Brd4 is required for chondrocyte differentiation and endochondral ossification.
Christopher R Paradise1, M Lizeth Galvan2, Oksana Pichurin2
1Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, USA; Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA.
Bone
|October 26, 2021
Summary
Bromodomain 4 (Brd4) is essential for bone development. Loss of Brd4 impairs chondrogenesis and endochondral ossification, affecting growth plate development and long bone formation in mice.
Area of Science:
- Epigenetics
- Developmental Biology
- Skeletal Biology
Background:
- Mesenchymal stromal cells (MSCs) differentiate into various cell types, guided by transcription factors.
- Bromodomain (BRD) proteins, like Brd4, recognize histone acetylation marks to regulate gene accessibility.
- Previous work established Brd4's role in osteoblast differentiation.
Purpose of the Study:
- To investigate the role of Brd4 in endochondral ossification and chondrogenesis.
- To elucidate the molecular mechanisms by which Brd4 influences skeletal development.
Main Methods:
- Conditional knockout (cKO) mouse model (Brd4 fl/fl: Prrx1-Cre) to study Brd4 function in the mesenchyme.
- Analysis of growth plate morphology and long bone formation in juvenile mice.
- Chondrogenic differentiation assays using ATDC5 cells and primary chondrocytes.
Main Results:
- Conditional loss of Brd4 in mesenchymal cells resulted in smaller mice with altered endochondral ossification.
- Brd4 cKO mice exhibited abnormal growth plate morphology, delayed long bone formation, and reduced proliferative/hypertrophic zones.
- Brd4 deficiency impaired chondrogenic differentiation, suppressed Sox9 expression, and reduced key chondrogenic gene expression.
Conclusions:
- Brd4 is a critical epigenetic regulator essential for normal chondrogenesis.
- Brd4 plays a vital role in endochondral ossification and skeletal development.
- Targeting Brd4 may offer therapeutic strategies for skeletal disorders.
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