Cbfβ deletion in mice recapitulates cleidocranial dysplasia and reveals multiple functions of Cbfβ required for skeletal development

Abstract

The pathogenesis of cleidocranial dysplasia (CCD) as well as the specific role of core binding factor β (Cbfβ) and the Runt-related transcription factor (RUNX)/Cbfβ complex in postnatal skeletogenesis remain unclear. We demonstrate that Cbfβ ablation in osteoblast precursors, differentiating chondrocytes, osteoblasts, and odontoblasts via Osterix-Cre, results in severe craniofacial dysplasia, skeletal dysplasia, abnormal teeth, and a phenotype recapitulating the clinical features of CCD. Cbfβ f/f Osterix-Cre mice have fewer proliferative and hypertrophic chondrocytes, fewer osteoblasts, and almost absent trabecular bone, indicating that Cbfβ may maintain trabecular bone formation through its function in hypertrophic chondrocytes and osteoblasts. Cbfβ f/f Collagen, type 1, alpha 1 (Col1α1)-Cre mice show decreased bone mineralization and skeletal deformities, but no radical deformities in teeth, mandibles, or cartilage, indicating that osteoblast lineage-specific ablation of Cbfβ results in milder bone defects and less resemblance to CCD. Activating transcription factor 4 (Atf4) and Osterix protein levels in both mutant mice are dramatically reduced. ChIP assays show that Cbfβ directly associates with the promoter regions of Atf4 and Osterix. Our data further demonstrate that Cbfβ highly up-regulates the expression of Atf4 at the transcriptional regulation level. Overall, our genetic dissection approach revealed that Cbfβ plays an indispensable role in postnatal skeletal development and homeostasis in various skeletal cell types, at least partially by up-regulating the expression of Atf4 and Osterix. It also revealed that CCD may result from functional defects of the Runx2/Cbfβ heterodimeric complex in various skeletal cells. These insights into the role of Cbfβ in postnatal skeletogenesis and CCD pathogenesis may assist in the development of new therapies for CCD and osteoporosis.osteoblast differentiation | chondrocyte differentiation | ossification | growth plate formation | endochondral bone formation

MiR‐455‐3p regulates early chondrogenic differentiation via inhibiting Runx2

“…Runx2 was highly expressed in hypertrophic chondrocytes and osteoblasts [19,27,28], and C/EBPb could enhance Runx2 activity in ossification [21]. The Runx2-dependent expression of sphingomyelin phosphodiesterase 3 (Smpd3) was increased by Bone morphogenic protein 2 (BMP-2) stimulation, and Smpd3 knockdown decreased the apoptosis of terminally matured ATDC5 chondrocytes [33].…”

CCAAT/Enhancer-binding Protein α (C/EBPα) Is Important for Osteoclast Differentiation and Activity

“…Western Blotting Analysis-Western blotting analysis was performed as described previously (32). Briefly, protein lysate was prepared and submitted to gel electrophoresis.…”

Fate of growth plate hypertrophic chondrocytes: Death or lineage extension?

“…RUNX2 also cooperates with OSX to regulate Mmp13 expression and promote cartilage mineralization (Enomoto et al 2000;Nishimura et al 2012). Binding partners of RUNX2, namely RUNX3 and core binding factor b (CBFb), also regulate chondrocyte maturation and Col10a1 expression (Kundu et al 2002;Yoshida et al 2002Yoshida et al , 2004Chen et al 2014). Cbfb helps to stabilize RUNX2/3 and regulates chondrocyte differentiation and proliferation and osteoblast differentiation (Qin et al 2014).…”