Creation and characterization of phosphorylation defective mutant Bcl2 transgenic mice

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Viability promoting genes such as Bcl2/Bcl-xL play an important function in the development of cancer. Bcl2 was originally cloned from a patient with Follicular lymphoma harboring t (14:18) chromosomal translocation. In vitro findings suggest that Bcl2 phosphorylation at mitotic phase of cell cycle can be detrimental to its antiapoptotic function. A transgenic approach was undertaken to further our understanding of the role of phosphorylation of Bcl2 in hematopoietic cells. We prepared mice that prominently expressed wild and mutant Bcl2 transgene in a B cell specific manner under the influence of immunoglobulin m chain enhancer. Wild and mutant Bcl2 cDNAs were cloned in B cell specific expression vector pJT1. The transcription units liberated from the positive clones were injected into the pro-nuclei of fertilized eggs of donor mice. The injected eggs were implanted to the oviduct of pseudopregnant foster mother. Initial examination of wild transgenic mice exhibited moderate enlargement of spleen whereas phosphorylation defective mutant transgenic had a profoundly large spleen perhaps by the enhanced expansion of some unidentified subset of B cells than that of wild counterpart. As prevalent in the literature, wild type Bcl2 transgenic mice developed lymphoma at low frequency after a long latency period. We are poised to ask whether the disruption of endogenous phosphorylation of Bcl2 might promote the pathogenesis of B lymphoid neoplasm inducing lymphoma with higher frequency. This phosphory lation defective mutant Bcl2 transgenic will provide an ideal model for studying the role of Bcl2 phosphorylation on cell viability during B lymphocyte development. Although others and we observe enhanced Bcl2 phosphorylation in the presence of microtubule damaging drugs, endogenous phosphorylation without treatment of any trigger can be detected if the M phase cells are elutriated. The role of endogenous M phase specific phosphorylation of Bcl2 remains elusive. The resultant cell fate under enforced expression of Bcl2 transgenes (wild and Ser70, 87 Ala mutant) in the context of a conducive intra and extracellular milieu and in isolation from homeostatic constraints will be discussed.