ANALYSIS OF PAIR OF RULE GENES IN SEQUENTIAL SEGMENTATIO

本实验室的长期研究目标是阐明水蛭胚胎（环节动物门）发育的细胞和分子机制，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协调节段结构组装的形态发生过程。在脊索动物和环节动物中，节段结构都是由由胚胎干细胞组成的后生长区产生的细胞片产生的。在水蛭中，这些细胞数量很少，可以单独识别，并且可以进行实验操作。因此，对实验可获得的水蛭胚胎的基础研究有助于理解和最终改善遗传和环境诱导的发育障碍。水蛭的中胚层和外胚层是由胚胎生发板中5个双侧配对的节段性创始细胞（m、n、o、p和q原代胚细胞）的后代，由前向后发育而成。每侧的五列胚细胞分别来自可识别的M、N和Q三种不同的成质细胞，以及一对同等能力的O/P成质细胞。在N系和Q系中，原代胚细胞都采用2种不同的命运，并且两个原代胚细胞（每种类型一个细胞）为每个节段贡献后代。在其他三种谱系（M、O和P）中，所有的胚细胞都遵循大致相同的命运，每个胚细胞都贡献了一个完整的子代。拟建项目期间的实验目标是研究果蝇对规则基因的同源性对于确定水蛭中末端细胞产生节段性发现细胞的干细胞分裂以及确定N和Q谱系中交替胚细胞的不同鉴定至关重要的假设。

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.