Int. J. Dev. Biol. 50: 619 - 625 (2006)

https://doi.org/10.1387/ijdb.062172am

Vol 50, Issue 7

Cloning and pattern of expression of the shiro-uo vasa gene during embryogenesis and its roles in PGC development

Original Article | Published: 1 August 2006

Akimitsu Miyake^1,2, Taiju Saito^1,3, Tohru Kashiwagi¹, Daisuke Ando¹, Akitsugu Yamamoto⁴, Tohru Suzuki⁵, Norio Nakatsuji⁶ and Takako Nakatsuji*

¹Department of Marine Biology, Graduate School of Marine Science and Technology, Tokai University, ²Department of Biological Science, Graduate School of Science, Tokyo University ³Laboratory of Breeding Science, Graduate School of Fisheries Science, Hokkaido University ⁴Cell Biology, Nagahama Institute of Bio-science and Technology ⁵Laboratory of Bio-industrial Informatics, Graduate School of Agricultural Science, Tohoku University and ⁶Institute for Frontier Medical Sciences, Kyoto University, Japan

Abstract

The vasa genes are expressed in the germ cell lineage in many organisms, but their expression patterns show large variations. Recent studies suggest that vasa transcripts are involved in germ cell lineage development. In this paper, we isolated the vasa cDNA clone from a teleost, shiro-uo, Leucopsarion petersii and examined its expression pattern during embryogenesis. Then, we examined the functional significance of vasa mRNA during the formation of primordial germ cells (PGCs). The amino acid sequence of shiro-uo VASA is 61.1% identical to that of zebrafish. In whole-mount in situ hybridization, vasa transcripts appeared at the 4- and 8-cell stages as four spots at both ends of two cleavage planes between the lower tier of blastomeres and the yolk cell mass. At the 16-cell stage, eight spots were observed. After the blastula stage, shiro-uo vasa transcripts showed similar localization as in the zeblafish. Ultrastructural analysis of 4-cell stage embryos revealed the presence of a subcellular organelle that resembled 'nuage' in the germ cell lineage observed in the embryos of various organisms. We carried out micromanipulation of 4- or 8-cell stage embryos to remove the vasa mRNA-containig spots and then measured the number of the vasa-expressing PGCs in the genital ridge of the manipulated embryos. The numbers decreased when all of the four spots were removed, indicating that the vasa-containing spots at early cleavage stages have important functions in the development of PGCs.

Keywords

Shiro-uo, vasa, primordial germ cell (PGC), mRNA localization, teleost