Epigenetic Regulations

Every cell within our own body contains the same genes. Epigenetics directs how our genes are expressed and controls which genes get turned on or off.

Epigenetic regulation is a mechanism where genetic, environmental, and aging risk factors have the potential to trigger differences in each hemisphere of the brain. DNA methylation signatures aid the specialization of neurons, explaining how people can seem to be either right-brain dominant or left-brain dominant [4].

The researchers found numerous epigenetic differences that are linked to variations in gene activity between the two sides of healthy brains [2]. During the early stages of the human lifespan, we start with pronounced differences between the two brain hemispheres; however, as we age, the hemispheres become more epigenetically similar.

Early brain asymmetry in DNA methylation is linked to the lateralization of the nervous system’s organization. Epigenetic divergence affects gene patterns on both hemispheres of the brain if pathogenic, this can contribute to the onset of Parkinson’s disease symptoms being unevenly distributed across the body [3].

Differential Regulation of Genes

Because brain lateralization develops early on, individuals that have more epigenetically similar halves of the brain at a young age had the disease progress faster due to the symptoms being more evenly distributed to both sides of the body.

Regional differences of certain genes within the brain can influence neuron survival in the brain. These differences contribute to the asymmetric response of the onset of Parkinson’s disease [2].

The reason for symptom asymmetry in Parkinson’s disease is that certain genes on the opposite sides of the brain can be switched either “on” or “off” through the process of epigenetic regulation[2].
In aging individuals, their neuronal epigenomes contribute to a decrease in hemispheric brain asymmetry. The convergence of Parkinson’s disease and aging in neuronal epigenomes potentially adds to the bilateral symptoms in Parkinson’s disease over time.

Parkinson’s disease patients with longer disease courses (> 15 years) tend to have greater symptom asymmetry than patients with shorter disease courses (<15 years). Determining that uneven neuronal methylation across the two sides of the brain has a significant role in patient endurance throughout the disease.

Neurons in Parkinson’s diseased brains have more significant hemispheric asymmetry than the healthy brains; this is primarily due to differential CpH methylation [2].

Parkinson’s disease patients with the longer course of the disease are primarily due to the higher contrasts between the right and left hemispheres of the brain being methylated.

These findings have the potential to bridge the gap between DNA expression of either brain hemisphere and the lateralization of the brain.

Parkinson’s Disease as a Model for Asymmetrical Epigenetic Variation

The asymmetrical fashion of Parkinson’s disease symptoms leads scientists to believe that the opposing hemispheres could affect how the disease progresses. One side of the brain could be the more susceptible hemisphere to the processes that cause the death of brain cells in Parkinson’s disease.

The differences in cell death between the two brain hemispheres affect the appearance of the disease, where one side of the body’s symptoms progresses faster [2].

This is one of the first studies to pull out the molecular reasoning behind brain asymmetry, providing insight on how we understand gene expression within the brain. They found numerous epigenetic differences that are linked to variations in gene activity between the two sides of healthy brains.

These revolutionary new findings on neuron methylation have promising potential for uncovering therapeutic strategies for diseased patients suffering from neurological disorders. Epigenetic research is contributing to new ways that epigenetic regulation can be applied to medical research and future therapies.