ECTS2016 Poster Presentations Cell biology: osteoclasts and bone resorption (35 abstracts)
1Kyungpook National University School of Medicine, Daegu, Republic of Korea; 2Dongguk University, Gyeongju, Republic of Korea; 3Kyungpook National University Hospital, Daegu, Republic of Korea; 4Korea Institute of Science and Technology, Seoul, Republic of Korea.
Engulfment adaptor phosphotyrosine-binding (PTB) domain containing 1 (GULP1) is an adaptor protein involved in the engulfment of apoptotic cells via phagocytosis. Although GULP1 is widely expressed in various tissues, including the brain, muscle, testis, and bone, the function of GULP1 has not been well studied. Here, we investigated whether GULP1 plays a role in the regulation of bone remodeling and examined its expression in bone cells. Conditional Gulp1 floxed mice were generated by homologous recombination in C57BL/6 embryonic stem cells. Then, Gulp1 knockout mice were prepared by crossing Gulp1 heterozygous mice generated by FLP- and Cre-mediated recombination in conditional Gulp1 floxed mice. The trabecular bone mass of the femur and tibia, as well as the lumbar vertebrae was significantly increased in Gulp1 knockout mice compared to that their wild-type littermates. The dynamic bone formation of osteoblasts in Gulp1 knockout mice did not differ from that in wild-type mice. However, the number of fully differentiated osteoclasts and the surface area of the resorption pit in bone slices were lower in Gulp1 knockout mice than in wild-type mice. Furthermore, actin ring and microtubule formation in osteoclasts were inhibited in Gulp1 knockout mice. These results indicate that GULP1 deficiency suppresses osteoclast differentiation and bone resorption, but does not alter the bone formation of osteoblasts, which ultimately increases bone mass. Taken together, these results suggest that GULP1 may be a novel positive regulator of osteoclast differentiation and bone resorption.