RESUMO
Asthma is an inflammatory airway disease characterized by increased serum IgE levels, mucus hypersecretion and infiltration of inflammatory cells, and is a multifactorial disease that exhibits genetic heterogeneity. Polymorphisms in the interleukin-4 (C-590T), interleukin-4 receptor (ile50val and gln576arg), and interleukin-13 (arg130gln) genes have been described as susceptibility alleles for asthma. This study was designed to determine whether asthma susceptibility is influenced by genotypic and allelic distribution of the above polymorphisms in three Mexican subpopulations. Four hundred and thirty-seven subjects from three Mexican subpopulations were classified into two groups: general population and affected/unaffected and genotyped for the above polymorphisms. We compared the distributions of the loci in the groups. In addition, we undertook association analysis between these loci and asthma phenotype in each affected/unaffected group, and determined Nei's genetic distance between the three subpopulations. The allelic and genotypic distributions of the polymorphisms differed between the three subpopulations. There was no association between any of the polymorphisms and asthma phenotype. However, there was a differential distribution of haplogroups (P < 0.0001) between the affected and the unaffected groups from the subpopulations of Jalisco and Guerrero. The genetic distribution of the four polymorphisms in the subpopulations did not influence susceptibility to asthma. Furthermore, the difference in the prevalence of asthma in these subpopulations is not attributable to the genetic background for the four polymorphisms analysed. However, haplogroup analysis suggests that the interaction of the polymorphisms and other predisposing alleles leads to the expression of the clinical phenotype.
Assuntos
Asma/genética , Interleucina-13/genética , Interleucina-4/genética , Polimorfismo Genético , Receptores de Interleucina-4/genética , Alelos , Etnicidade/genética , Feminino , Frequência do Gene , Haplótipos , Humanos , Masculino , México/etnologiaRESUMO
Recently we identified a P408S, P415L allele of beta-glucuronidase in several Mexican patients with mucopolysaccharidosis type VII (Sly syndrome) and presented evidence that both mutations are required to produce the MPS VII allele (Islam et al., 1996). In an attempt to determine whether either of these mutations exists as a benign polymorphism among Mexicans, we developed a PCR method to screen simultaneously for both mutations and used it to screen a population sample of 187 Mexican individuals in the Guadalajara area, all from the north-western states of Mexico. Neither mutation was present in 374 alleles studied. In addition, we had the opportunity to carry out prenatal diagnosis in a fetus at risk for homozygosity for this MPS VII allele at the 15th week of gestation using enzymatic assays as well as by analysis of genomic DNA isolated from cultured amniotic fluid cells. The fetus was found to be heterozygous for the P408S, P415L allele. The newborn's heterozygosity was confirmed after birth by enzyme assays on plasma and leukocytes, and by analysis of DNA from leukocytes.