VD

Study Notes on Epigenetics in Psychology

Introduction

  • The chapter by Ian Weaver has been adapted by Queen’s University Psychology Department for the NOBA project.

  • It highlights the profound influence early life experiences have on physical and mental health throughout life.

  • Emphasizes the relevance of the “Three-Step Method” for learning support, referring students to Queen’s Student Academic Success Services.

Learning Objectives

  • Define epigenetics and discuss its molecular machinery.

    • Epigenetics: Dynamic layer of information associated with DNA that varies among individuals and can be altered by experiences and environments.

    • Essential for understanding psychological disorders influenced by environmental factors alongside genetic factors (genome).

  • Explore the mechanisms of the initiation, maintenance, and heritability of epigenetic states in research related to

    • Learning and memory

    • Emotion

    • Social behavior

  • Discuss recent developments in epigenetics related to mental health.

  • Inventory challenges faced by psychological epigenetics in explaining how nurture influences nature.

Key Concepts in Epigenetics

  • Neural and developmental pathways regulated by epigenetic factors.

    • Example: Cognitive behaviors and personality traits influenced by epigenetic effects.

  • Misregulation of epigenetic mechanisms can lead to disease states.

    • Examples to discuss: Psychological disorders that may arise from misregulated epigenetics.

  • Therapeutic Targets: Understand that epigenetic machinery can be targets for therapeutic agents.

The Dynamic Nature of the Epigenome

  • The epigenome is viewed as a “missing piece” for understanding the development of psychological disorders in alignment with genetic factors.

  • It varies among cell types, tissues, and brain regions.

    • High-throughput techniques: Sequencing to study gene expression regulators unveiled insights into the epigenome (Gregg et al., 2010).

  • Epigenetics deals with phenotypic plasticity created through gene-environment interactions.

    • Allows organisms to adapt to environmental variations through synaptic remodeling and neural network developments.

Early Life and Development

  • Early childhood is crucial for both physical and mental development.

    • During this period, more than 700 neural connections form every second.

  • Genotype-environment interactions (G×E) create complex neural connections influencing cognitive traits.

  • The challenge for psychology includes integrating findings from genetics and environmental factors, such as:

    • Quality of infant-mother attachment

    • Influence on personality and mental health

Heritability Studies

  • Common DNA variations and rare mutations only account for 1%-2% of the risk for inheriting personality traits and mental disorders (Dick et al., 2010; Gershon et al., 2011).

  • Complex relationships make it hard to determine how DNA variations correlate with brain function and development (Petronis, 2010).

  • Epigenetics may provide insight into the unaccounted heritability regarding personality and mental health.

Epigenetic Mechanisms

Definition and Discussion of Epigenetics

  • Epigenetics: refers to the transmission of phenotype in relation to gene expression without altering the DNA sequence.

    • Etymology: epi- (Greek: επί-, meaning "over, above") + genetics (Waddington, 1942; Wolffe & Matzke, 1999).

Molecular Control of Gene Expression

  • Chromatin structure: DNA is compacted around proteins (histones) forming nucleosomes, crucial for gene regulation.

    • Approximately 2 meters of genomic DNA is compressed within a 2 μm nucleus.

  • Type of cytokines define whether genes are expressed or silenced:

    • DNA Methylation: The primary epigenetic mark, occurring mainly at CpG dinucleotides.

    • DNA methyltransferases (DNMTs) catalyze the transfer of methyl groups, crucial for gene expression regulation (Adams et al., 1979; Law & Jacobsen, 2010).

    • Histone Modification: Another vital mark influencing gene activation or repression and contributes to the concept of a “histone code” (Jenuwein & Allis, 2001).

    • Common modifications include acetylation (gene activation) versus deacetylation (gene silencing).

Impact of Life Experiences on Epigenetics

  • Life events (e.g., stressors in childhood) can modify histone proteins to affect personality traits.

    • Example: Upregulation of certain traits or responses may occur due to historical experiences (Weaver et al., 2004).

Parental Influence and Early Experiences

  • Importance of the infant-parent bond: Positive attachment influences stress response programming.

    • Evolutionarily, this allows developmental adaptations to the environment (Bradshaw, 1965).

    • Maternal nurturing in rats correlates with emotional and cognitive behaviors of offspring (Caldji et al., 1998; Francis et al., 1999).

Nutritional Epigenetics

  • Nutritional impacts: The food choices made by individuals can cause epigenetic modifications, altering long-term health (Wells, 2003).

  • Studies show that diet influences the expression of various genes via methylation processes or through altering substrates for enzymatic reactions.

Adverse Conditions Impacting Development

  • Significant historical events like WWII famines impacted populations, affecting health outcomes associated with prenatal stressors experienced by mothers.

    • Example: Individuals exposed to famine showed increased risks for chronic conditions later in life (Bateson, 2001; Heijmans et al., 2008).

Epigenetic Mechanisms in Learning and Memory

  • Neural Plasticity: Changes in neural pathways allow learning; influenced by epigenetic mechanisms essential for synaptic changes.

  • Epigenetic changes (DNA methylation and histone modifications) underlie memory formation and cognitive function, which are often disrupted in psychological disorders (Day & Sweatt, 2011).

Disorders and Epigenetics

  • Epigenetic studies link alterations in neurodevelopmental pathways with various psychological disorders (Mill et al., 2008).

  • Evidence suggests therapies targeting epigenetic mechanisms could ameliorate issues related to mental health.

Conclusion

  • Understanding the interaction between genes and environment through epigenetic frameworks provides insights into prevention and treatment through identifying therapeutic targets.

  • Ongoing research is crucial to shaping complex approaches to treatment and understanding individual differences in resilience against adversity.