Gene expression in renal growth and regrowth

To elucidate the molecular events associated with postnatal and compensatory renal growth, the expression of growth/differentiation genes (c-fos, c-myc, c-H-ras, c-K-ras), a stress-related gene (HSP70) and a structural gene (collagen type IV, alpha 1 and 2) were examined. Northern analysis of messenger ribonucleic acid from the newborn mouse reveals high levels of expression of HSP70, c-H-ras, and c-K-ras during the first week of life. By day 40 HSP70-related and c-H-ras expression decreases somewhat, c-K-ras remains unchanged and collagen type IV, which encodes for the renal glomerular basement membrane, expression decreases significantly. During compensatory renal growth increased expression of HSP70, c-H-ras and c-K-ras occurs. The results seem to indicate that growth/differentiation genes may be necessary for continued cell growth (hypertrophy) in postnatal and compensatory renal growth, and that collagen type IV formation continues up through week 2 of postnatal growth consistent with the interval of glomerular basement membrane formation.