In this regard, we have recently observed that the expression of the small GTPase Rac1 may distinguish HF from IF epithelial stem cell populations, as conditional deletion of Rac1 in the skin leads to the formation of rudimentary hair follicles showing reduction in length and absence of hair bulb structures without observing obvious phenotypes in the IF compartment [14]. The gene discussed is RAC1; the disease is hydrops fetalis.