Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru.
PLoS Negl Trop Dis. 2011 May 10;5(5):e1021. doi: 10.1371/journal.pntd.0001021.
Most of the Leishmania genome is reported to be constitutively expressed during the life cycle of the parasite, with a few regulated genes. Inter-species comparative transcriptomics evidenced a low number of species-specific differences related to differentially distributed genes or the differential regulation of conserved genes. It is of uppermost importance to ensure that the observed differences are indeed species-specific and not simply specific of the strains selected for representing the species. The relevance of this concern is illustrated by current study.
METHODOLOGY/PRINCIPAL FINDINGS: We selected 5 clinical isolates of L. braziliensis characterized by their diversity of clinical and in vitro phenotypes. Real-time quantitative PCR was performed on promastigote and amastigote life stages to assess gene expression profiles at seven time points covering the whole life cycle. We tested 12 genes encoding proteins with roles in transport, thiol-based redox metabolism, cellular reduction, RNA poly(A)-tail metabolism, cytoskeleton function and ribosomal function. The general trend of expression profiles showed that regulation of gene expression essentially occurs around the stationary phase of promastigotes. However, the genes involved in this phenomenon appeared to vary significantly among the isolates considered.
CONCLUSION/SIGNIFICANCE: Our results clearly illustrate the unique character of each isolate in terms of gene expression dynamics. Results obtained on an individual strain are not necessarily representative of a given species. Therefore, extreme care should be taken when comparing the profiles of different species and extrapolating functional differences between them.
大多数利什曼原虫基因组被报道在寄生虫的生命周期中持续表达，只有少数调节基因。种间比较转录组学证明，与差异分布基因或保守基因差异调节相关的物种特异性差异数量较少。至关重要的是要确保观察到的差异确实是物种特异性的，而不仅仅是代表物种选择的菌株的特异性。当前的研究说明了这一关注的重要性。
方法/主要发现：我们选择了 5 株具有不同临床和体外表型多样性的巴西利什曼原虫临床分离株。在整个生命周期的七个时间点上，对前鞭毛体和无鞭毛体阶段进行实时定量 PCR，以评估基因表达谱。我们测试了 12 个编码具有运输、基于硫醇的氧化还原代谢、细胞还原、RNA 多（A）尾代谢、细胞骨架功能和核糖体功能的蛋白质的基因。表达谱的总体趋势表明，基因表达的调节主要发生在前鞭毛体的静止期。然而，参与这种现象的基因在考虑的分离株之间似乎有很大的差异。
结论/意义：我们的结果清楚地说明了每个分离株在基因表达动力学方面的独特特征。在单个菌株上获得的结果不一定代表给定的物种。因此，在比较不同物种的图谱并推断它们之间的功能差异时，应格外小心。
