bHLH-PAS transcription factors are critical biological sensors of physiological (hypoxia, tryptophan metabolites, neuronal activity, and appetite) and environmental (diet derived metabolites and environmental pollutants) stimuli to homeostatically regulate genes involved in adaptation. My research focuses on an achieving and understanding of how transcription and gene regulation controls normal and pathological function, with a particular focus on the central nervous system. Using a combination of molecular techniques, mouse and cellular models I study the control of gene regulation in response to hypoxia, neuronal activity and appetite.  

Defining Target Gene Selection Rules

bHLH-PAS transcription factors execute discrete biological functions through regulation of distinct target genes. The mechanisms by which bHLH-PAS transcription factors select different target genes is largely unknown. Through integrated genomic and proteomic analysis we aim to define the rules by which transcription factors select and activate highly specific target gene expression. We are investigating the contribution of inherent DNA binding activities (both in vitro and in vivo) and the role of chromatin and DNA associated proteins and modifications in regulating site occupancy and selecting transcription factor specific target genes. The results of this work will provide a structural frame work to define the target gene selection rules for mammalian transcription factors.

Transcription and gene regulation in central nervous system development and function.

Neuronal PAS transcription factors control brain excitability

The Neuronal PAS transcription factors (NPAS1, NPAS3, NPAS4) collectively regulate the neuron network activity balance (excitatory and inhibitory inputs) in the brain, and, as such are implicated in diseases where activity imbalance is observed (Autism, Schizophrenia, and Seizures). NPAS4 mRNA and protein is rapidly and temporally regulated by neuronal activity (depolarisation) in both glutamatergic and GABAergic neurons to homeostatically regulate synaptic plasticity and memory formation. While NPAS1and NPAS3 have apposing roles in generation of GABAergic interneurons and inhibitory neuron signalling. We aim to understand the regulation of the expression and activity of the neuronal PAS transcription factors to regulate neuron network activity, providing key mechanistic insights into how dysfunction in neuronal activity can lead to disease.

Hypothalamic transcription factors control appetite disorders in humans

The hypothalamus is responsible for the regulation of many goal orientate behaviours including energy homeostasis, hunger and satiety signalling. It contains small numbers of highly specialised neuropeptide expressing neurons that relay peripheral circulating signals to the brain eliciting a homeostatic change in animal behaviour. We have found that two hypothalamically restricted transcription factors Single minded 1 (Sim1), a bHLH-PAS transcription factor and Orthopedia (OTP) a homeodomain transcription factor are mutated in individuals with severe obesity and Prader-Willi-like features (Sim1). We have also shown that knock-in mouse models containing these mutations phenocopy the severe obesity seen in human patients. We are therefore interested in the understanding the how transcription factor mediated changes in gene expression lead to ravenous hunger.  

GABA A receptor epsilon and its intronic encoded microRNA cluster miR-224/452 control neurotransmitter specification and function.

GABA is the main inhibitory neuron transmitter in the central nervous system and primarily acts through a pentameric GABA A receptor made up of 2 alpha subunits, 2 beta subunits and a gamma subunit to form a GABA responsive Cl^-  permeable ion channel. The GABRE subunit (a gamma-like subunit) has been shown to have a number of unique properties including conferring an insensitivity of the GABA A receptor to anaesthetics (pregnanolone and pentobarbital). We have found that GABRE is expressed in AGRP and POMC neuropeptide expressing neurons of the hypothalamus and hindbrain serotonergic neurons. We are currently investigating the role of GABRE and miR-224/452 in the development and function of neuronal subtypes in the brain.