Germline‐specific expression of the Oct‐4/green fluorescent protein (GFP) transgene in mice

TLDR

Oct‑4, a POU transcription factor, is germ‑cell specific and prior lacZ reporter studies have shown that an 18‑kb Oct‑4 genomic fragment can recapitulate its embryonic expression pattern in transgenic mice. The study aimed to generate GFP‑expressing transgenic mice using Oct‑4 regulatory elements to visualize germ cell development. They inserted GFP under Oct‑4 control and examined its expression across all stages of germ cell maturation. GFP appeared in primordial germ cells at 8 dpc, persisted in male and female germ cells throughout development except in postnatal type A spermatogonia, showed reduced expression in female meiotic prophase I, and the mice provide a powerful system for isolating living germ cells and identifying novel genes.

Abstract

The Pic‐1, Oct‐1,2, Unc‐86 (POU) transcription factor Oct‐4 is specifically expressed in the germ cell line, and a previous study has indicated that the expression of the lacZ gene inserted into an 18 kb genomic fragment encompassing the Oct‐4 gene can come close to mimicking the endogenous embryonic expression pattern of Oct‐4 in transgenic mice. In the present study transgenic mice expressing green fluorescent protein (GFP) in the germ cell line were generated using the same Oct‐4 genomic fragments and the expression pattern was analyzed in detail through all stages of germ cell development. The GFP expressing primordial germ cells were first detected as early as 8.0 days post‐coitum (d.p.c.; early head fold stage) at the base of the allantois in living embryos. The GFP expression was thereafter found in both male and female germ cells at all developmental stages except in male germ cells after differentiating into type A spermatogonia in the postnatal testis. There was also a lower level of expression in female germ cells in the prophase of the first meiotic division. These transgenic mice therefore proved to be powerful tools for isolating living germ cells at various developmental stages to study their nature and to isolate new genes.