The role of epidermal growth factor receptor (EGFR) in male reproductive tract differentiation: stimulation of EGFR expression and inhibition of Wolffian duct differentiation with anti-EGFR antibody.

We have shown previously that epidermal growth factor (EGF) plays a role in testosterone-dependent fetal Wolffian duct differentiation. To assess the role of EGF further, we examined EGF receptor (EGFR) expression during Wolffian duct differentiation and determined whether inhibition of EGFR results in inhibition of Wolffian duct differentiation. Using a polyclonal anti-EGFR antibody in the Western blot analysis, we have detected an immunoreactive band at the expected 180-kDa size, the molecular size for the EGFR protein, in the 18-day fetal male reproductive tract. The mouse 3T3 cell line, used as a positive control, also produced an immunospecific band at the same region. The intensity of the immunoreactive 180-kDa band in the 18-day male reproductive tract significantly decreased after pretreatment of the antibody with the 3T3 cell extract. Nonimmune serum produced no band at the 180- kDa region, suggesting EGFR specificity of the 180-kDa band. The level of the 180-kDa EGFR protein was found to be higher in the 18-day male than in the female reproductive tract. Testosterone increased expression of the EGFR level in the 18-day masculinized female reproductive tract, and it induced Wolffian duct morphogenesis. Under in vitro culture conditions, the anti-EGFR antibody prevented Wolffian duct differentiation, induced by the fetal testis, suggesting a direct role of EGFR in male reproductive tract differentiation. No such effect was found when tested with nonimmune serum. Anti-EGFR also blocked the development of the Wolffian duct in the female explant, induced by exogenous EGF. Thus, a role of EGFR mediating the effect of EGF during male reproductive tract differentiation is demonstrated.