Fig. 7.

R-spondin-1 and follistatin spatial and temporal expression patterns during medaka gonad primordium formation. Two BAC reporter fish transgenic lines expressing either GFP or mCherry were established to follow r-spo-1 and fst expression dynamics during gonad formation in vivo. Neither r-spo-1 nor fst expression was detected in the presumptive gonadal mesoderm at early stages of development (A–C). Between stages 33 and 35 in the dorsal region of the hindgut r-spo-1 and fst are co-expressed (D–F). At hatching stage, although ubiquitously expressed, neither r-spo-1 nor fst were detected in the gonadal primordium (G–I).