# data[].attributes.body
F1 and F2 MSUS both display increased resilience and active coping response to aversive stimuli.

F1 and F2 MSUS mice exhibit a decrease in methylation of GR and increased expression of GR, indicating transmissibility of epigenetic changes across generations.

F2 MSUS exposed to an enriched environment demonstrated a reversal of resilience and active coping responses.

# data[].attributes.body
Please watch with subtitles! (in settings)
MSUS = Mouse model of Unpredictable maternal Separation
EE = Environmental Enrichment

Video and drawings by K. Maksimovic

# data[].attributes.attachment_link.description
Please watch with subtitles. Methods summary video for Gapp et al. "Potential of Environmental Enrichment to Prevent Transgenerational Effects of Paternal Trauma" (2016). Neuropsychopharmacology.

# data[].attributes.headline
Physiological Responses to Stress and Trauma 

# data[].attributes.subject
Physiological Responses to Stress and Trauma 

# data[].attributes.body
In addition to psychological coping, the body initiates a physiological response to adapt to chronic stress (Selye 1936).  This response is mediated by activation of the hypothalamic-pituitary-adrenal (HPA) axis. Activation of HPA-axis results in the release of glucocorticoids and catecholamines from the adrenal glands into circulation. These molecules work in tandem to suppress immune and digestive activation to increase glucose bioavailability and cardiorespiratory function to help an organism adapt to stress (Smith & Vale 2006).

Over-activation of the HPA axis results in sustained levels of cortisol in circulation and can contribute to exhaustion and  mood disorders in more severe cases (Varghese et al. 2001). Thus, the function of a built-in negative feedback loop is necessary for regulating HPA-axis activity. Specifically, there are glucocorticoid receptors (GRs) in the hippocampus which negatively inhibit the activity of the hypothalamus when cortisol is present in high concentrations (Zhu et al. 2014). Considering this, expression of GR in the hippocampus is essential for preventing overactivity of the HPA-axis in response to chronic stress.

# data[].attributes.headline
Future Direction: overexpression of the GR gene compared to F2 MSUS mice

# data[].attributes.subject
Future Direction: overexpression of the GR gene compared to F2 MSUS mice

# data[].attributes.headline
Future Direction: influence of time on epigenetic and behavioural tests

# data[].attributes.subject
Future Direction: influence of time on epigenetic and behavioural tests

# data[].attributes.headline
Future Direction: The effects of social interaction vs. environmental exploration

# data[].attributes.subject
Future Direction: The effects of social interaction vs. environmental exploration

# data[].attributes.body
1. Study did not separate social interaction and stimulating activities (toys, mazes, exercise wheel). It is possible that one of these has a greater effect on environment enrichment, and therefore GR expression, than the other.
Maternal social interaction has been shown to contribute to epigenetic changes (Meaney 2001). No studies have been done on environment enrichment without social interaction.
2. Time spent in the enriched environment, and time of collecting tissues was not specified in the study. It is unsure how much time needs to be spent in the enriched environment to see changes in methylation.
3. The authors simply compared F2 MSUS EE mice to F2 control EE mice and implied a reversible of epigenetic changes. A comparison of F2 MSUS mice to F2 MSUS EE mice would have better demonstrated this finding.

4. Study did not explore epigenetic transmissibility past the F2 generation, or in female mice.
Epigenetic transmissibility becomes less stable over generational time; epigenetic changes were not maintained in Arabidopsis thaliana after F3 generation (Becker et al. 2011).

5. Study did not perform functional experiments to see if F2 MSUS results are consistent with over expression of the GR gene, or treatment of mice with demethylases (although this may target many genes and not just the GR gene).
6. Authors did not mention how study translates to humans and the implications of this study on the development of psychiatric disorders. Authors did not look at any other genes, which presents a bias in their analyses.

# data[].attributes.body
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th edition. Alrington, VA: American Psychiatric Association, 2013.

Becker C, Hagmann J, Koenig D, Stegle O, Borgwardt K, Weigel D. Spontaneous epigenetic variation in the Arabidopsis thaliana methylome. Nature. 2011. 480: 245-249.

Chourbaji S, Vogt MA, Gass P. Mice that under- or overexpression glucocorticoid receptors as models for depression or posttraumatic stress disorder. Progress in Brain Research. 2007. 167:65-77.

Dunn KE, Finan PH, Tompkins DA, Fingerhood M, Strain EC. Characterizing Pain and Associated Coping Strategies in Methadone and Buprenorphine Maintained Patients. Drug and alcohol dependence. 2015. 157:143-149.

Fraga MF. & Esteller M. DNA methylation: a profile of methods and applications. Biotechniques. 2002. 33(3):632, 634, 636-49.

Gapp K, Bohcek J, Grossmann J, Brunner AM, Manuella F, Nanni P, Mansuy IM. Potential of Environmental Enrichment to Prevent Transgenerational Effects of Paternal Trauma. Neuropsychopharmacology. 2016. 41:2749-2758.

Handy DE, Castro R, Loscalzo J. Epigenetic Modifications: Basic Mechanisms and Role in Cardiovascular Disease. Circulation. 2011. 123(19):2145-2156.

Herman J. Trauma and Recovery: The Aftermath of Violence. New York, NY: Basic Books, 1992.

Iribarren J, Prolo P, Neagos N, Chiappelli F. Post-Traumatic Stress Disorder: Evidence-Based Research for the Third Millennium. Evidence-based Complementary and Alternative Medicine. 2015. 2(4):503-512.

Kanherkar RR, Bhatia-Dey N, Csoka AB. Epigenetics across the human lifespan. Front Cell Dev Biol. 2014. 2:49.

Kurdyukov, S. & Bullock, M. DNA Methylation Analysis: Choosing the Right Method. Biology. 2015. 5:3.

Lazarus R, Folkman S. Stress, appraisal, and coping. New York, NY: Springer; 1984.

Liu D, Diorio J, Tannebaum B, Caldji C, Francis D, Freedman A, Sharma S, Pearson D, Plotsky PM, Meaney MJ.  Maternal care, hippocampal glucocorticoid receptors, and hypothalamic-pituitary-adrenal responses to stress. Science. 1997. 277, 1659-1662

Meaney MJ. Maternal care, gene expression, and the transmission of individual differences in stress reactivity across generations. Annu. Rev. Neurosci. 2001.  24:1161–1192.

Selye H. Stress and the General Adaptation Syndrome. British Medical Journal. 1950;1(4667):1383-1392.

Smith SM, Vale WW. The role of the hypothalamic-pituitary-adrenal axis in neuroendocrine responses to stress. Dialogues in Clinical Neuroscience. 2006. 8(4):383-395.

Varghese FP, Brown ES. The Hypothalamic-Pituitary-Adrenal Axis in Major Depressive Disorder: A Brief Primer for Primary Care Physicians. Primary Care Companion to The Journal of Clinical Psychiatry. 2001. 3(4):151-155.

Weaver ICG, Cervoni N, Champagne FA, D'Alessio AC, Sharma S, Seckl Jr, Dymov S, Szyf M, Meaney MJ. Epigenetic programming by maternal behaviour. Nat. Neurosci. 2004. 7:846-854.

Zhu LJ, Liu MY, Li H, et al. The Different Roles of Glucocorticoids in the Hippocampus and Hypothalamus in Chronic Stress-Induced HPA Axis Hyperactivity. Homberg J, ed. PLoS ONE. 2014. 9(5):e97689.

# data[].attributes.body
1. Are coping responses to paternal trauma transmissible to the next generation?
Yes, as seen by F1 and F2 MSUS displaying similar coping behaviours in response to aversive stimuli.

2. What epigenetic changes in the glucocorticoid receptor (GR) gene implicated in transmissibility?
MSUS mice (F1 and F2) exhibit a decrease in GR methylation and increased GR expression.

3. Can environmental factors reverse these changes?

Yes, through environmental enrichment.

# data[].attributes.headline
GR Expression is increased in F2 MSUS and corrected in F2 MSUS EE

# data[].attributes.subject
GR Expression is increased in F2 MSUS and corrected in F2 MSUS EE

# data[].attributes.body
In Hippocampal tissue:
(a) Measured by qRT-PCR

1. MSUS mice showed a statistical increase in GR expression.

2. MSUS + EE mice showed a less significant increase in GR expression.

(b) Assessed by bisulfite pyrosequencing in the GR exon 1-- 7 promoter

1. MSUS mice showed decreased methylation.

2. MSUS + EE mice showed a 'normalized' level of methylation.

Although not shown here, sperm cells from MSUS mice showed decreased methylation whereas MSUS + EE mice had 'normalized' levels of methylation. Prefrontal cortex tissue was also assessed in MSUS mice as well as MSUS + EE, showed increased methylation.

Western blotting should be used in addition to qRT-PCR to see increase in GR protein expression and not just mRNA expression.

Image: Gapp et al. 2016

# data[].attributes.headline
F2 MSUS mice from EE show a reversal in resilience and active coping behaviours

# data[].attributes.subject
F2 MSUS mice from EE show a reversal in resilience and active coping behaviours

# data[].attributes.body
(a) F2 EE MSUS mice spent reduced time in light compartment. This indicates an active stress response and reduced resiliency.
(b) F2 EE MSUS mice had reduced latency to enter the dark compartment.
(c) F2 EE MSUS mice demonstrate similar latency to react to the shock as F2 EE controls.
(d) F2 EE MSUS mice had similar number of shock escapes as F2 EE controls. This indicates a reversal in the previously observed active coping response.

Image: Gapp et al. 2016

# data[].attributes.headline
F2 MSUS mice show increased resilience and active coping behaviours

# data[].attributes.subject
F2 MSUS mice show increased resilience and active coping behaviours

# data[].attributes.body
(a) F2 MSUS mice spent an increased amount of time in the light compartment of the box. This indicates these mice have resilience to anxiety-provoking situations.
(b) F2 MSUS mice had similar latency to react to the opening of the dark compartment of the box as control mice.
(c) F2 MSUS mice had a shorter latency to react to the shock in the nose-poke box.
(d) F2 MSUS mice escaped the shock more frequently than the control mice by poking their nose in the hole to stop the shock. This indicates an increased active coping response by attempting to reduce negative outcomes.

Image: Gapp et al. 2016

# data[].attributes.body
Epigenetics is a DNA modification process resulting in regulation of gene expression. One such modification is methylation of cytosine on CpG sequences, leading to suppression of transcription and gene silencing, which can be heritable across generations (Handy et al. 2011). Environmental factors such as stress, are known to influence epigenetic changes. Repeated activation of the HPA axis alters expression of the glucocorticoid receptor (GR) in the hypothalmus due to methylation of the GR gene promoter (Weaver et al. 2004).

Image: K. Maksimovic 2017

# data[].attributes.body
In response to a stressor, individuals compare the demands of the perceived threat to their ability to overcome it (Lazarus & Folkman 1984).  During trauma, the demands of the stressor exceed an individual's ability to deal with the situation, resulting in negative emotions (Herman 1992). To reduce these negative emotions, people utilize two main coping strategies: problem-focused/active coping is when an individual deals with the cause of the stressor, whereas emotion-focused/passive coping is when an individual reduces negative emotions by relying on social support (Lazarus & Folkman 1984). Individuals that successfully use these coping strategies are resilient to trauma, while those that fail to do so may develop psychiatric disorders such as post-traumatic stress disorder (PTSD) (Iribarren et al. 2015).

In twin studies, it has been found that genetic variability significantly influences coping strategies (Dunn et al. 2015), suggesting the heritability of this trait. Interestingly, environments enriched by social interactions and exploration have been found to reduce resiliency to stress and trauma (Gapp 2016). Taken together, these findings suggest that there is a genetic diathesis that interacts with environmental factors to produce an individual's coping style in response to stress and trauma.

Image: E. Daniele 2017