Figure 1. Postnatal nucleostemin expression declines upon maturation.

(A) Confocal microscopy of myocardial sections 2 days after birth show widespread nucleostemin (green, at arrows) immunoreactivity relative to sections from hearts at 2 weeks or 2 months after birth. Tropomyosin (red) labels sarcomeric structure and nuclei are labeled with Topro-3 stain (blue). Single channel scans used for creation of color overlays are shown to the left of each panel. (B) Confocal microscopy and immunoblot (inset, lower right) of nucleostemin expression in cultured neonatal rat cardiomyocytes. Nucleostemin is predominately nucleolar. Immunloblot shows nucleostemin expression relative to Hela cell lysate positive control. (C) Decline in nucleostemin expression after birth assessed by quantitative immunoblot analyses. A statistically significant (p<0.01) decrease in nucleostemin expression occurs between 2 days and 2 weeks after birth and continues to decline from 2 weeks and 2 months after birth. Heart lysates signals are normalized to GAPDH to control for minor variation in protein loading.