Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA.
Dev Biol. 2010 May 1;341(1):167-75. doi: 10.1016/j.ydbio.2010.02.020. Epub 2010 Feb 21.
Leo1 is a component of the Polymerase-Associated Factor 1 (PAF1) complex, an evolutionarily conserved protein complex involved in gene transcription regulation and chromatin remodeling. The role of leo1 in vertebrate embryogenesis has not previously been examined. Here, we report that zebrafish leo1 encodes a nuclear protein that has a similar molecular structure to Leo1 proteins from other species. From a genetic screen, we identified a zebrafish mutant defective in the leo1 gene. The truncated Leo1(LA1186) protein lacks a nuclear localization signal and is distributed mostly in the cytoplasm. Phenotypic analysis showed that while the initial patterning of the primitive heart tube is not affected in leo1(LA1186) mutant embryos, the differentiation of cardiomyocytes at the atrioventricular boundary is aberrant, suggesting a requirement for Leo1 in cardiac differentiation. In addition, the expression levels of markers for neural crest-derived cells such as crestin, gch2, dct and mitfa are greatly reduced in leo1(LA1186) mutants, indicating a requirement for Leo1 in maintaining the neural crest population. Consistent with this finding, melanocyte and xanthophore populations are severely reduced, craniofacial cartilage is barely detectable, and mbp-positive glial cells are absent in leo1(LA1186) mutants after three days of development. Taken together, these results provide the first genetic evidence of the requirement for Leo1 in the development of the heart and neural crest cell populations.
Leo1 是聚合酶相关因子 1（PAF1）复合物的一个组成部分，该复合物是一种进化上保守的蛋白质复合物，参与基因转录调控和染色质重塑。Leo1 在脊椎动物胚胎发生中的作用以前尚未被研究过。在这里，我们报告说斑马鱼 leo1 编码一种核蛋白，其分子结构与来自其他物种的 Leo1 蛋白相似。通过遗传筛选，我们鉴定出一种斑马鱼 leo1 基因缺陷的突变体。截断的 Leo1（LA1186）蛋白缺乏核定位信号，主要分布在细胞质中。表型分析表明，尽管 leo1（LA1186）突变体胚胎中的原始心管初始模式不受影响，但房室边界处的心肌细胞分化异常，表明 Leo1 在心臓分化中是必需的。此外，神经嵴衍生细胞的标志物如 crestin、gch2、dct 和 mitfa 的表达水平在 leo1（LA1186）突变体中大大降低，表明 Leo1 对维持神经嵴细胞群体是必需的。与这一发现一致的是，黑色素细胞和黄色素细胞群体严重减少，颅面软骨几乎不可检测，mbp 阳性神经胶质细胞在 leo1（LA1186）突变体中缺失。综上所述，这些结果提供了 Leo1 在心脏和神经嵴细胞群体发育中必需的第一个遗传证据。
