Bioluminescence imaging of Cyp1a1-luciferase reporter mice demonstrates prolonged activation of the aryl hydrocarbon receptor in the lung.

Aryl hydrocarbon receptor (AHR) signalling integrates biological processes that sense and respond to environmental, dietary, and metabolic challenges to ensure tissue homeostasis. AHR is a transcription factor that is inactive in the cytosol but upon encounter with ligand translocates to the nucleus and drives the expression of AHR targets, including genes of the cytochrome P4501 family of enzymes such as Cyp1a1. To dynamically visualise AHR activity in vivo, we generated reporter mice in which firefly luciferase (Fluc) was non-disruptively targeted into the endogenous Cyp1a1 locus. Exposure of these animals to FICZ, 3-MC or to dietary I3C induced strong bioluminescence signal and Cyp1a1 expression in many organs including liver, lung and intestine. Longitudinal studies revealed that AHR activity was surprisingly long-lived in the lung, with sustained Cyp1a1 expression evident in discrete populations of cells including columnar epithelia around bronchioles. Our data link diet to lung physiology and also reveal the power of bespoke Cyp1a1-Fluc reporters to longitudinally monitor AHR activity in vivo.

Protein restriction during pregnancy alters Cdkn1c silencing, dopamine circuitry and offspring behaviour without changing expression of key neuronal marker genes.

We tracked the consequences of in utero protein restriction in mice throughout their development and life course using a luciferase-based allelic reporter of imprinted Cdkn1c. Exposure to gestational low-protein diet (LPD) results in the inappropriate expression of paternally inherited Cdkn1c in the brains of embryonic and juvenile mice. These animals were characterised by a developmental delay in motor skills, and by behavioural alterations indicative of reduced anxiety. Exposure to LPD in utero resulted in significantly more tyrosine hydroxylase positive (dopaminergic) neurons in the midbrain of adult offspring as compared to age-matched, control-diet equivalents. Positron emission tomography (PET) imaging revealed an increase in striatal dopamine synthesis capacity in LPD-exposed offspring, where elevated levels of dopamine correlated with an enhanced sensitivity to cocaine. These data highlight a profound sensitivity of the developing epigenome to gestational protein restriction. Our data also suggest that loss of Cdkn1c imprinting and p57KIP2 upregulation alters the cellular composition of the developing midbrain, compromises dopamine circuitry, and thereby provokes behavioural abnormalities in early postnatal life. Molecular analyses showed that despite this phenotype, exposure to LPD solely during pregnancy did not significantly change the expression of key neuronal- or dopamine-associated marker genes in adult offspring.

Endogenous bioluminescent reporters reveal a sustained increase in utrophin gene expression upon EZH2 and ERK1/2 inhibition.

Duchenne muscular dystrophy (DMD) is an X-linked disorder caused by loss of function mutations in the dystrophin gene (Dmd), resulting in progressive muscle weakening. Here we modelled the longitudinal expression of endogenous Dmd, and its paralogue Utrn, in mice and in myoblasts by generating bespoke bioluminescent gene reporters. As utrophin can partially compensate for Dmd-deficiency, these reporters were used as tools to ask whether chromatin-modifying drugs can enhance Utrn expression in developing muscle. Myoblasts treated with different PRC2 inhibitors showed significant increases in Utrn transcripts and bioluminescent signals, and these responses were independently verified by conditional Ezh2 deletion. Inhibition of ERK1/2 signalling provoked an additional increase in Utrn expression that was also seen in Dmd-mutant cells, and maintained as myoblasts differentiate. These data reveal PRC2 and ERK1/2 to be negative regulators of Utrn expression and provide specialised molecular imaging tools to monitor utrophin expression as a therapeutic strategy for DMD.

The anti-tumour activity of DNA methylation inhibitor 5-aza-2'-deoxycytidine is enhanced by the common analgesic paracetamol through induction of oxidative stress.

The DNA demethylating agent 5-aza-2'-deoxycytidine (DAC, decitabine) has anti-cancer therapeutic potential, but its clinical efficacy is hindered by DNA damage-related side effects and its use in solid tumours is debated. Here we describe how paracetamol augments the effects of DAC on cancer cell proliferation and differentiation, without enhancing DNA damage. Firstly, DAC specifically upregulates cyclooxygenase-2-prostaglandin E2 pathway, inadvertently providing cancer cells with survival potential, while the addition of paracetamol offsets this effect. Secondly, in the presence of paracetamol, DAC treatment leads to glutathione depletion and finally to accumulation of ROS and/or mitochondrial superoxide, both of which have the potential to restrict tumour growth. The benefits of combined treatment are demonstrated here in head and neck squamous cell carcinoma (HNSCC) and acute myeloid leukaemia cell lines, further corroborated in a HNSCC xenograft mouse model and through mining of publicly available DAC and paracetamol responses. The sensitizing effect of paracetamol supplementation is specific to DAC but not its analogue 5-azacitidine. In summary, the addition of paracetamol could allow for DAC dose reduction, widening its clinical usability and providing a strong rationale for consideration in cancer therapy.