TY - JOUR
T1 - Genetic analyses of atypical Toxoplasma gondii strains reveal a fourth clonal lineage in North America
AU - Khan, Asis
AU - Dubey, J. P.
AU - Su, Chunlei
AU - Ajioka, James W.
AU - Rosenthal, Benjamin M.
AU - Sibley, L. David
N1 - Funding Information:
We thank Jack Remington (Stanford University Sch. Med., USA), Marie Laure Dardé (University of Limoges, France), and Jack Frenkel (Santa Fe, New Mexico, USA) for T. gondii isolates, Michael Grigg (NIH, Bethesda MD, USA) for helpful discussions, and Julie Nawas for technical assistance. This work was supported in part by a grant from the National Institutes of Health, USA ( AI059176 ).
PY - 2011/5
Y1 - 2011/5
N2 - Toxoplasma gondii is a widespread parasite of animals that causes zoonotic infections in humans. Previous studies have revealed a strongly clonal population structure in North America and Europe, while strains from South America are genetically separate and more diverse. However, the composition within North America has been questioned by recent descriptions of genetically more variable strains from this region. Here, we examined an expanded set of isolates using sequenced-based phylogenetic and population analyses to re-evaluate the population structure of T. gondii in North America. Our findings reveal that isolates previously defined by atypical restriction fragment length polymorphism patterns fall into two discrete groups. In one case, these new isolates represent variants of an existing lineage, from which they differ only by minor mutational drift. However, in the second case, it is evident that these isolates define a completely new lineage that is common in North America. Support for this new lineage was based on phylogeny, principle components analysis, STRUCTURE analyses, and statistical analysis of gene flow between groups. This new group, referred to as haplogroup 12, contains divergent genotypes previously referred to as A and X, isolated from sea otters. Consistent with this, group 12 was found primarily in wild animals, as well as occasionally in humans. This new lineage also has a highly clonal population structure. Analysis of the inheritance of multilocus genotypes revealed that different strains within group 12 are the products of a single recombination event between type 2 and a unique parental lineage. Collectively, the archetypal type 2 has been associated with clonal expansion of a small number of lineages in the North, as a consequence of separate but infrequent genetic crosses with several different parental lines.
AB - Toxoplasma gondii is a widespread parasite of animals that causes zoonotic infections in humans. Previous studies have revealed a strongly clonal population structure in North America and Europe, while strains from South America are genetically separate and more diverse. However, the composition within North America has been questioned by recent descriptions of genetically more variable strains from this region. Here, we examined an expanded set of isolates using sequenced-based phylogenetic and population analyses to re-evaluate the population structure of T. gondii in North America. Our findings reveal that isolates previously defined by atypical restriction fragment length polymorphism patterns fall into two discrete groups. In one case, these new isolates represent variants of an existing lineage, from which they differ only by minor mutational drift. However, in the second case, it is evident that these isolates define a completely new lineage that is common in North America. Support for this new lineage was based on phylogeny, principle components analysis, STRUCTURE analyses, and statistical analysis of gene flow between groups. This new group, referred to as haplogroup 12, contains divergent genotypes previously referred to as A and X, isolated from sea otters. Consistent with this, group 12 was found primarily in wild animals, as well as occasionally in humans. This new lineage also has a highly clonal population structure. Analysis of the inheritance of multilocus genotypes revealed that different strains within group 12 are the products of a single recombination event between type 2 and a unique parental lineage. Collectively, the archetypal type 2 has been associated with clonal expansion of a small number of lineages in the North, as a consequence of separate but infrequent genetic crosses with several different parental lines.
KW - Clonality
KW - Genotype
KW - Linkage disequilibrium
KW - Network analysis
KW - Phylogeny
KW - Population
UR - http://www.scopus.com/inward/record.url?scp=79954889434&partnerID=8YFLogxK
U2 - 10.1016/j.ijpara.2011.01.005
DO - 10.1016/j.ijpara.2011.01.005
M3 - Article
C2 - 21320505
AN - SCOPUS:79954889434
SN - 0020-7519
VL - 41
SP - 645
EP - 655
JO - International Journal for Parasitology
JF - International Journal for Parasitology
IS - 6
ER -