peroxidases in the Drosophila genome. These enzymes act as acceptors for hydrogen peroxide and promote its reduction to water. Orthologs of Jafrac1 have been implicated in modulating signaling in yeast and mammalian cell culture. Our results suggest that redox-mediated signaling regulates germ cell migration. doi:10.1016/j.ydbio.2007.03.363 Program/Abstract # 255 IGF signaling cell-autonomously promotes primordial germ cell migration in zebrafish Antony W. Wood, Xianpeng Sang Vincent Center for Reproductive Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA Harvard Stem Cell Institute, Boston, MA, USA Whole-body suppression of insulin-like growth factor recep- tors (IGF1R) in zebrafish embryos results in reduced somatic growth, in addition to mismigration and elimination of primordial germ cells (PGCs). As PGCs rely upon migratory guidance cues from somatic cells, it is unclear whether the PGC defect in IGF1R- deficient embryos stems from defective somatic development, or whether PGCs cell-autonomously require IGF signaling for migration. We hypothesized that PGCs are cell-autonomously dependent upon IGF signaling for migration, based upon the chemotactic response of other cell types to IGF signaling. To test this hypothesis, we designed an expression construct encoding a dominant-negative IGF1R (dnIGF1R) fused to the 3′untranslated region (3′UTR) of the zebrafish nanos1 gene (nos1); the latter element prevents degradation of associated mRNA sequences in germ cells, but permits rapid degradation in somatic cells. This construct thus provides a means to suppress IGF1R function in PGCs while retaining normal IGF signaling in the soma. In accordance with our predictions, zebrafish embryos expressing dnIGF1R:nos1 exhibited normal somatic development, but had significantly fewer PGCs colonizing the genital ridges, and a corresponding increase in the number of mismigrated (ectopic) PGCs. These data support the hypothesis that PGCs in zebrafish are cell-autonomously dependent on signaling through IGF1R for migration to the genital ridges. doi:10.1016/j.ydbio.2007.03.364 Program/Abstract # 256 Induced sexual maturation in eel with embryonic zebrafish cell lines that constitutive produce LH and FSH Denhi Schnabel 1 , Arjan Palstra 2 , Guido Van den Thillart 2 , Herman P. Spaink 2 1 Instituto de Biotecnología, UNAM. Cuernavaca, Morelos, México 2 Institute of Biology, Leiden University, Leiden, The Netherlands Many fish species mature in response to environmental con- ditions. Two isoforms of gonadotropin-releasing hormones have been found in teleost species: the follicular stimulating hormone (FSH) and the luteinizing hormone (LH). FSH controls gonadal development and the early stages of gametogenesis and LH controls the final maturation stages. In aquaculture maturation is often artificially stimulated by regular injections with pituitary extracts. However, the intermittent injections cause large fluctua- tions in the circulating hormone levels and the regular injections cause major stress effects on the animal. Thus, minimising handling and particularly initiating maturation in a natural way will improve the reproduction success. The aim of this project is to develop a novel method to improve maturation of eggs using cells that produce constitutively LH and FSH. The hormone producing cells were transplanted into eels to provide a continuous source for the hormone, thereby reducing the need for regular injections. The presence of the cells was monitored weekly during 1 month. We were able to induce maturation shown as changes in the morphology of eyes and pectoral fins. We developed new molecular probes for testing induction of maturation. The results of the qRTPCR showed an increase in expression of vitelogenin genes, characteristic of the final maturation steps; these findings suggest a breakthrough towards fish reproduction. Work supported by European Commission 6th Framework Programme grant (LSHG-CT-2003-503496, ZF-Models). doi:10.1016/j.ydbio.2007.03.365 Program/Abstract # 257 Identification of the RCK/p54/Cgh-1 homolog in zebrafish Casandra E. Villava 1 , Rosa E. Navarro 2 , Ernesto Maldonado 1 1 Department of Molecular Genetics, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, UNAM, Mexico 2 Department of Cell biology, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Unam, Mexico Germ cells are specified early during development. Oocyte determination in zebrafish and other organisms is induced by the accumulation of maternal determinants in germ granules. After fertilization and during early cell divisions these determinants, which are proteins, mRNA and mitochondria, are segregated to only those cells that will give rise to the germline. Many proteins in germ granules have RNA binding domains. RCK/p54/Cgh-1 is a DEAD box RNA helicase highly conserved and present in germ granules from C. elegans to humans. This helicase regulates mRNA translation by maintaining maternal mRNA masked, it is also involved in cell cycle progression in yeast and germ cell apoptosis protection in C. elegans. RCK is an essential gene for Drosophila and in mammals it is found in the germ line as well in P-bodies from somatic cells, which is the place where the RNAi pathway takes place. We found in the zebrafish genome two RCK/p54/Cgh-1 homologs in chromosomes 18 and 16 that we named RCKa and RCKb respectively. We have cloned RCKa and we are in the process of cloning RCKb. RT-PCR experiments showed that RCKa it is expressed maternally in oocytes and also through all developmental stages from two cells to 5 days post- 384 ABSTRACTS / Developmental Biology 306 (2007) 382–386 brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Elsevier - Publisher Connector