Characterization of zebrafish primordial germ cells: Morphology and early distribution ofvasa RNA

A zebrafish vasa morphant abolishes Vasa protein but does not affect the establishment of the germline

“…To this end, we injected one-or two-cell-stage embryos with vasa morpholino and raised fish until two weeks or one month of age. In these fish, the PGCs were identified based on morphological criteria (Braat et al, 1999). We detected PGCs in the vasa morpholino-injected fish at comparable numbers as observed in the noninjected controls (nϭ4, data not shown).…”

“…During embryogenesis, the zebrafish PGCs are marked by the expression of vasa RNA (Yoon et al, 1997;Olsen et al, 1997;Braat et al, 1999), which is initially of maternal origin. Zygotic expression of vasa mRNA starts around the dome stage (Braat et al, 1999;Knaut et al, 2000), and Vasa protein in distinct cells is first detected at gastrulation (Braat et al, 2000;Knaut et al, 2000). The fact that newly formed PGCs maintain expression of vasa mRNA at equal levels as their ancestors throughout embryonic and early larval development strongly suggests a continuous zygotic vasa transcription in the germline.…”

“…The cloning of the zebrafish vasa cDNA (Yoon et al, 1997;Olsen et al, 1997) and analysis of localization and distribution of the vasa mRNA (Yoon et al, 1997;Olsen et al, 1997;Braat et al, 1999;Knaut et al, 2000) have demonstrated its maternal expression and its localization that is restricted to the presumptive primordial germ cells (pPGCs) and the PGCs in the embryo and larva. Unlike the vasa mRNA, the Vasa protein is uniformly distributed throughout the early embryo and can only be detected in a higher concentration from gastrulation onward in a subset of cells presumably pPGCs.…”

“…To investigate the function of the Vasa protein in germline development, we interfered with Vasa protein synthesis by vasa morpholino injection, which resulted in the disappearance of Vasa protein in the oneday-old zebrafish embryo as shown by immunostaining. Morphological characterization of zebrafish PGCs (Braat et al, 1999) in morpholino-injected embryos revealed cells with the typical PGC morphology, and morpholinoinjected embryos raised to adulthood were capable of producing offspring.…”

Developmental biotechnology for aquaculture, with special reference to surrogate production in teleost fishes

“…If the migration is mediated by different molecular mechanisms, PGCs could not move to the genital ridge in the host embryo. On the other hand, it was reported in zebrafish that the distribution of cytoplasmic components in PGCs varies during the migration period (Braat et al, 1999;Knout et al, 2000;Nagai et al, 2001). This suggests the possibility that the biochemical properties responsible for migration may change during development.…”