PRDM1 and hydrops fetalis: Consistent with this, gene expression analysis by real-time quantitative PCR (qPCR) revealed upregulation in the expression of CD34, CD49f and type XVII collagen (Col17a1), a marker for bulge HFSCs involved in their maintenance24, in both vibrissa and back skin cells, while no significant upregulation was observed for Lgr5, a marker for stem cells committed to lower pelage HF fate, or for Blimp1, a marker of upper HF cells and sebaceous gland stem cells (Fig. 1f, Supplemental Fig. S1b).