Thursday, 12 April 2012

The Role of Non-Coding DNA in Cardiovascular Heart Disease


Figure 1. (Protein: Protein Production n.d.)
Introns are spliced out of the RNA in protein synthesis.
Humans are incredibly complex organisms with a genome containing over three billion base pairs. Yet for reasons that are still unclear a mere 2% of this genetic material plays an actual role in the coding of proteins (Fang 2010). This 2% consists of sections of DNA known as exons which are the genetic material that defines and builds an organism. The remaining 98% contains introns and other material that isn’t involved in protein production (Refer to Figure 1) (Fang 2010).

Back in the 1970s a scientist named Susumu Ohno referred to non-coding DNA as ‘junk DNA’ in one of his papers and ever since then the name has stuck (Gregory 2007). However, this assumption that non-coding DNA is useless and has no specific purpose within the cell is now widely refuted after evidence emerged of its contribution to important regulatory functions (Campbell et al. 2009). A team of researchers at the Berkley National Laboratory in California led a study looking at the link between non-coding intervals and heart disease with some very significant results. 


Figure 2. (Lhynnelli 2009)
Cause of Heart Disease
Cardiovascular heart disease kills more than seventeen million people each year, an astounding figure comparable to roughly nine times the population of Brisbane (Refer to Figure 2)(Australian Bureau of Statistic 2011). Previous studies have identified a gene located on a section of ‘junk’ DNA known as chromosome 9p21 which has a direct impact on the risk of developing heart disease (Wein 2010). The researchers in California aimed to further our understanding of the link between non-coding DNA and heart disease by genetically modifying mice.

Mice have a chromosome equivalent to the human 9p21 chromosome which the scientists were able to delete using recombinant techniques (Visel et al. 2010). Genetically modified mice were then monitored for any signs of abnormality. Their study found that the expression of two genes within a distance of 100,000 base pairs from the deletion were significantly inhibited in vascular tissues (Vickers 2010). These genes known as cyclin-dependent kinase 2A and 2B are involved in cell cycle and their absence in the mice resulted in increased cell division in aortic muscle cells. As a result, the new cells could cause an obstruction to blood flow, leading to many of the symptoms present in heart disease. 

While the genetic material removed in the mice corresponds with the human form of the gene, translation of the study’s findings to human cases of heart disease is still unclear. Moreover, further investigation is necessary to clarify the mechanics of the relationship between ‘junk’ DNA and the two cell cycle genes and their association with heart disease. However, the study did find that non-coding segments of DNA have the potential to affect genes within a definitive number of base pairs, suggesting that unlike scientists’ previous beliefs ‘junk’ DNA is far from useless. The rapid progression of genetic technology in the 21st century will allow future studies to discover far more about non-coding DNA, not just in relation to disease of the heart, but many other genetically influenced diseases.

Lucy Tudehope
42878768

References
Australian Bureau of Statistics 2011, Causes of Death Australia, viewed 17 March 2012, http://www.abs.gov.au/ausstats/abs@.nsf/Products/B6940E9BF2695EE1CA25788400127B0A?opendocument
Campbell, A et al. 2009, Biology, 8th edn, Pearson Education Australia, Sydney.
Fang, J 2010, Junk DNA holds clues to heart disease, viewed 17 March 2012, http://www.nature.com/news/2010/100221/full/news.2010.82.html
Gregory, RT 2007, A word about ‘junk DNA’, viewed 17 March 2012, http://www.genomicron.evolverzone.com/2007/04/word-about-junk-dna/
Junk DNA Proves Useful 2008, Viewed 17 March 2012, http://www.redorbit.com/news/science/1597610/junk_dna_proves_useful/
Lhynnelli, RH 2009, Coronary Heart Disease, Viewed March 17 2012, http://nursingcrib.com/nursing-notes-reviewer/coronary-artery-disease/
Vickers, K 2010, ‘The Role of Noncoding “Junk DNA” in Cardiovascular Disease’, Clinical Chemistry, vol. 56, no. 10, viewed 17 March 2012, http://www.clinchem.org.ezproxy.library.uq.edu.au/content/56/10/1518.full
Visel. A, et al. 2010, ‘Targeted deletion of the 9p21 non-coding coronary artery disease risk interval in mice’, Nature, vol. 464, no. 7287, viewed 17 March 2012, < http://search.proquest.com.ezproxy.library.uq.edu.au/docview/204545729/abstract
Wein, H 2010, How Junk DNA Affects Heart Disease, viewed 17 March 2012, http://www.nih.gov/researchmatters/march2010/03012010heart.htm

No comments:

Post a Comment