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Stingele, Silvia (2013): The consequences of aneuploidy in human cells. Dissertation, LMU München: Faculty of Biology



Aneuploidy is a change in number or structure of one or more chromosomes that are not a multiple of the whole chromosome set. One of the best known pathological aneuploidies is trisomy 21 (Down syndrome), with chromosome 21 present in three instead of two copies. Patients with Down syndrome display severe mental retardation and growth defects. In fact, most abnormal aneuploid karyotypes lead to spontaneous abortions during embryogenesis, indicating that aneuploidy is not well tolerated in humans. Aneuploidy was also shown to be a common hallmark of cancer tissues; however, the debate is ongoing whether aneuploidy is rather a by-product or a trigger of tumorigenesis. Even though aneuploid karyotypes were already identified more than 100 years ago little is understood about cellular physiology of aneuploidy cells, especially in humans. To uncover the consequences of numerical aneuploidy in human cells, I generated aneuploid cell lines derived from the human cell lines HCT116 and RPE-1 hTERT. First, we showed that aneuploid cells proliferate slower compared to their disomic counterparts. A detailed cell cycle analysis revealed that this delay was due to a prolonged G1 and S phase, whereas G2 and M phase remained unperturbed. Furthermore, we conducted an in depth genome wide comparison of DNA, mRNA and protein levels in aneuploid cells. Using CGH, mRNA array and SILAC technology, we quantified the changes in DNA, mRNA and protein abundance. We revealed that extra chromosomes are actively transcribed and translated. However, the abundance of some proteins, particularly subunits of protein complexes and protein kinases, are adjusted towards disomic levels. Additionally, we asked how the cellular physiology is affected by the addition of a specific chromosome. Two scenarios are possible: either the cellular response depends on the additional chromosomes or all aneuploid cells show the same changes of cellular physiology. Indeed, we found that all aneuploid cell lines show similar physiological responses, irrespective of the type of additional chromosome. All aneuploid cell lines down-regulate DNA and RNA metabolism and up-regulate among others energy metabolism, lysosome function and membrane biosynthesis pathways. Lysosomes which are involved in autophagy are besides the ubiquitin-proteasome system important for cellular protein turn over. We found p62-dependent selective autophagy increased in all analyzed cell lines with extra chromosomes suggesting a role of p62-dependent selective autophagy in maintenance of protein homeostasis upon expression of extra protein in these cell lines.