PLN and hydrops fetalis: In line with functional findings, LV gene expression levels of Nppa, encoding natriuretic peptide A (ANP), a well-established marker for heart disease [21], progressively increased with HF progression in PLN-R14 Δ/Δ mice to 16-, 40- and 60-fold elevations in 5-, 6- and 8-week-old mice, respectively (Figure 3C).