Ectopic formation of primordial germ cells by transplantation of the germ plasm: Direct evidence for germ cell determinant in Xenopus

• Published in: Developmental biology 2012-11, Vol.371 (1), p.86-93
• Main Authors: Tada, Haru, Mochii, Makoto, Orii, Hidefumi, Watanabe, Kenji
• Format: Article
• Language: English
• Subjects: amphibians; Animals; Animals, Genetically Modified; Cell Movement - physiology; chimerism; Choristoma - embryology; Cytoplasmic Structures - genetics; Cytoplasmic Structures - physiology; Cytoplasmic Structures - transplantation; DNA Primers - genetics; Ectopic transplantation; eggs; Female; Gametogenesis; genetically modified organisms; Germ Cells - cytology; Germ plasm; Germline determination; germplasm; gonads; Green Fluorescent Proteins; hosts; Immunohistochemistry; In Situ Hybridization; Male; Polymerase Chain Reaction; Primordial germ cell; spermatozoa; Transgenic Xenopus; Xenopus; Xenopus - embryology
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/j.ydbio.2012.08.014

In many animals, the germ line is specified by a distinct cytoplasmic structure called germ plasm (GP). GP is necessary for primordial germ cell (PGC) formation in anuran amphibians including Xenopus. However, it is unclear whether GP is a direct germ cell determinant in vertebrates. Here we demonstrate that GP acts autonomously for germ cell formation in Xenopus. EGFP-labeled GP from the vegetal pole was transplanted into animal hemisphere of recipient embryos. Cells carrying transplanted GP (T-GP) at the ectopic position showed characteristics similar to the endogenous normal PGCs in subcellular distribution of GP and presence of germ plasm specific molecules. However, T-GP-carrying-cells in the ectopic tissue did not migrate towards the genital ridge. T-GP-carrying cells from gastrula or tailbud embryos were transferred into the endoderm of wild-type hosts. From there, they migrated into the developing gonad. To clarify whether ectopic T-GP-carrying cells can produce functional germ cells, they were identified by changing the recipients, from the wild-type Xenopus to transgenic Xenopus expressing DsRed2. After transferring T-GP carrying cells labeled genetically with DsRed2 into wild-type hosts, we could find chimeric gonads in mature hosts. Furthermore, the spermatozoa and eggs derived from T-GP-carrying cells were fertile. Thus, we have demonstrated that Xenopus germ plasm is sufficient for germ cell determination. ► We transplanted EGFP-labeled germ plasm into extremely ectopic region in Xenopus embryo. ► Germ plasm retains its properties in the ectopic region. ► PGCs are formed at the ectopic region by transplantation of germ plasm. ► Ectopic PGCs can become functional germ cells, sperms and eggs. ► We have proven directly that “Germ plasm includes the germ cell determinant” in vertebrates.