Epigenetics: Fundamentals

Epigenetics & Identical Twins

What is Epigenetics?

Epigenetics is the study of heritable changes in gene expression (active versus inactive genes) that does not involve changes to the underlying DNA sequence — a change in phenotype without a change in genotype — which in turn affects how cells read the genes. Epigenetic change is a regular and natural occurrence but can also be influenced by several factors including age, the environment/lifestyle, and disease state. Epigenetic modifications can manifest as commonly as the manner in which cells terminally differentiate to end up as skin cells, liver cells, brain cells, etc. Or, epigenetic change can have more damaging effects that can result in diseases like cancer. At least three systems including DNA methylation, histone modification and non-coding RNA (ncRNA)-associated gene silencing are currently considered to initiate and sustain epigenetic change.[1] New and ongoing research is continuously uncovering the role of epigenetics in a variety of human disorders and fatal diseases.

The Evolving Landscape of Epigenetic Research: A Brief History

What began as broad research focused on combining genetics and developmental biology by well-respected scientists including Conrad H. Waddington and Ernst Hadorn during the mid-twentieth century has evolved into the field we currently refer to as epigenetics. The term epigenetics, which was coined by Waddington in 1942, was derived from the Greek word “epigenesis” which originally described the influence of genetic processes on development.[2] During the 1990s there became a renewed interest in genetic assimilation. This lead to elucidation of the molecular basis of Conrad Waddington’s observations in which environmental stress caused genetic assimilation of certain phenotypic characteristics in Drosophila fruit flies. Since then, research efforts have been focused on unraveling the epigenetic mechanisms related to these types of changes.[3]

Currently, DNA methylation is one of the most broadly studied and well-characterized epigenetic modifications dating back to studies done by Griffith and Mahler in 1969 which suggested that DNA methylation may be important in long term memory function.[4] Other major modifications include chromatin remodeling, histone modifications, and non-coding RNA mechanisms. The renewed interest in epigenetics has led to new findings about the relationship between epigenetic changes and a host of disorders including various cancers, mental retardation associated disorders, immune disorders, neuropsychiatric disorders and pediatric disorders.

[show 4 sources]

  1. Egger G. et al. Epigenetics in human disease and prospects for epigenetic therapy. Nature 429, 457-463 (2004).
  2. Waddington C.H. “The epigenotype”. Endeavour 1: 18–20 (1942)
  3. Brouwer J.R. (2012, April 4). A Crash Course in Epigenetics Part 1: An intro to epigenetics. Bitesize Bio. Retrieved June 18, 2013 from bitesizebio.com.
  4. Holliday, R. Epigenetics: A Historical Overview. Epigenetics, 1:2 76-80 (2006).