Visualizing primordial germ cell migration in embryos of rice field eel (Monopterus albus) using fluorescent protein tagged 3′ untranslated regions of nanos3, dead end and vasa.

In rice field eel (Monopterus albus), germ cell development in the developing gonad has been revealed in detail. However, it is unclear how primordial germ cells (PGCs) migrate to the somatic part of the gonad (genital ridge). This study visualized PGC migration by injecting a chimeric mRNA containing a fluorescent protein fused to the 3′ untranslated region (3′UTR) of three different genes, nanos3 of zebrafish (Danio rerio) and dead end (dnd) and vasa of rice field eel. The mRNAs were injected either alone or in pairs into embryos at the one-cell stage. The results showed that mRNAs containing nanos3 and dnd 3′UTRs labeled PGCs over a wider time frame than those containing vasa 3′UTR, suggesting that nanos3 and dnd 3′UTRs are suitable for visualizing PGCs in rice field eel. Using this direct visualization method, the normal migration route of PGCs was observed from the 50%-epiboly stage to hatching stage for the first time, and the ectopic PGCs were also visualized during this period in rice field eel. These findings extend our knowledge of germ cell development, and lay a foundation for further research on the relationship between PGCs and sex differentiation, and on incubation conditions for embryos in rice field eel. Unlabelled Image • A chimeric mRNA with nanos3 or dead end 3′UTR is suitable for visualizing PGCs in rice field eel embryos. • Reveling normal migration route of PGCs in live rice field eel embryos. • Labeling ectopic PGCs in rice field eel embryos. [ABSTRACT FROM AUTHOR]