Importantly, Ptch1 deletion did not trigger HF cell migration towards the IFE or TD as we never observed Tomato-tracing spanning from a pre-existing HF – via the infundibulum – to the IFE or TD in any control or Gli1creERT2;R26Tom;Ptch1fl/fl skin (Figure 1—figure supplement 3; Figure 2—figure supplement 1). The gene discussed is PTCH1; the disease is hydrops fetalis.