Tissue-specific gene expression and repression of certain housekeeping genes during maturation of rat islets (A,B) and mouse liver (C,D). (A) mRNA expression level in extracts from rat pancreatic islets from age 1 d (P1) to 4 wk (P28) after birth measured by real-time qPCR; data were normalized for signal in islets of adult animals (10 wk; dashed line). Maturation-dependent up-regulation of genes that are important for beta-cells, such as insulin 2 (Ins2) and pyruvate carboxylase (Pc), was observed during this period. (B) In parallel we observed maturation-dependent repression of monocarboxylate transporter 1 (Mct1) and lactate dehydrogenase (Ldha), genes that are profoundly repressed in adult mouse islets (Table 1). (C,D) mRNA expression level in extracts from mouse fetal and neonatal liver between embryonic day E15.5 and 6 wk after birth. A progressive up-regulation (linear increasing trend P < 0.001) of Hmgcs2 (C) mirrors a progressive loss (linear decreasing trend P < 0.001) of expression of Oxct1 (D). Data in panels A–D are means ± SEM of three to four individual experiments. Statistical significance of the difference between postnatal and adult expression signal was calculated by one-way ANOVA with a Dunnett post-hoc test. *P < 0.05; **P < 0.01; ***P < 0.001.
