Early life stress and its association with epigenetics and immune system response

Sammanfattning: Stress can induce prolonged deleterious effects on many characteristics in chickens (Gallus gallus). Particular interest has been paid to early life stress. Social isolation as an early life stressor results in increased plasma corticosterone levels. Moreover, it induces behavioural and physiological changes as well as gene expression modifications in the hypothalamus. In the first part of my study, I aim to inquire into social isolation impacts on the short and long-term. Short and long-term effects were assessed by immune system, behaviour and weight. 82 male chickens were assigned to three groups (stress, control and enrichment). The stress group was exposed to social isolation, the enrichment group was provided with enrichment substrates while the control group was left untreated. According to my knowledge, this is the first study that investigates the effects of social isolation on the interuleikn-6 levels as an indicator of immune system response. My findings suggest that social isolation induces short and long-term effects on immune response as well as on body weight. In the second part of my study, I aim to develop a method investigating effects of early stress on DNA methylation in blood and sperm. For this purpose, two methods GBS (Genotyping by sequencing) and MeDIP (Methylated DNA immuneprecipitation) were f using pooled DNA from all individuals for the first time. Moreover, I developed a protocol for extracting sperm DNA from frozen testis. Combining both methods has many advantages, such as cost effectiveness and the ability to evaluate epigenetic signatures in large number of individuals