title: Evidence of substantial recombination among Trypanosoma cruzi II strains from Minas Gerais.
abstract: Due to the scarcity of evidence of sexuality in Trypanosoma cruzi, the causative agent of Chagas disease, it has been general accepted that the parasite reproduction is essentially clonal with infrequent genetic recombination. This assumption is mainly supported by indirect evidence, such as Hardy-Weinberg imbalances, linkage disequilibrium and a strong correlation between independent sets of genetic markers of T. cruzi populations. However, because the analyzed populations are usually isolated from different geographic regions, the possibility of population substructuring as generating these genetic marker imbalances cannot be eliminated. To investigate this possibility, we firstly compared the allele frequencies and haplotype networks using seven different polymorphic loci (two from mitochondrial and five from different nuclear chromosomes) in two groups of TcII strains: one including isolates obtained from different regions in Latin America and the other including isolates obtained only from patients of the Minas Gerais State in Brazil. Our hypothesis was that if the population structure is essentially clonal, Hardy-Weinberg disequilibrium and a sharp association between the clusters generated by analyzing independent markers should be observed in both strain groups, independent of the geographic origin of the samples. The results demonstrated that the number of microsatellite loci in linkage disequilibrium decreased from 4 to 1 when only strains from Minas Gerais were analyzed. Moreover, we did not observed any correlation between the clusters when analyzing the nuclear and mitochondrial loci, suggesting independent inheritance of these markers among the Minas Gerais strains. Besides, using a second subset of five physically linked microsatellite loci and the Minas Gerais strains, we could also demonstrate evidence of homologous recombination roughly proportional to the relative distance among them. Taken together, our results do not support a clonal population structure for T. cruzi, particularly in TcII, which coexists in the same geographical area, suggesting that genetic exchanges among these strains may occur more frequently than initially expected.
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Rodrigo de Paula
authors.initials: Rde P
authors.lastname: Baptista
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Daniella Alchaar
authors.initials: DA
authors.lastname: D'Ávila
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Marcela
authors.initials: M
authors.lastname: Segatto
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Ítalo Faria
authors.initials: ÍF
authors.lastname: do Valle
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Glória Regina
authors.initials: GR
authors.lastname: Franco
authors.affiliation: Universidade Federal de São João del-Rey, Campus Centro-Oeste Dona Lindu, Divinópolis, Minas Gerais, Brazil.
authors.forename: Helder Magno Silva
authors.initials: HM
authors.lastname: Valadares
authors.affiliation: Departamento de Medicina Preventiva e Social, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Eliane Dias
authors.initials: ED
authors.lastname: Gontijo
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil; Centro de Ciências da Saúde, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil.
authors.forename: Lúcia Maria da Cunha
authors.initials: LM
authors.lastname: Galvão
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Sérgio Danilo Junho
authors.initials: SD
authors.lastname: Pena
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Egler
authors.initials: E
authors.lastname: Chiari
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. Electronic address: crmachad@icb.ufmg.br.
authors.forename: Carlos Renato
authors.initials: CR
authors.lastname: Machado
authors.affiliation: Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. Electronic address: andrea@icb.ufmg.br.
authors.forename: Andréa Mara
authors.initials: AM
authors.lastname: Macedo
mesh_terms: D001938:Brazil; D014355:Chagas Disease / Q000469:parasitology*; D016054:DNA, Protozoan / Q000032:analysis / Q000235:genetics; D006239:Haplotypes; D006801:Humans; D015810:Linkage Disequilibrium / Q000235:genetics; D018895:Microsatellite Repeats / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics*; D014349:Trypanosoma cruzi / Q000145:classification* / Q000235:genetics*
chemical_list: D016054:DNA, Protozoan
keywords: Clonality; Population substructuring; Recombination; Sex reproduction; Trypanosoma cruzi II; Wahlund effect