Fig. 9. CM-der induces neural tissue in ectodermal explants. Embryos were injected at the animal pole at the one-cell stage with 25 pg noggin mRNA or 2 ng CM-der mRNA and explants were cultured until stage 20 and analyzed by RT-PCR. Both noggin- and CM-der-treated animal caps express the neural markers nrp-1 and n-cam in the absence of muscle actin (MA, a mesoderm-specific transcript) and at the expense of epidermal keratin (EK, an epidermal marker).