Identification of microRNAs in the West Nile virus vector Culex tarsalis

Background: microRNAs (miRNAs) represent a group of small non-coding RNAs that are crucial gene regulators of important biological functions including development and pathogen defense in most living organisms. Presently, there is a lack of availability of information regarding the miRNAs in the mosquito Culex tarsalis, which is one of the most important vectors of West Nile virus (WNV) in the United States. We used small RNA sequencing data and in vitro and in vivo experiments to identify and validate the presence of a repertoire of miRNAs in Cx. tarsalis mosquitoes. Results: Using bioinformatic approaches we analyzed small RNA sequencing data from the Cx. tarsalis CT embryonic cell line to discover 86 miRNAs. Consistent with other mosquitoes such as Aedes albopictus and Cx. quinquefasciatus, mi-184 was found to be the most abundant miRNA in Cx tarsalis. We also identified an additional 20 novel miRNAs from the recently sequenced Cx. tarsalis genome, for a total of 106 miRNAs identified in this study. The presence of selected miRNAs was biologically validated in both cell line and adult Cx. tarsalis mosquitoes using RT-qPCR and sequencing. Conclusions: Cx. tarsalis is an important vector of many medically important pathogens including WNV and Western Equine encephalitis. Here we report a detailed insight into the miRNA population in Cx. tarsalis mosquitoes. These results will open new avenues of research deciphering the role of miRNAs in different Cx. tarsalis biological events such as development, metabolism, immunity and pathogen infection.