| Popis: |
Over-expression studies in cultured B cells showed that both TIS11b and TIS11d were able to block plasma cell differentiation in vitro. This action was specific as class switch recombination was not affected. TIS11b conditional knockout mice showed normal lymphocyte development and maturation and a normal humoral immune response. TIS11b conditional knockout mice lacked marginal zone B cells and had reduced numbers of peritoneal B1 cells. However they mounted a normal humoral response to immunisation with NP-KLH, with normal affinity maturation and a normal memory response. Single knockouts were inter-crossed to create double knockout (dKO) mice. Unexpectedly, close to 100% of dKO mice developed T-lymphoblastic leukaemia from three months of age. Pre-leukaemic mice showed arrested B cell development at the pro-B stage and significantly perturbed thymic development. This included the aberrant passage of thymocytes through the β-selection checkpoint in the absence of expression of a functional T cell receptor β chain. A genome-wide approach to identify deregulated TIS11b/d targets in pre-leukaemic mice showed elevated expression of the oncogenic transcription factor Notch1. Bioinformatic analysis revealed potentials binding sites for TIS11b and TIS11d within a highly conserved region of the Notch1 3’UTR. The ability of TIS11b and TIS11d to interact and suppress expression of Notch1 was demonstrated by electromobility shift assay (EMSA) and luciferase reporter assays. Furthermore, development and proliferation of T-ALL was Notch1 dependent, both in vivo and in vitro. |
