However, because of high similarities in miRNA sequences, computational algorithms may predict a large number of putative miRNA binding sites on mRNA targets [33] . Thus, experimental validation in biological system is fundamental to complete the target prediction [44] ; the currently available methods [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] are listed in Table 3 . Of these, antagomir studies or immunoprecipitation of Ago-bound mRNAs have been specifically developed for miRNA-mRNA studies. Antagomirs represent a novel class of chemically engineered oligonucleotides used to silence endogenous microRNAs [64, 65] . Immunoprecipitation is then based on the observation that each member of the Argonaute (Ago) protein family (catalytic components of the RNA-induced silencing complex) can bind to miRNAs and to partially complementary sequences in the 3'-UTR of specific target mRNAs. Thus, using highly specific monoclonal antibodies against members of the Ago protein family, Ago-bound mRNAs can be co-immunoprecipitated [66, 67] .