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Browsing by Author "Jorge, Xavier Santana"

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  • The molecular mechanisms underlying erroneous segregation on Warsaw Breakage Syndrome
    Publication . Jorge, Xavier Santana; Carvalhal, Sara
    Given the vast number of mechanisms where cohesin is involved, problems that affect the structure of cohesin or its cofactors can lead to a variety of pathologies, namely cancer and some rare syndromes. The term cohesinopathies is used to describe rare syndromes that share mutations in the cohesin complex or at its regulators. Warsaw Breakage Syndrome (WABS) belongs to the group of cohesinopathies due to overlapping clinical features and to be caused by a bi-allelic mutation in the protein DDX11, known to regulate cohesin. In addition, DDX11 functions as a DNA helicase during replication. The etiology of this disease is still unknown, but two no-mutual exclusive hypotheses have been proposed: the first is that it can be caused by problems in DNA replication and reparation, and the second is that it can be caused by problems during mitosis. In this project, we aim to try to better understand the mechanisms that underline WABS etiology using WABS patient cell lines and RPE-1 CRISPR DDX11 KO cell lines in combination with imaging techniques. For that, we capitalized in ongoing research in the lab to evaluate three possible outcomes of how mis-regulate mitosis contributes to WABS etiology. We evaluated the localization of the DDX11 during mitosis, but unspecific binding of the antibody made it impossible for us to draw conclusions about the DDX11 importance during this cell cycle stage. Then we studied the localization of the Aurora B kinase, an important protein involved in the metaphase checkpoint. Despite previous publications suggesting that DDX11 impacts Aurora B, in our system the impact on Aurora B was more subtle. Finally, we studied the localization of Topoisomerase II a, a protein responsible for resolve the DNA catenation. This isomerase has a later localization across the chromosomes upon DDX11 perturbations. Topoisomerase typical more centromeric localization changed to an almost even distribution along all the chromosomes in WABS models. From this work execution, we identified at least one very promising candidate to explore, yet more experiments are necessary in the future to strengthen results and final conclusions about the mechanisms underlining this disease.
    2023-03-16Master thesis Open access Show more