Fig. 1. Experimental design. (A) The method of temporal induction of clones: OHT binds to the mutated estrogen receptor (ER^T) inducing nuclear translocation of CreERT and excision of the LoxP-flanked-stop-sequence, allowing lacZ transcription and leading to inheritable ß-galactosidase expression. (B) Experiments 1-3: D0, day of depilation; induction, OHT injection on D8 (day 8) in experiment 1, D11 in experiment 2 and D3 in experiment 3. Skin biopsies and observations are as indicated. (C) HF growth is linear. The length of 40 HFs proximodistal axis (y-axis) was recorded after depilation (x-axis). (D-K) Cell morphologies. (D) Transverse section of ROSA26 HF. (E-K) In toto views of CMV Cre ER^TxR26R F1 HF displaying labeling in medulla (E), cortex (F), hair cuticle (G), IRS (H), ORS (I,J). (K) GATA-3 nls lacZ HF; ß-galactosidase stains IRS (Huxley and IRS cuticle layers) cell nuclei (red arrowheads). The adjacent hair cuticle and Henlé layers are negative (white arrowheads). Scale bars: 25 µm in D,E,I,J; 50 µm in F-H.