Fig. 1.

RT-22-rtTA/tet-O-Cre/Ai9 line. A and B: doxycycline (Dox) E10–18 analyzed at PN 4 wk (n = 7): widespread TdTomato (tdT) expression in Pdpn⁺ TI cells. Arrowheads indicates a rare TdTomato⁻/Pdpn⁺ area, shown at higher magnification in inset. C and D: Dox E12–15 analyzed at PN 4 wk (n = 4) results in very few TdTomato⁺/Pdpn⁺ cells (arrowheads); colocalization of TdTomato (red) and Pdpn (green) results in D orange color. E and F: Dox E15–18 at E18 (n = 3) results in TdTomato⁺ pre-TI cells that are Pdpn⁺. Much of the Pdpn⁺ surface area is TdTomato⁺; some Pdpn⁺ areas (asterisks) are TdTomato⁻. G: Dox E15–18 analyzed at PN day 7 (d7; n = 3): widespread expression of TdTomato in Pdpn⁺ TI cells (see Fig. 2F for comparison with line 114 at the same time point). Occasional areas (asterisks) are TdTomato⁻. H: Dox E15–18 analyzed at PN 4 wk (n = 8): rare TdTomato⁺/ Sftpc⁺ cell (~0.1% of TdTomato⁺ cells). E, embryonic day; PN, postnatal.