Genetic screening of a pedigree with osteogenesis imperfecta type Ⅰ and identification of a novel mutation in COL1A2 pathogenic gene.

To uncover the molecular pathogenic mechanism of congenital osteogenesis imperfecta (OI) type I, all the 103 exons of the COL1A1 (Collagen, type Ⅰ, alpha 1) and COL1A2 (Collagen, type Ⅰ, alpha 2) genes in a child with OI type Ⅰ were screened using PCR-DNA direct sequencing. The results showed no pathological mutation in COL1A1 gene, but a novel mutation c.946G>T/p.G316C in the exon 19 of COL1A2 gene, which was inherited from her father. This mutation was not found in her mother and other six phenotypically normal relatives. By denaturing high performance liquid chromatography (DHPLC) screening, the abnormal double-peak was visualized in PCR products of exon 19 of COL1A2 gene in the proband and her father, while the normal single-peak was shown in those of her mother and all the healthy controls. Using allele specific amplification (ASA) screening, a specific band of 391 bp in COL1A2 exon 19 was amplified only in the proband and her father, but not in other samples. The amino acid encoded by the mutation site is evolutionarily highly conserved, and this mutation was a "damaging" or "probably damaging" factor to OI type Ⅰ, based on the predicting results using SIFT and Polyphen-2 softwares. In conclusion, the novel c.946G>T/p.G316C mutation in COL1A2 gene is a pathogenic mutation that could result in OI type Ⅰ. If the couple wants to get pregnant again, it is necessary to screen the mutation site in COL1A2 gene through the prenatal genetic diagnosis in the first trimester or through preimplantation genetic diagnosis (PGD) in the progestation.