CENTROSHAPE · Shaping up for mitosis: the origins and consequences of the 3D structure of mitotic centromeres

The centre of the iconic X-shape of human chromosomes is the centromere. It is an extensive locus of specialised chromatin that assembles the kinetochore machinery to connect chromosomes to spindle microtubules for their correct segregation during cell division. How these centromeres obtain three-dimensional (3D) structures that coordinate assembly of kinetochores and resist substantial microtubule-based pulling forces is unknown. We discovered that vertebrate chromosomes are naturally dicentric: their centromeres are two-domain (‘bipartite’) structures, irrespective of underlying DNA sequence or position along the chromosome. Bipartite centromeres assemble bipartite kinetochores that connect to double microtubule bundles, fundamentally altering our view on chromosome-spindle interactions. Chromosome segregation errors in cancer are marked by split centromeres, linking centromere structural integrity to chromosomal instability. Our findings raise many elementary questions about the molecular origins, the 3D structure and the functional consequences of a bipartite mitotic centromere. In CENTROSHAPE, we will integrate advanced imaging and sequencing technologies with state-of-the-art cell models of neocentromeres, inducible centromeres and cancer, to uncover:-How centromere bipartition originates and is maintained,-What 3D chromatin structure shapes the bipartite centromere, and-How destabilisation of bipartite centromeres predisposes to chromosomal instability and centromere damage.The results of CENTROSHAPE will illuminate a hitherto ‘dark’ region of vertebrate mitotic chromosomes – the 3D organisation of centromeres. They will inform on the mechanisms that create this highly specialised chromatin domain in dividing cells and contribute to our understanding of the origins of chromosomal copy number alterations in diseases such as cancer.