Mammary gland development in wild type and NG2 null mice. Whole mounts of #4 mammary glands from female wild type (WT: A, B, C) and NG2 null (NG2 KO: D, E, F) mice at the ages of four weeks, ten weeks, and 16 days of gestation (Gest 16d) were stained with carmine alum to visualize development of the mammary epithelium . No changes in mammary gland expansion or branching were noted in the NG2 null mouse. LN: lymph node. (G-I). Whole mounts of normal #4 mammary gland from a 12-week old wild type female were immunostained for NG2 (G, red) and CD31 (H, blue). Panel I shows merged images from the boxed area in G and H. NG2 expression is seen on adipocytes (arrowheads) and on pericytes (arrows) that are closely apposed to CD31-positive endothelial cells. Scale bar = 60 μm (G, H) and 30 μm (I). NG2, nerve-glial antigen 2.