Prevalence of −α3.7 and αααanti3.7 alleles in sickle cell trait and β-thalassemia patients in Mexico

The aim of this study was to determine the frequency of α-globin gene mutations in three groups of Mexican unrelated individuals. The first two groups were normal and sickle cell trait individuals from the Costa Chica region, a place with a 12.8% frequency of HbS carriers, and the third group comprised of Mexican mestizo patients with β-thalassemia. We searched for −α3.7 and −α4.2 α+-thalassemia deletion alleles, as well as the αααanti3.7 triplication through long-gap PCR. The alleles −α3.7 and αααanti3.7 were found in the heterozygote state only; 19% of the normal subjects had the −α3.7 allele, and 2% showed the αααanti3.7 allele. In individuals with the sickle cell trait, 17% had the −α3.7 deletion, and the αααanti3.7 triplication was observed in 3% of these individuals. We revealed that 16% of the subjects with β-thalassemia showed the −α3.7 deletion and 28% the αααanti3.7 triplication. The −α4.2 deletion was not detected in any individual. The frequency of the −α3.7 allele was roughly the same in the three groups studied; this can be explained by the fact that the three groups have common genes from Africa and the Mediterranean, where a high prevalence of α+-thalassemia has been observed. To our knowledge, the frequency of αααanti3.7 triplication observed in the Mexican β-thalassemia patients is the highest reported. As the −α3.7 and αααanti3.7 alleles are very common in our selected populations, we believe that there is a need to investigate systematically the α-globin gene mutations in all hemoglobinopathies in the Mexican population.