dna methylation

WHY CANCER INCIDENCE INCREASES WITH AGE

AND

PERMANENT CHANGES IN BRAIN GENES MAY NOT BE SO PERMANENT AFTER ALL

Daniela Hincapié TabaresMedical student-III Semester

Mutations can appear because the incorporation of an incorrect base during the replication, spontaneous changes or because the exposure to chemical agents and radiation. There are 3 DNA repair mechanisms: •Direct reversion of damaged DNA•Excision repair•Repair of double strand breaks

INTRODUCTION


• Cancer incidence increases with age, but the cause of this had been unclear until now. Scientists think that it could be related with the DNA methylation because there are some sites across the human genome that change as people age.

• Methylation is the process that prevents the cell from turning into certain genes, Zongli Xu and Jack Taylor demonstrated in their study that if a cell can not turn into a gene, the possibility of becoming a cancer cell increases.

ScienceDaily, February 3, 2014


• The study was done with blood samples from 1000 women, Xu and Taylor used a microarray with 27000 specific methylation sites to analyze the human genome. The results were really surprising because they found a high percent of sites which had an augmentation of methylation in all seven cancer types.

• The scientists that participate on the study came to the conclusion that age related methylation could affect negatively the expression of some genes, this fact stimulate the transition of certain cells to cancer.



• The research also showed that the accumulation of methylation process in cells occurs at a rate of one per year; so as old as you get, more methylation will you have.

• DNA methylation belongs to the normal aging process and it happens in genes that are related with the development of the cell. The methylation process is tightly related with cancer cells because this disease consists in the wrong proliferation of the cells, where a group of cells divide withou control and autonomously.



• Xu and Taylor will do a bigger research with the purpose of determining if environmental exposures during adulthood or infancy affect DNA methylation.

• DNA methylation is one of the most important epigenetic devices that have the capacity of regulating gene expression without changing the DNA sequence.


PERSONAL OPINION• I found this article extremely interesting

and useful, because it might bring excellent bases for the treatment of

severe diseases such as cancer, and also a way to prevent them. In my opinion, scientists should do more research on the human genome because they can discover the main causes of genetic

disorders. This can give people a better lifestyle, preventing the incidence of

these diseases.


• ScienceDaily, January 27, 2014

• Cells can turn off genes they do not need by a process called DNA methylation, which consists in the addition of a methyl group to the DNA. Scientists thought that this event can only happen with an specific DNA sequence CpG (cytosine-guanine), but recently they found methylation in other sequences different from CpG, which they called non CpG, in stem cells and neurons.



• The research was done by the team Hopkins, they discovered that non CpG methylation is more dynamical and it takes place in mature cells. These characteristics allows it to function as a system of gene regulation, which was extremely helpful with the Rett Syndrome.

• Non CpG methylation stops genes from being expressed because it has it´s own niche that empower it to act in an independent way.



• Before discovering non CpG methylation, scientists thought that the process was irreversible, meaning that if a methyl group was attached to a cytosine, the gene was shut off forever. But, non CpG methylation is ruled in a different way because it operates in mature cells, so the reaction can be reversible for being an active process.



• Non CpG methylation and CpG methylation are both read by MeCP2, which is an enzyme that participates as a player in methylation. Rett Syndrome patients have a mutation in MePC2, so the understanding of DNA methylation means the understanding of this syndrome.

PERSONAL OPINION• This article has a huge medical utility

because it leads scientists to understand Rett Syndrome, this fact can allows them to find the cure for

this syndrome or to decrease its incidence in people. Personally, I found

it really absorbing because it shows the importance of DNA in different

pathologies and it encourages me to learn more about this amazing topic that has a big influence in medicine.

MEDICAL UTILITY 1

• This study is the beginning of an excellent and big research that in a future could give us the cure of cancer, or at least the way to prevent it. It sounds amazing and unrealistic but it is true, because if scientists discovered something that can slow down the speed of the accumulation of methylation events in cells, maybe they will be able to establish a new treatment for cancer, that is less invasive and less harmful for the healthy cells of the human body.

MEDICAL UTILITY 1

• The explanation of why cancer incidence increases with age may be related with the DNA methylation according to this study. I think that the study of the human genome is the base for discovering the main cause of many diseases, and if we know the element that causes them, maybe we can invent something that cures them.

MEDICAL UTILITY 2

• The discovery of non CpG methylation demonstrated that permanent changes in brain genes may not be not be so permanent after all. Because through this new system of gene regulation, a methylation can be a reversible process which depends of the presence of the enzymes needed for the addition of the methyl group. The reversible mechanism can revolutionize the treatments that are used for diseases caused by a DNA disorder.

MEDICAL UTILITY 2

This article has its main influence in the Rett Syndrome because the mutation that causes this syndrome is located in the MePC2, which is the enzyme that function as a player in the

methylation process of CpG methylation and non CpG methylation. This study encourages scientists to do a deeply investigation of this syndrome, and if they can understand it

completely, they can propose new treatments to cure it or to minimize its effects. Once again, science has proved that DNA is the most important element in the genetic information and

that the research focused on the study of DNA have a relevant influence in medicine, specially for therapeutic purposes.

BIBLIOGRAPHY

• Martínez S. Lina María. Biología Molecular. Séptima Edición. Medellín. Universidad Pontificia Bolivariana. Facultad de Medicina. 2012. 85-88 P.

• Z. Xu, J. A. Taylor. Genome-wide age-related DNA methylation changes in blood and other tissues relate to histone modification, expression and cancer. Carcinogenesis, 2013; 35 (2): 356 DOI: 10.1093/carcin/bgt391. (online magazine) http://www.sciencedaily.com/releases/2014/01/htm.

• Junjie U Guo, Yijing Su, Joo Heon Shin, Jaehoon Shin, Hongda Li, Bin Xie, Chun Zhong, Shaohui Hu, Thuc Le, Guoping Fan, Heng Zhu, Qiang Chang, Yuan Gao, Guo-li Ming, Hongjun Song. Distribution, recognition and regulation of non-CpG methylation in the adult mammalian brain. Nature Neuroscience, 2013; DOI: 10.1038/nn.3607. (online magazine) http://www.sciencedaily.com/2014/01/htm.

dna methylation

Documents

cpg methylation

related methylation

augmentation of methylation

cancer cells

age cancer incidence

cancer incidence increases

specific methylation

permanent changes