Abstract
Key points Haem oxygenase 1 (Hmox1) is a cytoprotective enzyme with anti‐inflammatory and anti‐oxidant properties that is induced in response to multiple noxious environmental stimuli and disease states.Tools to enable its expression to be monitored in vivo have been unavailable until now.In a new Hmox1 reporter model we provide high‐fidelity, single‐cell resolution blueprints for Hmox1 expression throughout the body of mice.We show for the first time that Hmox1 is constitutively expressed at barrier tissues at the interface between the internal and external environments, and that it is highly induced in muscle cells during systemic inflammation.These data suggest novel biological insights into the role of Hmox1 and pave the way for the use of the model to study the role of environmental stress in disease pathology. Hmox1 protein holds great promise as a biomarker of in vivo stress responses as it is highly induced in stressed or damaged cells. However, Hmox1 expression patterns have thus far only been available in simple model organisms with limited relevance to humans. We now report a new Hmox1 reporter line that makes it possible to obtain this information in mice, a premiere model system for studying human disease and toxicology. Using a state‐of‐the‐art strategy, we expressed multiple complementary reporter molecules from the murine Hmox1 locus, including firefly luciferase, to allow long‐term, non‐invasive imaging of Hmox1 expression, and β‐galactosidase for high‐resolution mapping of expression patterns post‐mortem. We validated the model by confirming the fidelity of reporter expression, and its responsiveness to oxidative and inflammatory stimuli. In addition to providing blueprints for Hmox1 expression in mice that provide novel biological insights, this work paves the way for the broad application of this model to establish cellular stresses induced by endogenous processes and those resulting from exposure to drugs and environmental agents. It will also enable studies on the role of oxidative stress in the pathogenesis of disease and its prevention.
Highlights
Across all kingdoms of life, organisms adapt to environmental stress by inducing key evolutionarily conserved genes involved in damage prevention, mitigation, and repair [1,2]
We expected that four separate polypeptides, Heme oxygenase 1 (Hmox1), -gal, hCG, and luciferase would be expressed from this engineered allele
Hmox1 expressed from the reporter allele contains the T2A amino acid sequence at its C-terminus and is distinguishable upon electrophoresis from Hmox1 expressed from the wild type allele
Summary
Across all kingdoms of life, organisms adapt to environmental stress by inducing key evolutionarily conserved genes involved in damage prevention, mitigation, and repair [1,2] Classic examples of these cytoprotective genes are those encoding heat-shock- and DNA repair proteins, and detoxication and anti-oxidant enzymes [3]. Genome-wide libraries of reporter strains have made access to gene expression patterns, including those encoding cytoprotective proteins, a routine task in model organisms, such as E. coli, S. cerevisiae, C. elegans, and D. melanogaster [7,8,9,10], these evolutionarily distant species are of limited relevance to human biology They are unsuited to addressing toxicological issues as they do not adsorb, distribute, metabolise, and excrete (ADME) compounds in the same way as humans and these and other species differences make it difficult to extrapolate results obtained with them to humans [11]. Reporter strategies have been less widely adopted by the mouse community than their counterparts working on simpler model organisms
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