Fig. 3. Expression of mezzo is regulated by a TGFß/TARAM-A signalling pathway. Animal pole views of embryos at 50% epiboly showing mezzo in situ hybridisation (purple). (A) Control uninjected embryo. (B) Embryo injected at the eight-cell stage into one blastomere with 40 pg of TARAM-A^* and with 100 pg of mRNA encoding a nuclear ß-Gal (blue colour) as a lineage tracer. TARAM-A^* induces confluent patches of mezzo-expressing cells. (C) Expression of mezzo transcripts was barely detectable in embryos injected with 50 pg of antivin mRNA.