Fig 1.
Dazl expression in germ cells displays an A-P gradient along the genital ridge.
(A) Scatterplots represent transcript densities of Dazl and Oct4 in individual germ cells along A-P axis of genital ridge of E11.5 embryos (n = 3), as measured by smFISH. (B) Dazl transcript density was normalized against Oct4 transcript density for each individual cell to obtain relative Dazl:Oct4 transcript density per cell. Lines in plots represent average transcript density of cells (A) or ratio of densities (B) at a particular A-P position.
Fig 2.
Germ cells in Gata4 cKO embryos do not express DAZL or MVH.
(A) Schematic illustration of transverse section through embryo trunk that contains urogenital ridge. Red boxes indicate areas imaged, shown in B and D. a, adrenal gland; ce, coelomic epithelium; d, dorsal aorta; gr, genital ridge; m, mesentery. (B and D) Immunofluorescent staining for SSEA1, DAZL, MVH, and GATA4 protein in transverse sections of control (Gata4+/flox) and Gata4 ubiquitous cKO (CAG-CreER) embryos on a mixed genetic background. Representative germ cells are indicated by white arrows. Germ cells mis-migrating to the adrenal gland (yellow arrows) also express DAZL and MVH. Scale bars: 50 μm. (C and E) Percentage of germ cells that are positive for DAZL or MVH expression in control and Gata4 cKO (CAG-CreER) embryos. SSEA1 marks all germ cells at this age. Plotted here are means ± standard deviation from biological replicates (n ≥ 3 for each genotype). *, P < 0.05 (two-tailed Student’s t-test).
Fig 3.
Germ cells in Gata4 cKO embryos retain characteristics of PGCs.
Immunofluorescent staining for PGC and GCC marker proteins in transverse sections of control (Gata4+/flox) and Gata4 cKO (CAG-CreER) urogenital ridge cultures on a mixed genetic background. Arrows indicate representative germ cells. Scale bars: 50 μm.
Fig 4.
Germ cells in Gata4 cKO embryos do not enter meiosis.
Immunofluorescent staining for SSEA1, SYCP3, and GATA4 proteins in transverse sections of control (Gata4+/flox) and Gata4 cKO (CAG-CreER) urogenital ridge cultures on a mixed genetic background. Inset shows higher magnification of cells. Scale bars: 50 μm.
Fig 5.
A proposed model for somatic induction of germ cell differentiation, in three steps.
1) Germ cell specification induced by signals, such as BMP4, from extraembryonic ectoderm [53,54]; 2) germ cell licensing induced by the genital ridge, which arises from the coelomic epithelium following Gata4 expression; and 3) GCCs embark on either spermatogenesis or oogenesis in response to cues from somatic testis or ovary, respectively [12,13].