Time‐lapse analysis reveals different modes of primordial germ cell migration in the medaka Oryzias latipes

Abstract

Previous studies have shown that medaka primordial germ cells (PGC) are first distinguishable by olvas expression during late gastrulation, and that they migrate to the gonadal region through the lateral plate mesoderm. Here, we demonstrate that medaka nanos expression marks the germ line at early gastrulation stage. By marking the germ line with green fluorescent protein (GFP) fused to the nanos 3′ untranslated region, we were able to visualize the behavior of PGC using time-lapse imaging. We show that there are three distinct modes of PGC migration that function at different stages of development. At early gastrulation stage, PGC actively migrate towards the marginal zone, a process that requires the function of a chemokine receptor, CXCR4. However, at late gastrulation stage, PGC change the mode and direction of their movement, as they are carried towards the midline along with somatic cells undergoing convergent movements. After aligning bilaterally, PGC actively migrate to the posterior end of the lateral plate mesoderm. This posterior movement depends on the activity of both HMGCoAR and a ligand of CXCR4, SDF-1a. These results demonstrate that PGC undergo different modes of migration to reach the prospective gonadal region of the embryo.

Sox9b/sox9a2‐EGFP transgenic medaka reveals the morphological reorganization of the gonads and a common precursor of both the female and male supporting cells

“…Microinjection of DNA into medaka was performed as described previously (Kurokawa et al, 2006;Nakamura et al, 2006) using BAC DNA at a concentration of 300 ng/ml. We established two stable lines from approximately 350 injected embryos.…”

Accessibility of host cell lineages to medaka stem cells depends on genetic background and irradiation of recipient embryos

“…In zebrafish, the founder cells of the germline, the primordial germ cells (PGCs), are predetermined by maternal factors at cleavage stages [26,27]. In medaka, PGCs are visible until stage 13 of pregastrulation by 12 h post-fertilization (hpf) [28,29], and PGC formation also appears to be maternally determined [30]. It remains to be elucidated whether the germline and/or the somatic cells of the gonad primordium in these fishes is accessible to cultured ES cell donors.…”

Analysis of a novel gene, Sdgc, reveals sex chromosome-dependent differences of medaka germ cells prior to gonad formation

“…1I). When endogenous germ cells were removed by inhibiting germ-cell migration using nanos3/cxcr4-morpholinos (Kurokawa et al, 2006(Kurokawa et al, , 2007, the Sdgc signal totally disappeared ( Fig. 1E-I).…”