fertilization. It will be of interest to determine if these genes are expressed in germ granules or in P-bodies from zebrafish. doi:10.1016/j.ydbio.2007.03.366 Program/Abstract # 258 Expression analysis of the rap55 homolog in the zebrafish germline Carlos Lozano, Ernesto Maldonado Department of Molecular Genetics, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, UNAM, Mexico The zebrafish is a model organism that reproduces sexually, then requires to produce specialized germ cells. Oocytes are loaded with ribonucleo-proteins and mRNA of maternal origin clustered in germ granules. During the first 10 cell cycles in early zebrafish development, transcription is absent and maternal mRNA clustered at the germ granules, is the main source for protein translation. In zebrafish some germ granules components have been described such as the protein or mRNA of the genes vasa, gcl, dead end and nanos. Recently the protein Rap55/Car- 1/Trailer hitch/Lsm14/Rap55 was found to be another germ granule component in organisms like Drosophila melanogaster, Caenorhabditis elegans and Xenopus laevis. This is the Scd6 homolog described in Saccharomyces cerevisiae, that is located in P-bodies (Processing bodies), therefore Rap55 is possible involved in mRNA processing. We have found three zebrafish homologous genes for Rap55 located in chromosomes 13, 23 and 25 respectively. These genes have highly conserved do- mains, as the Lsm domain in the amino-terminal region and the FDF domains: DFDF, FFD and TFG. They contain also RGG boxes located in glycine-rich regions in the c-termini. RGG boxes are RNA binding domains. RT-PCR analysis showed that the three homologs were expressed in all developmental stages from two cells to 5 days post-fertilization. We are currently studying the expression pattern of a GFP-fusion protein from one isoform that express in ovary, besides analyzing the effect of blocking its expression by morpholino antisense injections. doi:10.1016/j.ydbio.2007.03.367 Program/Abstract # 259 Spermatogenesis in Cuban endemic amphibians Ana Sanz 1 , Yamilka Rodriguez 1 , Lourdes Segura 2 , Luis F. Jimenez 2 1 Dept. Animal Biol., Fac. Biol., Havana Univ., Havana City, Cuba 2 Dept. Cell Biol., Sci. Fac., UNAM, Mexico DF, Mexico Amphibians in Cuba constitute 60 species of Anura with an astonishing 94.5% endemism. Bufonidae (toads) and Leptodac- tylidae (little frogs) are families that exhibit a great diversity and little is known about its biology. The aim of this work is to obtain a better understanding of spermatogenesis process as well as the structure of germ cells in these Cuban amphibians. Four males of Bufo fustiger, B. longinasus, Eleutherodactylus goini and E. riparius were collected in the western part of the Island of Cuba in the summer season. The specimens were anaesthetized and dissection was carried out. The gonads (in the case of toads Bidder's organ was cut) were fixed in 4% paraformaldehyde and 2.5% glutaraldehyde and were processed by inmunofluorescence and transmission electron microscopy. Suspensions of spermato- zoa of some species were also prepared and observed by Atomic Force Microscopy. In the seminiferous tubules spermatogonias, primary and secondary spermatocytes, spermatides in different stages and spermatozoa, are arranged themselves in cysts. The spermatogenetic lineage cells were differentiated and identified according to the cellular and cystic morphology. The presence of numerous pigment-containing cells randomly distributed in the albuginea tunic and testicular interstitium in the gonad of B. longinasus was a peculiar characteristic. Fluorescence spots were located in spermatogonia and spermatocytes nuclei. The spermatozoa features were analyzed in Bufo and Eleutherodac- tylus species showing conic head and undulating membrane. This investigation was conducted as a part of a WWF project. doi:10.1016/j.ydbio.2007.03.368 Program/Abstract # 260 Involvement of transforming growth factor beta on germ cell distribution in the chicken embryo ovary Rene Escalona 1 , Marlon De Ita 1 , Veronica Rodríguez 2 , Carmen Mondragón 1 , Carmen Méndez 1 , Enrique Pedernera 1 1 Dept. Embriología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico 2 Dept. Biología Celular y Tisular, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico The aim of this study was to explore the involvement of transforming growth factor beta (TGF-β) and stromal cell derived factor 1 (SDF-1) in directing germ cells (GC) distribution in the chicken embryo gonad. Gonads of 9-day-old embryos, both male and female, were evaluated for the expression of the mRNA of the growth factors and its receptors. They expressed two of the three TGF-β isoforms (TGF-βII and III) and both receptors; as well as SDF-1 and its receptor, supporting their possible role as regulators of GC distribution. Heparin coated acrylic beads were treated with TGF-β and located inside cultured ovaries during 72 h. At the end of the culture, the histological study showed that the TGF-β treated bead was enclosed with several layers of fibroblast-like and collagen fibers. In these ovaries oogonia were shown to migrate towards the TGF-β treated bead. In order to evaluate a direct chemotactic effect of TGF-β, a purified population of oogonia was seeded on a Boyden chamber to asses their ability to migrate in a TGF-β gradient. In this model oogonia showed the same migration index towards TGF-β as in the control medium. These results suggest that in the migration induced by TGF-β more than a directed chemotaxis was caused by a gradient of 385 ABSTRACTS / Developmental Biology 306 (2007) 382–386