BackgroundToxocara canis is the causative agent of toxocariasis of humans and other animals. This parasitic nematode (roundworm) has a complex life cycle, in which substantial developmental changes and switches occur. As small non-coding RNAs (sRNAs) are key regulators of gene expression in a wide range of organisms, we explored these RNAs in T. canis to provide a basis for future studies of its developmental biology as well as host interactions and disease at the molecular level.MethodsWe conducted high-throughput RNA sequencing and bioinformatic analyses to define sRNAs in individual male and female adults of T. canis.ResultsApart from snRNA and snoRNA, 560 and 619 microRNAs (miRNAs), including 5 and 2 novel miRNAs, were identified in male and female worms, respectively, without piRNAs being detected in either sex. An analysis of transcriptional profiles showed that, of 564 miRNAs predicted as being differentially transcribed between male and female individuals of T. canis, 218 miRNAs were transcribed exclusively in male and 277 in female worms. Functional enrichment analysis predicted that both male and female miRNAs were mainly involved in regulating embryonic morphogenesis, hemidesmosome assembly and genetic information processing. The miRNAs differentially transcribed between the sexes were predicted to be associated with sex determination, embryonic morphogenesis and nematode larval development. The roles of miRNAs were predicted based on gene ontology (GO) and KEGG pathway annotations. The miRNAs Tc-miR-2305 and Tc-miR-6090 are proposed to have roles in reproduction, embryo development and larval development, and Tc-let-7-5p, Tc-miR-34 and Tc-miR-100 appear to be involved in host-parasite interactions. Together with published information from previous studies, some miRNAs (such as Tc-miR-2861, Tc-miR-2881 and Tc-miR-5126) are predicted to represent drug targets and/or associated with drug resistance.ConclusionsThis is the first exploration of miRNAs in T. canis, which could provide a basis for fundamental investigations of the developmental biology of the parasite, parasite-host interactions and toxocariasis as well as applied areas, such as the diagnosis of infection/disease, drug target discovery and drug resistance detection.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1508-3) contains supplementary material, which is available to authorized users.
Toxocara canis is an intestinal nematode of canids with a worldwide distribution, causing an important but neglected parasitic zoonosis in humans. Aquaporins (AQP) are a family of water channel proteins, which function as membrane channels to regulate water homeostasis. In this study, the coding sequence of aquaporin-1 gene of T. canis (Tc-aqp-1) was cloned and characterized. The obtained Tc-aqp-1 coding sequence was 933 bp in length, which predicted to encode 311 amino acids. Two conserved asparagine-proline-alanine (NPA) motifs were identified in the multiple sequence alignments. Phylogenetic analysis revealed the closest relationship between T. canis and Opisthorchis viverrini based on aquaporin-1 amino acid sequence. A structure was predicted with ligand binding sites predicted at H93, N95, N226, L94, I79, and I210 and with active sites predicted at I256 and G207. Gene Ontology (GO) annotations predicted its cellular component term of integral component of plasma membrane (GO: 0005887), molecular function term of channel activity (GO: 0015250), and biological process term of water transport (GO: 0006833). Tissue expression analysis revealed that the Tc-aqp-1 was highly expressed in the intestine of adult male. The findings of the present study provide the basis for further functional studies of T. canis aquaporin-1.
Toxocara canis is a zoonotic parasite with worldwide distribution. ATP-binding cassette (ABC) transporters are integral membrane proteins which involve in a range of biological processes in various organisms. In present study, the full-length coding sequence of abcg-5 gene of T. canis (Tc-abcg-5) was cloned and characterized. A 633 aa polypeptide containing two conserved Walker A and Walker B motifs was predicted from a continuous 1902 nt open reading frame. Quantitative real-time PCR was employed to determine the transcriptional levels of Tc-abcg-5 gene in adult male and female worms, which indicated high mRNA level of Tc-abcg-5 in the reproductive tract of adult female T. canis. Tc-abcg-5 was expressed to produce rabbit polyclonal antiserum against recombinant TcABCG5. Indirect-fluorescence immunohistochemical assays were carried out to detect the tissue distribution of TcABCG5, which showed predominant distribution of TcABCG5 in the uterus (especially in the germ cells) of adult female T. canis. Tissue transcription and expression pattern of Tc-abcg-5 indicated that Tc-abcg-5 might play essential roles in the reproduction of this parasitic nematode.
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