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

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.

Cbfa1, a candidate gene for cleidocranial dysplasia syndrome, is essential for osteoblast differentiation and bone development

We have generated Cbfa1-deficient mice. Homozygous mutants die of respiratory failure shortly after birth. Analysis of their skeletons revealed an absence of osteoblasts and bone. Heterozygous mice showed specific skeletal abnormalities that are characteristic of the human heritable skeletal disorder, cleidocranial dysplasia (CCD). These defects are also observed in a mouse Ccd mutant for this disease. The Cbfa1 gene was shown to be deleted in the Ccd mutation. Analysis of embryonic Cbfa1 expression using a lacZ reporter gene revealed strong expression at sites of bone formation prior to the earliest stages of ossification. Thus, the Cbfa1 gene is essential for osteoblast differentiation and bone formation, and the Cbfa1 heterozygous mouse is a paradigm for a human skeletal disorder.

Mutations involving the transcription factor CBFA1 cause cleidocranial dysplasia

Cleidocranial dysplasia (CCD) is an autosomal-dominant condition characterized by hypoplasia/aplasia of clavicles, patent fontanelles, supernumerary teeth, short stature, and other changes in skeletal patterning and growth. In some families, the phenotype segregates with deletions resulting in heterozygous loss of CBFA1, a member of the runt family of transcription factors. In other families, insertion, deletion, and missense mutations lead to translational stop codons in the DNA binding domain or in the C-terminal transactivating region. In-frame expansion of a polyalanine stretch segregates in an affected family with brachydactyly and minor clinical findings of CCD. We conclude that CBFA1 mutations cause CCD and that heterozygous loss of function is sufficient to produce the disorder.

Sibs with cleidocranial dysplasia born to normal parents: germ line mosaicism?

Cleidocranial dysplasia (CCD) is classically an autosomal dominant disorder. However, the possibility of an autosomal recessive form of CCD has been suggested based on a report of 2 consanguineous families, one with a single affected child, the second with affected sibs, born to normal parents. We present a family with sibs with CCD born to normal parents, and suggest germ line mosaicism as the more likely mechanism for this occurrence.

Mapping of the gene for cleidocranial dysplasia in the historical Cape Town (Arnold) kindred and evidence for locus homogeneity

Cleidocranial dysplasia (CCD) is an autosomal dominant disorder, features of which include a patient anterior fontanelle, a bulging calvarium, hypoplasia or aplasia of the clavicles, a wide public symphysis, dental anomalies, vertebral malformation, and short stature. The Cape Town kindred which is under our genetic management was originally described more than four decades ago and now consists of more than 1000 people. Following reports of rearrangements on chromosomes 6 and 8 in people with CCD, we have carried out linkage analyses between highly information microsatellite dinucleotide repeat markers in the rearranged regions and the disorder in a branch of this South African CCD kindred, consisting of 38 subjects, 18 of whom are affected. Maximum lod scores (at theta = 0.00) of 7.14 (for marker D6S459), 4.32 (TCTE), 4.99 (D6S452), 5.97 (D6S269), and 3.95 (D6S465) confirm linkage of the disorder to the short arm of chromosome 6. Our data indicate that the CCD gene is located within a minimal region of approximately 10 cM flanked by the marker D6S451 distally and D6S466 proximally. This information is vital towards isolating and characterising the gene for CCD, and is being used to construct a physical map of 6p21.1-6p21.3. More importantly, mapping of the locus in the South African kindred of mixed ancestry, in which the "founder" of the disorder was of Chinese origin, suggests that a single locus is responsible for classic CCD.

Cleidocranial dysplasia. Case report

A 29-year-old Caucasian woman who presented with short stature and multiple unerupted supernumerary teeth is described. Radiological investigations of her cranial and skeletal abnormalities revealed cleidocranial dysplasia. Because of the advanced age of the patient and contraindication for orthodontic treatment, only surgical and prosthetic treatment were performed. The characteristics and treatments of this rare autosomal dominant disorder are discussed.

Genetic mapping of the cleidocranial dysplasia (CCD) locus on chromosome band 6p21 to include a microdeletion

Cleidocranial dysplasia (CCD) is a generalized skeletal dysplasia with autosomal dominant inheritance. Recently, the CCD disease locus was localized to 23 [Mundlos et al., 1995] and 17 cM regions [Feldman et al., 1995], of chromosome band 6p21 by linkage studies of seven affected families. Of note, the 23 cM region contained a microdeletion detected in one family at D6S459, an interval that was excluded in the 17 cM overlapping region. Here, linkage of CCD to 6p21 was independently confirmed with a maximal two-point LOD score of Z = 5.12 with marker D6S452 at theta = 0.00. Recombinant events in two affected individuals defined a CCD region of 7 cM from D6S465 to D6S282, which overlapped with the CCD region containing the microdeletion but did not overlap with the 17 cM critical region from D6S282 to D6S291. These results suggest the refined localization of the CCD region to 6 cM spanning markers D6S438 to D6S282, thereby reviving the possibility that the CCD gene lies within the microdeletion at D6S459.

A gene for cleidocranial dysplasia maps to the short arm of chromosome 6

Cleidocranial dysplasia (CCD) is an autosomal dominant generalized bone dysplasia characterized by mild-to-moderate short stature, clavicular aplasia or hypoplasia, supernumerary and ectopic teeth, delayed eruption of secondary teeth, a characteristic craniofacial appearance, and a variety of other skeletal anomalies. We have performed linkage studies in five families with CCD, with 24 affected and 20 unaffected individuals, using microsatellite markers spanning two candidate regions on chromosomes 8q and 6. The strongest support for linkage was with chromosome 6p microsatellite marker D6S282 with a two-point lod score of 4.84 (theta = .03). Furthermore, the multipoint lod score was 5.70 in the interval between D6S282 and D6S291. These data show that the gene for autosomal dominant CCD is located within a 19-cM interval on the short arm of chromosome 6, between D6S282 and D6S291.

Genetic mapping of cleidocranial dysplasia and evidence of a microdeletion in one family

Cleidocranial dysplasia (CCD) is an autosomal, dominantly inherited disorder of high penetrance affecting skeletal ossification and tooth development. Typically, affected individuals have hypoplastic/aplastic clavicles, patent fontanelles and sutures, supernumerary teeth, and short stature. We have used a candidate locus approach to map the responsible gene in two families with typical features of CCD. Linkage was established between CCD and four loci (D6S426, D6S451, D6S459, TCTE1) that span a region of 10 cM on chromosome 6p. A maximum lod score, Zmax, of 4.1 at a recombination fraction of zero was obtained at D6S451. One highly polymorphic microsatellite from this region (D6S459) showed allelic loss in all affected members of one family with two different sets of primers. The presence of a deletion in this area was confirmed by Southern blot analysis using a probe derived from the amplification product of the D6S459 marker. The data assign a gene for CCD to chromosome 6p21 and suggest that a microdeletion within an area of tight linkage to the CCD-phenotype has been identified.

Genetic skeletal dysplasias in the Museum of Pathological Anatomy, Vienna

Skeletal material in the Museum of Pathological Anatomy, Vienna, has been appraised in order to modify existing descriptive designations and to establish diagnoses of specific genetic disorders. In this way osseous material relating to classical genetic syndromes has been identified and will be available for further study. Among the skeletons of adults in the museum, the following genetic conditions could be diagnosed: achondroplasia, Marfan syndrome, cleidocranial dysostosis, and diaphyseal aclasia. In adult sisters with dwarfism and a rickety bone disorder, the final diagnosis was uncertain. Infantile bone dysplasias, genetic conditions involving the skull, and malformation syndromes which are all represented in the museum are currently being analyzed.

Synergistic interactions between two skeletal mutations in mice: individual and combined effects of the semidominants cleidocranial dysplasia (Ccd) and short digits (Dsh)

Heterozygotes for cleidocranial dysplasia (Ccd) and short digits (Dsh) were crossed to test whether synergistic interactions occur between different dominant mutations whose individual pleiotropic phenotypic effects exhibit a common feature. These unlinked mutations are homozygous lethal, and they are congenic on the C57BL/10 background. Each mutation caused more than 10 different anomalies and showed variable expressivity. Each mutation produced several malformations that were present in every heterozygote. Seven different synergistic interactions were found, including one that yielded an entirely new abnormality not predicted from any abnormalities found in either of the single heterozygotes. Although synergistic interactions between dominant mutations have not, to our knowledge, been described in humans, these findings in mice increase the probability that they occur in humans. Under certain circumstances in human populations, the segregation of mutations causing synergistic interactions of the type demonstrated might be confused with recessive inheritance. It will be important to learn whether synergistic interactions can occur between other mutations. If they can, it will probably become important to take synergistic interactions into account when estimating the genetic hazards to humans from mutagens. Three antagonistic interactions were also found.

Pericentric inversion of chromosome 6 in a patient with cleidocranial dysplasia

We describe a male patient with a pericentric inversion of chromosome 6 and classic cleidocranial dysplasia (CCD), mild to moderate mental retardation, hearing deficiency, and unusual facial appearance. We conclude that there is a causal relationship between the chromosomal disorder and the CCD.

Apparent cleidocranial dysplasia associated with abnormalities of 8q22 in three individuals

Cleidocranial dysplasia is an autosomal dominant, generalised skeletal disorder characterised by variable clavicular hypoplasia, frontal bossing, multiple Wormian bones, and delayed eruption of the teeth. The gene locus for this syndrome has not yet been assigned. Three individuals with manifestations of cleidocranial dysplasia associated with rearrangements of chromosome 8q22 are described. The evidence presented suggests that the gene for cleidocranial dysplasia may be located on chromosome 8q in humans in a region showing homology to mouse chromosome 3.

Intrafamilial variability in cleidocranial dysplasia: a three generation family

We present a 3-generation family, ascertained after the birth of a child with cleidocranial dysplasia (CCD). The propositus presented with respiratory distress (due to a narrow thorax) and hypoplasia and discontinuity of both clavicles. The mother, aunt, and grandmother had varied features of the condition. This intrafamilial variation illustrates the need for clinical assessment of family members following the birth of an apparent sporadic case of CCD.

Development of the dentition in cleidocranial dysplasia

The purpose of the present investigation was to describe the formation, maturation and eruption of the dentition, including supernumerary teeth in a sample of patients with cleidocranial dysplasia. The dentition was evaluated from orthopantomograms, intraoral radiographs, cephalometric films, surgically removed teeth and intraoral photographs in 19 patients (9 men, 10 women), aged 3.5 to 34 years. Formation of primary teeth was normal, whereas all patients but one had supernumerary permanent teeth. Frequency of supernumerary teeth ranged from 22% in the maxillary incisor region to 5% in the molar regions. Supernumerary teeth were formed lingually and occlusally to the normal teeth. Maturation of the primary dentition was normal, while permanent teeth were delayed from 1 to 4 yr. Supernumerary teeth were delayed about 4 years in relation to normal permanent teeth. Eruption of primary teeth was normal, whereas all patients had severe eruption problems of permanent teeth. It was hypothesized that the dental lamina for both primary and permanent dentition is normal, but does not resolve completely and therefore may form supernumerary teeth. Abnormalities of tooth morphology is related to inadequate space and arrested eruption. Delayed or arrested eruption is probably caused by diminished resorption of bone and of primary teeth and to the presence of multiple supernumerary teeth.

Congenital pseudarthrosis of the tibia associated with cleidocranial dysostosis and osteogenesis imperfecta. A case report

A neonatal boy with cleidocranial dysostosis presented with congenital pseudarthrosis of the tibia. Clinical observation later revealed he also had osteogenesis imperfecta. The osteogenesis imperfecta was classified as Type I and the congenital tibial pseudarthrosis as Type II. Cleidocranial dysostosis, osteogenesis imperfecta, and congenital pseudarthrosis of the tibia have not been previously reported to coexist in one individual.