Frequency of haplotypes in the beta globin gene cluster in a selected sample of the mexican population.

Abstract

Five polymorphic restriction enzyme sites in the beta globin gene cluster (HindIII Gγ-Hind III Aγ-, Ava IIINV-2 β-and Hpa I and Bam HI 3'β-globin gene) were studied in individuals from 13 families: 13 homozygote patients for sickle cell anemia, two double heterozygotes (one SC and one S/βThal ), 35 AS heterozygotes (23 parents and 12 siblings), one father (A/βThal ), and three normal siblings. In addition, 17 normal unrelated Mexican subjects were studied. All subjects were from the state of Veracruz on the coast of the Gulf of Mexico. The Southern blot technique was used. Fifteen haplotypes were identified in the 142 chromosomes. Five were the most frequent: two haplotypes, (+-+++) (52.4%) and (--+-+) (19.0%) were associated with βS chromosomes; two haplotypes, (--+++) (38.2%) and (---++) (19.7%), were linked with βA chromosomes, and the fifth (--++-) was present in both types of chromosomes. Haplotype (+-+++) corresponded to the Bantu or Senegal type. With Hinc II analysis after PCR amplification in both the 5' and 3' regions of the ψβ-globin gene, it was possible to distinguish between these African types, as in the former both restriction sites are absent. This analysis was done in 23 βS and 10 βA subjects. All βS chromosomes disclosed the Bantu type, while βA were similar to Caucasians. Bantu and Benin haplotypes have been found with high frequency in African populations, indicating the great influence of African genes in the population of the Mexican coasts. In addition, two previously unidentified haplotypes were found: (++--+) and (-++++). These can be explainded by crossing-over events and/or by new mutations. © 1995 Wiley-Liss, Inc.