Quantitative RT-PCR analysis of gene expression in the hearts. Total cellular RNAs were extracted from the hearts dissected from five wild-type and five Rae28^–/– embryos at 9.5 dpc. As indicated by the wedges, twofold serial dilutions of cDNAs were used as templates for PCR amplification with primers specific for MLC2a, MLC2v, αMHC, ANF, Nkx2.5, Hand1, and β-actin. Signals for β-actin mRNA were used as controls to adjust the amount of cDNAs. Equal amounts of cDNAs were subjected to the PCR assays in lanes 1 and 4 as well as in lanes 2 and 5. Although the expression domain of ANF in RV was affected in Rae28^–/– (Figure 2b), RT-PCR analysis did not detect a significant difference in the amount of ANF mRNA.