Detection Of Genetic Defect And Analysis Of Ocular Presentation Of Osteogenesis Imperfecta In A Chinese Pedigree

ObjectiveTo identify the genetic defect and to analyze the ocular presentation of OsteogenesisImperfecta in a large Chinese family of five generations.MethodsSeventeen members in an Osteogenesis Imperfecta (OI) type I family were recruited.The genomic DNA was isolated and identified from peripheral blood. All themembers were genotyped with microsatellite markers at loci associated with OI.Allele-sharing analysis and exclusive analysis was performed. Haplotype analysiswas performed using the Cyrillic 2.0. A two-point LOD score was calculated usingthe Linkage package, A mutation was detected by direct sequencing. The mutationwas confirmed by DHPLC. The bioinformatic analysis was performed about themutation.ResultsAllele-sharing analysis confirmed the linkage of the disease in the family withCOL1A1 and no linkage with COLA2. Haplotype analysis showed that all theaffected individuals shared a common haplotype with markers D17S1293, D17S1180,D17S1319 and D17S788 at 17q11. 2-22. Significant evidence of linkage wasobserved with microsatellite markers D17S1180 (LOD score [Z]=2.91, atrecombination fraction [0]=0.0) and D17S1319 (Z=2.20, at 0=0.0), respectively.Direct cycle sequencing of the amplified fragments of COLIA1 identified a singlebase alteration of C2464T in exon 36 of COL1A1, which resulted in a substitution of Gin at codon 644 to a stop codon (Q644X). Denaturing HPLC analysis confirmedthis mutation, which co-segregated with all affected individuals in the family, andwas not observed in any of the unaffected family members or 100 normal controls.Bioinformatic analysis showed that Q644 is located in a highly conserved region.The sclerae of all the affected individuals in the family have been blue since theywere born. The proband (V:3) was a 14-year-old boy with blue sclerae. Hisuncorrected visual acuity was: OD, 20/10; OS, 20/10. The IOP (Goldmann tonometry)were: OD, 14.7mmHg; OS, 18.3mmHg. The corneal curvatures were: OD, K1 43.3,K2 43.6; OS, K1 43.0, K2 44.0. The ocular axis lengths were normal: OD, 24.03mm;OS, 24.23mm, and his CCT were low: OD, 434μm; OS, 441μm.Conclusions1. This study is the first report that OI is associated with the mutation of Q644X ofCOL1A1.2. The CCT of the OI patients are lower than normal.