Fig. 1.

Mammary line formation and gland nomenclature. Images of flanks of wild-type (C57Bl6/J) mouse embryos hybridized with a Wnt10b probe showing the mammary line between arrows, at E11.25 visible as a fragmented expression pattern, and at E11.75 as a continuous line between forelimb (f.l.) and hindlimb (h.l.). The first mammary rudiment to appear is #3 (and #8 on the contralateral side, not shown). By E12.5, all five pairs are formed, shown here for the left side (#1–5) after removal of the limbs. Mammary rudiments and glands are numbered in anterior-posterior sequence, 1–5 on the left side and 6–10 on the right side, as shown in the cartoon. Corresponding but variable other nomenclature in the literature is also indicated