Molecular analysis of HLA class I alleles in the Mexican Seri Indians: implications for their origin

Abstract

The molecular analysis of HLA class I loci has demonstrated that, although, the genetic profile is restricted in Amerindians, several micropolymorphisms may be important in conferring a biological advantage. We analyzed the HLA-A and B genetic profile of Seris, a Mexican Indian tribe living in northwestern Mexico in the state of Sonora. There are presently only 619 individuals. Our study included 100 Seris belonging to nine families. HLA-A and -B loci typing was performed by polymerase chain reaction using an amplification refractory mutation system (PCR-ARMS) on a select group of samples; all of them were typed by polymerase chain reaction using sequence-specific oliogonuoleotide probes (PCR-SSOP) at a low-intermediate resolution level. The correlation between the techniques was 100%. Only five HLA-A alleles and seven HLA-B alleles were found. A*0201, A*68, A*31, A*24, B*3501, B*40, B*51, B*3512 and B*15 were present in over 5% of the individuals. B*27052 was detected in 2%. B27 is absent in any other Mexican Indian groups previously studied. The presence of B27 may be the result of a founder effect due to different waves of southward migrations. The B-locus is more diverse and the prevalent haplotypes were: A*0201-B*3501, A*0201-B*40, A*0201-B*3512, A*31-B*51, A*68-B*3501 and A*68-B*40. This genetic profile is different from the pattern of other Mexicans. The phylogenetic tree suggests that Seris are more closely related to the Warao Indians from Venezuela, who live in a similar ecosystem, and to some groups of Argentina, than they are to the Mexican Lacandones who live in the jungle. These data emphasize the relevance of the interaction between genes and environment.

Molecular analysis of HLA‐DRB1, DQA1, DQB1, DQ promoter polymorphism and extended class I/class II haplotypes in the Seri Indians from Northwest Mexico

“…Data from 24 individuals were used to confirm these haplotypes and frequencies were assessed by direct counting with data from the 48 chromosomes. Class I alleles were previously typed in 22 Seri (36); thus Table 3 includes the extended class I/II haplotypes assembled that were also confirmed by verification in family members. The classical method (46) to test whether every genotype met the Hardy–Weinberg equilibrium for each analyzed locus was used to demonstrate if the system was in genetic equilibrium.…”

“…All of them, except Seri, belonged to the same linguistic group. The latter belong to the Hokano‐Coahuitleca family, and their general characteristics have been described previously (36). They have intimate knowledge of the sea and desert and can predict the movement of the currents, tides and winds for their own benefit.…”

“…Twenty‐two of these samples also had results from HLA‐A and HLA‐B molecular typing and were used to define class I and class II extended combinations for these samples. The genealogies of these families were published previously (36).…”

“…In the present study, we analyzed class II loci in a Mexican Indian group from the state of Sonora, for which the genetic pattern of class I loci was published previously (36). The Seri are one of the 68 Mexican native groups.…”

Distribution of TAP gene polymorphisms and extended MHC haplotypes in Mexican Mestizos and in Seri Indians from northwest Mexico

“…The subjects included herein were unrelated individuals; the spouses of each of the nine families plus 14 truly unrelated subjects were included to determine allele frequencies; the family pedigrees were shown in the class I paper. 66 The Mestizos: A group of 89 unrelated individuals was included. The group was formed by volunteers, students and blood bank donors.…”