Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Microarray evidence for off target effects and the optimisation of targeted RNAi mediated gene silencing in the cattle tick Rhipicephalus (Boophilus) microplus

ABSTRACT: The NimbleGen cattle tick custom microarray based on the BmiGI.V2 database of R. microplus ESTs was used to screen the resulting mRNA harvested from ticks treated with the tick Ubiquitin-63E 600bp dsRNA in comparison to controls. A total of 144 ESTs including TC6372 (Ubiquitin-63E) were down-regulated with 136 ESTs up-regulated following treatment. The results obtained substantiated the knockdown phenotype with ESTs identified as associated with ubiquitin proteolysis as well as oogenesis, embryogenesis, fatty acid synthesis and stress responses. A stringent bioinformatics analysis was undertaken to predict off target effects (OTE) resulting from the in silico dicing of the 600bp Ubiquitin-63E dsRNA which identified 10 down (including TC6372) and 13 up-regulated ESTs within the list of differentially expressed probes on the microarrays. Subsequent knockdown experiments utilising 196bp and 109bp dsRNAs, and a cocktail of short hairpin RNAs targeting Ubiquitin-63E demonstrated similar phenotypes for the dsRNAs but nil effect following shRNA treatment. Quantitative real time PCR analysis confirmed TC6372 and predicted off target differential expression. Our study demonstrates the effectiveness and specificity for utilising ~100bp dsRNA products for targeted tick gene knockdown with nil identified off targets. The microarray was conducted by NimbleGen Systems Inc following the method reported by Saldivar [Saldivar L et al., Insect Mol Biol 2008, 17(6):597-606]. Briefly, Custom high-density single channel oligonucleotide arrays were constructed by NimbleGen Systems Inc. using 13 601 of the 13 643 members of BmiGI Version 2 with 14 perfect match 50-mer probes per BmiGI target. No mismatched probes were included on the arrays, although probes with randomly generated sequences were included. These random sequence probes were designed to match the melting temperature (Tm) of the other probes on the array and to reflect the distribution of non-specific signal intensities for binding events to probes with approximately the same composition as the perfect match probes but with random sequences. The associated GEO dataset can be found online at http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GPL6373. Each microarray chip includes two in-slide replicates (spot replicates). In this experiment two biological replicates for each sample were hybridized to assess variability between individual samples. Each pooled sample consisted of 30 female adult ticks (N strain) as the source of RNA. Four technical replicates were processed, i.e. repeated measurements of the same pooled R. microplus mRNA, consisting of two chip replicates with two spot replicates. The chip replicates were hybridized on different dates to different chips, while spot replicates indicate the same probe was spotted on different locations on the chip. Four R. microplus samples were hybridized to separate microarrays at NimbleGen Systems Inc. (Madison, WI, USA). Data Processing: Statistical analysis Following array hybridization the raw intensity values were background corrected using convolution and normalized using quantile normalization to adjust for technical sources of variation. Final log2 expression intensities were generated using the Robust Multichip Average (RMA) algorithm [Irizarry et al.,Biostatistics 2003, 4:249-264]; [Groeneveld E, et al.,Proceedings 6th World Cong Genet Appl Livest Prod,: 1998; Armidale, NSW, Australia; 455-458] implemented in R. Differential expression was tested on the RMA normalized intensities using a mixed model of the form yijkr=?+BSrk+Gi+GTij+Eijkr where yijkr are the log2 RMA normalized signal intensities; i =gene, j=treatment, r=block, k=slide/array, the main fixed effect is BSrk (block by slide interaction), Gi is the main random effect of the gene; GTij is the random interaction term of the gene by treatment; E is just the error term; and normal assumptions for the random effects – iid are assumed. The model was fitted using VCE4.0 [Groeneveld E, et al., 1998]. Differentially expressed (DE) probes were considered as those which were three or more standard deviations away from the mean (p-value <0.001). The contrast of interest was the 600pb dsRNA microinjected ticks (R. microplus Ubiquitin-63E homologue as per Kurscheid et al 2009, BMC Molecular Biology 10:26) compared to normal untreated controls in order to examine the knockdown effect associated with phenotype. Kurscheid et al 2009 reported a strong knockdown phenotype following dsRNA knockdown and the subsequent differentially expressed ESTs were examined in this array experiment. The putative identities of the lists of up and down regulated tick sequences (DE probes) were then subsequently analysed using bioinformatic tools to predict function (described below). Bioinfomatics: Nimblegen tick microarray differentially expressed probes with fold changes >1.5 and p-value <0.001 were screened against the following databases on the CCG [Centre for Comparative Genomics: http://ccg.murdoch.edu.au], Grendel HPC system [Hunter A, et al.,Australasian Workshop on Grid Computing and e-Research 2005:2-3]; NCBI protein (nr and patent) [National Centre for Biotechnology Information: http://www.ncbi.nlm.nih.gov], String [Mering von C., et al.,Nucleic Acids Research 2006:00: D01-D05], COG [Tatusov R, et al., BMC Bioinformatics 2003, 4], tigr_bmigi.062608 [Wang et al.,BMC Genomics 8:368], NCBI Conserved Domain database [Goonesekere N, et al., Proteins 2008, 71(2):910-919], and KEGG (Kanehisa & Goto 2000 Nucleic Acids Res. 28, 27-30; Kanehisa et al 2006 Nucleic Acids Research 34, D354-D357; Kanehisa et al 2010 Nucleic Acids Research 38, D355-D360). Further analysis of differentially expressed transcripts identified in the microarray experiments was undertaken using the BLAST program suite (Altschul et al., 1997) for similarity searches in the UniProt database (TheUniProtConsortium, 2010 Nucleic Acids Res 38, D142-D148.) and in the protein sequence database of Ixodes scapularis tick (available from http://www.vectorbase.org/Ixodes_scapularis/Info/Index; last accessed 2010-11-21). The results of the blastx searches against the I. scapularis protein sequences where used to map the R. microplus ESTs to unique identifiers in the DAVID Bioinformatics Resource and perform a subsequent functional annotation to Gene Ontology terms in the categories “Biological Process (BP)”, “Cellular Component (CC)”, and “Molecular Functions (MF)” (Dennis et al 2003 Genome Biology 4: P3; Huang et al 2009 Nature Protoc. 4: 44-57.).

ORGANISM(S): Rhipicephalus microplus

SUBMITTER: Ala Lew-Tabor

PROVIDER: E-GEOD-27453 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Anti-tick vaccines have proved to be an effective and sustainable method for the control of tick infestations and tick-borne diseases with clear advantages over the application of chemical acaricides (Šmit and Postma, 2016; de la Fuente, 2018; Ndawula and Tabor, 2020). Moreover, the efficacy of acaricide application against Ornithodoros ticks is seriously limited owing to their endophilic/nidicolous life style, which make these ticks less accessible to the chemical acaricides (Astigaraga et al., 1995). Success in tick vaccine development is largely dependent on identification of new and highly protective tick antigens. Searching of new candidate protective antigens is currently being approached among tick molecules that play important biological functions at the tick-host interface, and more precisely among the salivary and intestinal proteins involved in biological processes specifically evolved by ticks to adapt to haematophagy (de la Fuente et al., 2016; Oleaga et al., 2021; Pérez-Sánchez et al., 2021). Accordingly, next-generation sequencing (NGS) and high-throughput proteomics technologies are been used to explore the transcriptome and proteome of the salivary glands/saliva and midguts of an increasing number of tick species and obtain the corresponding sialomes and mialomes (Chmelař et al., 2016; Almeida-Martins et al., 2020; Mans et al., 2020; Oleaga et al., 2021). These studies have identified a wealth of tick molecules related to tick haematophagy, tick-host interplay and pathogen transmission, which can then be scrutinized and filtered in vaccinomics pipelines for selecting candidate protective antigens (Chmelař et al., 2016; Maruyama et al., 2017; Antunes et al., 2018; de la Fuente et al., 2018; Ren et al., 2019; Couto et al., 2021). Similarly, we were also interested in characterizing the O. erraticus sialome. As far as O. erraticus saliva must contain all the bioactive molecules that the tick need to successfully feed, decoding its composition will lead to the discovery of new antigen targets for developing vaccines for the control and prevention of O. erraticus infestations and the diseases it transmits. Accordingly, the objective of the present work was to obtain the proteome of the saliva of O. erraticus adult ticks. For this, we have used a proteomics informed by transcriptomics approach to analyse female and male saliva separately using two different mass spectrometry approaches: liquid chromatography-tandem mass spectrometry (LC-MS/MS) in data-dependent acquisition (DDA) mode, and Sequential Window Acquisition of all Theoretical fragment ion spectra Mass Spectrometry (SWATH MS). SWATH MS is a specific variant of data-independent acquisition (DIA) methods that combines deep proteome coverage capabilities with quantitative consistency and accuracy (Ludwig et al., 2018). Here we reported the identification of 387 non-redundant proteins in the saliva of O. erraticus adult ticks as well as a qualitative and quantitative comparison of the saliva protein composition between both sexes. The integration of O. erraticus sialoproteomic and sialotranscriptomic datasets facilitate a better understanding of the physiology of feeding in O. erraticus and will drive the discovery of new and more effective antigen targets for development of anti-tick vaccines.

Project description:Ticks are among the most economically important arthropod parasites due to the heavy infestations they provoke, affecting human and animal health and food production. Ticks are also important vectors of pathogens, mediating the dispersion of livestock and zoonotic diseases. Some examples of livestock diseases vectored by ticks include bovine babesiosis, anaplasmosis, theileriosis, and/or heartwater disease, all of which are enlisted by the World Organization for Animals as possible threats to animals and public health. The family Ixodidae (hard ticks) is of veterinary relevance, and many ixodid tick species within the genera Ixodes, Dermacentor, Amblyomma, Haemophysalis, Hyalomma, and Rhipicephalus, among others, impact farming production worldwide. However, there is no doubt that most pernicious tick species is Rhipicephalus microplus, commonly known as the southern cattle fever tick. This specie is not only the major economically important tick parasite for livestock production, but it is also the vector of Babesia bovis and B. bigemina, the causal agents of babesiosis, a severe disease that affects cattle from tropical and subtropical regions. Currently, global economic losses of the cattle industry attributable to R. microplus are estimated at around $18.7 US billion dollars per year. The economic impact is the leading reason to develop different strategies to constrains R. microplus and its vector-borne pathogens, including chemical, mechanical or environmental treatments, biological control, and/or genetic methods. Chemical, among other methods, are the most frequently applied, but the intense use worldwide, has led to the selection of acaricidal-resistant ticks populations. The molecular adaptations of ticks to overcome the effects of acaricides (e.g., deltamethrin, cypermethrin, amitraz, ivermectin) includes metabolic detoxiﬁcation mechanisms and/or the selection of mutated molecular targets. Recently, a couple of systematic reviews pointed out a significant increment in the number of studies intended to understand the acaricidal resistance in ticks. These reports highlighted the acaricide resistance observed in R. microplus and the wide geographical dispersion of this problem. Whereas many acaricide-resistant R. microplus populations have been reported in Brazil, India, and Mexico, the lack of strict regulatory policies on tick control, leaving the application of acaricides at discretion of farmers. Therefore, the correct implementation of existing strategies together with novel sustainable control methods may be crucial to safeguard livestock production in the context of growing population and global warming. However, until the implementation of such sanitary measures becomes the rule, the main control strategy will still rely on the use of chemical acaricides, such as ivermectin (IVM). Ivermectin is an antiparasitic macrocyclic lactone used to control the populations of R. microplus and other ticks in livestock farming. As occurs in other countries, in Mexico ivermectin is the primary synthetic antiparasitic drug, and its abuse during the last three decades represents an important selection pressure that boosted the development of ivermectin-resistant populations of R. microplus. Therefore, the understanding of the molecular basis of the R. microplus resistance to ivermectin, especially in those cases occurring in tropical and subtropical areas of developing countries, can help to underpin the development of novel strategies to tackle this problem. In this context, omics tools can provide helpful information for the discovery of the molecular mechanisms behind the ivermectin resistance in R. microplus and other related tick species. Previous studies identified the main proteomic components of ovaries of R. microplus, including proteins involved in protein synthesis, post-translational modification, nuclear regulation, cytoskeleton, proteasome, transcriptional regulation, energetic metabolism, detoxification metabolism, or energy storage. Recently, the vitellogenin receptor (VgR) was suggested as a target for tick control because of its essential role in egg formation and maturation. However, molecular information on tick ovaries currently available limits explores the feasibility of VgR or other reproduction-related molecules as promissory targets for tick control.

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Microarray evidence for off target effects and the optimisation of targeted RNAi mediated gene silencing in the cattle tick Rhipicephalus (Boophilus) microplus

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