Functional analysis of genes controlling germ-cell migration in zebrafish

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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.