THE SITE AND TIME OF EXPRESSION OF MIF IN FROG DEVELOPMENT

A ventrally localized melanization-inhibiting factor (MIF) has been su ggested to play a role in the expression of dorsal-ventral pigment pat terns in amphibia. Here we investigate the onset and localization of M IF appearance in frog development. The expression of MIF was analyzed in the wild-type and gray-eyed mutant (g/g) of Rana japonica by immuno blotting and immunohistochemistry using an anti-MIF neutralizing monoc lonal antibody. Western blot analysis revealed that the anti-MIF antib ody recognized similar to 51 kDa and similar to 58 kDa bands. The 51 k Da band first appeared at the external gill stage, while 58 kDa band w as additionally detected at the hindlimb bud stage. With the use of im munohistochemistry, it was found that the anti-MIF antibody stained th e whole epidermis of the embryos at the external gill stage; however, the staining was stronger in lateral and ventral epidermis than in dor sal. Staining with the anti-MIF antibody was observed only in the oute r epidermis of the ventral skin, but not in the dorsal skin during and after metamorphosis. The spatial expression of MIF in the wild-type w as the same as that in the gray-eyed mutant. The same immunohistochemi cal result was obtained in the adults of R. nigromaculata. These resul ts suggest that MIF is involved in the formation of the dorsal-ventral pigment pattern.