Simple and convenient detection of a HindIII polymorphic site in intron 19 of factor VIII using PCR

A founder effect in hemophilia A patients from Russian Ural region with a new p.(His634Arg) variant in F8 gene

Hemophilia A is a clotting disease caused by defects in the F8 gene. A lot of them are described and most are unique or have polyphyletic origin. We here study the origin of a pathogenic variant found in a few patients. We sequenced F8 gene for seven hemophilia A patients from the Ural region, Sverdlovskaya oblast, Russia. We constructed haplotypes for them and for 21 hemophilia A patients with other defects from the same area as a control group using four previously described X-chromosome loci associated with F8 gene. We identified a new missense variant p.(His634Arg) in seven apparently unrelated patients with mild hemophilia A from Sverdlovskaya oblast. The haplotype analysis showed that all patients share the same haplotype, absent in the other patients, suggesting a founder effect. The most recent common ancestor for the p.(His634Arg) patients is estimated to exist around the end of XVII century; however, the 95% confidence interval spans from XII to early XX century. The Ural region did not suffer from the recent bottlenecks or isolation. Therefore, the founder effect could be a natural consequence of population structuring in a relatively stable population. We identified a founder effect mutation in hemophilia A, which is a quite rare event for this disease.

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.

Analysis of Factor VIII polymorphic markers as a means for carrier detection in Brazilian families with haemophilia A

Haemophilia A is an X-linked, recessively inherited bleeding disorder of varying severity, which results from the deficiency of procoagulant factor VIII f(8). Linkage diagnosis using polymorphic markers in the f8 gene is widely used to detect carriers. The objective of this study was to verify the informativeness of three polymorphic markers in the Brazilian population, to evaluate the usefulness of such markers in carrier detection procedures. Sixty-three unrelated healthy volunteers and 10 haemophilic families were studied. Two microsatellite repeats and one HindIII RFLP markers were used. Carrier and non-carrier status could be determined in 80% of females investigated. Intron 13 markers presented the highest heterozygosity rate (79%) followed by intron 22 (68%) and intron 19 (57%). When all three markers were used together, linkage analysis informativeness increased significantly. We conclude that these markers are suitable for carrier detection in the Brazilian population and we recommend their use in combination to maximize diagnostic efficiency.

Carrier detection and prenatal diagnosis in haemophilia in India: realities and challenges

Organizing services for haemophilia in developing countries with few resources is a formidable task. There is wide variation in haemophilia care and management between developing and developed countries. The management of a genetic disorder such as haemophilia becomes difficult in developing countries where scanty resources are allocated mainly to nutrition and infectious diseases as a first priority. In a country such as India, with one billion people and with a wide diversity in cultural, educational and financial conditions, educating people about such diseases is difficult and will take a long time to have an effect on attitudes. Meanwhile, attempts are being made at several centres in India to develop carrier detection and prenatal diagnosis for this disease. Counselling a carrier for detection of her carrier status remains problematic in India because marriages are still largely arranged by the parents of prospective brides and bridegrooms. Hence, the very idea of communicating the carrier status to the bridegrooms' families may lead to cancellation of the marriages, and concealing the carrier status is associated with guilt both for the bride's parents as well as the bride. Prenatal diagnosis and carrier detection in India therefore must be discussed in this context.

Factor VIII gene inversions and polymorphisms in Brazilian patients with haemophilia A: carrier detection and prenatal diagnosis

In families afflicted with haemophilia A, genetic counselling is often requested. Inversion mutations and polymorphic sites of the FVIII gene have been examined in a Brazilian population, with the aim of developing a strategy that would be accurate and informative for carrier analysis and prenatal diagnosis in Brazil. Patients with haemophilia A and families were studied. Inversion mutations in the FVIII gene were detected in 39.4% of severely affected patients, 85% of them being of distal type. No inversions were observed in patients with mild or moderate forms of the disease. Two bi-allelic polymorphisms were studied. Intron 18 SSCP and intron 19 RFLP analyses indicated the presence of a restriction site in 39.5% and 42.9% of haemophilics, respectively. Two multiallelic microsatellite polymorphisms in introns 13 and 22 were also studied; eight different alleles were detected in each system with a heterozygosity rate of 83.08% and 78.77%, respectively. When all four intragenic loci were examined in linkage analysis, the cumulative reliability was 100%. In conclusion, inversion mutation analysis should be the first-line test for Brazilian patients with severe haemophilia A. In cases of severe haemophilia A where no inversion could be detected or in mild or moderate haemophilia A, the use of all four polymorphisms is very informative for linkage analysis and should be used for carrier detection and genetic counselling in the Brazilian population.

Factor VIII gene polymorphisms in the Asian Indian population

Little is known about the heterozygous frequency of factor VIII gene markers in the Asian Indian population. The objective of this study was to establish the heterozygous frequency of polymorphic markers within and flanking the factor VIII gene in Indians and identify those most informative for carrier screening and prenatal diagnosis. Factor VIII gene polymorphism analysis at intragenic and extragenic sites was carried out by the polymerase chain reaction (PCR) method and Southern blot procedure. Sixty-three Asian Indian haemophiliacs and their families were screened. A control group of 150 women from nonhaemophilic families were screened for two markers, HindIII and BclI. Among the intragenic markers studied, the HindIII restriction fragment length polymorphism (RFLP) showed the highest heterozygous frequency (0.52) followed by the intron 13 (0.47) and intron 22 (0. 44) short tandem repeats (STRs). Among extragenic markers, TaqI had the highest heterozygous frequency (0.75) followed by BglII (0.54). The intron 22 inversion mutation was observed in eight (40%) of 20 severe cases. In the population studied the most diagnostic polymorphisms were the intragenic markers, intron 22 (70%) STR followed by the intron 13 (52%) STR and HindIII (52%) RFLP, and the TaqI (50%) extragenic marker. Application of HindIII, BclI and the intron 22 dinucleotide repeat combined were diagnostic in 87.2% of haemophilia A families studied.

Determination of haemophilia A carrier status from hair samples using polymerase chain reaction technique

The usefulness of intragenic restriction fragment length polymorphisms (RFLPs) for BclI, HindIII and XbaI, adapted for polymerase chain reaction (PCR), was tested for the detection of haemophilia A carrier status in the consultant of a family in which only haematological information was available on the inheritance of the trait. Hair follicles were used as the non-invasive source of DNA. The mother was found to be homozygous for BclI and heterozygous for HindIII sites, whereas her status as regards informativeness could not be established for XbaI. On the basis of HindIII RFLP, the daughter was found to be a carrier of the haemophilia trait. This was confirmed by sequencing the amplified intron 19 of the mother and the daughter. The RFLP for XbaI did not appear to be suitable for carrier detection using PCR due to the difficulty of establishing homozygosity or heterozygosity from the results of digestion of the amplified product.

Allele frequencies and molecular diagnosis in haemophilia A and B patients from Russia and from some Asian republics of the former U.S.S.R

RFLP analysis of some intra- and extra-genic polymorphic sites of Factor VIII (FVIII) and Factor IX (FIX) genes with relevant DNA probes or by polymerase chain reaction (PCR) was carried out in Slavic populations from the European part of Russia and also in the native ethnic groups of Uzbekistan and Kazahstan. The allele frequencies for the HindIII (intron 19) and XbaI (intron 22) polymorphic sites (PSs) in the FVIII gene were very similar in the two populations studied, but different for the intron 13 (CA)n repeat. Significant variations in the TaqI (intron d) and DdeI (intron a) polymorphisms of the FIX gene were evident between the Russian and Asian populations. Two unusual alleles (4.35 and 4.2 kb) for the extragenic PS St14/TaqI were registered in Slavs and one new allele (380 bp) for the DdeI polymorphic site of FIX was discovered in both Asian populations. Altogether, 210 haemophilia A (HA) and 24 haemophilia B (HB) families were subjected to molecular studies. So far, 160 HA and 12 HB families have been found to be informative for DNA analysis. Carrier status was ascertained in 42 HA and 6 HB female relatives, and rejected in 52 and 10 of them, respectively. The origin of some HA and HB mutations was traced with relevant polymorphic markers in several at-risk families. Prenatal diagnosis was accomplished in 28 HA and three HB families, resulting in the identification of 20 affected male fetuses.

A linkage between DNA markers on the X chromosome and male sexual orientation

The role of genetics in male sexual orientation was investigated by pedigree and linkage analyses on 114 families of homosexual men. Increased rates of same-sex orientation were found in the maternal uncles and male cousins of these subjects, but not in their fathers or paternal relatives, suggesting the possibility of sex-linked transmission in a portion of the population. DNA linkage analysis of a selected group of 40 families in which there were two gay brothers and no indication of nonmaternal transmission revealed a correlation between homosexual orientation and the inheritance of polymorphic markers on the X chromosome in approximately 64 percent of the sib-pairs tested. The linkage to markers on Xq28, the subtelomeric region of the long arm of the sex chromosome, had a multipoint lod score of 4.0 (P = 10(-5), indicating a statistical confidence level of more than 99 percent that at least one subtype of male sexual orientation is genetically influenced.

Molecular diagnosis of some common genetic diseases in Russia and the former USSR: present and future

The current state of molecular diagnosis of some common genetic diseases, including cystic fibrosis, Duchenne muscular dystrophy, haemophilia A and B, phenylketonuria, and thalassaemia, in Russia and elsewhere in the former USSR is reviewed. Data on carrier detection and prenatal diagnosis are presented and some objective problems and obstacles hampering efficient molecular diagnosis in Russia are discussed. The necessity for molecular diagnosis of some other inherited diseases (for example, von Willebrand's disease, Martin-Bell syndrome, polycystic kidney disease, Huntington's disease, and myotonic dystrophy) is stressed. The need for establishing new diagnostic centres dealing with the most common diseases, as well as rare genetic diseases, is substantiated. Perspectives on the implementation of new molecular methods and new technical approaches (preimplantation embryo diagnosis, fetal cells selected from maternal blood) are briefly outlined.

Identification of mutations in two families with sporadic hemophilia A

Direct sequencing of segments of the factor VIII gene in 30 hemophiliacs with sporadic disease (32+ kb of sequence in total) revealed two missense transitions: glutamate 1704 to lysine (E1704----K) in a patient with severe hemophilia A and proline 2300 to serine (P2300----S) in a patient with mild hemophilia. Both transitions are likely to be causative mutations because the amino acids affected were evolutionarily conserved. Haplotype and sequence analysis of the mother and grandparents of patient HA12 (E1704----K) indicate that the mutation arose in the grandfather who was 27 years old when his daughter was conceived. The origin of mutation in patient HA39 (P2300----S) could not be determined. As mutations that cause mild disease can be found in seemingly unrelated families, 96 unrelated hemophiliacs were screened rapidly for the P2300----S mutation with polymerase chain reaction (PCR) amplification of specific alleles (PASA). None of these patients had the mutation. PASA was also used to conveniently assess a polymorphic site in intron 7. The polymorphism is estimated to be informative in 13% of Korean females and in 23% of Western European females.