Extreme inbreeding in Leishmania braziliensis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 25; pp. 10224 - 10229
• Main Authors: Rougeron, Virginie, De Meeûs, Thierry, Hide, Mallorie, Waleckx, Etienne, Bermudez, Herman, Arevalo, Jorge, Llanos-Cuentas, Alejandro, Dujardin, Jean-Claude, De Doncker, Simone, Le Ray, Dominique, Ayala, Francisco J, Bañuls, Anne-Laure
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 23-06-2009; National Acad Sciences
• Subjects: Animals; Biological Sciences; Bolivia; Genetic diversity; Genetic loci; Genetics; Genotype & phenotype; Heterozygote; Humans; Inbreeding; Leishmania braziliensis; Leishmania braziliensis - genetics; Life Sciences; Linkage Disequilibrium; Medical genetics; Microbiology and Parasitology; Microsatellite Repeats - genetics; Microsatellites; Parasites; Parasitic protozoa; Parasitism; Peru; Polymorphism; Polymorphism, Genetic; Population genetics; Population structure; Reproduction - genetics; Viannia; Bolivia; Peru
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0904420106

Leishmania species of the subgenus Viannia and especially Leishmania braziliensis are responsible for a large proportion of New World leishmaniasis cases. The reproductive mode of Leishmania species has often been assumed to be predominantly clonal, but remains unsettled. We have investigated the genetic polymorphism at 12 microsatellite loci on 124 human strains of Leishmania braziliensis from 2 countries, Peru and Bolivia. There is substantial genetic diversity, with an average of 12.4 ± 4.4 alleles per locus. There is linkage disequilibrium at a genome-wide scale, as well as a substantial heterozygote deficit (more than 50% the expected value from Hardy-Weinberg equilibrium), which indicates high levels of inbreeding. These observations are inconsistent with a strictly clonal model of reproduction, which implies excess heterozygosity. Moreover, there is large genetic heterogeneity between populations within countries (Wahlund effect), which evinces a strong population structure at a microgeographic scale. Our findings are compatible with the existence of population foci at a microgeographic scale, where clonality alternates with sexuality of an endogamic nature, with possible occasional recombination events between individuals of different genotypes. These findings provide key clues on the ecology and transmission patterns of Leishmania parasites.