Figure 3.

TLK2 is required for placental development. (a) Semiquantitative analysis of histological phenotypes in Tlk2^−/− placentas. In each case, Tlk2^−/− placentas (n=10) at the indicated age were compared with wild-type littermates. Phenotypes are abbreviated as follows: placental thickness (Pl.Th), numbers/size of Labyrinth trophoblasts (LT), syncytiotrophoblasts (Syn.T), spongiotrophoblasts including glycogen cells (TS), giant cell trophoblasts (Gi.T) and vasculature (Vas). Summary of the grading system used⁴⁸ was provided in the Materials and Methods. (b) Sections from E11.5 and E12.5 littermate placentas stained with Hematoxylin and eosin (H&E). Tlk2^−/− placentas are thinner, less cellular and poorly vascularized compared with Tlk2^+/+. Scale bars=500 μm. (c) CD31 staining reveals that the vasculature of Tlk2^−/− placentas is miniaturized, collapsed and appears slit-like (red arrowheads) compared with the well-developed, widely opened vasculature of Tlk2^+/+ (blue arrowheads). Scale bar=20 μm. (d) H&E staining from the indicated age and genotype showing fewer and smaller trophoblasts (arrows) and syncytiotrophoblasts (blue arrowheads) with an absence of fetal vasculature (red arrowhead) in Tlk2^−/− placentas. Scale bar=20 μm. (e) H&E staining of placentas showing a thinner trophospongium (spongiotrophoblasts and glycogen cells) in Tlk2^−/− placentas. The trophospongium (TS), labyrinth (L) and decidua (D) are indicated. Scale bar=50 μm