Multiple near-identical genotypes of Schistosoma japonicum can occur in snails and have implications for population-genetic analyses |
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Authors: | Yin Mingbo Hu Wei Mo Xiaojin Wang Shengyue Brindley Paul J McManus Donald P Davis George M Feng Zheng Blair David |
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Institution: | aNational Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, 207 Rui Jin Rd II, Shanghai 200025, PR China;bChinese National Human Genome Center at Shanghai, 250 Bi Bo Road, Shanghai 201203, PR China;cDepartment of Microbiology, Immunology &; Tropical Medicine, George Washington University Medical Center, Ross Hall, 2300 Eye Street, NW, Washington, DC 20037, USA;dQueensland Institute of Medical Research, 300 Herston Road, Brisbane, Qld 4029, Australia;eSchool of Marine and Tropical Biology, James Cook University, Townsville, Qld 4811, Australia |
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Abstract: | We genotyped (using 16 or 17 microsatellite loci) numerous adult Schistosoma japonicum raised in rabbits exposed to pooled cercariae from small numbers of naturally infected snails from several localities in China. As expected, duplicate multi-locus genotypes (MLGs) were found among these worms. Additionally, many more MLGs, often near-identical, were found than snails used as sources of cercariae. Explanations for these results include (i) genotyping errors, (ii) development within each infected snail of multiple sibling miracidia and (iii) somatic mutation producing genetically varied cercariae from a single miracidium. To control for genotyping errors we re-analysed samples from many individual worms, including repeating the initial PCR. Explanations invoking the development of multiple sibling miracidia within a single snail are not likely to be correct because almost all duplicate MLGs fell within same-sex clusters in a principal coordinates analysis. We would expect both sexes to be represented in a multi-miracidium infection. In addition, we exposed several snails to infection by a single miracidium. One such snail, via an experimentally infected mouse, yielded 48 adult worms. The presence of at least nine near-identical MLGs among these worms was confirmed by re-genotyping. We regard somatic mutation as the most likely explanation for our results. The implications of multiple MLGs for population-genetic studies in S. japonicum are discussed. |
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Keywords: | China Clonal replication Genotyping Microsatellites Multi-locus genotype Oncomelania Schistosoma japonicum Somatic mutation |
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