Core binding factor beta (Cbf?) controls the balance of chondrocyte proliferation and differentiation by upregulating Indian hedgehog (Ihh) expression and inhibiting parathyroid hormone-related protein receptor (PPR) expression in postnatal cartilage and bone formation.

ABSTRACT: Core binding factor beta (Cbf?) is essential for embryonic bone morphogenesis. Yet the mechanisms by which Cbf? regulates chondrocyte proliferation and differentiation as well as postnatal cartilage and bone formation remain unclear. Hence, using paired-related homeobox transcription factor 1-Cre (Prx1-Cre) mice, mesenchymal stem cell-specific Cbf?-deficient (Cbf?(f/f) Prx1-Cre) mice were generated to study the role of Cbf? in postnatal cartilage and bone development. These mutant mice survived to adulthood but exhibited severe sternum and limb malformations. Sternum ossification was largely delayed in the Cbf?(f/f) Prx1-Cre mice and the xiphoid process was noncalcified and enlarged. In newborn and 7-day-old Cbf?(f/f) Prx1-Cre mice, the resting zone was dramatically elongated, the proliferation zone and hypertrophic zone of the growth plates were drastically shortened and disorganized, and trabecular bone formation was reduced. Moreover, in 1-month-old Cbf?(f/f) Prx1-Cre mice, the growth plates were severely deformed and trabecular bone was almost absent. In addition, Cbf? deficiency impaired intramembranous bone formation both in vivo and in vitro. Interestingly, although the expression of Indian hedgehog (Ihh) was largely reduced, the expression of parathyroid hormone-related protein (PTHrP) receptor (PPR) was dramatically increased in the Cbf?(f/f) Prx1-Cre growth plate, indicating that that Cbf? deficiency disrupted the Ihh-PTHrP negative regulatory loop. Chromatin immunoprecipitation (ChIP) analysis and promoter luciferase assay demonstrated that the Runx/Cbf? complex binds putative Runx-binding sites of the Ihh promoter regions, and also the Runx/Cbf? complex directly upregulates Ihh expression at the transcriptional level. Consistently, the expressions of Ihh target genes, including CyclinD1, Ptc, and Pthlh, were downregulated in Cbf?-deficient chondrocytes. Taken together, our study reveals not only that Cbf? is essential for chondrocyte proliferation and differentiation for the growth and maintenance of the skeleton in postnatal mice, but also that it functions in upregulating Ihh expression to promoter chondrocyte proliferation and osteoblast differentiation, and inhibiting PPR expression to enhance chondrocyte differentiation.

SUBMITTER: Tian F 

PROVIDER: S-EPMC4644666 | biostudies-other | 2014 Jul

REPOSITORIES: biostudies-other