for resorption and degradation to occur. Iron transport In the pregnant sow, uteroferrin is highly expressed in the uterine fluids. Due to the unique anatomy of the porcine uterus, and the specific, progesterone-induced expression of TRAP; it is hypothesized that uteroferrin acts as an iron transport protein. Cell growth and differentiation factor TRAP is associated with osteoclast migration to bone resorption sites, and, once there, TRAP is believed to initiate osteoclast differentiation, activation, and proliferation. This hypothesis was formed from the examination of the bone structure of TRAP-null mice. It was noted that, in addition to osteopetrosis, bone formation occurred in a haphazard manner, where the microarchitecture was highly irregular. In TRAP overexpressing mice, it has been found that the affected mice are grossly obese. This has led to the hypothesis that TRAP has involvement in hyperplastic obesity. References External links EC 3.1.3.2