Strategy for prenatal diagnosis of osteogenesis imperfecta by linkage analysis to the type I collagen loci COL1A1 and COL1A2.

To improve prenatal diagnosis of osteogenesis imperfecta (OI) in Lithuania, possibilities of indirect molecular genetic diagnosis were investigated in 11 families with dominant OI. Segregation of polymorphic DNA markers closely linked to COL1A1 and COL1A2 genes with OI phenotype was investigated. Polymorphic DNA markers applied were individual haplotypes constructed using a set of restriction enzyme sites within or close to the genes. Comparison of phenotypic features with the concordant collagen locus showed that in four pedigrees with OI Sillence type I segregated with COL1A1, while two pedigrees with OI Sillence type I and OI type IV segregated with COL1A2. Out of six remaining pedigrees with OI Sillence type I, three were concordant at both loci, two pedigrees were discordant at the locus COL1A2 and non-informative at the locus COL1A1 and one pedigree was concordant at the locus COL1A1 and non-informative at the locus COL1A2. Informativity of DNA markers applied was also investigated in the Lithuanian OI families. The frequencies of six restriction enzyme site dimorphisms in type I collagen loci were estimated and polymorphism information content (PIC) values were calculated for each restriction site and for a combination of three sites. COL1A1 locus dimorphisms A/MspI, B/RsaI and F/MnlI, showed PIC values of 0.327, 0.191 and 0.366, respectively, giving a combined PIC of 0.656 at the locus, while COL1A2 locus dimorphisms C/EcoRI, D/MspI and E/RsaI RFLPs had PIC values of 0.357, 0.168 and 0.331, respectively, giving a combined PIC of 0.655 at the locus.