Toll-like receptor-mediated down-regulation of the deubiquitinase cylindromatosis (CYLD) protects macrophages from necroptosis in wild-derived mice.

Pathogen recognition by the innate immune system initiates the production of proinflammatory cytokines but can also lead to programmed host cell death. Necroptosis, a caspase-independent cell death pathway, can contribute to the host defense against pathogens or cause damage to host tissues. Receptor-interacting protein (RIP1) is a serine/threonine kinase that integrates inflammatory and necroptotic responses. To investigate the mechanisms of RIP1-mediated activation of immune cells, we established a genetic screen on the basis of RIP1-mediated necroptosis in wild-derived MOLF/EiJ mice, which diverged from classical laboratory mice over a million years ago. When compared with C57BL/6, MOLF/EiJ macrophages were resistant to RIP1-mediated necroptosis induced by Toll-like receptors. Using a forward genetic approach in a backcross panel of mice, we identified cylindromatosis (CYLD), a deubiquitinase known to act directly on RIP1 and promote necroptosis in TNF receptor signaling, as the gene conferring the trait. We demonstrate that CYLD is required for Toll-like receptor-induced necroptosis and describe a novel mechanism by which CYLD is down-regulated at the transcriptional level in MOLF/EiJ macrophages to confer protection from necroptosis.

Identification of a Locus in Mice that Regulates the Collateral Damage and Lethality of Virus Infection.

Arenaviruses can cause severe hemorrhagic disease in humans, which can progress to organ failure and death. The underlying mechanisms causing lethality and person-to-person variation in outcome remain incompletely explained. Herein, we characterize a mouse model that recapitulates many features of pathogenesis observed in humans with arenavirus-induced hemorrhagic disease, including thrombocytopenia, severe vascular leakage, lung edema, and lethality. The susceptibility of congenic B6.PL mice to lymphocytic choriomeningitis virus (LCMV) infection is associated with increased antiviral T cell responses in B6.PL mice compared with C57BL/6 mice and is T cell dependent. Pathogenesis imparted by the causative locus is inherited in a semi-dominant manner in F1 crosses. The locus includes PL-derived sequence variants in both poorly annotated genes and genes known to contribute to immune responses. This model can be used to further interrogate how limited genetic differences in the host can remarkably alter the disease course of viral infection.