Epigenetics: The Future of Psychology - Latest News The Future of Psychology & Neuroscience Richard E. Brown Psychology Department Dalhousie University Halifax, NS, B3H 4J1Authors:

Epigenetics: The Future of

Psychology & Neuroscience

Richard E. Brown

Psychology Department

Dalhousie University

Halifax, NS, B3H 4J1

Nature versus NurtureDespite the belief that the Nature vs. Nurture argument about the causes

of neurobehavioral phenomena is dead (Traynor & Singleton, 2010) it

persists in many areas of Psychology and Neuroscience. Indeed, the

nature vs. nurture issue seems alive in discussions of development,

athletic ability, neural disorders, aging, etc.

The Central Dogma of

Molecular Biology

(F. Crick, 1970, Nature,

227, 561-563)

Transcription of DNA to RNA

protein: This dogma forms the

backbone of molecular biology

and is represented by four

major stages.

1. The DNA replicates its information in a process that involves many enzymes:

replication.

2. The DNA codes for the production of messenger RNA (mRNA) during

transcription.

3. In eukaryotic cells, the mRNA is processed (essentially by splicing) and migrates

from the nucleus to the cytoplasm.

4. Messenger RNA carries coded information to ribosomes. The ribosomes “read” this

information and use it for protein synthesis. This process is called translation.

Proteins do not code for the production of protein, RNA or DNA.

They are involved in almost all biological activities, structural or enzymatic.

Behaviour Genetics and The Central Dogma

Genes Brain Behaviour

Altered

Genes

Altered

Brain

Altered

Behaviour

BUT

What about environmental influences?

Brain

Genes Behaviour

Environment

Genes x Environment Brain Behaviour

?

??

The central dogma of molecular biology: what about and the

environment?

Genes & environment interact“True, the old dogma of nature versus nurture is dead, but

unfortunately it has been replaced by a puzzle even harder to

solve.” (Traynor & Singleton, 2010, p.199)

The solution to the nature versus nurture problem has been to

propose that genes and behavior interact in the determination of

neural and behavioral development (Hebb, 1953; Dowling, 2004).

Hebb, D.O. (1953). British Journal of Animal Behaviour 1:43-47.

Heredity and Environment in Mammalian BehaviourD.O. HebbMcGill University, Montreal, Canada

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are needed to see this picture.







Environmental enrichment facilitates neural development.

C. D. Allis, T. Jenuwein, D. Reinberg, M.-L. Caparros (Eds). Epigenetics. CSHL Press, 2007.

Genetic mutations of the DNA template are heritable somatically and through the germ line.

Epigenetic variations in chromatin structure modulate the use of the genome by:

(1) Histone modifications (mod)

(2) Chromatin remodeling (remodeler)

(3) Histone variant composition (yellow nucleosome)

(4) DNA methylation (Me) and

(5) Noncoding RNAs.

Marks on the chromatin template may be heritable through cell division and collectively contribute to determining

cellular phenotype.

Ch.3, p29

Epigenetic processes provide a mechanism for environmental

factors to modulate gene activity.

Neurochemical signaling mechanisms regulate chromatin.

Coordinated Modification of

Chromatin.

The transition of a naïve chromatin

template to active euchromatin

(left) or the establishment of

repressive heterochromatin (right),

involving a series of coordinated

chromatin modifications. In the

case of transcriptional activation,

this is accompanied by the action

of nucleosome-remodeling

complexes and the replacement of

core histones with histone variants

(yellow, namely H3.3). (Figure 11,

Allis et al., 2007)

Changes from active to silent chromatin states as the

result of feedback loops between intermediate

states.

(A) Different chromatin states. Both DNA and

histone modifications interact to determine

whether genes are active or silent.

Transcriptional activators or repressors also

determine whether genes are activated or

repressed.

(B) For example, histone H3K9 when acetylated via

HAT (histone acetyltransferase) activates

genes, but when deacetylated, or methylated,

or when CpG methylation occurs, then gene

repression (silencing) occurs.

Environmental stimuli (light, temperature), diet,

hormones and diseases such as cancer can act

as epigenetic factors to regulate gene activation

and gene silencing.

How do epigenetic processes integrate environmental and genetic

information?

Big Questions in Epigenetic Research. The many experimental systems used in epigenetic

research have unveiled numerous pathways and novel insights into the mechanisms of

epigenetic control. Many questions, as show in the figure, still remain and require further

elucidation or substantiation in new and existing model systems and methods. (From: Allis et

al., 2007, Ch 3, p.55)







Epigenetics, Psychology and Neuroscience

Early studies by Meaney showed that maternal behavior is an

epigenetic mechanism in development.











Epigenetic mechanisms are involved in learning and memory.

Epigenetic mechanisms function in all

areas of neuroscience, including neural

development, the neural basis of learning

and memory, drug addiction, sexual

differentiation of brain and behavior, aging

and neurodegeneration and psychiatric

disorders.

Neural development

Learning & Memory

Drug Addiction

Sexual differentiation

Aging

Neurodegeneration

Psychiatric disorders

Epigenetic mechanisms are involved in all

areas of psychology: developmental, social,

cognition, learning and memory, aging, and

clinical.

Cognitive

DevelopmentalSocial

Age-related learning & memory loss

Clinical disorders

Epigenetics as a unifying principle in

psychology and neuroscience.

The New Central Dogma

Environment

Neurochemistry (Extra- and intra-cellular)

Epigenetic mechanisms

DNA

mRNA

Protein Synthesis

Brain Development

Behaviour

Conclusions• Epigenetic mechanisms are central to the

understanding of brain-behavior relationships.

• Epigenetic mechanisms can form unifying principles linking diverse areas of psychology and neuroscience; from neuro-behavioral development through social, cognitive, clinical and aging mechanisms.

• Epigenetic mechanisms may provide new theories for diagnosing or treating neuro-behavioral and psychological disorders, such as schizophrenia, autism, depression and Alzheimer’s disease.

• Epigenetics should form a central principle in the teaching of psychology and neuroscience.

Epigenetics: The Future of Psychology - Latest News The Future of Psychology & Neuroscience Richard E. Brown Psychology Department Dalhousie University Halifax, NS, B3H 4J1Authors:

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