Intriguingly, the majority (14/20) of the identified key regulators belonged to cluster K1 (Fig. 3, K1, labeled in red), including HOXC13, MSX1, FOXN1, DLX1, ELF5, DLX4, DLX3, MSX2, ARID3A, MDFI, CUX2, CSDC2, BHLHE23, and VAX2. Many of these genes were previously identified as key regulators during HF cycling in humans and mice. The gene discussed is MSX1; the disease is hydrops fetalis.