TCblR/CD320 and megalin expression in reproductive tissues of WT pregnant mice. A) TCblR/CD320 is expressed in the trophoblast cells on the fetal side of the placenta in the labyrinth (A1, 2). Megalin is expressed in the visceral yolk sac, specifically toward the apical side of the endodermal epithelium (A3, 4; n = 10). B) In the TCblR/CD320-KO mice (n = 6), colocalization of injected dsRed-TC was found on the apical side of the epithelial layer of yolk sac (B1), where megalin is expressed (B2). Magnification: ×40 (B1, 4); ×100 (B7). Insets: ×40 (B5); ×100 (B8). B3, 6, and 9 were respective negative controls (n = 6).