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Raaijmakers, J. A.

Publications and source records attributed to Raaijmakers, J. A..

3 recordsLinked to original sources

Reduction of chromosomal instability and inflammation is a common aspect of adaptation to aneuploidy

Aneuploidy, while detrimental to untransformed cells, is notably prevalent in cancer cells. This indicates that cancer cells have the ability to surmount the initial stress responses associated with aneuploidy, enabling rapid proliferation despite aberrant karyotypes. To generate more insight into key processes and requirements underlying the adaptation to aneuploidy, we generated a panel of aneuploid clones in p53-deficient RPE-1 cells and studied their behavior over time. As expected, de novo generated aneuploid clones initially displayed reduced fitness, enhanced levels of chromosomal instability and an upregulated inflammatory response. Intriguingly, after a prolonged period of culturing, aneuploid clones exhibited increased proliferation rates while maintaining aberrant karyotypes, indicative of an adaptive response to the aneuploid state. Interestingly, all adapted clones displayed reduced chromosomal instability (CIN) and reduced inflammatory signaling, suggesting that these are common aspects of adaptation to aneuploidy. Collectively, our data suggests that CIN and concomitant inflammation are key processes that require correction to allow for fast growth. Finally, we provide evidence that amplification of oncogenic KRAS can promote adaptation.

cell biology↗

Monosomies, trisomies and segmental aneuploidies differentially affect chromosomal stability

Aneuploidy and chromosomal instability are both commonly found in cancer. Chromosomal instability leads to karyotype heterogeneity in tumors and is associated with therapy resistance, metastasis and poor prognosis. It has been hypothesized that aneuploidy per se is sufficient to drive CIN, however due to limited models and heterogenous results, it has remained controversial which aspects of aneuploidy can drive CIN. In this study we systematically tested the impact of different types of aneuploidies on the induction of CIN. We generated a plethora of isogenic aneuploid clones harboring whole chromosome or segmental aneuploidies in human p53-deficient RPE-1 cells. We observed increased segregation errors in cells harboring trisomies that strongly correlated to the number of gained genes. Strikingly, we found that clones harboring only monosomies do not induce a CIN phenotype. Finally, we found that an initial chromosome breakage event and subsequent fusion can instigate breakage-fusion-bridge cycles in segmental aneuploidies. This suggests that monosomies, trisomies and segmental aneuploidies have fundamentally different effects on chromosomal instability and these results help us to decipher the complex relationship between aneuploidy and CIN.

cell biology↗

Condensin’s ATPase Machinery Drives and Dampens Mitotic Chromosome Condensation

Chromosome condensation by condensin is essential for faithful chromosome segregation. Metazoans have two complexes, named condensin I and II. Both are thought to act by creating looped structures in DNA, but how they do so is unknown. Condensins SMC subunits together form a composite ATPase with two pseudo-symmetric ATPase sites. We reveal that these sites have opposite functions in the condensation process. One site drives condensation, while the other site rather has a dampening function. Mutation of this dampener site hyperactivates both condensin I and II complexes. We find that hyperactive condensin I efficiently shortens chromosomes in the total absence of condensin II. The two complexes form loops with different lengths, and specifically condensin II is key to the decatenation of sister chromatids and the formation of a straight chromosomal axis.

molecular biology↗