Cleidocranial dysplasia: molecular genetic analysis and phenotypic-based description of a Middle European patient group.

Cleidocranial dysplasia (CCD) (OMIM 119600) is a rare dysplasia of osseous and dental tissue. Characteristic features are typical facial and dental appearance plus morphologic anomalies. RUNX2 (OMIM 600211), the responsible gene for CCD, is considered to be a master gene for bone development and bone homeostasis. This study describes the genotype-phenotype correlation based on craniofacial features involving an interdisciplinary approach. Our patient cohort consisted of 31 CCD patients from 20 families; five patients from two families were unavailable for clinical examination. Since CCD mostly affects the craniofacial region, phenotypic characterization of each individual focused on craniofacial and dental aspects. After recording patient medical and family history, the phenotypic data was analyzed using homogeneity analysis (HOMALS), a statistical procedure for data reduction in categorical data analysis. The coding sequence of the RUNX2 gene was analyzed using PCR, direct sequencing, and restriction endonuclease digestion. Eight unpublished and four known heterozygous mutations in a total of 14/20 index patients (70%) were identified. In total, we detected 7 missense mutations, 5 frameshift mutations, and 2 nonsense mutations in 14 index patients (35%, 25%, 10%, respectively). The overall CCD phenotype varied from mild to fullblown expression. Using HOMALS, we were able to discriminate four groups of patients showing significant differences in phenotypic expressivity, thereby simplifying the grouping of our large patient cohort into clear distinguishable entities. Analysis of the mutation patterns revealed that mutational frequency and types of mutations found can be attributed to the gene's structure and function.

Expression of tropoelastin in human periodontal ligament fibroblasts after simulation of orthodontic force.

The ability of elastic fibers to respond to mechanical stimuli suggests that they play a central role in physiological adaptation to external stimuli including application of orthodontic force. The purpose of this study was to examine the effect of external pressure simulating orthodontic force on tropoelastin gene expression in cultured human periodontal ligament fibroblasts (hPDLF). External pressure simulation was achieved by centrifugation for 10, 30, 60, 90 and 120 min of hPDLF in a horizontal microplate rotor. Semi-quantitative RT-PCR analysis of tropoelastin mRNA was performed and beta-actin was used as an internal invariant control. While centrifugal force on mRNA levels of beta-actin showed almost no change, the mRNA levels of tropoelastin increased significantly to a peak level of more than four-fold after 30 min. Thereafter, at 60 min, the mRNA levels remained at more than three-fold. After 90 min, mRNA levels decreased to control levels. The finding that no changes in mRNA levels of beta-actin occurred during the first 90 min of centrifugation validates its use as an invariant control gene in such an experimental model. This study demonstrated that tropoelastin is expressed in hPDLF and that the pressure caused significant time-dependent upregulation of the tropoelastin gene. The responsiveness of the tropoelastin gene to force shows its possible clinical importance in orthodontic tooth movement. Further studies, however, are essential in order to learn whether the high expression of the gene in vitro will also be followed by corresponding protein synthesis and deposition in vivo in the extracellular matrix (ECM) of the periodontal ligament (PDL).

[On the effect of mutations of the fibroblast growth factor receptors as exemplified by three cases of craniosynostoses]. / Uber die Wirkung von Mutationen der Fibroblastenwachstumsfaktorrezeptoren (FGFR) am Beispiel dreier Fälle mit Kraniosynostosen.

PURPOSE: Craniosynostoses are premature ossifications of cranial sutures. They occur isolated and syndromic. Syndromic craniosynostoses are mainly associated with mutations of the Fibroblast Growth Factor Receptors (FGFR) 1 - 3. This paper gives an overview of the etiology and pathophysiology of isolated and syndromic craniosynostoses and discusses the molecular genetic results in 21 index cases (19 seemingly isolated craniosynostoses, 2 cases with a clinical diagnosis of Crouzon's syndrome). METHOD: Mutation analysis in exons of the FGFR 1 - 3 known to be preferentially affected in craniosynostoses was performed on DNA samples from peripheral blood and bone specimen excised at the time of surgery to correct the craniosynostosis. RESULTS: In a girl with seemingly isolated plagiocephaly we identified a P250L (749C-->T) mutation in FGFR3. Her mother showed minor signs of craniosynostosis when the family was re-evaluated. She was shown to carry the same mutation. In two patients with suspected Crouzon's syndrome 2 different mutations were detected at the same nucleotide (1025G-->A or C) and confirmed the clinical diagnosis. No mutation was found in 18/19 seemingly isolated craniosynostosis cases. CONCLUSION: In contrast to syndromic forms isolated craniosynostoses are rarely associated with mutations in FGFR. The affection of further family members is a strong indication of involvement of FGFR mutations. Because of variable expressivity, parents should be examined carefully in isolated craniosynostoses to identify minor signs.

Evidence of intrafamilial variability of CBFA1/RUNX2 expression in cleidocranial dysplasia--a family study.

AIM: To investigate the phenotypical expression of an identical mutation of the CBFA1/RUNX2 gene within a family with cleidocranial dysplasia. PATIENTS AND METHOD: A five-member family underwent clinical examination. Two members, father and son, showed dissimilar symptoms of cleidocranial dysplasia. The two affected patients were examined for syndrome-typical symptoms, and the genotype was determined by molecular-genetic analysis. RESULTS: In both patients an identical missense mutation (G146R) in exon 2 of the CBFA1/RUNX2 gene was identified. In father and son the dental disturbances were similarly clearly expressed. However, the craniofacial skeleton of the son exhibited fewer dysostotic ossification features than that of the father. In the three clinically healthy family-members no mutation of the CBFA1/RUNX2 gene was found. CONCLUSION: In two patients with cleidocranial dysplasia an identical missense mutation in the CBFA1/RUNX2 gene leading to a divergent craniofacial phenotype was determined. The results indicate marked variability in the phenotypical expression of CBFA1/RUNX2 mutations.