Haemophilia B: database of point mutations and short additions and deletions--third edition, 1992.

The data base below lists known point mutations and short deletions and additions in the factor IX gene, causing the bleeding disorder haemophilia B or Christmas disease (for reviews, see Brownlee 1988, Giannelli 1989, Thompson 1990, Green et al 1991a) These mutations result in a defective clotting factor EX—a glycoprotein of 415 amino acid residues normally present in plasma and an essential component of the clotting cascade. The disease is an X-linked inherited recessive disorder affecting 1 in about 30,000 males and only very rarely females. The purpose of this database is to update last year's one (Giannelli et al, 1991) by collecting in an accessible, summary form, molecular data on the causative mutations of haemophilia B patients worldwide. It is not intended to replace primary publications although it does contain a significant amount of unpublished work. As in previous years, we have included repeat observations of the same mutation, as well as molecularly unique mutations. We have continued our database numbering system (Giannelli etal (1991) giving all patients a unique Patient Identity Number (PIN or ID number). The factor IX gene lies on the long arm of the X chromosome at Xq27 and its entire sequence of 33 kb is known (Yoshitake et al, 1985). It contains 8 exons (a-h) encoding 6 major domains of factor IX. These are: (1) exon a—a hydrophobic signal peptide which targets the protein for secretion from the hepatocyte into the blood stream. (2) exons b and c—a propeptide and gla domain,—the latter containing 12 7-carboxyglutamyl residues. This post-translational modification is required for the correct folding and calcium binding of factor IX. (3) exon d—a type B, or first epidermal growth factor-like domain, which shows homology to epidermal growth factor (EGF) and, in addition, contains conserved carboxylate residues including a j3-hydroxyaspartate at amino acid 64. This domain binds an additional Ca 2+ with high affinity (Handford et al, 1991). (4) exon e—a type A, or second epidermal growth factor-like (EGF) domain which lacks the conserved carboxylate residues of the EGF type B domain. (5) exon f—an activation domain, within which factor XIa cleaves twice, converting factor IX to IXa; (6) exons g and h—the serine protease or catalytic domain, responsible for the proteolysis of factor X to Xa. This region is homologous to other well studied serine proteases (e.g. chymotrypsin) and it is thought likely that his (221), asp (269) and ser (365), all …