OBJECTIVETo identify the RUNX2 gene mutation in two unrelated Chinese families with cleidocranial dysplasia (CCD), and to assess the feasibility of gene diagnosis for patients with CCD.

METHODSGenomic DNA was isolated from peripheral blood samples of 4 patients and 4 healthy members in the two pedigrees as well as 102 unrelated healthy controls. All 7 coding exons and their flanking intronic sequences of the RUNX2 gene were amplified by PCR, then the PCR products were sequenced bi-directionally. The sequencing results were compared with normal sequences in GenBank to identify the mutation. The mutation was confirmed by RFLP with restriction endonuclease.

RESULTSIn one family, a novel heterozygous missense mutation c.346T to A (W116R) in exon 1 of the RUNX2 gene was detected in the two affected individuals, and the mutation was further confirmed with Bsr I restriction endonuclease digestion. In the other family, a novel nonsense mutation c.610A TO T (K204X) was identified in the two patients. No above sequence change was found in the 102 healthy controls.

CONCLUSIONTwo novel RUNX2 mutations were found in two unrelated Chinese families with cleidocranial dysplasia. The identification of these mutations further extended the mutation spectrum of RUNX2 gene and will facilitate prenatal diagnosis and gene diagnosis of CCD.