Lab of Modern Environmental Toxicology, Department of Public Health and Preventive Medicine, Wuxi School of Medicine, Jiangnan University, Wuxi 214122, China.
Department of Basic Medicine, Wuxi School of Medicine, Jiangnan University, Wuxi 214122, China.
Int J Mol Sci. 2023 Feb 21;24(5):4305. doi: 10.3390/ijms24054305.
Epigenetic modifications are critical for cell differentiation and growth. As a regulator of H3K9 methylation, Setdb1 is implicated in osteoblast proliferation and differentiation. The activity and nucleus localization of Setdb1 are regulated by its binding partner, Atf7ip. However, whether Atf7ip is involved in the regulation of osteoblast differentiation remains largely unclear. In the present study, we found that Atf7ip expression was upregulated during the osteogenesis of primary bone marrow stromal cells and MC3T3-E1 cells, and was induced in PTH-treated cells. The overexpression of Atf7ip impaired osteoblast differentiation in MC3T3-E1 cells regardless of PTH treatment, as measured by the expression of osteoblast differentiation markers, Alp-positive cells, Alp activity, and calcium deposition. Conversely, the depletion of Atf7ip in MC3T3-E1 cells promoted osteoblast differentiation. Compared with the control mice, animals with Atf7ip deletion in the osteoblasts () showed more bone formation and a significant increase in the bone trabeculae microarchitecture, as reflected by μ-CT and bone histomorphometry. Mechanistically, Atf7ip contributed to the nucleus localization of Setdb1 in MC3T3-E1, but did not affect Setdb1 expression. Atf7ip negatively regulated Sp7 expression, and through specific siRNA, Sp7 knockdown attenuated the enhancing role of Atf7ip deletion in osteoblast differentiation. Through these data, we identified Atf7ip as a novel negative regulator of osteogenesis, possibly via its epigenetic regulation of Sp7 expression, and demonstrated that Atf7ip inhibition is a potential therapeutic measure for enhancing bone formation.
表观遗传修饰对于细胞分化和生长至关重要。Setdb1 作为 H3K9 甲基化的调节剂，参与成骨细胞的增殖和分化。Setdb1 的活性和核定位受其结合伴侣 Atf7ip 调节。然而，Atf7ip 是否参与成骨细胞分化的调节在很大程度上尚不清楚。本研究发现，Atf7ip 在原代骨髓基质细胞和成骨细胞系 MC3T3-E1 成骨过程中表达上调，并在 PTH 处理的细胞中诱导表达。Atf7ip 的过表达无论是否用 PTH 处理，都损害了 MC3T3-E1 细胞中的成骨分化，表现为成骨分化标志物、Alp 阳性细胞、Alp 活性和钙沉积的表达降低。相反，在 MC3T3-E1 细胞中敲低 Atf7ip 则促进成骨分化。与对照组小鼠相比，成骨细胞中 Atf7ip 缺失的小鼠 () 表现出更多的骨形成，骨小梁微结构明显增加，反映在 μ-CT 和骨组织形态计量学上。机制上，Atf7ip 有助于 Setdb1 在 MC3T3-E1 中的核定位，但不影响 Setdb1 的表达。Atf7ip 负调控 Sp7 的表达，通过特异性 siRNA 敲低 Sp7 减弱了 Atf7ip 缺失对成骨分化的增强作用。通过这些数据，我们确定 Atf7ip 是成骨作用的一种新的负调控因子，可能通过其对 Sp7 表达的表观遗传调控，并且证明 Atf7ip 抑制是增强骨形成的一种潜在治疗措施。
