An HhaI polymorphism is present in factor IX genes of Asian subjects

Polymorphisms associated with the FVIII and FIX genes in the Turkish population

In order to determine the gene frequencies of nine polymorphic sites associated with FVIII and FIX genes in the Turkish population a sample of 50-235 unrelated X chromosomes from healthy individuals were analysed by using PCR-based assays. The Turkish population was found to be as polymorphic as Europeans in the FVII and FIX genes. Analysis of FIX haplotypes revealed that the most frequent haplotype observed in European populations and Anglo-Americans was also very common among Turks. The present population-based study indicates that two marker loci, namely HindIII and St14 in the factor VIII gene and DdeI and HhaI in the factor IX gene, are highly informative and useful markers that can be used in DNA linkage analysis for the assessment of haemophilia carriers and affected fetuses in the Turkish population.

Factor IX gene haplotypes in Brazilian blacks and characterization of unusual DdeI alleles

Analysis of factor IX gene polymorphisms is considered the best approach for prenatal diagnosis and carrier detection of haemophilia B when the identification of the gene mutation is not possible. Studies involving factor IX gene polymorphisms in Black populations are scarce and essentially restricted to the North-American Black population whose composition is substantially different from that of the Brazilian and presumably other Black populations of South America. In this paper we report the analysis of eight factor IX gene polymorphisms in Brazilian Blacks: 5' BamHI, DdeI, intron 2 BamHI, XmnI, TaqI, TaqI, MspI, MnlI and HhaI. Characterization of the VNTR-like DdeI polymorphism revealed six different alleles: B, AB, A2B, A2B2, A3B and A5B, the last being described here for the first time. The 5' BamHI, DdeI, MspI and HhaI polymorphisms showed the highest heterozygosities (0.40-0.50) and are in linkage equilibrium with one another. 19 complete haplotypes could be identified in this population. Based on the results we propose a systematic strategy for carrier detection and prenatal diagnosis of haemophilia B in this population. The combined analysis of four polymorphisms (5' BamHI, HhaI, MspI and DdeI) provided an informative genetic marker in 85% of the females. The use of all eight polymorphisms allows information in 95% of females. Additionally, differences in gene frequencies and haplotype distribution suggest dissimilarities in factor IX gene polymorphisms between the Brazilian and the North-American Black populations.

Alu repeats in the human factor IX gene: the rate of polymorphism is not substantially elevated

Previous data suggested an elevated rate of polymorphism in Alu sequences. Direct genomic sequencing was performed on five Alu repeats in the factor IX gene in at least 20 unrelated males of European and Asian descent (40 kb total). In these Alu sequences, the estimated rate of polymorphism in Caucasians (HE = 7.1 x 10(-4); HN = 4.5 x 10(-4) is similar to previously examined nonrepetitive sequences in the factor IX gene, and about twofold lower than previous estimates of the average rate of polymorphism for the X-chromosome which utilized random genomic clones to detect RFLPs. The aggregate data on the rate of polymorphism in Alu sequences suggest that mutations due to gene conversions at these sites are infrequent.

CG dinucleotide transitions in the factor IX gene account for about half of the point mutations in hemophilia B patients: a Seattle series

Hemophilia B is due to multiple molecular defects in the factor IX gene. Over 80% of mutations are single base substitutions. By amplification and direct sequencing, 51 single base substitutions were found in the transcribed sequence of the factor IX genes of patients from 50 distinct families with hemophilia B. These include 30 mutations in 29 families not previously reported by us; of these, 12 are novel, i.e., not previously published in other series. Of the 51 substitutions in our overall series 23 (45%) occurred as C-to-T or G-to-A transitions at 11 sites within CG dinucleotides. It is estimated that CG transitions occur from one to two orders of magnitude more frequently than mutations in nucleotides that are not within a CG pair. More than one family had identical defects for 6 of the CG mutations. At 4 of these sites, most patients had different haplotypes compatible with distinct mutations. Non-CG-type mutations occurred throughout the coding regions with only one mutation in more than one family. The latter included 7 families with a 397 Ile-to-Thr defect that all share a rare haplotype, suggesting a common ancestor.