[Analysis of type IV osteogenesis imperfecta caused by two mutations occurred simultaneously in COL1A1 gene in a Chinese child]

To detect potential mutations of COL1A1 and COL1A2 genes with polymerase chain reaction-high-resolution melting analysis(PCR-HRMA) in a proband diagnosed with osteogenesis imperfecta (OI).

Peripheral blood samples were collected from the proband and members of his family as well as healthy controls. The mutations were detected by PCR-HRMA and confirmed by direct sequencing. Potential effects of the mutations were predicted using softwares including PolyPhen, SIFT and Align GVGD.

The PCR-HRMA has indicated mutations in exon 45 of the COL1A1 gene in the proband as well as his parents, which were presented as the difference in the melting curves between the patients and the control samples. Sequencing analysis confirmed that the proband has carried two heterozygous mutations (c.3235G>A, p.Gly1079Ser and c.3247G>A, p.Ala1083Thr) in exon 45 of the COL1A1 gene. Among them, c.3235G>A was predicted to have impeded alpha helix structure domain, which was inherited from the father who also had OI. c.3247G>A was inherited from mother who had a normal phenotype. All three softwares predicted that the c.3235G>A mutation can interfere with the function of the protein, while the c.3247G>A may have a benign effect by PolyPhen analysis.

The study identified two mutations (c.3235G>A and c.3247G>A) occurred simultaneously in COL1A1 gene in a case. The case is the first reported in human collagen mutation database. As identified,mutation of c.3235G>A may be the major cause of the disease in the proband.