| Aneuploidy is a hallmark of most human tumors and is a poor prognostic marker. Mouse models of aneuploidy rely on altering the levels of proteins involved in the Spindle Assembly Checkpoint (SAC). The SAC is a mechanism by which the cells ensure faithful chromosome segregation to the two daughter cells during mitosis. Therefore, altering the levels of SAC components results in chromosome segregation errors and aneuploidy. An important caveat of aneuploidy models generated by altering the SAC proteins is that these proteins have well defined roles outside of mitosis also. Hence, it is unclear whether the tumor phenotypes observed in these aneuploidy models are a result of the generated aneuploidy or the impaired non-mitotic functions of the SAC proteins. The focus of my thesis project was to create a 'pure' aneuploidy model to shed light on the causality of aneuploidy on tumorigenesis.;We utilized a Cre-recombinase mediated strategy to delete chromosomes 9,10,12 and 14 in mouse embryonic fibroblasts (MEFs). Interestingly, while the aneuploid cells (which have lost the chromosomes) had an in vitro growth disadvantage relative to the control cells, they displayed a significantly enhanced tumor forming potential, as evidenced by larger, aggressive tumors with shorter latencies, when injected subcutaneously in the flanks of immuno-compromised mice. The aneuploid cells also displayed increased genomic instability, suggesting that the original chromosome loss could initiate an instability cascade, which endowed the aneuploid cells to evolve rapidly in unfavorable conditions in vivo..;Finally, we have adapted a previously published computational strategy to determine the contribution of losing a particular mouse chromosome to tumorigenesis. Additionally, we also established genetic crossing and screening strategies necessary to generate MEFs in which other chromosomes can be targeted for deletion. Combining these two approaches, it would be possible to study the consequences of losing specific chromosomes in addition to potentially uncovering general, chromosome loss mechanisms mediating tumor formation. |
