Oncogenesis and Development Section, National Human Genome Research Institute/NIH, Bethesda, MD 20892, USA.
Dev Dyn. 2012 May;241(5):879-89. doi: 10.1002/dvdy.23774. Epub 2012 Mar 29.
Vertebrate hematopoiesis is a complex developmental process that is controlled by genes in diverse pathways. To identify novel genes involved in early hematopoiesis, we conducted an ENU (N-ethyl-N-nitrosourea) mutagenesis screen in zebrafish. The mummy (mmy) line was investigated because of its multiple hematopoietic defects.
Homozygous mmy embryos lacked circulating blood cell types and were dead by 30 hr post-fertilization (hpf). The mmy mutants did not express myeloid markers and had significantly decreased expression of progenitor and erythroid markers in primitive hematopoiesis. Through positional cloning, we identified a truncation mutation in dhx8 in the mmy fish. dhx8 is the zebrafish ortholog of the yeast splicing factor prp22, which is a DEAH-box RNA helicase. mmy mutants had splicing defects in many genes, including several hematopoietic genes. mmy embryos also showed cell division defects as characterized by disorganized mitotic spindles and formation of multiple spindle poles in mitotic cells. These cell division defects were confirmed by DHX8 knockdown in HeLa cells.
Together, our results confirm that dhx8 is involved in mRNA splicing and suggest that it is also important for cell division during mitosis. This is the first vertebrate model for dhx8, whose function is essential for primitive hematopoiesis in developing embryos.
脊椎动物造血是一个受不同途径基因控制的复杂发育过程。为了鉴定参与早期造血的新基因，我们在斑马鱼中进行了ENU（N-乙基-N-亚硝脲）诱变筛选。由于其多种造血缺陷，我们研究了木乃伊（mmy）品系。
纯合 mmy 胚胎缺乏循环血细胞类型，在受精后 30 小时（hpf）死亡。mmy 突变体不表达髓系标志物，在原始造血中前体细胞和红细胞标志物的表达显著降低。通过定位克隆，我们在 mmy 鱼中鉴定出 dhx8 的截断突变。dhx8 是酵母剪接因子 prp22 的斑马鱼同源物，prp22 是一种 DEAH-box RNA 解旋酶。mmy 突变体在许多基因中存在剪接缺陷，包括一些造血基因。mmy 胚胎还表现出细胞分裂缺陷，表现为有丝分裂纺锤体排列紊乱，有丝分裂细胞中形成多个纺锤极。这些细胞分裂缺陷在 HeLa 细胞中敲低 DHX8 后得到了证实。
总之，我们的结果证实 dhx8 参与 mRNA 剪接，并表明它在有丝分裂过程中的细胞分裂中也很重要。这是 dhx8 的第一个脊椎动物模型，其功能对于胚胎发育中的原始造血至关重要。
