IDENTIFICATION OF 9 NOVEL MUTATIONS IN TYPE-I ANTITHROMBIN DEFICIENCYBY HETERODUPLEX SCREENING

We have utilized DNA heteroduplex detection as a method for screening sequences of the antithrombin (AT) gene for the presence of mutations. Affected individuals from 41 kindreds with type la antithrombin defic iency were investigated. Heteroduplexes were detected in 12 cases; dir ect sequencing of the appropriate exons revealed nine cases with novel mutations, and two with previously described mutations. In addition, a new polymorphism in the 5' untranslated region was characterized. Th e defects included minor insertions and deletions which lead to the re moval of intact codons or premature termination, and single base subst itutions leading to premature termination or amino acid substitution. In all cases, the affected individuals were heterozygous for the defec t and variant AT protein was not detected. In keeping with previous re ports the defects associated with type la AT deficiency are extremely heterogeneous, the vast majority being point mutations. This study als o demonstrates the efficiency of hydrolink gel electrophoresis as a me thod of screening for unknown mutations by heteroduplex detection.