Poster Presentation Lorne Infection and Immunity 2022

High frequency human MLKL mutation causes innate immune response defects and hematopoietic dysfunction in CRISPR-cas9 generated mouse model. (#152)

Sarah E Garnish 1 2 , Katherine R Martin 1 2 , Maria Kauppi 1 2 , Rebecca Ambrose 3 4 , Jaclyn S Pearson 3 4 5 , John Silke 1 2 , James M Murphy 1 2 , Joanne M Hildebrand 1 2
  1. University of Melbourne, Department of Medical Biology, Parkville, Australia
  2. The Walter and Eliza Hall Institute, Parkville, VIC, Australia
  3. Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia
  4. Department of Molecular and Translational Science, Monash University, Clayton, VIC, Australia
  5. Department of Microbiology, Monash University, Clayton, VIC, Australia

Programmed cell death has long been implicated in the progression of human disease. Recently, there has been a major focus on the inflammatory lytic form of programmed cell death, necroptosis, in human pathogen responses. Necroptotic signaling is mediated by the terminal executioner protein, pseudokinase mixed lineage kinase domain-like (MLKL), and its upstream activating kinase, receptor interacting protein kinase 3 (RIPK3). These integral necroptotic proteins have been comprehensively revealed as potent drivers and suppressors of human disease in pre-clinical murine models. The investigation of MLKL’s role in human disease within the ‘real world’ of diverse environmental challenges and genetic backgrounds is limited. Here, we present investigations of a high frequency missense polymorphism in human MLKL that is carried by 2-3% of the general population. This gene variant encodes a serine to proline substitution at position 132 within MLKL’s regulatory brace region and is enriched in trans with similar MLKL polymorphisms in a cohort of Chronic Recurrent Multifocal Osteomyelitis patients. Primary patient cells heterozygous for MLKLS132P and exogenous expression systems in immortalized cell lines were examined for their response to necroptotic and inflammatory stimuli in vitro. To study the potential disease modulating effects of MLKLS132P, on a systemic level, we have generated a mouse model that expressed the mouse equivalent variant, MlklS131P. MlklS131P/S131P mice exhibit innate immune cell defects in the bone marrow at steady state. Following challenge with Salmonella, MlklS131P/S131P mice exhibited impeded bacterial clearance and innate immune cell defects in peripheral blood. Furthermore, MlklS131P/S131P mice were susceptible to bone marrow failure characterized by hematopoietic dysfunction following sublethal irradiation or transplantation. Our work highlights that this human MLKL polymorphism may be an important modulator of disease progression under everyday environmental challenge and raises important questions about the historical circumstances that have led to its high frequency.