Question

Understanding control of gene expression by chromatin regulation We discussed how maternal grooming behavior regulates anxiety and stress response in rats. Rats raised by low-care mothers grow up to be more anxious and guarded adults. Rats raised by high-care mothers on the other hand become more relaxed adults. Below are two key results from the study that discovered this phenomenon. Scientists looked at DNA methylation in the promoter of a gene called glucocorticoid receptor which is expressed in the hippocampus of the brain. When they compared methylation of this region in rats raised by low-care or high-care (more nurturing) mothers, this is what they found: L: Low Care H: High Care D C-methylation (%) What is the result and the conclusion of this experiment? HINT: think about what this result means in terms of glucocorticoid receptor gene expression and anxiety in adulthood

Answer 1

Answer: The result of the study shown in the graph indicated that the DNA methylation percentage in the promoter of glucocorticoid receptor gene is very high in rats raised by low care mother when compared to high mothers. DNA methylation is epigenetic mechanism that involves addition of methyl groups to the bases such as cytosine and adenine in the DNA. DNA methylation in the promoter gene repress the expression of genes that are under the control of that promoter. Glucocorticoid receptors are involved glucocorticoid stimulated signaling that control expression of various genes involved in regulating anxiety disorders. Dysregulation of Glucocorticoid receptor signaling is implicated in the psychopathologies related disorders including mood and anxiety disorders. In the current study, the rats raised by low care mothers grows as more anxious and guarded adults. This is due to high cytosine methylation percentage in the promoter of glucocorticoid receptor gene. High methylation repress the gene expression of glucocorticoid receptor gene, leading to dysregulation of glucocorticoid receptor signaling and anxiety in adulthood. In contrast, the rats raised by high care mothers grow as relaxed adults. This due to low cytosine methylation percentage in the promoter of glucocorticoid receptor gene. Low methylation leads to increased gene expression of glucocorticoid receptor gene, leading to normal functioning of glucocorticoid receptor signaling that controls anxiety. The rats raised by low care mothers will have more stress compare to those raised by high care mothers. This leads to epigenetic changes such as methylation in the promoter glucocorticoid receptor gene in rats raised by low care mothers, leading to anxiety.