Peng Jun, Kitchen Susan M, West Richard A, Sigler Robert, Eisenmann Kathryn M, Alberts Arthur S
Laboratory of Cell Structure and Signal Integration, Van Andel Research Institute, Grand Rapids, Michigan 49503, USA.
Cancer Res. 2007 Aug 15;67(16):7565-71. doi: 10.1158/0008-5472.CAN-07-1467.
Rho GTPase-effector mammalian diaphanous (mDia)-related formins assemble nonbranched actin filaments as part of cellular processes, including cell division, filopodia assembly, and intracellular trafficking. Whereas recent efforts have led to thorough characterization of formins in cytoskeletal remodeling and actin assembly in vitro, little is known about the role of mDia proteins in vivo. To fill this knowledge gap, the Drf1 gene, which encodes the canonical formin mDia1, was targeted by homologous recombination. Upon birth, Drf1+/- and Drf1-/- mice were developmentally and morphologically indistinguishable from their wild-type littermates. However, both Drf1+/- and Drf1-/- developed age-dependent myeloproliferative defects. The phenotype included splenomegaly, fibrotic and hypercellular bone marrow, extramedullary hematopoiesis in both spleen and liver, and the presence of immature myeloid progenitor cells with high nucleus-to-cytoplasm ratios. Analysis of cell surface markers showed an age-dependent increase in the percentage of CD11b+-activated and CD14+-activated monocytes/macrophages in both spleen and bone marrow in Drf1+/- and Drf1-/- animals. Analysis of the erythroid compartment showed a significant increase in the proportion of splenic cells in S phase and an expansion of erythroid precursors (TER-119+ and CD71+) in Drf1-targeted mice. Overall, knocking out mDia1 expression in mice leads to a phenotype similar to human myeloproliferative syndrome (MPS) and myelodysplastic syndromes (MDS). These observations suggest that defective DRF1 expression or mDia1 function may contribute to myeloid malignancies and point to mDia1 as an attractive therapeutic target in MDS and MPS.
Rho GTP酶效应蛋白哺乳动物透明相关成束蛋白（mDia）相关的成束蛋白组装非分支肌动蛋白丝，作为细胞过程的一部分，包括细胞分裂、丝状伪足组装和细胞内运输。尽管最近的研究已经对成束蛋白在体外细胞骨架重塑和肌动蛋白组装方面进行了全面的表征，但对于mDia蛋白在体内的作用却知之甚少。为了填补这一知识空白，通过同源重组对编码典型成束蛋白mDia1的Drf1基因进行了靶向操作。出生时，Drf1+/-和Drf1-/-小鼠在发育和形态上与它们的野生型同窝小鼠没有区别。然而，Drf1+/-和Drf1-/-都出现了年龄依赖性的骨髓增殖性缺陷。该表型包括脾肿大、纤维化和细胞增多的骨髓、脾脏和肝脏中的髓外造血，以及存在高核质比的未成熟髓系祖细胞。细胞表面标志物分析显示，Drf1+/-和Drf1-/-动物的脾脏和骨髓中，CD11b+激活的和CD14+激活的单核细胞/巨噬细胞百分比随年龄增加。红系分析显示，在Drf1靶向小鼠中，处于S期的脾细胞比例显著增加，红系前体细胞（TER-119+和CD71+）扩增。总体而言，敲除小鼠中的mDia1表达会导致一种类似于人类骨髓增殖综合征（MPS）和骨髓增生异常综合征（MDS）的表型。这些观察结果表明，DRF1表达缺陷或mDia1功能可能导致髓系恶性肿瘤，并指出mDia1是MDS和MPS中一个有吸引力的治疗靶点。
