Mesenchymal stem cells (MSC) have been extensively studied and gained wide popularity due to their therapeutic potential. Spontaneous transformation of MSC, from both human and murine origin, has been reported in many studies. MSC transformation depends on the culture conditions, the origin of the cells and the time on culture; however, the precise biological characteristics involved in this process have not been fully defined yet. In this study, we investigated the role of p53 in the biology and transformation of murine bone marrow (BM)-derived MSC. We demonstrate that the MSC derived from p53KO mice showed an augmented proliferation rate, a shorter doubling time and also morphologic and phenotypic changes, as compared to MSC derived from wild-type animals. Furthermore, the MSC devoid of p53 had an increased number of cells able to generate colonies. In addition, not only proliferation but also MSC differentiation is controlled by p53 since its absence modifies the speed of the process. Moreover, genomic instability, changes in the expression of c-myc and anchorage independent growth were also observed in p53KO MSC. In addition, the absence of p53 implicates the spontaneous transformation of MSC in long-term cultures. Our results reveal that p53 plays a central role in the biology of MSC.
Adult neurogenesis is restricted to specific brain regions. Although involved in the continuous supply of interneurons for the olfactory function, the role of neural precursors in brain damage-repair remains an open question. Aiming to in vivo identify endogenous neural precursor cells migrating towards a brain damage site, the monoclonal antibody Nilo2 recognizing cell surface antigens on neuroblasts, was coupled to magnetic glyconanoparticles (mGNPs). The Nilo2-mGNP complexes allowed, by magnetic resonance imaging in living animals, the in vivo identification of endogenous neural precursors at their niche, as well as their migration to a lesion site (induced brain tumor), which was fast (within hours) and orderly. Interestingly, the rapid migration of neuroblasts towards a damage site is a characteristic that might be exploited to precisely localize early damage events in neurodegenerative diseases. In addition, it might facilitate the study of regenerative mechanisms through the activation of endogenous neural cell precursors. A similar approach, combining magnetic glyconanoparticles linked to appropriate antibodies could be applied to flag other small cell subpopulations within the organism, track their migration, localize stem cell niches, cancer stem cells or even track metastatic cells.
Cu2+ binding is so far the best characterized property of the prion protein. This interaction has been mapped to the Nterminal domain of the prion protein where multiple His residues occur largely embedded within the repetitive PHGGGWGQ sequence known as octarepeats. When Cu 2+ interaction is studied using a solution of full-length bovine prion protein containing six octarepeats at protein concentrations above 25 W WM, a drastic increase in solution turbidity is observed due to the formation of insoluble cation^protein complexes that appear as bidimensional polymer meshes. These bidimensional meshes consist of a single layer of protein molecules crosslinked by Cu 2+ cations. Polymer formation is a cooperative process that proceeds by nucleation of protein molecules with a Cu 2+ site occupancy of above 2. These results support the hypothesis that the N-terminal domain of prion protein is a ligand binding module that promotes crosslinked assembly, and suggest the existence of inter-repeat Cu 2+ sites.
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