Tuesday, 22 May 2012

Epigenetics in the Ice Age

Recent research highlighted by the New Scientist article “Fossil DNA has clues to surviving rapid climate change” suggests that epigenetics played a significant role in the adaptions animals made during the last ice age. It focussed on research by a team from the University of Adelaide and University of New South Wales, headed by Alan Cooper and Catherine Suter, who made the discovery after investigating the genetic sequence found in some specimens of extinct bison (Holmes 2012).

Figure 1: Bison bones used in the research, found in the Canadian Arctic (University of Adelaide, 2012)
Figure 2: The basic idea of DNA methylation (Winer, M, 2011)

Epigenetic inheritance involves the inheritance of characteristics from one generation to another, by processes that do not involve the nucleotide sequence of DNA (Reece et al, 2011, p. 364). Therefore, Cooper and Suter’s team looked at the characteristics that animals developed, which may have been passed down to future generations, when the animals were exposed to the change in environment. This was done by finding the bones of a bison that lived around 26,000 years ago in the Canadian arctic permafrost (Figure 1), before extracting the DNA contained within these bones (Holmes 2012). Tests were then performed, using the bisulfate sequencing technique, searching for DNA methylation (Holmes 2012). DNA methylation is when a methyl group joins to a base of DNA, commonly cytosine (Reece et al, 2011, p. 364) (Figure 2). According to the website Sigma-Aldrich, “DNA methylation is an epigenetic modification that changes the appearance and structure of DNA without altering its sequence” (2008). Further research completed by the team of scientists proved that some of the DNA methylations they found in the bison were in the same places of modern cow DNA (Holmes 2012). This discovery is very important, as it shows that there was some form of epigenetics during the time period that the fossils lived. As for the similar methylations that were discovered in modern cows, Holmes suggests that this “is strong evidence that the ancient methylations were not the product of chemical damage occurring after the bison’s death” (2012). More tests on five other specimens of bison found gave the scientists no results (Holmes 2012), which proves that this area of research is very difficult. Noting that scientists currently have limited knowledge when it comes to understanding epigenetic signals (Holmes 2012), advances in this field are hard to make. There are a number of different techniques scientists can use to tell if epigenetic modification has occurred, like bisulfate sequencing, fluorescent insitu hybridisation and DNA adenine methyltransferase identification for example (Medindia, n.d.). Despite this, far more research is required to understand what that information is saying, and to get anything out of it.

There is still a lot of work to be done on this before any major conclusions can be drawn. But this research has found that at the start of the last ice age, animals may have undergone epigenetic change to adapt to the changing environment. With the current climate change situation facing humans, this find in the remains of a 26,000-year-old bison could be important in the future. 

Bibliography

Holmes, B 2012, Fossil DNA has clues to surviving rapid climate change, New Scientist, viewed 12 March 2012, <http://www.newscientist.com.ezproxy.library.uq.edu.au/article/dn21410-fossil-dna-has-clues-to-surviving-rapid-climate-change.html?full=true>

Medindia n.d., Epigenetics Molecular Basis of Epigenetics, viewed 15 March 2012, <http://www.medindia.net/patients/patientinfo/epigenetics-molecular-basis.htm>

Reece, J, Meyers, N, Urry, L, Cain, M, Wasserman, S, Minorsky, P, Jackson, R & Cooke, B 2011, Campbell biology, Ninth Edition Australian Version, Pearson, Australia

Sigma-Aldrich 2008, DNA Methylation and Transcription Repression, viewed 15 March 2012, <http://www.sigmaaldrich.com/life-science/your-favorite-gene-search/pathway-overviews/dna-methylation-and-transcription-repression.html>

University of Adelaide 2012, Ancient DNA holds clues to climate change adaptation, viewed 17 March 2012, <http://www.adelaide.edu.au/news/news50641.html>

Winer, M 2011, ESET- A Second Pathway for Silencing Retroviruses, viewed 17 March 2012, <http://www.martincwiner.com/eset-a-second-pathway-for-silencing-retroviruses/

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