Effect of GSK-3 activity, enzymatic inhibition and gene silencing by RNAi on tick oviposition and egg hatching.

Glycogen synthase kinase-3 (GSK-3) is classically described as a key enzyme involved in glycogen metabolism in mammals. It has been shown to be highly conserved among several organisms, mainly in the catalytic domain region. This enzyme has already been described in Rhipicephalus (Boophilus) microplus and the ovaries of females appeared to be the major site of GSK-3 transcription. The treatment with GSK-3 specific inhibitor (alsterpaullone, bromo-indirubin-oxime 6 and indirubin-3-oxime) caused a reduction in oviposition and egg hatching in completely engorged female ticks. The effect was more pronounced in partially engorged females when alsterpaullone was administrated by artificial capillary feeding. Moreover, GSK-3 gene silencing by RNAi in partially engorged females reduced significantly both oviposition and hatching. The study of tick embryogenesis and proteins that participate in this process has been suggested as an important means for the development of novel strategies for parasite control. GSK-3 is an essential protein involved in embryonic processes and for this reason it has already been suggested as a possible antigen candidate for tick control.