Fig. 5. TPA but not EDN1 rescues pigmentation in KITL-treated, tyrosinase-positive Ednrb-deficient melanoblasts. (A-C) Cultures from embryos with the indicated genotypes were kept in the presence of KITL for 6 days, and then in the presence of KITL and TPA (A,C) or KITL alone (B) for another 8 days. Mature melanocytes are present in TPA-treated Ednrb^lacZ/+ and Ednrb^lacZ/Ednrb^lacZ cultures (A,C) but absent in melanocytes in Ednrb^lacZ/Ednrb^lacZ cultures when TPA was omitted (B). (D,E) Cultures of the indicated genotypes were treated with KITL and EDN1 for 14 days. Pigmented cells are not present in Ednrb^lacZ/Ednrb^lacZ cultures (E).