Ckip-1 Gene Knockout Mouse Model To Establish Its Physiological Functions In The Bone, The Immune System

The disorder of bone development and function can lead to many skeletal diseases, such as osteoporosis. Thus, it is critical to understand the molecular details of the anabolic signaling pathways that control bone homeostasis for developing novel bone anabolic agents to reverse osteoporosis.In healthy adults targeted remodeling is a continuous physiological process, and initially bone formation was shown to always follow bone resorption leading to full replenishment of removed bone matrix with newly synthesized bone. Bone remodeling, thus, is understood as a cycle of bone resorption by osteoclasts and formation of new bone by osteoblasts. In contrast to the wealth of knowledge that has been acquired in the osteoclast field, we still know relatively little about osteoblast. There are currently a number of FDA-approved drugs for the prevention and treatment of postmenopausal osteoporosis that work by inhibiting bone resorption .The only FDA-approved agent capable of stimulating new bone formation for reversing bone loss in patients with high risk for osteoporotic fracture is parathyroid hormone (PTH).Since the genes related to bone development are highly conserved between human and mouse, mouse can be used as an ideal animal model. By this means, we have learned a lot about the mechanisms by which the bone is formed and regulated in the past twenty years.Gene targeting is a technique by which targeted gene can be modified accurately at the DNA level. Since the first knockout mice was reported in 1987, gene targeting is now being applied to virtually all areas of biomedicine– from basic research to the development of new therapies. Now deletion of any gene at both temporal and spatial level is feasible. Gene targeting has become one of the most important techniques to uncover the functions of genes in vivo.CKIP-1 (casein kinase 2 interacting protein 1) is implicated in regulation of cell differentiation and apoptosis. All of the previous studies were performed at the molecular and celluler levels. At present, the physiological function of CKIP-1 remains unclear due to lack of genetic evidence. In this study we established the CKIP-1 gene knockout mice model and then performed the phenotype analysis. CKIP-1 deficient mice were born normally, with no apparent gross abnormalities, and were fertile, suggesting that CKIP-1 is not required for embryonic development. Further phenotype analysis showed that compared to wild-type mice, the CKIP-1 deficient mice showed an age-dependent increase in bone mass and bone mineral density. This increase is caused by the enhanced activity of osteoblast differentiation and mineralization. Studies at molecular level showed that the activity of HECT-type E3 ligase Smurf1 decreased significantly in CKIP-1 KO mice. Consistently, the protein level of MEKK2, which is a substrate of Smurf1, was markedly upregulated in the absence of CKIP-1. This leads to the JNK-AP-1 pathway jubilantly regulated. Thus using the CKIP-1 KO mice, we uncovered the physiological role of CKIP-1 in regulation of bone homeostasis, and also confirmed the regulatory role of CKIP-1 on Smurf1 activity in vivo.Our primary data showed that CKIP-1 gene expression was upregulated or downregulated in certain activated immune cells compared with the resting cells. We then further explored the possible role of CKIP-1 in immune regulation using the wild-type and KO mice, we revealed that the number of CD4+CD25+ double positive cells in spleen and granulocytes in bone marrow was increased in CKIP-1 KO mice. These data suggested that CKIP-1 may participate in the regulation of these cells. We also found that the secretion of IL-5 and IFN-γin serum was upregulated when CKIP-1 gene was deficient. Further analysis of CKIP-1 in immune system is under investigation.Taken together, the current study established the CKIP-1 gene knockout mice model and provided the first genetic evidence of physiological function of CKIP-1.Our findings revealed the negative regulatory role of CKIP-1 on bone formation. We also supplied primary analysis of the immune system of CKIP-1 KO mice. These data deepen our understanding of CKIP-1 gene function, and provide new clues for the therapy of bone diseases including osteoporosis.