NPPA and hydrops fetalis: Consistent with the reduced EF in R14Δ/+ and R14Δ/+DWORF−/− mice at 18 mo of age, gene expression of the HF marker Nppa [atrial natriuretic peptide (ANP)] and the ratio myosin heavy chain 7, encoding β-MHC, and myosin heavy chain 6, encoding α-MHC (Myh7/Myh6) were increased in these groups compared with the expression in aged WT mice (Fig. 2, A and B).