Deletion of <i>Atbf1</i> promotes ductal elongation and bifurcation in pubertal mammary gland.

<p>(A) Hematoxylin-stained whole-mount images of the fourth abdominal mammary glands from mice at indicated ages. Panels at far right are higher magnification images of indicted areas from 8-week old mammary glands. Three to five mice were used for each genotype. (B–F) Determination of degree of ductal invasion and the numbers of branches and TEBs in mammary glands of mice with indicated genotypes and ages of 5 or 6 weeks (B–D) or 8 weeks (E, F). Degree of ductal invasion was determined by dividing the duct length by the mammary gland length from mid-point of lymph node; and the numbers of total branches and TEBs were determined in whole-mount images by the ImageJ program. (G–J) Comparisons of the numbers and areas of ducts among different genotypes. Shown are representative images from hematoxylin and eosin (HE)-stained tissue sections (Magnification: 100×) from mammary glands at the age of 6-week old, the average number of ducts per mm² (H), ductal area to gland area ratio (ductal coverage) (I), and the average cross-section size per duct (10⁻³ mm²) (all ducts were measured for each mouse) (J). HE-stained tissue sections (G) were used for these analyses. Each bar is the average from three mice for each genotype. * and ** indicate <i>P</i><0.05 and <i>P</i><0.01 respectively. For panels H–I, one-way ANOVA was used for statistical analysis, while univariate analysis (sum of squares: type I) was used for panel J.