Polymorphism distribution of Int13, Int22, and St14 VNTRs in a Mexican population and their application in carrier diagnosis of hemophilia A.

Variable nucleotide tandem repeats (VNTR) Int13, Int22, and St14 were analyzed to determine polymorphic distribution in normal individuals from Mexico's central region and their efficacy in detecting hemophilia A carriers. Polymerase chain reaction (PCR) was carried out on 166 X chromosomes from unrelated Mexicans, and the same method was applied to detect carriers in hemophilia A families. Screening revealed the existence of at least eight different alleles for Int13, 4 alleles for Int22, and 10 alleles for St14. Their heterozygosity rates were 41.3%, 52.6%, and 83%, respectively. Compared to Caucasians, the Mexican population showed a markedly low heterozygosity rate for the Int13 marker. However, Int22 showed a heterozygosity that was similar to Turkish and Chinese populations. The St14 marker was the most informative in carrier diagnosis, and a new 680-bp allele not previously reported was detected. Carrier diagnosis was performed in 39 women from eight different hemophilia A families. Fifteen (38%) females were not carriers, 16 (41%) females were carriers, and 8 (21%) were homozygous. Determination of polymorphisms in VNTR markers revealed that St14 was the most useful for hemophilia A carrier detection in Mexico.