Resumen de Dechipering the role of rbm10 in development and cancer using a genetic mouse model
Ana Margarita Maldonado Barragan
Bladder cancer represents a high economic burden for the health systems since patients frequently relapse. Most BC are urothelial tumors; these are clinically and molecularly heterogeneous and are characterized by a high mutational burden, including mutations in several genes coding for proteins involved in splicing. RBM10 was found by our laboratory as a recurrently mutated gene in BC, although at low frequency (2-5%). RBM10 mutations have also been reported in lung (7-9%), pancreatic, and colorectal cancers. RBM10 maps to the X chromosome and encodes an RNA-binding protein involved in alternative splicing. The majority of RBM10 somatic mutations lead to a premature stop codon and loss of protein expression, supporting the notion that it is a tumor suppressor gene. In addition, germline RBM10 mutations cause TARP syndrome, a severe developmental condition with early male lethality.
To reveal how RBM10 loss contributes to development and cancer we have established Rbm10 constitutive and conditional knockout mouse models and have analyzed phenotypes at the organismal and cellular level. Constitutive inactivation of Rbm10 in the mouse germline results in partial male embryonic lethality and partially recapitulates TARP syndrome, although some mutant mice survive into adulthood. Tissue-wide Rbm10 inactivation in young mice is well tolerated, indicating that the protein is dispensable in adulthood. I have established normal urothelial organoids to induce Rbm10 inactivation in vitro and show that, compared to their wild type counterparts, their growth is partially EGF-independent. Rbm10 KO organoids acquire more prominent cystic features, related to urothelial differentiation. RNA-Seq analysis of the organoids in proliferative conditions revealed significant up-regulation of luminal and stratified epithelium signatures. Down-regulation of cell cycle and translation-related signatures were observed in proliferation, while translation was up-regulated in differentiation conditions. Several splicing events associated with RBM10 inactivation in bladder tumors have been validated using the mouse organoids models. The analysis of human tumors reveals that RBM10 inactivation is an early genetic alteration in bladder carcinogenesis.
I have also generated several tools to further analyze the molecular mechanisms through which RBM10 loss-of-function contributes to bladder cancer. Altogether, the results validate the newly developed strain as a valuable model to study TARP syndrome and urothelial cancer, allowing the identification of RBM10-related splicing targets and molecular mechanisms relevant to disease progression.
