Missense mutations abolishing DNA binding of the osteoblast-specific transcription factor OSF2/CBFA1 in cleidocranial dysplasia

Abstract

Cleidocranial dysplasia (CCD) is an autosomal dominant disorder characterized by hypoplastic or absent clavicles, large fontanelles, dental anomalies and delayed skeletal development. The phenotype is suggestive of a generalized defect in ossification and is one of the most common skeletal dysplasias not associated with disproportionate stature. To date, no genetic determinants of ossification have been identified. CCD has been mapped to chromosome 6p21, where CBFA1, a gene encoding OSF2/CBFA1, a transcriptional activator of osteoblast differentiation, has been localized. Here, we describe two de novo missense mutations, Met175Arg and Ser191Asn, in the OSF2/CBFA1 gene in two patients with CCD. These two mutations result in substitution of highly conserved amino acids in the DNA-binding domain. DNA-binding studies with the mutant polypeptides show that these amino acid substitutions abolish the DNA-binding ability of OSF2/CBFA1 to its known target sequence. Concurrent studies show that heterozygous nonsense mutations in OSF2/CBFA1 also result in CCD, while mice homozygous for the osf2/cbfa1 mull allele exhibit a more severe lethal phenotype. Thus, these results together suggest that CCD is produced by haploinsufficiency of OSF2/CBFA1 and provide direct genetic evidence that the phenotype is secondary to an alteration of osteoblast differentiation.

Histological development and dynamic expression of Bmp2–6 mRNAs in the embryonic and postnatal mousecranial base

“…Similar defects have been observed in FGFR transgenic mouse strains Eswarakumar et al, 2002Eswarakumar et al, , 2004. Mutations in RUNX2 and TWIST give rise to cleidocranial dysplasia and Saethre-Chotzen syndromes, respectively, which are characterized by defects in the cranial base (Evans and Christiansen, 1976;Kreiborg et al, 1981;Howard et al, 1997;Lee et al, 1997). In addition, abnormalities in the cranial base have been reported in syndromes with chromosome abnormalities, such as Cri-du-Chat, Down's, Meckel, Seckel, Turner, and Williams, as well as in human triploid fetuses (Jensen, 1985;Kjaer et al, 1997Kjaer et al, , 1999Kjaer et al, , 2001Andersen et al, 2000;Quintanilla et al, 2002;Axelsson et al, 2005).…”

Revisiting the supernumerary: the epidemiological and molecular basis of extra teeth

“…Cleidocranial dysplasia occurs as a result of mutation in the Runt-related transcription factor RUNX2, which is essential for the normal differentiation of bone-forming osteoblasts. 30,31 In the mouse, Runx2 is expressed in the mesenchymal compartment of the tooth and a complete loss of function is associated with arrested tooth development; 32 however, in the heterozygous mutant, which models the human genotype, rudimentary supernumerary tooth formation takes place lingual to the fi rst molar tooth germs. The mechanism underlying this is not fully understood but in the lower molars at least, Runx2 transcription in the mesenchyme is able to repress Shh signalling in the epithelium.…”

Runx3 is required for the differentiation of lung epithelial cells and suppression of lung cancer

“…RUNX1 and RUNX2 are essential for hematopoiesis and osteogenesis, respectively, and are often mutated in leukemia and bone disease (Okuda et al, 1996;Lee et al, 1997;Look, 1997;Mundlos and Olsen, 1997;Otto et al, 1997). RUNX3 is involved in neurogenesis Levanon et al, 2002) and thymopoiesis (Taniuchi et al, 2002;Woolf et al, 2003), and it functions as a tumor suppressor in gastric cancer (Guo et al, 2002;Li et al, 2002;Kim et al, 2005b;Ito et al, 2008).…”