Osteoblast differentiation and skeletal development are regulated by Mdm2-p53 signaling.
Mdm2 is required to negatively regulate p53 activity at the peri-implantation stage of early mouse development. However, the absolute requirement for Mdm2 throughout embryogenesis and in organogenesis is unknown. To explore Mdm2-p53 signaling in osteogenesis, Mdm2-conditional mice were bred with Col3.6-Cre-transgenic mice that express Cre recombinase in osteoblast lineage cells. Mdm2-conditional Col3.6-Cre mice die at birth and display multiple skeletal defects. Osteoblast progenitor cells deleted for Mdm2 have elevated p53 activity, reduced proliferation, reduced levels of the master osteoblast transcriptional regulator Runx2, and reduced differentiation. In contrast, p53-null osteoprogenitor cells have increased proliferation, increased expression of Runx2, increased osteoblast maturation, and increased tumorigenic potential, as mice specifically deleted for p53 in osteoblasts develop osteosarcomas. These results demonstrate that p53 plays a critical role in bone organogenesis and homeostasis by negatively regulating bone development and growth and by suppressing bone neoplasia and that Mdm2-mediated inhibition of p53 function is a prerequisite for Runx2 activation, osteoblast differentiation, and proper skeletal formation.
Department of Cell Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Christopher J
CJ
Lengner
Heather A
HA
Steinman
James
J
Gagnon
Thomas W
TW
Smith
Janet E
JE
Henderson
Barbara E
BE
Kream
Gary S
GS
Stein
Jane B
JB
Lian
Stephen N
SN
Jones
D000818:Animals; D001846:Bone Development / Q000235:genetics*; D001859:Bone Neoplasms / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics*; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D020022:Genetic Predisposition to Disease / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D012863:Skeleton; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000502:physiology
D050659:Core Binding Factor Alpha 1 Subunit; C493716:Runx2 protein, mouse; D016159:Tumor Suppressor Protein p53; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2