 2008 Oct 29.
The zebrafish is an established model system for studying the embryonic emergence of tissues and organs, including the hematopoietic system. We hypothesized that key signaling pathways controlling embryonic hematopoiesis continue to be important in the adult, and we sought to develop approaches to test this in zebrafish, focused on the bone morphogenetic protein (BMP) signaling pathway. Functions for this pathway in adult hematopoiesis have been challenging to probe in other models.
Several approaches tested the function of BMP signaling during adult zebrafish hematopoiesis. First, we evaluated steady-state hematopoiesis in adult fish that are heterozygous for mutant alleles of Smad5, or are homozygous for mutant alleles, and rescued to adulthood by injection of RNA encoding Smad5. Second, we tested the relative ability of smad5 mutant fish to recover from hemolytic anemia. Third, we generated a transgenic line that targets the expression of a dominant-negative BMP receptor to adult-stage Gata1+ progenitor cells.
Adult fish with a strong mutant smad5 allele are anemic at steady state and, in addition, respond to hemolytic anemia with kinetics that are altered compared to wild-type fish. Fish expressing a mutant BMP receptor in early Gata1+ definitive progenitors generate excessive eosinophils.
Our study provides proof of principle that regulation of adult hematopoiesis can be studied in zebrafish by altering specific pathways. We show that the BMP signaling pathway is relevant for adult hematopoiesis to maintain steady state erythropoiesis, control the erythropoietic response following stress anemia, and to generate normal numbers of eosinophils.
斑马鱼是研究包括造血系统在内的组织和器官胚胎发育的成熟模型系统。我们推测控制胚胎造血的关键信号通路在成体中仍然很重要，并且我们试图开发在斑马鱼中测试这一推测的方法，重点是骨形态发生蛋白（BMP）信号通路。在其他模型中探究该通路在成体造血中的功能一直具有挑战性。
几种方法用于测试BMP信号在成年斑马鱼造血过程中的功能。首先，我们评估了成年鱼的稳态造血情况，这些成年鱼对于Smad5突变等位基因是杂合的，或者对于突变等位基因是纯合的，并通过注射编码Smad5的RNA挽救至成年。其次，我们测试了smad5突变鱼从溶血性贫血中恢复的相对能力。第三，我们构建了一个转基因品系，该品系将显性负性BMP受体的表达靶向成年期Gata1 +祖细胞。
具有强突变smad5等位基因的成年鱼在稳态时贫血，此外，与野生型鱼相比，它们对溶血性贫血的反应动力学发生了改变。在早期Gata1 +确定性祖细胞中表达突变BMP受体的鱼会产生过多的嗜酸性粒细胞。
我们的研究提供了原理证明，即通过改变特定通路可以在斑马鱼中研究成体造血的调控。我们表明，BMP信号通路与成体造血相关，以维持稳态红细胞生成、控制应激性贫血后的红细胞生成反应，并产生正常数量的嗜酸性粒细胞。
