Developmental Transcriptomic Features of the Carcinogenic Liver Fluke, Clonorchis sinensis

Clonorchis sinensis is the causative agent of the life-threatening disease endemic to China, Korea, and Vietnam. It is estimated that about 15 million people are infected with this fluke. C. sinensis provokes inflammation, epithelial hyperplasia, and periductal fibrosis in bile ducts, and may cause cholangiocarcinoma in chronically infected individuals. Accumulation of a large amount of biological information about the adult stage of this liver fluke in recent years has advanced our understanding of the pathological interplay between this parasite and its hosts. However, no developmental gene expression profiles of C. sinensis have been published. In this study, we generated gene expression profiles of three developmental stages of C. sinensis by analyzing expressed sequence tags (ESTs). Complementary DNA libraries were constructed from the adult, metacercaria, and egg developmental stages of C. sinensis. A total of 52,745 ESTs were generated and assembled into 12,830 C. sinensis assembled EST sequences, and then these assemblies were further categorized into groups according to biological functions and developmental stages. Most of the genes that were differentially expressed in the different stages were consistent with the biological and physical features of the particular developmental stage; high energy metabolism, motility and reproduction genes were differentially expressed in adults, minimal metabolism and final host adaptation genes were differentially expressed in metacercariae, and embryonic genes were differentially expressed in eggs. The higher expression of glucose transporters, proteases, and antioxidant enzymes in the adults accounts for active uptake of nutrients and defense against host immune attacks. The types of ion channels present in C. sinensis are consistent with its parasitic nature and phylogenetic placement in the tree of life. We anticipate that the transcriptomic information on essential regulators of development, bile chemotaxis, and physico-metabolic pathways in C. sinensis that presented in this study will guide further studies to identify novel drug targets and diagnostic antigens.

华支睾吸虫（Clonorchis sinensis）是一种致死性疾病的病原体，该疾病流行于中国、韩国及越南。据估算，全球约有1500万人感染此吸虫。华支睾吸虫可引发胆管炎症、上皮增生与胆管周围纤维化，慢性感染者还可能诱发胆管细胞癌。近年来，针对该肝吸虫成虫阶段的大量生物学信息被积累，推动了学界对该寄生虫与宿主间病理相互作用的认知。然而，目前尚无华支睾吸虫的发育基因表达谱的相关研究发表。本研究通过分析表达序列标签（expressed sequence tags，ESTs），构建了华支睾吸虫三个发育阶段的基因表达谱。研究人员从华支睾吸虫的成虫、囊蚴及虫卵三个发育阶段构建了互补DNA（cDNA）文库。共计获得52745条EST序列，经组装得到12830条华支睾吸虫组装EST序列，随后依据生物学功能与发育阶段对这些组装序列进行分类。不同发育阶段差异表达的多数基因与对应发育阶段的生物学及生理特征相符：成虫阶段高表达高能量代谢、运动与繁殖相关基因；囊蚴阶段高表达低代谢与终宿主适应相关基因；虫卵阶段则高表达胚胎发育相关基因。成虫体内葡萄糖转运蛋白、蛋白酶及抗氧化酶的高表达，使其能够高效摄取营养并抵御宿主免疫攻击。华支睾吸虫所携带的离子通道类型与其寄生生活方式及系统发育地位相符。我们预期，本研究中呈现的华支睾吸虫发育调控、胆管趋化性及生理代谢通路关键调控因子的转录组信息，将为后续筛选新型药物靶点与诊断抗原的研究提供重要指导。