Expression of transforming growth factor-α and epidermal growth factor receptor in human fetal kidneys

Abstract

Beginning at the fifth week of fetal life, successive generations of individual nephrons are induced by contact between metanephric mesenchyme and ureteric bud. Following phenotypic transformation, cells of each primitive renal vesicle undergo a phase of rapid cell division. In order to identify genes which might regulate nephron development in man, we screened adult and fetal kidney RNA for expression of a panel of growth-related genes. Among the genes which were expressed at higher levels in fetal kidney was the epidermal growth factor (EGF) receptor. There is controversy as to the most likely physiologic EGF receptor ligand in fetal kidney; we were able to identify a transcript for transforming growth factor-α (TGF-α) but not EGF on Northern blots of fetal kidney RNA. Since the abundance of TGF-α mRNA is low, we confirmed its presence by polymerase chain reaction amplification. Using specific radioimmunoas-says, we also provide direct evidence for TGF-α but not EGF peptide in extracts of fetal kidney and mid-gestational amniotic fluid. We suggest that TGF-α/EGF receptor interactions may serve an important function in development of human fetal kidney.