Expression of growth-related genes in human fetal kidney.

By the end of gestation, nephron formation in the human kidney is complete. Following local induction of metanephric mesenchyma, committed cells of each primitive renal vesicle must undergo a phase of rapid cell division. In order to identify genes which might regulate these events, we examined the expression profile of 22 proto-oncogenes in fetal versus adult human kidney. Among those expressed at especially high levels in the fetal tissue was the gene for epidermal growth factor receptor (EGFR). We were able to detect mRNA (by polymerase chain reaction [PCR] amplification) and peptide (by specific radioimmunoassay) for transforming growth factor-alpha (TGF-alpha) in fetal kidney, whereas epidermal growth factor (EGF) peptide was undetectable in midgestation kidney and amniotic fluid. TGF-alpha/EGFR interactions may direct renal cell proliferation in fetal life.