Elucidating the role of centromere dysfunction in genome instability – CenBreak

Division is an essential stage in the life of all cells: it participates in an organism’s development and growth, in wound repair, combating infection, and cell turnover. When a cell separates during cell division it needs to equally distribute its chromosomes, the molecular basis of genetic heredity, between its two daughter cells.
The centromere is a small region on each chromosome that serves as an anchor point for the attachment of the cell machinery that delivers one copy of each duplicated chromosome to each daughter cell. Defects in centromere formation and function lead to incorrect distribution of the number of chromosomes among the daughter cells, a phenomenon called aneuploidy, and to structural defects with loss or gain of genetic material. Interestingly, DNA breaks, rearrangements and structural aberrations at centromeric regions are found in several types of cancer cells and human genetic diseases. To understand how cells avoid these defects, it is crucial to understand how centromeres are formed and their integrity maintained throughout generations. Further, cells have developed surveillance mechanisms to maintain cell homeostasis and to prevent the arising of DNA damage and genome instability. Failure to activate these surveillance mechanisms leads to abnormal karyotypes that in turn are the cause of developmental disorders such as Down and Turner syndromes and a variety of cancers. How cells sense and respond to these types of aberrations is still under debate. The presence of both centromere breaks and aneuploidy in these different pathological states points towards a central role of centromeres in maintaining genome stability during cell division.
The centromere is a complex structure made of repetitive DNA and proteins. In most species, it contains a specific chromatin enriched for the histone H3-variant Centromere Protein A (CENP-A) and repetitive DNA, known in human as satellite DNA and bound by the protein CENP-B. CENP-A is essential to preserve centromere position over cell divisions and to recruit other factors required for correct centromere functioning. Little is known, however, on the particular environment that centromeric chromatin and its underlying repetitive sequences create at centromeres and on their role in centromere function and stability. Recent findings from our lab point towards an important role of CENP-B, the only protein known to bind centromeric DNA, in mediating equal chromosome separation. Further, we have shown that removal of CENP-A leads to an increase in aberrant centromere recombination, indicating that CENP-A might directly contribute to centromere stability.
The goal of our research project is to study the role that centromere failure plays in the onset of genome instability and the molecular mechanisms that are activated in response to such defects. To this end, our consortium will combine genome editing with state of the art microscopy, cell genetics, and ongoing cutting-edge developments, such as quantitative and comparative locus-specific chromatin proteomics analysis and recombination based-approaches at centromeric regions. This proposal will convey crucial insight in centromere biology that will be fundamental to understand the genesis of chromosome instability, which is the basis of many human diseases.