A 4 BASE-PAIR INSERTION POLYMORPHISM IN THE 3'-UNTRANSLATED REGION OFTHE COL1A1 GENE IS HIGHLY INFORMATIVE FOR NULL-ALLELE TESTING IN PATIENTS WITH OSTEOGENESIS IMPERFECTA TYPE-I

In patients with osteogenesis imperfecta (OI) type I, a decrease in sy nthesis of type I collagen is usually observed as a result of a COL1A1 null allele. Testing for COL1A1 null alleles can be done using polymo rphic markers in the coding region of the COL1A1 gene. Until now only one marker for polymorphism in the 3' untranslated region (3' UTR) of the COL1A1 gene has been available. We have identified a 4 bp insertio n in the 3' UTR of the COL1A1 gene localized downstream of the MnlI RF LP and used both markers in combination for the analysis of patients w ith OI type I. In a total of 50 patients, 28 showed heterozygosity for one of the two markers; 14 of them were shown to have a COL1A1 null a llele.