Project description:Osteoporosis is characterized by an imbalance between osteoclast-mediated bone resorption and osteoblast-related bone formation, particularly increased osteoclastogenesis. However, the mechanisms by which epigenetic factors regulate osteoclast precursor differentiation during osteoclastogenesis remain poorly understood. Here, we show that the specific knockout of the chromatin remodeling factor Arid1a in bone marrow?derived macrophages (BMDMs) results in increased bone mass. The loss of Arid1a in BMDM inhibits cell?cell fusion and maturation of osteoclast precursors, thereby suppressing osteoclast differentiation. Mechanistically, Arid1a increases the chromatin access in the gene promoter region of sialic acid?binding Ig-like lectin 15 (Siglec15) by transcription factor Jun/Fos, which results in the upregulation of Siglec15 and promotion of osteoclast differentiation. However, the loss of Arid1a reprograms the chromatin structure to restrict Siglec15 expression in osteoclast precursors, thereby inhibiting BMDM differentiation into mature osteoclasts. Deleting Arid1a after ovariectomy (a model for postmenopausal bone loss) alleviated bone loss and maintained bone mass. In summary, epigenetic reprogramming mediated by Arid1a loss suppresses osteoclast differentiation and may serve as a promising therapeutic strategy for treating bone loss diseases.
Project description:Clarification of the mechanisms underlying osteoclast differentiation enable us to understand the physiology of bone metabolism as well as the pathophysiology of bone diseases, such as osteoporosis. Recently, it has been reported that epigenetics can determine the cell fate and regulate cell type specific gene expression. However, little is known about epigenetics during osteoclastogenesis. To reveal a part of epigenetics, especially focused on chromatin dynamics, during early osteoclastogenesis and identify novel transcription factors involved in osteoclastogenesis, we investigated genome-wide analysis of open chromatin during receptor activator of nuclear factor-M-NM-:B ligand (RANKL)-induced osteoclastogenesis using DNase I hypersensitive sites sequencing (DNase-seq). DNase-seq was performed using the extracted nuclei obtained from RAW264 cells treated with or without RANKL for 24 hours, followed by several bioinformatic analyses. DNase I hypersensitive sites (DHSs) during RANKL-induced osteoclastogenesis were dynamically changed and accumulated in promoter regions, although the distributions of DHSs among cis-regulatory DNA regions were identical regardless of RANKL stimulation. Motif discoveries from DHSs successfully identified well-known osteoclastogenic transcription factors such as Jun, CREB1, FOS, ATF2 and ATF4, but also novel transcription factors for osteoclastogenesis such as Zscan10, Atf1 Nrf1 and Srebf2. siRNA knockdown of these identified novel transcription factors impaired osteoclastogenesis. Taken together, DNase-seq can be a useful tool for comprehension of epigenetics, especially chromatin dynamics during osteoclastogenesis and for identification of novel transcription factors involved in osteoclastogenesis. This study may reveal underlying mechanisms that determine cell-type specific differentiation of bone cells and may lead to investigate novel therapeutic targets for osteoporosis. Examination of genome-wide DNase Hypersensitive Sites in differentiated and undifferentiated RAW264 cells.
Project description:Arid1a has a critical role for modulating epithelial proliferation which is a critical requisite for fertility We used microarrays for detail the mechanism underlying Arid1a loss during early pregnancy.
