The Primordial Journey

Bettina P. Mihalas, Brendan J. Houston, Ella S. Green, Elizabeth Ann L. Enninga, Eric A.Rhon Calderón

Research output: Contribution to journalEditorialOtherpeer-review


Development and differentiation of primordial germ cells (PGCs) marks the origin of the gamete and is essential for sexual reproduction. During mouse embryogenesis, PGCs migrate from the base of the allantois through the embryonic hindgut to colonize the gonadal ridge and undergo mitotic proliferation. It is only upon reaching the embryonic gonad that PGCs go through sex‐specific differentiation into precursors for either the female (oocyte) or male (sperm) gamete.

The peripheral cytoplasm of PGCs contains higher alkaline phosphatase (AP) activity than that of the surrounding somatic cells, making AP staining a useful tool to observe PGCs in situ. For this vision, whole precursor testis (left) and ovaries (right) from CD1 mice at embryonic day (E) 13.5 were stained for AP. The AP substrate used was alpha‐naphthyl phosphate, which becomes yellow upon hydrolysis. Embryonic gonads were visualized by light microscopy with adjustments to the phase contrast to give the germ cells (GCs) a ‘shiny’ effect. The colour balance was modified using NIH imageJ software to enhance orange or pink tones in male or female GCs, respectively.

At E13.5, the gonads have been completely colonised, peaking at 25,000 GCs. It is at E13.5 that the first morphological sign of sex‐specific GC differentiation can be visualized. Here, female PGCs cease proliferation and begin to asynchronously transition into meiosis (oogenesis). Female GCs then arrest at prophase I until just prior to ovulation. In contrast, male GCs, now enclosed in testis chords (seen as distinct lines), continue to proliferate until E14.5 before entering a period of quiescence. Male GCs will again resume proliferation (during the first wave of spermatogenesis) 1 to 2 days postpartum.
Original languageEnglish
Pages (from-to)809-809
Number of pages1
JournalMolecular Reproduction and Development
Issue number11
Publication statusPublished - 1 Nov 2018


  • differentiation
  • embryogenesis
  • oogenesis
  • primordial germ cell
  • spermatogenesis

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