Factor VIII gene haplotypes and linkage disequilibrium for the indirect genetic analysis of hemophilia A in India

Application of Indirect Linkage Analysis for Carrier Detection of Hemophilia A in Kurdistan Region of Iraq: Usefulness of Intron 18 BclI T>A, Intron 19 HindIII C>T, and IVS7 nt27 G>A Markers

Hemophilia A (HA) is the most common congenital X-linked coagulopathy caused by mutations in the factor VIII gene. One in 5000 to 10 000 male persons worldwide suffer from HA. It is the archetype of high-cost, low-volume disease. Therefore, identification of carriers is crucial to avoid the birth of affected males. Tracking of the defective X chromosome through indirect linkage analysis represents the most practical method for screening for carriers in developing countries. In this study, 227 individuals from 41 families with HA and 100 normal participants were recruited from the Kurdistan region of Iraq and evaluated for intron 18 BclI, intron 19 HindIII, and IVS7 nt 27 markers by polymerase chain reaction restriction fragment length polymorphism and direct sequencing. Among the studied women, 49%, 42%, and 14% were discovered to be heterozygous for BclI, HindIII, and IVS7 markers, respectively. Using BclI, HindIII, and IVS7 markers, 56%, 46%, and 17% of the families were informative, respectively. The combined informativity of these polymorphic sites reaches 66%. The current study illustrates the effectiveness of the BclI and HindIII markers for the diagnosis of HA carriers among the Iraqi Kurdish population.

Interlocus non-random association of multiallelic polymorphisms spanning the coagulation factor VIII gene on human chromosome distalmost Xq28

The most common severe hereditary bleeding disorder phenotype in humans, the coagulation factor VIII (F8) deficiency haemophilia A (HEMA), maps on Xq28 band, a region that comprises 11.7% of genes and 14.2% of phenotypes on X chromosome. Information about the distribution and extent of gametic disequilibrium (GD) covering the F8 gene is scarce, despite its relevance for linkage and association studies. The aim of this study was to determine the patterns, by frequency and strength, of non-random multiallelic interallelic associations between two-locus combinations of seven microsatellite loci (REN90833, F8Int25.2, F8Int22, F8Int13.2, HEMA154311.3, TMLHEInt5 and HEMA154507.3, in that physical order) spanning 0.813 Mb on distalmost Xq28. We measured sign-based interallelic D' coefficients in 106 men and in 100 women drawn from a single unrelated Brazilian population. Significance and patterns of GD using haploid and phased diploid sample probabilities were close to conformity. Only 9.18% of the variance of D' could be accounted for by changes in length, indicating that GD is not a monotonically decreasing function of length. We defined two regions of overlapping long-range GD extending 698 735 base pairs (bp) (REN90833/TMLHEInt5 block) and 689 900 bp (F8Int13.2/HEMA154507.3 block) The extent of GD overlap is 575 637 bp (F8Int13.2/TMLHEInt5 interstice). Extended haplotype homozygosity analysis centred at the F8 intronic loci revealed that the most frequent core haplotypes decay the least in the flanking GD. The F8 intronic loci attend distinct non-random association forces; F8Int13.2 serves at maintenance of the long-range overlapping pattern of GD, whereas F8Int25.2 and F8Int22 serve at lessening it in force or effect.