UMMS Affiliation

Department of Medicine, Division of Rheumatology; Li Weibo Institute for Rare Diseases Research

Publication Date


Document Type



Amino Acids, Peptides, and Proteins | Cell Biology | Cells | Developmental Biology | Enzymes and Coenzymes | Molecular Biology | Musculoskeletal Diseases | Musculoskeletal, Neural, and Ocular Physiology | Skin and Connective Tissue Diseases


Mitogen-activated protein kinases (MAPKs) are a family of protein kinases that function as key signal transducers of a wide spectrum of extracellular stimuli, including growth factors and pro-inflammatory cytokines. Dysregulation of the extracellular signal-regulated kinase (ERK) MAPK pathway is associated with human skeletal abnormalities including Noonan syndrome, neurofibromatosis type 1, and cardiofaciocutaneous syndrome. Here, we demonstrate that ERK activation in osteoprogenitors is required for bone formation during skeletal development and homeostasis. Deletion of Mek1 and Mek2, kinases upstream of ERK MAPK, in osteoprogenitors (Mek1(Osx)Mek2(-/-)), resulted in severe osteopenia and cleidocranial dysplasia (CCD), similar to that seen in humans and mice with impaired RUNX2 function. Additionally, tamoxifen-induced deletion of Mek1 and Mek2 in osteoprogenitors in adult mice (Mek1(Osx-ERT)Mek2(-/-)) significantly reduced bone mass. Mechanistically, this corresponded to decreased activation of osteoblast master regulators, including RUNX2, ATF4, and beta-catenin. Finally, we identified potential regulators of osteoblast differentiation in the ERK MAPK pathway using unbiased phospho-mass spectrometry. These observations demonstrate essential roles of ERK activation in osteogenesis and bone formation.


ERK, MAPK, MEK1, MEK2, cleidocranial dysplasia, osteoblast, osteopenia

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Copyright © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (

DOI of Published Version



Int J Mol Sci. 2019 Apr 12;20(8):1803. pii: ijms20081803. doi: 10.3390/ijms20081803. Link to article on publisher's site

Journal/Book/Conference Title

International journal of molecular sciences

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PubMed ID


Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.