A novel small deletion mutation in RUNX2 gene in one Chinese family with cleidocranial dysplasia.

Cleidocranial dysplasia (CCD) is a skeletal dysplasia with autosomal-dominant inheritance. The runt related transcription factor 2 (RUNX2) gene is the only gene in which mutations are known to cause CCD. We report identification of a novel small deletions mutation in the RUNX2 gene in a Chinese family with CCD. A 29-year-old female was diagnosed as proband of CCD based on the clinical findings, which show delayed closure of the fontanels, hypoplastic or aplastic clavicles and dental anomalies. Similar dental and skeletal symptoms were also observed in the other three affected individuals. We prepared genomic DNA from all four affected individuals, unaffected individual from her family members, as well as 100 unrelated healthy controls. PCR was conducted using the above genomic DNA as template and the RUNX2 gene-specific primers. The PCR product was subjected to direct sequencing and the sequence was compared to that of RUNX2 gene within the NCBI database. We detected a small deletion CCTA from nucleotide 635 to nucleotide 638 in exon 3 of RUNX2 gene of the proband. This will lead to the introduction of a translational stop codon at codon 220, resulting in a truncated RUNX2 protein, and therefore within the runt domain of the RUNX2 protein. We detected the same mutation in the the other three affected individuals, and did not detect any mutation in the unaffected family members or the 100 unrelated healthy controls, demonstrating that this is a novel missense mutation in RUNX2 gene and therefore, contributes to the molecular diagnosis of CCD.