Epigenetic control of gene transcriptional and behavioural responses to stress in the dentate gyrus

Stress affects the lives of both humans and animals in our society. Most debilitating for mental welfare and wellbeing in humans is psychological stress, for instance marital problems, job insecurity, and bullying. In farmed and companion animals, examples of psychological stress include overcrowding (e.g. chickens, pigs), long-lasting transports (e.g. cows, sheep, pigs) and abuse. Successful coping with such stressful events involves adaptive and cognitive processes in the brain that make the individual more resilient to repeated stress in the future. Some events, however, are so traumatic that the memories of them become a tremendous burden, leading to psychosomatic and behavioural disturbances and psychiatric diseases (anxiety and depression). To help people to cope with stress in their lives, to develop directives to reduce stress and to improve wellbeing of our companion, farmed and laboratory animals, we need to obtain better insight into how the brain processes stress and creates memories of psychologically stressful events. At present it is unclear how the healthy brain adapts to and learns from stressful events. We have recently discovered that after stress certain molecular processes ("epigenetic modifications") occur in the nucleus of nerve cells which are crucial for the expression of genes necessary for the adaptation of these cells to a stressful event. Our proposal aims to investigate the role of these epigenetic modifications in the regulation of gene expression and the identity of the genes affected by these modifications. Obtaining this information is crucial to understand how nerve cells "learn" from stressful events. Insight into these processes and the function of the genes involved will help to develop new ways to reduce the burden of stress-related disorders in humans and animals.

Dealing with a psychologically stressful event requires, in addition to generation of the acute stress response, cognitive processing so that memories can be formed enabling appropriate responses in case of future recurrences. Insight into the molecular and cellular mechanisms underlying stress coping and stress processing in the brain is clearly vital for the development of strategies to improve the quality of life and maintaining (life-long) health in humans and animals. We have found that, in the case of a learned behavioural response to stress in rats and mice, this process involves (1) chromatin remodelling (driven by phosphorylation and subsequent acetylation of histone H3 (H3S10p-K14ac)) to facilitate transcriptional induction of immediate-early genes (IEGs; c-Fos, Egr-1) in sparse dentate gyrus (DG) neurons in the limbic brain and (2) the transcription factor CREB which is a main trans-activator of IEG gene transcription but found to be phosphorylated (pCREB) in all DG neurons. We hypothesise that 1. The psychological stress-induced H3S10p-K14ac epigenetic marks within gene promoters in DG neurons are a prerequisite for pCREB to gain access to CREs within the egr-1, c-fos and other promoters for activating gene transcription which is required for the consolidation of stress-related memory; and 2. Consequently, the CRE-dependent gene transcriptional response in DG neurons showing the H3S10p-K14ac histone marks will be distinct from the CRE-dependent transcriptional response in dentate neurons not presenting these marks. To test these hypotheses we will use state-of-the-art lentiviral-driven RNA interference technology, chromatin immuno-precipitation (ChIP), gene promoter identification using Illumina next generation sequencing (ChIPseq), and RNA Sequencing (RNA-seq) analyses in combination with neuroanatomical, immunohistochemical and behavioural analyses.

Who will benefit from this research?

There are a number of beneficiaries for whom this research could be helpful in the longer term:

1. Owners of companion and farmed animals with stress-related behavioural disturbances
2. Patients suffering from stress-related disorders
3. Family and friends of such patients
4. The economy
5. The government and the National Health Service
6. Academia


How will they benefit from this research?

1. Owners of companion and farmed animals with stress-related behavioural disturbances. Stress is a common problem for companion and farmed animals. It can lead to behavioural (e.g. stereotypy, aggression), reproductive (e.g. infertility) and other disturbances. Our research will help to improve treatment of such animals which will benefit their health and wellbeing. Owners of companion animals will have a much more pleasant pet and farmers will have less economic loss. From a different perspective, our research will increase the awareness that stress has indeed a long-term impact on the animals' behaviour. Since (bad) experiences of the animals appear to become hardwired into their brain it may take substantial efforts to undo these changes and obtain a healthy animal again. This should motivate pet owners and farmers to treat their animals properly. Our research may also help to improve legislation.

2. Patients suffering from stress-related disorders. Clearly, at present there is no satisfactory treatment for stress-related disorders such as psychosomatic disturbances (e.g. low-back pain, gastro-intestinal complaints) and psychiatric diseases (anxiety and major depressive disorders). The main reason for this situation is that the underlying neurobiology of these disorders is still unknown. Our research has the potential to lead to the development of new drugs for the treatment of stress-related disorders in the future. It should be noted that these disorders are extremely disruptive for the patient's life in personal terms (misery, suicide), social terms (divorce) and economic terms (job loss, poverty).

3. Family and friends of such patients. As mentioned, stress-related disorders can be very disruptive for someone's social life often leading to divorce and social isolation which is devastating for the partners, children and friends of the patient. Thus, the social environment of the patient would benefit greatly from a better treatment of the patient.

4. The economy. The economy in general would benefit because patients suffering from stress-related disorders are often unable to work. If skilled people drop out of the work force it can have a major negative impact on the management, development and productivity of companies. Research has shown that stress leads to the loss of over 15 million work days per year and many billions Pound Sterling in economic damages. A better treatment would doubtless be beneficial for the economy. The pharmaceutical industry would benefit as this research would spark new avenues in drug development.

5. The government and the National Health Service (NHS). It is logical that the social, economic and health problems of such patients are a great burden for the government and the NHS. Clearly, an improved treatment of these patients would alleviate this burden significantly. Better insight into the effects of stress on animals could be beneficial to improve legislation for a better treatment of our companion and farmed animals.

6. Academia. International academia in the fields of preclinical and clinical psychiatry, and molecular, cellular and behavioural neuroscience would greatly benefit from the scientific progress made by this research. This is underlined by the fact that our research output has been highly cited in the scientific literature (see CV Reul). Therefore, it may be anticipated that our results will have a major impact on academia (See also 'Academic Beneficiaries').