Because HH signalling is associated with cell proliferation in the skin (St-Jacques et al, 1998; Chiang et al, 1998; Mill et al, 2003; Park et al, 2018), we next investigated whether changes in HF progenitor cell proliferation were associated with the HF defects in Gli2EKO and Gli2/3EKO mutant mice. Here, GLI2 is linked to hydrops fetalis.