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J Exp Med. 2006 Dec 25;203(13):2939-51. Epub 2006 Dec 18.

Puma cooperates with Bim, the rate-limiting BH3-only protein in cell death during lymphocyte development, in apoptosis induction.

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Division of Developmental Immunology, Biocenter, Innsbruck Medical University, A-6020 Innsbruck, Austria.


The physiological role of B cell lymphoma 2 (Bcl-2) homology 3-only proteins has been investigated in mice lacking the individual genes identifying rate-limiting roles for Bim (Bcl-2-interacting mediator of cell death) and Puma (p53-up-regulated modulator of apoptosis) in apoptosis induction. The loss of Bim protects lymphocytes from apoptosis induced by cytokine deprivation and deregulated Ca++ flux and interferes with the deletion of autoreactive lymphocytes and the shutdown of immune responses. In contrast, Puma is considered the key mediator of p53-induced apoptosis. To investigate the hypothesis that Bim and Puma have overlapping functions, we generated mice lacking both genes and found that bim-/-/puma-/- animals develop multiple postnatal defects that are not observed in the single knockout mice. Most strikingly, hyperplasia of lymphatic organs is comparable with that observed in mice overexpressing Bcl-2 in all hemopoietic cells exceeding the hyperplasia observed in bim-/- mice. Bim and Puma also have clearly overlapping functions in p53-dependent and -independent apoptosis. Their combined loss promotes spontaneous tumorigenesis, causing the malignancies observed in Bcl-2 transgenic mice, but does not exacerbate the autoimmunity observed in the absence of Bim.

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