Assembly and phylogeographic analysis of novel Taenia solium mitochondrial genomes reveal further differentiation between and within Asian and African-American genotypes
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Abstract
Background
Taenia solium is a parasite that hampers human health, causing taeniasis and cysticercosis. The genetic variability in its mitochondrial genome is related to the geographical origin of the specimen. Two main genotypes have been identified: The Asian and the African-American. The geographic genetic variability is expected to cause different clinical manifestations. Thus, characterizing differences between and within genotypes is crucial for completing the epidemiology of T. solium diseases.
Methods/Principal Findings
Here, two Peruvian (one complete and one partial; 7,811X and 42X of coverage, respectively) and one Mexican (complete, 3,395X) T. solium mitochondrial genomes were assembled using the Chinese reference. Variant calling with respect to the reference was performed. Thirteen SNPs that involved a change in the amino acid physicochemical nature were identified. Those were present in all the assembled genomes and might be linked to differences in aerobic respiration efficiency between Latin American (African-American) and Asian genotypes. Then, phylogeographic studies were conducted using Cytochrome C oxidase subunit I and cytochrome B from these genomes and other isolates. The analysis showed that Indonesian samples are the most ancient and related to the modern T. solium ancestor of the Asian genotype. Finally, a consistent subdivision of the African-American genotype into two subgroups was found. One subgroup relates to East African countries, while the other is West Africa. The East African linage suggests a previously unnoticed influence of the Indian Ocean trade in the genetic structure of Latin America T. solium .
Conclusions/Significance
Overall, this study reports novel mitochondrial genomes valuable for further studies. New Latin American SNPs were identified and suggest metabolic differences between parasites of the Asian and African-American genotypes. Moreover, the phylogeographic analysis revealed differences within each genotype that shed light on T. solium’s historical spread. Overall, the results represent an important step in completing T. solium genetic epidemiology.
Author Summary
Taenia solium is a human parasite that causes taeniasis and cysticercosis. Eradicated from developed countries, they are still a public health problem in developing nations. T. solium differences in the mitochondrial genetic material depend on its geographical origin. This is expected to cause different clinical manifestations. Despite the importance of genetics to the epidemiology of T. solium diseases, few efforts have been made to assemble and compare their genomes. We aimed to help fill this knowledge gap by assembling three mitochondrial genomes from Latin America and comparing them to the Chinese reference. Additionally, two genes from the Latin American genomes and from other isolates were employed to assess T. solium genetic distribution. We found thirteen mutations with respect to the Chinese genome present in all Latin American samples, which involved a change in the amino acid physicochemical nature. Those might be causing metabolic differences between Asian and Latin American parasites that could change their affinity to specific human tissues. Moreover, we determined that Indonesian samples are the most ancient and related to the modern T. solium ancestor. Finally, we identified a previously unnoticed influence of East African countries in T. solium phylogeny, with which our assembled genomes are closely related.
