Restriction fragment length polymorphism of the C1 inhibitor gene in hereditary angioneurotic edema.

Hereditary angioneurotic edema (HANE) results from the deficiency of the inhibitor of the first component of human complement (C1-INH). It is inherited as an autosomal dominant trait. Heterogeneity of this defect has been shown at the protein and mRNA level. Southern blot analysis of genomic DNA was performed after digestion with six different restriction endonucleases in 24 families affected with type 1 HANE (low antigenic and functional C1-INH levels) and five with type 2 (low functional C1-INH levels and normal or elevated levels of dysmorphic C1-INH). Blots were hybridized with a C1-INH cDNA probe of 1,227 bp. With one enzyme (Pst I), two different patterns of restriction fragment length polymorphism (RFLP) were detected. One was present in one kindred with type 1 HANE and the other appeared the same in one type 1 and in one type 2 family, thus indicating that each RFLP resulted from a different mutation. Analysis of a total of 34 members of these three families suggested that the polymorphisms are tightly linked to the mutation responsible for the disease. Using a 170-bp probe we showed that the three different mutations leading to these polymorphisms are located in the same region of the C1-INH gene. These data suggest that different mutations in the same region of the C1-INH gene are responsible for C1-INH deficiency in these families. Most of these mutations are probably point mutations or other "minor" defects and do not appear to be due to major deletions or rearrangements.