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，并与其他门进行比较。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起作用。特别令人感兴趣的是形态发生的过程，编排节段结构的组装。 在脊索动物和环节动物中，节段结构都是由包含胚胎干细胞的后生长区产生的细胞片层产生的。 在水蛭中，这些细胞数量很少，可单独识别并可用于实验操作。 因此，对水蛭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。在水蛭，节段性中胚层和外胚层出现在一个前到后的进展作为五个双边配对列的节段性创始人细胞（m，n，o，p和q初级原始母细胞）在胚胎的生殖板的后代。 每侧的五列原始细胞来自唯一可识别的M，N和Q端细胞，加上一对等效的O/P端细胞。 在N和Q谱系中，原代母细胞以精确交替的方式采用2种不同的命运，并且两个原代母细胞（每种类型一个细胞）为每个片段贡献后代。 在其他三个谱系（M、O和P）中，所有母细胞遵循大致相同的命运，每个母细胞都贡献了后代的完整节段互补。建议的项目期间的实验目标是调查的假设，果蝇配对规则基因的同源物是必不可少的指定的干细胞分裂，端细胞产生节段性发现细胞在水蛭，并确定不同的身份交替原始细胞在N和Q谱系。

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.