Chapter 5 author: Eric B. Keverne

Introduction

The brain is a product of gene-environment interactions. Environmental factors can play a huge role in human development. In adverse environments, which might include maternal malnutrition or smoking, fetuses can experience disruptions in genetic developmental planning.

Genomic Imprinting

Genomic printing is a gene-dosage regulatory mechanism that provides for transgenerational epigenetic inheritance for a subset of genes that are monoallelically expressed according to a parent of origin. Genes are regulated by differentially methylated regions (DRMs), also known as imprint control regions (ICRs). One downside of this process is that the failure of ICR methylation can lead to a host of pathological syndromes.

In Utero Influence on Transgenerational Brain Development

In the womb, there are many biological interactions between fetus and mother. The hormone progesterone suppresses fertility and increases maternal foot intake for the infant. The fetal genome also hormonally regulates the maternal hypothalamus to help the interests of the fetus. Additionally, the placenta and fetal hypothalamus are developmentally synchronized.

Neocortical Development and Environmental Influences

Brain development is not just influenced by the in utero environment; it is also affected by the postnatal environment for some 20 years in humans. In animal studies, there is a causal relationship between early-life adversity and changes in the methylation of genes, and this phenomenon might also occur in humans. Changes in modern diets and a lack of physical exercise have advanced the onset of puberty in humans, and puberty is itself a vulnerable period for the development of behavioral problems caused by epigenetics and based on environmental factors.