The branch of biology called epigenetics aims to understand how a person's environment, behavior, and a host of other factors affect the function and behavior of his or her genes — and a new study helps shed light on one of its mysteries.
A team of biologists from the University of Bath in the UK and the University of Vienna in Austria has discovered new "imprinted genes" in the genome of mice. Results of their findings are published in the latest Nature Communications journal, in a report titled Genomic imprinting in mouse blastocysts is predominantly associated with H3K27me3.
How Imprinted Genes Work
Imprinted genes refer to the expression of genes as an effect of inheritance. For example, the human body contains more than 30 trillion cells, most of which contain genes coming from an individual's parents: a father and a mother. Each of these parents contributes one version of each gene, with the unique combination of these genes being partly responsible for making a unique individual with virtually no exact copies.
In common cases, each gene in a pair is either equally active or inactive. However, this is not the case for imprinted genes, about less than one percent of more than 20,000 genes. Additionally, imprinted genes are usually more active in one parental version compared to the other.
Before the new study from the Universities of Bath and Vienna, there are 388 recorded genes with parent-of-origin expression bias, according to the Gene Imprint website, including some 130 well-documented imprinted genes.
In a press release from the University of Bath, Professor Tony Perry from the Department of Biology & Biochemistry explains that imprinting has something to do with an "important family of genes," having implications for understanding health and diseases. He said that the new discovery of "the seventy-plus new ones add an important piece of the jigsaw."
Their new study revealed that the switching of imprinted genes on and off is not always because of DNA methylation or the process of methyl group molecules being added to genomic DNA. The process has been previously identified as capable of repressing gene activity, therefore switching them off. DNA methylation is the first known type for imprinted genes, identified some three decades ago. In the new study, histones are found to have a greater contribution toward imprinted genes than previously thought. Histones are a family of basic proteins that integrate with DNA in the nucleus.
Importance of Understanding Gene Imprinting
The main importance of understanding the nature and mechanism of genomic imprinting is the risks of diseases that could arise from imperfections in the process. Mutations and deletions in particular sections of imprinted genes would definitely have an effect on the offspring. The same can be said for cases of uniparental disomy, or when an offspring only inherits two copies of a chromosome from one parent and no copy from the other, as explained in a 2008 Nature Education article.
In the new study, researchers are still working to understand how a parental version of a given gene can be switched on and off and maintain its state while keeping another in an opposite state. While it has been known that switching occurs during the formation of the sperm and egg cells, the exact mechanisms remain unclear.
"We may underestimate how important the relationship between imprinting and disease is, as well as the relationship of imprinting to the inheritance of parentally-acquired disease, such as obesity," Professor Perry explains in a press release from Bath. "Hopefully, this improved picture of imprinting will increase our understanding of disease."
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