Functional analysis of genes controlling germ-cell migration in zebrafish

在许多生物体中，原始生殖细胞必须从它们被指定的位置迁移到它们产生配子的发育性腺。对果蝇、小鼠、鸡和爪蟾的原始生殖细胞迁移的广泛研究已经确定了在这一过程中重要的体细胞组织，并证明了特定分子在指导细胞向目标移动方面的作用。在初步研究中，我们描述了野生型斑马鱼胚胎中PGCs的迁移过程。为了获得体细胞组织在生殖细胞迁移过程中提供位置线索的来源信息，我们分析了斑马鱼突变胚胎的迁移模式。这些早期研究指出了中胚层外侧边界作为PGCs的中间靶点的重要性，并确定了早期胚胎中位于特定背-腹侧和前后位置的一个假定的吸引中心。本研究旨在确定引导PGCs走向中胚层外侧边缘的中间靶点的分子线索，以及识别在早期体细胞发生阶段吸引PGCs走向特定聚集位置的信号分子。为此，将构建一个cDNA文库，丰富靶组织和生殖细胞本身表达的转录本。该文库将筛选以表明在PGC迁移中起作用的模式表达的cdna。这些克隆将被分子表征，并将在功能上进行测试，以指导PGCs的迁移。

In many organisms the primordial germ cells have to migrate from the position where they are specified towards the developing gonad where they generate gametes. Extensive studies of the migration of primordial germ cells in Drosophila, mouse, chick and Xenopus have identified somatic tissues important for this process and demonstrated a role for specific molecules in directing the cells towards their target. In preliminary studies we have characterized the migration process of the PGCs in wild type zebrafish embryos. To obtain information on the origin of the positional cues provided to the germ cells by somatic tissues during their migration, we analyzed the migration pattern in mutant zebrafish embryos. These early studies point at importance of the lateral border of the mesoderm as an intermediate target for the PGCs and identify a putative attraction center located at a specific dorsal-ventral and anteriorposterior position in early embryos. This proposal is aimed at identifying the molecular cues directing the PGCs towards their intermediate target at the lateral border of the mesoderm as well as identifying signaling molecules attracting the PGCs towards specific clustering positions during early somitogenesis stages. Towards this end a cDNA library enriched for transcripts expressed in the target tissue and in the germ cells themselves will be constructed. This library will be screened for cDNAs that are expressed in a pattern suggesting a role in PGC migration. These clones will be molecularly characterized and will be tested functionally for a role in directing the migration of the PGCs.