RESUMO
Screening for mutations at the G-6-PD gene by PCR-SSCP combined with restriction enzyme analysis and DNA sequencing was performed in nine G-6-PD deficient individuals with negative results for the presence of the most frequent G-6-PD mutations previously observed in Mexican population. The variants G-6-PD Valladolid(406T), G-6-PD Durham(713G), and G-6-PD Viangchan(871A) and four new G-6-PD mutant alleles were identified. The new mutations are located at cDNA nt 376 A --> T (126 Asn --> Tyr), nt 770 G --> T (257 Arg --> Leu), nt 1094 G --> A (365 Arg --> His), and nt 1285 A --> G (429 Lys --> Glu) and they were named G-6-PD San Luis Potosi, G-6-PD Zacatecas, G-6-PD Veracruz, and G-6-PD Yucatán, respectively. To date, a total of 18 different G-6-PD variants have been observed in Mexico and several of them are common in Africa, South Europe, and Southeast Asia.
Assuntos
Testes Genéticos , Glucosefosfato Desidrogenase/genética , Mutação Puntual , Sequência de Bases , Análise Mutacional de DNA , Variação Genética , Humanos , MéxicoRESUMO
Several years ago, a project aiming to determine (i) the molecular basis of G-6-PD deficiency, (ii) the distribution of four different mutant alleles previously detected, and (iii) the whole of polymorphic alleles that account for the overall prevalence of G-6-PD deficiency in Mexico was implemented. Nearly 5000 individuals-from the general population and patients with hemolytic anemia-belonging to at least 14 States were screened for G-6-PD deficiency. Seventy-six G-6-PD-deficient subjects were detected and the prevalence of G-6-PD deficiency in 4777 individuals from the general population was 0.71%. Screening for both mutations associated with enzyme deficiency and silent polymorphisms at the G-6-PD gene was performed in the enzyme-deficient individuals by PCR-SSCP combined with restriction enzyme analysis; the silent polymorphisms as well as the nondeficient variant G-6-PD A(376G) were also investigated in 366 G-6-PD normal individuals from the general population. In 88% of the enzyme-deficient individuals it was possible to define the mutation responsible and the type G-6-PD A- variants were the more common in both individuals from the general population and patients with hemolytic anemia. G-6-PD deficiency is heterogeneous at the DNA level in Mexico and up to date 10 different variants-8 in the present project and 2 previously-have been observed: G-6-PD A(-202A/376G), G-6-PD A(-376G/968C), G-6-PD Santamaria(376G/542T), G-6-PD Vanua Lava(383C), G-6-PD Tsukui(del561-563), G-6-PD "Mexico City"(680A), G-6-PD Seattle(844C), G-6PD Guadalajara(1159T),G-6-PD Nashville(1178A), and G-6-PD Union(1360T). The G-6-PD A(-) variants have a relatively homogeneous distribution and along with G-6-PD Santamaria(376G/542T), they account for 82% of the overall prevalence of G-6-PD deficiency in Mexico; all other seven variants represent 9% of the mutant alleles examined, and in the rest of the chromosomes the mutation responsible for the enzyme deficiency remains to be defined. Several of the variants observed in Mexico are common in Africa, South Europe, and Southeast Asia. The prevalence for the variant G-6-PD A(376G) was 1.64%. From 256 possible haplotypes only 14 were observed and haplotype analysis suggests that some of the G-6-PD variants probably were imported to Mexico by population flow from South Europe, Africa, and Southeast Asia. This work (i) identified the G-6-PD variants prevalent in Mexico, (ii) defines their geographical distribution, (iii) contributes to the knowledge of the genetic structure of the Mexican population, and (iv) will facilitate the molecular analysis of the G-6-PD gene in enzyme-deficient Mexican individuals.
Assuntos
Heterogeneidade Genética , Deficiência de Glucosefosfato Desidrogenase/genética , Análise Mutacional de DNA , Enzimas de Restrição do DNA , Frequência do Gene , Variação Genética , Geografia , Glucosefosfato Desidrogenase/análise , Glucosefosfato Desidrogenase/genética , Deficiência de Glucosefosfato Desidrogenase/diagnóstico , Haplótipos , Humanos , México/epidemiologia , Mutação PuntualRESUMO
Since no data have previously been reported concerning both the (TA) n polymorphism at the promoter of the UGT1A1 gene in the Mexican population and the use of single-strand conformation polymorphism (SSCP) for the detection of such polymorphism, genotyping by SSCP in 375 G-6-PD normal (Group A) and 81 G-6-PD-deficient (Group B) mestizos belonging to 14 states was carried out. Allele frequencies for (TA)6 and (TA)7 repeats were 0.654 and 0.334, respectively, in Group A and 0.685 and 0.315 in Group B; in the former group, the (TA)5 allele was also observed with a frequency of 0.012. The frequencies of the genotype (TA)7/(TA)7 were 10.1% (Group A) and 8.6% (Group B). The (TA)7/(TA)8 genotype was also observed in a patient with unconjugated hyperbilirubinemia. Due to the importance of its potential medical implications, the observed high frequency (10%) of the (TA)7/(TA)7 genotype is stressed. Genotyping by SSCP of the (TA) n polymorphism is an adequate methodological option.