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Activating transcription factor 4 regulates osteoclast differentiation in mice
Huiling Cao1, Shibing Yu, Zhi Yao
1Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
The Journal of Clinical Investigation
|July 15, 2010
Summary
Activating transcription factor 4 (ATF4) is essential for osteoclast differentiation and bone resorption. Targeting ATF4 may offer a new therapeutic strategy for bone diseases characterized by excessive osteoclast activity.
Area of Science:
- Cell Biology
- Bone Biology
- Molecular Biology
Background:
- Activating transcription factor 4 (ATF4) is known for its role in osteoblast function and bone formation.
- Its direct involvement in osteoclast (OCL) biology has not been previously established.
Purpose of the Study:
- To investigate the direct role of ATF4 in osteoclast differentiation and function.
- To explore ATF4's regulatory mechanisms in osteoclastogenesis.
Main Methods:
- Utilized genetically modified mice with targeted ATF4 expression in the OCL lineage (Trap promoter) or ATF4 deletion (Atf4-/-).
- Assessed OCL differentiation in bone marrow monocyte (BMM) cultures and mouse bone samples.
- Investigated ATF4's regulatory interactions with key signaling pathways (RANKL, MAPK, M-CSF, PI3K/AKT) and transcription factors (Nfatc1).
Main Results:
- ATF4 deficiency in BMMs and mice led to significantly reduced OCL differentiation and bone formation.
- Overexpression of ATF4 in OCLs resulted in severe osteopenia, increased osteoclastogenesis, and heightened bone resorption.
- ATF4 was identified as an upstream activator of Nfatc1 and crucial for RANKL-mediated MAPK signaling.
- ATF4 regulates M-CSF-induced RANK expression on BMMs, preventing their differentiation into macrophages.
Conclusions:
- ATF4 plays a critical and direct role in regulating osteoclast differentiation and bone resorption.
- ATF4 is a key mediator of M-CSF and RANKL signaling in osteoclast precursors.
- ATF4 represents a potential therapeutic target for bone diseases involving heightened osteoclast activity.
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