Regulatory Mechanism of the Factor IX Gene

The molecular basis of haemophilia B

Over the past 15 years, our knowledge of the molecular basis of haemophilia B has increased dramatically. Following the cloning and characterization of the factor IX gene in 1982, major advances have been made in documenting the molecular pathology that underlies this condition. This review will summarize the current state of information in this area, and the reader is referred to the Haemophilia B Mutation Database World Wide Web site at http://www.umds.ac.uk/molgen/haemBdatabase for a complete current listing of the mutations that cause this phenotype. In addition, other recent reviews have discussed complementary issues relating to this topic.

Characterization of human protein C gene promoter: insights from natural human mutants

Human protein C is a liver-produced plasma anticoagulant. Four heterozygous point mutations located in the promoter region have been identified in families with type I protein C deficiency and recurrent venous thrombosis. However, detailed analysis of regulatory elements and their interacting factors remains to be undertaken. This report presents results of biochemical and functional characterizations of several cis-elements located in the 5'-upstream regulatory region and the trans-acting factors that interact with them. A cloned DNA fragment from nucleotides (nt) -418 to +45 could confer tissue specificity, whereas nt -88 to +45 was sufficient for basal promoter activity of protein C gene. Five cis-elements corresponding to HNF-1, HNF-3, and NF-I/CTF binding sites have been identified. Four heterozygous mutations have been shown to disrupt HNF-3 [mutants of A(-32)G and T(-27)A] and HNF-1 [T(-14)C and C(-10)T] binding. Mutation in the NF-I-binding site also significantly impairs the promoter activity. Viewed as a whole, these results indicate that HNF-1, HNF-3, and NF-I/CTF play critical roles in transcriptional regulation of the protein C gene.

The factor IX gene as a model for analysis of human germline mutations: an update

The variation generated by germline mutation is essential for evolution, but individuals pay a steep price in the form of Mendelian disease and genetic predisposition to complex disease. Indeed, the health of a species is determined ultimately by the rate of germline mutation. Analysis of the factor IX gene in patients with hemophilia B has provided insights into the human germline mutational process. Herein, seven topics will be reviewed with emphasis on recent advances: (i) proposed mechanisms of deletions, inversions, and insertions; (ii) discordant sex ratios of mutation and associated age effects; (iii) somatic mosaicism; (iv) founder effects; (v) mutation rates; (vi) the factor IX gene as a germline mutagen test; and (vii) cancer as a possible mechanism for maintaining a constant rate of germline mutation.