ANALYSIS OF PAIR OF RULE GENES IN SEQUENTIAL SEGMENTATIO

本实验室的长期研究目标是阐明水蚤胚胎(环节动物门)的细胞和分子发育机制，以便与其他门进行比较。这种比较使我们能够确定在果蝇等生物体中发现的发育机制的哪些特征更有可能在人类发育中发挥作用。特别令人感兴趣的是编排节段结构组装的形态发生过程。在脊索动物和环节动物中，节状结构都是由包含胚胎干细胞的后部生长带产生的细胞片形成的。在水蛭中，这些细胞数量很少，可以单独识别，并可用于实验操作。因此，对实验上可获得的水蚤胚胎的基础研究有助于理解和最终改善遗传和环境引起的发育障碍。在水蚤中，节状中胚层和外胚层以从前到后的方式出现，作为胚胎生发板中五个两侧成对的节段性创始细胞(m、n、o、p和q初级母细胞)的后代。每一侧的五列原始细胞来自唯一可识别的M、N和Q端粒细胞，外加一对相等的O/P端粒细胞。在N和Q谱系中，原代母细胞有两个完全不同的命运交替，两个原代母细胞(每种类型一个细胞)为每个片段提供后代。在其他三个谱系(M、O和P)中，所有的原始细胞遵循大致相同的命运，每个原始细胞贡献一个完整的子代节段性补充。计划期间的实验目标是研究这样一种假设，即果蝇配对规则基因的同源基因对于确定干细胞分裂以及确定N和Q谱系中交替的原始细胞的不同识别是必不可少的。

The long term research objective in this laboratory is to elucidate cellular and molecular mechanisms of development in leech embryos (phylum Annelida), for comparison with other phyla. Such comparisions allow us to determine which features of developmental mechanisms discovered in organisms such as Drosophila are more likely to be operating in human development. Of particular interest are the morphogenetic processes orchestrating the assembly of segmental structures. In both chordates and annelids, segmental structures arise from sheets of cells generated by a posterior growth zone comprising embryonic stem cells. In leech, these cells are few in number, individually identifiable and accessible for experimental manipulation. Thus, basic research on the experimentally accessible leech embryo can contribute to the understanding and eventual amelioration of genetic and environmentally induced developmental disorders. In leech, segmental mesoderm and ectoderm arise in a anterior-to- posterior progression as the progeny of five bilaterally paired columns of segmental founder cells (m, n, o, p and q primary blast cells) in the germinal plate of the embryo. The five columns of blast cells on each side arise from uniquely identifiable M, N and Q teloblasts, plus a pair of equipotent O/P teloblasts. In both the N and Q lineages, primary blast cells adopt 2 distinct fates in exact alternation, and two primary blast cells (one cell of each type) contribute progeny to each segment. In each of the other three lineages (M, O and P), all blast cells follow roughly identical fates and each blast cell contributes a full segmental complement of progeny. The experimental goal for the proposed project period is to investigate the hypothesis that homologs of Drosophila pair rule genes are essential for specifying the stem cell divisions by which teloblasts generate segmental found cells in leech, and for determining distinct identifies of alternate blast cells in the N and Q lineages.