Figure 8: BMP signalling is necessary for GPCs to form gonad.

(a) GPCs were transfected with Noggin expression plasmid. (b–d) Transverse views and a illustration, corresponding to the boxed region in a in a control EGFP-electroporated embryo. (e–g) Magnified views of the boxed regions in b–d. The gonad was observed as a swell that expressed GATA4 (arrows in e) and retained PGCs (arrowheads in f), as illustrated in g. (h–j) Transverse views of gonad in Noggin-overexpressing embryo. (k–m) Magnified views of the regions outlined in h–j. No GATA4-expressing swell formed at the presumptive gonadal region (arrows in k), and PGCs were scattered rather than gathered (arrowhead in l), as illustrated in m. (n) A scheme summarizing our findings. In E2.0 embryos, GPCs are localized at a site facing dorsal aorta (DA). Hedgehog signalling (Hh) is activated in GPCs but not MCPCs, and this Hedgehog signalling triggers gonadogenesis by causing GPCs to undergo ingression, inducing GATA4 expression and creating PGC niche activity, through BMP4 expression. SHH, a Hedgehog ligand, is expressed in endoderm, adjacent to the GPCs and more distant from the MCPCs. Scale bars, 100 μm (b,c,h,i); 50 μm (e,f,k,l).