| Genetic analysis of germ cell development in zebrafish has identified several germ cell autonomous genes that are required for different stages of germ cell development, such as nanos1, deadend, and ziwi, the homologue of the drosophila piwi. However, no germ cell non-autonomous factors that are required for germ cell maintenance have so far been described. Recently, the Draper lab has discovered that mutations in the gene encoding the Fibroblast growth factor (Fgf) ligand, Fgf24, results in the majority of animals being sterile. In addition to the sterility, all fgf24 mutant animals develop as phenotypic males, similar to that of ziwi mutants, suggesting that PGC or gonocyte survival may be impaired. The germline phenotype of fgf24 mutants suggests that fgf24 function is required in the gonad during larval development. The goal of the project is to determining if germ cells require an intact Fgf signaling pathway for their survival. To test the hypothesis that germ cells require Fgf signaling for their survival, I wanted to disrupt the Fgf signaling pathway by over expressing a dominant-negative Fgf receptor specifically in germ cells. However, no germ cell-specific promoter that drives gene expression in all germ cells including pre-meiotic germ cells has been described. It was therefore necessary to first identify such a promoter.;In chapter 1, I cloned and tested the promoter activity of a 4.8 kb fragment upstream of ziwi, a gene known to be expressed in all germ cells, including pre-meiotic germ cells, I found that this fragment is capable to drive heterologous gene expression in all stages of germ cells. In chapter 2 I intended to determine if germ cells require an intact Fgf signaling pathway for their survival by overexpressing a dnFgfr in germ cells using the ziwi promoter. Unfortunately, because of mistakes made in construction of the dnfgfr transgenes, I have so far been unable to fully test the hypothesis. |
