Mutation Detection Of An Osteogenesis Imperfect Pedigree

Osteogenesis imperfecta (OI) is an autosomal dominant hereditary connective tissue disorder, with bone fragility and bone deformity, accompanied by blue sclera, hearing loss, etc. The prevelance of the disease is about one in every twenty thousand newborns. According to the number of new born from2002to2011in China, there are about800children with OI every year. It is reported that over90%OI is caused by mutations in the COL1A1/COL1A2genes which encode the chains of type Ⅰ procollagen. Based on the clinical symptoms, the OI can be divided into seven subtypes, in which the symptom of type Ⅰ is the slightest as well as the type Ⅱ is the severest.ObjectiveTo analyse genetic pattern of a Chinese OI family, determine type of OI and candidate gene of mutation detection, find gene mutation sites, and identify genetic causes by clinical manifestation. We will provide the evidence for understanding diagnosis, prevention and genetic counseling about OI.MethodsIn this study we collected on a Henan family with OI, in which there were35members including13patients characterized by slight bone fragility, non-bone deformity, short statureor not, blue sclera, tooth agenesis or not. Based on the clinical manifestations and criteria of the classical classification standard provided by Sillence, the phenotype of these patients was OI Type I, and candidate gene should be COL1A1peripheral blood of Affected family members were taken, genomic DNA of the OI proband was extracted and an Epstein-Barr transformed cell line was used for RNA anlysis. Exon and exon-intron region of COL1A1of the proband and his son were amplified and sepuenced. Then RT-PCR as used to investigate the effect of the mutation on mRNA in OI patients.Results(1) Results of mutation detection:A novel splicing mutation c.3207+1G>A in COL1A1gene was identified, which is firstly reported.(2) Results of RT-PCR and cDNA sequencing:sequence overlapping was observed afte c.3200, suggesting a abnormal splicing variant detected. After cDNA sequencing, two splicing variants of gene expression of patients were found. One was normal and the other was a new splicing variant with eight nucleotides deletion r.3200-3207del at exon43. The deletion resulted in change of open reading frame shift of COL1A1gene and amino acid sequences after1067of collagen type I alpha1. Then a truncated protein was produced.Conclusions(1)A novel splicing mutation c.3207+1G>A in COL1A1gene causes type Ⅰ OI in a Henan family.(2) The mutation c.3207+1G>A leads to a new splicing site of donors in the end of3’of exon43, and caused the a frame shift mutation. Then a truncated protein was produced.