Yin Mingbo, Hu Wei, Mo Xiaojin, Wang Shengyue, Brindley Paul J, McManus Donald P, Davis George M, Feng Zheng, Blair David
National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, 207 Rui Jin Rd II, Shanghai 200025, PR China.
Int J Parasitol. 2008 Dec;38(14):1681-91. doi: 10.1016/j.ijpara.2008.05.015. Epub 2008 Jun 12.
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.
我们对大量在兔体内饲养的日本血吸虫成虫进行了基因分型（使用16或17个微卫星位点），这些兔暴露于来自中国几个地区少量自然感染钉螺的混合尾蚴。正如预期的那样，在这些虫体中发现了重复的多位点基因型（MLGs）。此外，发现的MLGs数量更多，通常非常相似，比用作尾蚴来源的钉螺还要多。这些结果的解释包括：（i）基因分型错误；（ii）每个受感染钉螺体内多个同胞毛蚴的发育；（iii）体细胞突变导致单个毛蚴产生基因不同的尾蚴。为了控制基因分型错误，我们重新分析了许多单个虫体的样本，包括重复最初的PCR。认为单个钉螺体内多个同胞毛蚴发育的解释不太可能正确，因为在主坐标分析中，几乎所有重复的MLGs都落在同性簇内。我们预计在多毛蚴感染中会同时出现雌雄两性。此外，我们让几只钉螺感染单个毛蚴。其中一只这样的钉螺通过实验感染的小鼠产生了48条成虫。通过重新基因分型证实，这些虫体中至少存在9个几乎相同的MLGs。我们认为体细胞突变是我们结果最可能的解释。本文讨论了多个MLGs对日本血吸虫群体遗传学研究的影响。
