Figure 3.

The fate of pubertal Notch2⁺ lineages in pregnancy. (a–j) Low(a,b) and high-power magnification images (c–j) of x-gal-labelled mammary whole-mount preparations from a N2-CreERT2^SAT/R26R^LacZ female induced with 4-OHT at 7 weeks of age and euthanized in early pregnancy (8 dpc; days post-coitus). (c–f) Early stage of alveologenesis. The lumen of tertiary branches (c) and alveolar buds (d–f) is filled with transit LacZ⁺ cells. The arrow in d points to a single large LacZ⁺ cell (L cell) positioned in the distal portion of a sprouting alveolar bud. (g–j) Advanced stage of alveolar bud formation. The luminal space is cleared, with the exception of one or two L cells (arrows) that remain present in each alveolar bud. (k) Schematic representation of LacZ⁺ cell distribution in early and late stages of alveologenesis. Scale bars, 200 μm (a,b); 100 μm (c,e,g); 20 μm (d,f,h–j).