In vivo target validation using gene invalidation, RNA interference and protein functional knockout models: it is the time to combine

Most diseases have multifactorial origins and their study requires complex in vivo validation strategies selected for their particular relevance. Most of the in vivo models used to date have been selected according to their availability and the accessibility of the corresponding technology platform. With the rapid development of new technologies, an increasing number of relevant systems for in vivo target validation are now available. In this review, we present in vivo loss-of-function tools acting at three biological levels (the gene, the messenger RNA and the protein); we discuss the specificity of each strategy and how the three techniques can be combined during the validation process in order to overcome the limitations of each one. Thus, combination will broaden the spectrum of the available validation systems and will enable target validation that predicts the situation in humans as accurately as possible.