Major histocompatibility complex (MHC) class III genetics in two Amerindian tribes from Southern Brazil: the Kaingang and the Guarani

Abstract

Population genetic studies of the major histocompatibility complex (MHC) class III region, comprising C2, BF and C4 phenotypes, and molecular genetic data are rarely available for populations other than Caucasoids. We have investigated three Amerindian populations from Southern Brazil: 131 Kaingang from Ivaí (KIV), 111 Kaingang (KRC) and 100 Guarani (GRC) from Rio das Cobras. Extended MHC haplotypes were derived after standard C2, BF, C4 phenotyping and restriction fragment length polymorphism (RFLP) analysis with TaqI, together with HLA data published previously by segregation analysis. C2 and BF frequencies corresponded to other Amerindian populations. C4B*Q0 frequency was high in the GRC (0.429) but low in the Kaingang. Unusual C4 alleles were found, viz. C4A*58, A*55 and C4B*22 (presumably non-Amerindian) and aberrant C4A*3 of Amerindian origin occurring with a frequency of 0.223 in the GRC. C4A*3 bands of homo- and heterozygous individuals carrying this variant were Rodgers 1 positive and Chido 1,3 positive, showed a C4A specific lysis type and a C4A like alpha-chain. Polymerase chain reaction studies and sequencing showed that this is based on a C4A*3 duplication with a regular C4A*3 and a partially converted C4A*0304 carrying the C4B specific epitopes Ch 6 and Ch 1,3. Associations of class III haplotypes with particular RFLP patterns were similar to those reported for Caucasoids. The previously described association between combined C4A and CYP21P deletions and the 6.4 kb TaqI fragment was not seen in these Amerindians. This fragment occurred within a regular two locus gene structure in the Kaingang, representing a "short" gene at C4 locus I. C4 and CYP21 duplications were frequently observed. The distribution of extended MHC haplotypes provides evidence for a close relationship between the KIV and KRC and a larger genetic distance between the two Kaingang groups and the GRC.

Duplication of the CYP21A2 gene complicates mutation analysis of steroid 21-hydroxylase deficiency: characteristics of three unusual haplotypes

“…Haplotype F2, which has not been described before in the literature, has the rare feature of lacking a long C4 gene despite being multimodular. Bimodular (Hillarby et al 1990;Schneider 1990) and trimodular (Weg-Remers et al 1997) haplotypes without a long C4 gene have been previously found, but their frequency is very low in Caucasians.…”

Deficiency of mannan-binding lectin associated serine protease-2 due to missense polymorphisms

“…Approved consent, according to the Helsinki Declaration, was given by the blood donors before samples were drawn. The samples from Amerindians were from two tribes, Kaingang and Guarani, 39 the most numerous Indian tribes living in South Brazil. They are two different ethnic groups that differ culturally, and to some extent genetically, from each other.…”

Modular Variations of the Human Major Histocompatibility Complex Class III Genes for Serine/Threonine Kinase RP, Complement Component C4, Steroid 21-Hydroxylase CYP21, and Tenascin TNX (the RCCX Module)

“…Bimodular haplotypes with two CYP21A genes (haplotypes 3 and 6) and a monomodular haplotype with a CYP21A gene (haplotype 11) are present in CAH patients. In two Brazilian tribes, a fifth RCCX organization with two short C4 genes is found (60). This bimodular C4(S)-C4(S) combination (haplotype 13) is extremely rare in other ethnic groups.…”