Trophoblast giant cells in the rodent placenta form the outermost layer of the extraembryonic
compartment, establish direct contact with maternal cells, and produce a number of
pregnancy-specific cytokine hormones. Giant cells differentiate from proliferative
trophoblasts as they exit the cell cycle and enter a genome-amplifying endocycle, a process
we show involves decreased expression of the G1 checkpoint proteins p53 and Rb.
Although p53 mRNA levels are unchanged in proliferative compared to differentiated …