Suitability of four polymorphic DNA markers for indirect genetic diagnosis of haemophilia A in Japanese subject

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.

Detection of hemophilia a carriers in Azeri Turkish population of Iran: usefulness of HindIII and BclI markers

Hemophilia A (HA) is an inherited X-linked coagulation disorder caused by the deficiency of factor VIII (FVIII). Linkage analysis is a common indirect method for the detection of female carriers in families with HA. In the current study, 173 patients from 30 unrelated families with HA were recruited from the Azeri Turkish population of northwest Iran and analyzed for BclI and HindIII markers by polymerase chain reaction-restriction fragment length polymorphism. We investigated the potential of using these markers for the detection of mutation in carriers through linkage analysis, which would be of tremendous use in prenatal diagnosis. Among the tested women, 47% and 35% were found to be heterozygous for BclI and HindIII polymorphic markers, respectively. The BclI and HindIII markers were informative for the detection of 63% and 17% potential carriers, respectively, demonstrating the effectiveness of the BclI marker for the detection of HA carriers among the Azeri Turkish population.

Analysis of five polymorphic DNA markers for indirect genetic diagnosis of haemophilia A in the Brazilian population

Hemophilia A is an X-linked, inherited, bleeding disorder caused by the partial or total inactivity of the coagulation factor VIII (FVIII). Due to difficulties in the direct recognition of the disease-associated mutation in the F8 gene, indirect diagnosis using polymorphic markers located inside or close to the gene is used as an alternative for determining the segregation of the mutant gene within families and thus for detecting carrier individuals and/or assisting in prenatal diagnosis. This study characterizes the allelic and haplotype frequencies, genetic diversity, population differentiation and linkage disequilibrium of five microsatellites (F8Int1, F8Int13, F8Int22, F8Int25.3 and IKBKG) in samples of healthy individuals from São Paulo, Rio Grande do Sul and Pernambuco and of patients from São Paulo with haemophilia A to determine the degree of informativeness of these microsatellites for diagnostic purposes. The interpopulational diversity parameters highlight the differences among the analyzed population samples. Regional differences in allelic frequencies must be taken into account when conducting indirect diagnosis of haemophilia A. With the exception of IKBKG, all of the microsatellites presented high heterozygosity levels. Using the markers described, diagnosis was possible in 10 of 11 families. The F8Int22, F8Int1, F8Int13, F8Int25.3 and IKBKG microsatellites were informative in seven, six, five and two of the cases, respectively, demonstrating the effectiveness of using these microsatellites in prenatal diagnosis and in carrier identification in the Brazilian population.

Screening for hemophilia A carriers: utility of PCR-RFLP--based polymorphism analysis

Health schemes are promoting application of molecular diagnosis and screening in peripheral diagnostics labs. Intragenic restriction fragment length polymorphisms in the intron 18 (BclI), intron 19 (HindIII), and intron 22 (XbaI) of the Factor VIII gene were studied in 100 patients with hemophilia A and their relatives at risk from different regions of north India. For Bcl I, HindIII, and XbaI, the positive allele frequency was 0.57, 0.38, and 0.43, respectively, and heterozygosity was 0.54, 0.49, 0.41, respectively, whereas the heterozygosity in terms of informativity of the above markers was 53% for BclI, 44% for HindIII, and 34% for XbaI. Combined informativity of these markers was 77%. Review of Indian and world literature shows a marked variation in the informativity of polymorphic sites. Screening for carriers forms the baseline for prevention of hemophilia A. Polymerase chain reaction-restriction fragment length polymorphism is a low-cost procedure, efficient in the north Indian population.

The use of DNA markers for carrier detection and prenatal diagnosis of haemophilia A in Egyptian families

Haemophilia A is the most common inherited X-linked recessive bleeding disorder. The aim was to investigate the usefulness of two DNA markers in linkage analysis, one intragenic BCL1 affecting restriction site in intron 18, and is detected as restriction fragment length polymorphism (RFLP), and one extragenic variable number of tandem repeat (VNTR) locus DXS52 (St14) to formulate an informative and accurate carrier detection and prenatal diagnosis. The study included 46 families with at least one child affected with haemophilia A, and 30 unrelated normal females as control group. Polymerase chain reaction (PCR) and restriction enzyme analysis were used to study the polymorphism in BCL1, and long-distance PCR for detection of VNTR (ST14) alleles. The incidence of BCL1 (+) allele was 74%, 72% and 60% in patients, mothers and control group, respectively. Expected heterozygosity for BCL1 was 40% in mothers of affected cases compared with 48% in the female control group. However, observed heterozygosity was found to be 48% in the mothers of affected cases, compared with 60% in the control group. Thus, 48% of the studied families are informative for this marker alone. Nine different alleles of VNTR (St14) were observed in mothers and six alleles in affected cases and six in the control group. The most prevalent alleles were 1300 bp (45.5% and 34%) and 700 bp (13.6% and 20%) in patients and their mothers, respectively. Observed heterozygosity in mothers was 41% compared with 43.3% in controls. The combined use of both BCL1 and St14 markers raised the informative rate to 63.6%. Carrier detection and prenatal diagnosis is possible in haemophilia A families using both DNA markers. We suggest screening haemophilic families first for BCL1 polymorphism followed by analysis of St14 locus.

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

Genomic consequences of factor VIII gene haplotypes for the indirect genetic analysis of haemophilia A has not been done in India hitherto. Consequently, BclI/intron18, HindIII/intron 19, and XbaI/intron 22 restriction sites were investigated in 159 individuals from 42 families with hemophilia A. The frequencies of haplotype II, IV, VI, that is, BclI (+)-HindIII (-)- XbaI (+), BclI (+)HindIII (+)-XbaI (-), and BclI (-)-HindIII (-)-XbaI (+) were 0.312, 0.198, and 0.164 respectively. The high heterogeneity of haplotype II highlighted its potential for indirect genetic diagnosis of factor VIII. Analysis revealed strong but incomplete linkage disequilibrium (D' = 0.76, 0.68, and 0.51) between BclI/HindIII, HindIII/XbaI, and BclI/XbaI, respectively. The overall cumulative polymorphism information content (PIC) of these three markers increased from 0.36 to 0.80. Escalation of PIC up to 80% in the present study suggests that haplotyping of factor VIII gene determines better prognosis in the direction of indirect genetic analysis of hemophilia A.

HindIII polymorphism in carrier detection of hemophilia A in India: a new primer design

HindIII polymorphism studies were done in 67 north Indian families with hemophilia A using a new primer sequence and comparing results with the standard protocol. Amplified segment was 608 bp in size. Genetically positive hemizygous males (+) and homozygous females (+/+) showed 427, 100, and 81 size fragments, whereas heterozygous females (+/-) had 427, 181, 100, and 81-bp segments. Genotypically negative hemizygous (-) males and homozygous females (-/-) show that 427-bp and 181-bp fragments dimer formation was minimal and results matched with standard protocol in 20 cases where both polymerase chain reactions were run. The frequency of positive allele for HindIII polymorphism in 67 families was 0.38 and heterozygosity in terms of informativity was 0.46.

Haemophilia A: molecular insights

Haemophilia A is the most common inherited bleeding disorder caused by defects in the

Clin Chem Lab Med 2007;45:450–61.

Allele frequencies of three factor VIII gene polymorphisms in Iranian populations and their application in hemophilia A carrier detection

Hemophilia A is an X-linked recessive bleeding disorder caused by a quantitative or qualitative deficiency of blood coagulation factor VIII (FVIII). ARMS (amplification refractory mutation system) primers were designed to determine allele frequencies of three FVIII gene linked markers, IVS7 nt 27 G/A SNP, BclI/intron 18, and HindIII/intron 19 among 85 normal Iranian women from unrelated families. Then same method was applied to perform carrier detection for hemophilia A families. The allele frequencies of IVS7 nt 27 "G"/"A" allele, BclI "T"/"A" allele, and HindIII "C"/"T" allele among normal women were 0.88/0.12, 0.52/0.48, and 0.48/0.52, respectively. The three polymorphisms were found to be in strong linkage disequilibrium, which decreased the overall heterozygosity to 51%. Twenty-one women from 15 unrelated hemophilia A families were referred to us for hemophilia A carrier detection. Taking advantage of these three biallelic polymorphisms in conjunction with multiallelic St14 VNTR (locus DXS52), IVS13 (CA)n STR, and IVS22 (CA)n STR, carrier status was determined in 16 women (16/21 or 76% of the at-risk women) from 11 families (11/15 or 73% of the families). The used ARMS methods are rapid and can easily be applied in conjunction with other FVIII gene linked polymorphisms for indirect mutation detection of hemophilia A where they are informative.

A rapid multifluorescent polymerase chain reaction for genetic counselling in Chinese haemophilia A families

Linkage analysis is a widely used strategy for genetic counselling in haemophilia A (HA) families. We attempted to develop more informative markers closely linked to factor VIII (FVIII) gene and establish a rapid multifluorescent polymerase chain reaction (PCR) method with these markers. Five extragenic (DXS15, DXS9901, G6PD, DXS1073 and DXS1108) and one intragenic (F8Civs13) markers were examined in 118 healthy individuals and 12 HA families which had been diagnosed before. Five extragenic markers were within an interval of about 1.5 Mb to FVIII gene and located on each side of the gene. The expected heterozygote rate (HR) of DXS15, DXS9901, G6PD, DXS1073, DXS1108 and F8Civs13 were 74.97%, 79.77%, 56.06%, 59.92%, 39.97% and 47.61%, while the observed HR were 88.24%, 82.35%, 21.57%, 62.75%, 35.29% and 52.94%. When six polymorphic markers were combined together, all the studied females were informative in at least one of these markers and 29.41% of them were detected informative in three markers with the highest frequency. The diagnostic rates of DXS15, DXS9901, G6PD, DXS1073, DXS1108 and F8Civs13 in 12 haemophilia families were 75.00%, 91.67%, 41.67%, 75.00%, 33.33% and 66.67% respectively. All the genetic diagnosis was consistent with the result we analysed before and no recombination was observed. Family 1 was given as an example in this study and was found to be informative in three polymorphic markers DXS15, DXS9901 and DXS1073. The patient's sister was detected the same allele as the proband, but her male fetus did not inherit the affected allele from her, which was consistent with the result of sequencing. It was demonstrated that the multifluorescent PCR method established in this study was convenient and efficient and can be applied to carrier detection and prenatal diagnosis in HA families.

Identification of new dinucleotide-repeat polymorphisms in factor VIII gene using fluorescent PCR

Haemophilia A is an X-linked inherited bleeding disorder. Linkage diagnosis using polymorphic markers in the factor VIII gene is used to archive the carrier detection and prenatal diagnosis. The objective of this study was to establish the allele frequency and heterozygosity rate (HR) of two new intragenic markers (Intron 1 and 24) and other markers (Intron 13 and 22) using fluorescent PCR. Five hundred unrelated healthy women were screened and haemophilic family was studied for carrier detection and prenatal diagnosis. We observed five different alleles of Intron 1, 10 of Intron 24, nine of Intron 13 and six of Intron 22. The observed HR for Intron 1, 24, 13 and 22 were 34.0, 35.2, 53.0 and 42.6%, while the expected HR were 33.6, 36.3, 50.1 and 44.3%, respectively. Heterozygosity rate with the combined use of all four intragenic markers was 76.6% (383/500). In prenatal diagnosis of a haemophilic family, a pregnant woman was heterozygous with three intragenic (Intron 1, 13 and 22) and one extragenic St14 VNTR (DXS52) markers. She was considered to be a carrier, and she carried a male foetus by AMXY PCR and chromosome analysis of amniocytes. Foetus did not have mutant haplotype as his uncle, suggesting a normal male status. Our study demonstrates the utility of two new intragenic markers in FVIII gene for carrier detection and prenatal diagnosis of haemophilic families.

Informativeness of linkage analysis for genetic diagnosis of haemophilia A in India

The objective of this study was to assess the frequency of factor VIII (FVIII) gene intron 1 and intron 22 inversions and the informativeness of polymorphic markers for the genetic diagnosis of patients with haemophilia A (HA). Fifty unrelated patients with HA were first assessed for the intron 1 and intron 22 inversion mutations. Inversion-negative families were then screened for the bi-allelic intragenic markers--intron 7 G-->A polymorphism, HindIII site in intron 19 and XbaI site in intron 22 and the multiallelic dinucleotide CA repeat alleles in introns 13 and 22. The extragenic, multiallelic VNTR DXS52 (st14) was also analysed. Intron 22 inversion mutation was found in 38% (n = 19) of all patients and 46% of those with severe HA. Intron 1 inversion was found in one (2%) patient. Of the 30 inversion-negative families, XbaI site polymorphism was the single most informative marker (70%, n = 21/30) followed by HindIII (60%, n = 18/30), intron 13 CA repeats (56.66%, n = 17/30), intron 22 CA repeats (50%, n = 15/30), DXS52 VNTR (23.33%, n = 7/30) and intron 7 G-->A polymorphism (6.66%, n = 2/30). The combined use of these markers was informative in 92% (n = 46/50) of HA families. Based on the informativeness of these markers a comprehensive algorithm has been proposed for genetic diagnosis of HA in India.