Diverse serotonin 2C receptor mediated behaviours resulting from snoRNA regulated post-transcriptional modification

Chemical signaling in the brain is highly dependent on specific neurotransmitter receptors. Different physical forms (isoforms) of these receptors can dramatically affect neurotransmitter signaling. One of the receptors to which the neurotransmitter serotonin binds, the 2C receptor (5HT2CR) exists in numerous different forms (isoforms) which have varying levels of functionality. The abundance of different 5HT2CR isoforms is dependent on the degree of subtle molecular changes known as post-transcriptional modifications. Preliminary studies have shown that when the regulation of post-transcriptional modification is altered and less functional forms of the receptor are generated, this can lead to behavioural effects that are specific to the function of the 5HT2CR. However, 5HT2CRs regulate many aspects of behaviour and the extent to which these molecular changes and the subsequent receptor variants contribute to different behavioural processes is still not fully understood. The proposed project aims to address this by looking at how the degree of post-transcriptional modification of 5HT2CRs varies through the brain and link these molecular findings to effects on behaviour. To do this we will examine animals lacking an important regulatory component of the post-transcription modification machinery. Our work will lead to a better understanding of how different versions of 5HT2CRs function in brain and may translate into better therapies for clinical conditions such as depression, suicide and schizophrenia, which have been linked to alterations in this receptor.

In vitro studies suggest the functional efficacy of serotonin 2C receptors (5HT2CR) in brain can be dramatically altered by post-transcriptional modifications of the Htr2c gene pre-RNA. At present we know very little about the normal, physiological regulatory mechanisms controlling post-transcriptional modifications (RNA-editing and alternate splicing) of Htr2c in brain in vivo, and almost nothing about the precise behavioural effects of interfering with these processes. In this context, we recently published the first evidence showing that the exclusively brain expressed imprinted small nucleolar (sno)RNA, Snord115, physiologically regulates the degree of editing of the Htr2c pre-RNA in mouse brain and that this editing modification can lead to highly specific effects on 5HT2CR-mediated behaviour. We focused on Snord115 because this snoRNA (and its human equivalent, SNORD115) is the only known gene containing a recognition sequence for the edited region of the Htr2c pre-RNA, and there is evidence from in vitro studies that Snord115 negatively modulates post-transcriptional modification both in terms of editing and alternate splicing such that the expression of this snoRNA tends to maintain the more functionally active 5HT2CR protein isoforms. We want to investigate the relevance of these in vitro findings to functioning in the whole animal by examining behaviour in animals lacking Snord115. We will focus on established effects of 5HT2CR function on response control and feeding, using molecular and neurobiological evidence to directly link any behavioural changes we observe to Snord115 mediated post-transcriptional modifications of Htr2c pre-RNA. The strong likelihood is that both RNA editing and alternate splicing are important molecular mechanisms contributing to the ways in which efficacy of 5HT2CR neurotransmission remains sensitive to changing environmental conditions and that abnormal functioning contributes to behavioural disorders and psychopathology.

The proposed research will generate new knowledge that will be of practical use to understanding how serotonin 2C receptors (5HT2CR) function in the brain and how they may go wrong in brain disorders.

Who will benefit from this research, and how?

5HT2CRs play key roles in the regulation of brain function and behaviour and have been shown to be involved in the pathogenesis of a number of common brain disorders, including anxiety, depression and eating abnormalities. Consequently,
5HT2CRs have attracted intense scrutiny as targets for therapeutics but the drugs developed for clinical use have thus far not been optimal. A main benefit of the present basic research, therefore, will be to exploit novel findings about the way post-transcriptional modifications of the gene coding for the 5HT2CR, Htr2c, impacts on the diversity of serotonergic action in the mammalian brain; and thereby assess their likely involvement in 5HT2CR dysfunction. In short, our research on editing and alternate splicing of Htr2c pre-RNA, which was instigated via collaboration with the pharmaceutical company GlaxoSmithKline, may lead to better drugs for patients. As a result, the scope and reach of the work will extend to both UK plc and the general public.

How will the users be engaged?

Dr Anthony Isles has extensive experience of communicating with the general public through podcasts recorded for Nature and the local and national press. He has also regularly been asked to address non-specialised scientists and lay audiences (Science and Philosophy Cafes, to NACWOs and Veterinary groups). Both investigators will continue with these public engagement activities.

Prof Lawrence Wilkinson has close links with a number of pharmaceutical companies, including GSK, who as noted above have direct interest in the proposed work. Wilkinson is a founder member of the Lilly Centre for Cognitive Neuroscience and the P1vital Ltd (Oxford) Experimental Medicine Consortium Academic Panel. Regular meetings and discussions will continue to be held with senior representatives of these and other companies to discuss opportunities for translation of the basic findings into the drug discovery process, and for training opportunities.