FIG. 2.

Schematic representation of constitutive, conditional, and inducible knockout mouse models. (A) In a wild-type mouse, the GOI is functional. In a constitutive knockout mouse the GOI is not functional and therefore not expressed. The generated Tg-mouse might show phenotypic changes, depending on which gene has been knocked out. (B) In a tissue-specific knockout mouse the GOI is not functional in a specific tissue, while normal gene functionality is detected in the rest of the organism. In the cartoon the red targeted area illustrates that the gene is inactivated only in tendon tissues such as in the tail and Achilles tendons. (C) Inducible knockout systems allow the inactivation of a GOI by the addition of an inducer (in defined doses) at a given time point and within a specific tissue, before that, gene of interest is functional. Figure was adapted from [154–156]. GOI, gene of interest