FIG. 5.

Effects of R654W pRb on the placenta and FLM differentiation. (A) Hematoxylin-and-eosin-stained sections of E13.5 placentae are shown. sp, spongiotrophoblast layer; lb, labyrinth. (B) E14.5 liver sections were stained for F4/80 (brown) and TER119 (pink). The squares show the regions of the images magnified in the lower panels. Arrows indicate F4/80-positive FLM, while arrowheads designate some of the TER119-positive cells associated with FLM in erythroblastic islands. Note the lack of extensive cytoplasmic projections of Rb1 null FLM and the relative dearth of associated TER119-positive cells. (C) The percentages of F4/80-positive cells associated with ≥5 TER119-positive cells and the densities of prominently stained F4/80-positive cells per microscopic field of view (FOV) in liver sections are shown. The data points represent the means and standard deviations for at least three embryos, counting three nonconsecutive sections per embryo. *, significant difference between R654W and Rb1 null livers (P < 0.01). (D) MEF or liver tissue extracts of the indicated genotypes were immunoprecipitated with Id2 antibody or an immunoglobulin G (IgG) control. The immunoprecipitates were analyzed for the presence of pRb by Western blotting. The relative input levels of pRb and Id2 were determined by Western blotting (panels at right). β-Actin served as a loading control.