Importance of Receptor Usage, Fli1 Activation, and Mouse Strain for the Stem Cell Specificity of 10A1 Murine Leukemia Virus Leukemogenicity

Abstract

Murine leukemia viruses (MuLV) induce leukemia through a multistage process, a critical step being the activation of oncogenes through provirus integration. Transcription elements within the long terminal repeats (LTR) are prime determinants of cell lineage specificity; however, the influence of other factors, including the Env protein that modulates cell tropism through receptor recognition, has not been rigorously addressed. The ability of 10A1-MuLV to use both PiT1 and PiT2 receptors has been implicated in its induction of blast cell leukemia. Here we show that restricting receptor usage of 10A1-MuLV to PiT2 results in loss of blast cell transformation capacity. However, the pathogenicity was unaltered when the env gene is exchanged with Moloney MuLV, which uses the Cat1 receptor. Significantly, the leukemic blasts express erythroid markers and consistently contain proviral integrations in the Fli1 locus, a target of Friend MuLV (F-MuLV) during erythroleukemia induction. Furthermore, an NB-tropic variant of 10A1 was unable to induce blast cell leukemia in C57BL/6 mice, which are also resistant to F-MuLV transformation. We propose that 10A1-and F-MuLV actually induce identical (erythro)blastic leukemia by a mechanism involving Fli1 activation and cooperation with inherent genetic mutations in susceptible mouse strains. Furthermore, we demonstrate that deletion of the Icsbp tumor suppressor gene in C57BL/6 mice is sufficient to confer susceptibility to 10A1-MuLV leukemia induction but with altered specificity. In summary, we validate the significance of the env gene in leukemia specificity and underline the importance of a complex interplay of cooperating oncogenes and/or tumor suppressors in determining the pathogenicity of MuLV variants.

Protease-sensitive prion species in neoplastic spleens of prion-infected mice with uncoupling of PrPSc and prion infectivity

“…All procedures involving animals were performed in accordance with the institutional guidelines from the animal facility of the University Medical Center Hamburg-Eppendorf and were in compliance with the Guide for the Care and Use of Laboratory Animals. Mice were inoculated with MoMuLV on post-natal day 5 with~7610 4 IU to achieve virus persistence (Krasemann et al, 2012;Rodenburg et al, 2007;Schwieger et al, 2002). For prion-only infection or infection with both pathogens (MoMuLV+prion), strain RML 5.0 prions (Prinz et al, 2003b) were injected on day 21.…”

Persistent retroviral infection with MoMuLV influences neuropathological signature and phenotype of prion disease

“…Cell culture supernatants, bodily fluids or tissue homogenates were tested for replication competent viral particles with a cell-based assay [69,71]. Briefly, stably transfected cells carrying a packaging-defective retroviral construct with a GFP-reporter were incubated overnight with the sample material and cultivated 3 days.…”

“…Determination of viral titers was only carried out for sera. SC1 cells expressing a GFP-reporter construct were infected with sera from mice challenged with MoMuLV or Mock (60, 90, 220 dpi) and titers were determined in serial dilutions according to [69].…”

Homing and invasiveness of MLL/ENL leukemic cells is regulated by MEF2C

“…22 Retroviral integration sites were isolated from genomic DNA of tumors using a modified protocol of the ligase-mediated extension-primer tag selection PCR reaction. 23 …”