Role of N-myc in the developing mouse kidney.

N-myc is a transcription factor expressed in the developing metanephric kidney and other organs. In mice, complete disruption of the N-myc gene results in fetal death on the first day of renal organogenesis. In addition to the null N-myc allele, others have generated a hypomorphic N-myc allele. In this study, combinations of these mutant genes were used to demonstrate that reduction in N-myc protein levels correlate with fewer developing glomeruli and collecting ducts in embryonic kidney explants. Histological sections revealed that the mutant kidneys were hypoplastic with normal developing structures. The data indicate that the hypoplasia is due to a reduction in proliferation rather than an increase in apoptosis. Thus, N-myc loss causes a decrease in numbers of ureteric bud tips and developing glomeruli in explants and hypoplastic kidneys in vivo, in a dose-dependent manner. Copyright 2000 Academic Press.