Centrosomes organize the microtubule cytoskeleton in mitosis and interphase. cell routine arrest (15), whereas traveling centrosome amplification in mice mind results in a developmental lack of Canagliflozin pontent inhibitor neural stem cells by p53-reliant apoptosis (16). Greater than a hundred years ago, Boveri suggested a link between acquisition of too many centrosomes and tumorigenesis (17). TLR2 Nevertheless, whether and how centrosome amplification impacts mammalian tumor development remains untested. Here we have developed a mouse model in which centrosome amplification can be induced by Cre-recombinaseCmediated elevation in Plk4 expression. In the presence of the p53 tumor suppressor, widespread elevation of Plk4 drove the production and accumulation of too many centrosomes in liver and skin cells, but this did not accelerate tumorigenesis. Chronic elevation of Plk4 levels in mice without functional p53 produced widespread accumulation of cells with centrosome amplification. Even here, however, centrosome amplification did not drive new tumors or affect the development of thymic tumors driven by loss of p53. Thus, in either the presence or the absence of p53, centrosome amplification is not a universal driver of tumor development in mammals. Results Creation of a Mouse Model to Study the Effects of Centrosome Amplification. Centrosome duplication is controlled by Polo-like kinase 4 (Plk4), and increased expression of Plk4 gives rise to the formation of multiple centrosomes in the same cell cycle (15, 18C21). To establish the effects of centrosome amplification in vivo, we developed a transgenic mouse line in which murine Plk4-EYFP could be conditionally increased in cells after expression of Cre recombinase (Fig. 1and Fig. S1panel presenting heart tissue lysates also appears in Fig. 1and and Fig. S1and and 0.005; value of unpaired test calculated on the mean values from five and six independent measurements. ( 0.01; value of unpaired test calculated on the mean values from five and six independent measurements. ( 0.01; value of unpaired test calculated on the mean values from five and six impartial measurements. (and and = 3 Plk4 OE (+) mice and = 5 nontransgenic controls (?). (= 3 Plk4 OE (+) mice and = 6 nontransgenic controls (?). A minimum of 107 centrin-positive cells were counted for each data point. To visualize centrosomes in tissue sections, we introduced a Rosa26-targeted, lox-STOP-lox-Centrin 1-GFP construct into Plk4 OE;ERT-Cre animals. In triply transgenic animals (Plk4 OE;ERT-Cre;Centrin-GFP), the action of Cre inactivates H2B-mRFP expression and activates both Plk4 and Centrin-GFP expression, the latter providing a marker to count centrosomes in cells exposed to active Cre (Fig. 3and and = 3 mice with Plk4 OE (+) and = 6 nontransgenic control mice (?). (= 3 mice with Plk4 OE (+) and = 6 nontransgenic animals (?). A minimum of 86 centrin-positive cells were counted for each animal. (= 2 mice with Plk4 OE (+) and = 3 nontransgenic mice (?). A minimum of 25 centrin-positive cells were counted for Canagliflozin pontent inhibitor each animal. (and and Fig. S2and Canagliflozin pontent inhibitor and Fig. S2 and and and and Fig. S3 and = 4 animals for each group. * 0.05; value of unpaired test calculated around the mean values from four impartial measurements. (= 6 mice with Plk4 OE activation and = 6 without Plk4 OE activation. ns, 0.05; value of unpaired test calculated around the mean values from six impartial measurements. A minimum of 177 centrin-positive cells Canagliflozin pontent inhibitor were counted for each animal. (= 15 mice with tamoxifen treatment and = 9 without tamoxifen treatment. (= 6 mice for tamoxifen-induced and = 4 for uninduced. * 0.05; value of unpaired test calculated around the mean values from four and six indie measurements. (= 6 mice with Plk4 OE.