Immunocytochemical localization of epidermal growth factor receptor in early embryos of the Japanese medaka fish (Oryzias latipes)

This study was undertaken to localize epidermal growth factor receptor (EGF R) during early development of Japanese medaka embryos using immunocytochem istry. Specific staining was observed in all stages studied. All of the cel ls of the embryonic disc from the germinal disc (1 cell) through the late h igh blastula stages stained moderately for EGFR. Beginning with the flat bl astula stage, the surface and lateral cells of the embryonic disc and the c ells migrating around the yolk stained intensely for EGFR, and this continu ed throughout the study period. The presence of the keel at the late gastru la stage did not affect the moderate staining of the majority of the embryo nic disc cells. When somites first appeared, the keel region stained less i ntensely than before, but scattered individual cells stained intensely for EGFR. Embryos with 12 somites had a neural tube that was lightly stained ex cept for a few intensely stained individual cells. The neural tube, notocho rd and somites in 24-somite embryos lacked immunostaining. However, the sur face epithelium, aorta, intestinal epithelium and pronephric duct demonstra ted EGFR immunostaining. This study demonstrates that EGFR is present durin g medaka development and supports the hypothesis that EGFR ligands are impo rtant during cleavage, gastrulation and early organogenesis.