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The p38 MAPK pathway is essential for skeletogenesis and bone homeostasis in mice.

ABSTRACT: Nearly every extracellular ligand that has been found to play a role in regulating bone biology acts, at least in part, through MAPK pathways. Nevertheless, much remains to be learned about the contribution of MAPKs to osteoblast biology in vivo. Here we report that the p38 MAPK pathway is required for normal skeletogenesis in mice, as mice with deletion of any of the MAPK pathway member-encoding genes MAPK kinase 3 (Mkk3), Mkk6, p38a, or p38b displayed profoundly reduced bone mass secondary to defective osteoblast differentiation. Among the MAPK kinase kinase (MAP3K) family, we identified TGF-beta-activated kinase 1 (TAK1; also known as MAP3K7) as the critical activator upstream of p38 in osteoblasts. Osteoblast-specific deletion of Tak1 resulted in clavicular hypoplasia and delayed fontanelle fusion, a phenotype similar to the cleidocranial dysplasia observed in humans haploinsufficient for the transcription factor runt-related transcription factor 2 (Runx2). Mechanistic analysis revealed that the TAK1-MKK3/6-p38 MAPK axis phosphorylated Runx2, promoting its association with the coactivator CREB-binding protein (CBP), which was required to regulate osteoblast genetic programs. These findings reveal an in vivo function for p38beta and establish that MAPK signaling is essential for bone formation in vivo. These results also suggest that selective p38beta agonists may represent attractive therapeutic agents to prevent bone loss associated with osteoporosis and aging.

SUBMITTER: Greenblatt MB

PROVIDER: S-EPMC2898605 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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The p38 MAPK pathway is essential for skeletogenesis and bone homeostasis in mice.

Greenblatt Matthew B MB Shim Jae-Hyuck JH Zou Weiguo W Sitara Despina D Schweitzer Michelle M Hu Dorothy D Lotinun Sutada S Sano Yasuyo Y Baron Roland R Park Jin Mo JM Arthur Simon S Xie Min M Schneider Michael D MD Zhai Bo B Gygi Steven S Davis Roger R Glimcher Laurie H LH

The Journal of clinical investigation 20100614 7

Nearly every extracellular ligand that has been found to play a role in regulating bone biology acts, at least in part, through MAPK pathways. Nevertheless, much remains to be learned about the contribution of MAPKs to osteoblast biology in vivo. Here we report that the p38 MAPK pathway is required for normal skeletogenesis in mice, as mice with deletion of any of the MAPK pathway member-encoding genes MAPK kinase 3 (Mkk3), Mkk6, p38a, or p38b displayed profoundly reduced bone mass secondary to ...[more]

PMID: 20551513

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Project description:Apert syndrome is characterized by craniosynostosis and limb abnormalities and is primarily caused by FGFR2 +/P253R and +/S252W mutations. The former mutation is present in approximately one third whereas the latter mutation is present in two-thirds of the patients with this condition. We previously reported an inbred transgenic mouse model with the Fgfr2 +/S252W mutation on the C57BL/6J background for Apert syndrome. Here we present a mouse model for the Fgfr2+/P253R mutation.We generated inbred Fgfr2(+/P253R) mice on the same C56BL/6J genetic background and analyzed their skeletal abnormalities. 3D micro-CT scans of the skulls of the Fgfr2(+/P253R) mice revealed that the skull length was shortened with the length of the anterior cranial base significantly shorter than that of the Fgfr2(+/S252W) mice at P0. The Fgfr2(+/P253R) mice presented with synostosis of the coronal suture and proximate fronts with disorganized cellularity in sagittal and lambdoid sutures. Abnormal osteogenesis and proliferation were observed at the developing coronal suture and long bones of the Fgfr2(+/P253R) mice as in the Fgfr2(+/S252W) mice. Activation of mitogen-activated protein kinases (MAPK) was observed in the Fgfr2(+/P253R) neurocranium with an increase in phosphorylated p38 as well as ERK1/2, whereas phosphorylated AKT and PKCalpha were not obviously changed as compared to those of wild-type controls. There were localized phenotypic and molecular variations among individual embryos with different mutations and among those with the same mutation.Our in vivo studies demonstrated that the Fgfr2 +/P253R mutation resulted in mice with cranial features that resemble those of the Fgfr2(+/S252W) mice and human Apert syndrome. Activated p38 in addition to the ERK1/2 signaling pathways may mediate the mutant neurocranial phenotype. Though Apert syndrome is traditionally thought to be a consistent phenotype, our results suggest localized and regional variations in the phenotypes that characterize Apert syndrome.

Dataset Information

The p38 MAPK pathway is essential for skeletogenesis and bone homeostasis in mice.

Publications

The p38 MAPK pathway is essential for skeletogenesis and bone homeostasis in mice.

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