For each
tissue or cell groups in multicellular organisms, cells express specific
activity and phenotype, different from other tissues’ cells; despite all of
them have the same genetic material. This differentiation happens due to
epigenetic mechanism: a regulation of genes that controls which genes will be
expressed and which will be ignored. Epigenetics enables identical twins, with
identical genes, to have different traits and personalities (Williams, 2013).
Epigenetics is composed by
chemical flags and markers on genes that are copied with genes during the DNA
replication. It can alter gene expression without altering the DNA sequence by
blocking or activating a gene expression. Evidences show that the environment
may alter the epigenetic regulation. Also, epigenetic modifications can confer
phenotypic plasticity and in some cases heritability to offispring (Arinmondo,
2012).
DNA methylation is one type of
epigenetic regulation. The linking of methyl groups to certain nitrogenous
bases impedes the gene expression. Another way to regulates genes is by histone
modifications. Histones are proteins whereby DNA is enrolled around to compact
(part of chromatin structure). The turning out of histones enables the DNA
transcription (activating gene expression). Paola Arinmondo (2012) affirmed
that other epigenetic modifications have been discovered and she cited
nucleosome positioning and non-coding RNAs.
Epigenetics is related to
certain important phenomena of controlling gene expression. Imprinting and
X-chromosome inactivation are among these phenomena. Imprinting occurs when one
allele of certain gene is activated while another one is methylated in cases of
gene expression by one single allele. X-chromosome inactivation is one
interesting mechanism whereby women balance the quantity of gene expression in
their genome by methylation of one of their X-chromosomes. As men have little
gene expression in their Y-chromosome, women would have excessive gene
expression if both their X-chromosomes were active.
Biologists are interested in epigenetics
researches due to the non-evident genetic causes of certain diseases. Abnormal
epigenetic patterns are found in many diseases, including cancer. For example, the
decrease in methylation could cause excessive or improper expression of genes
such as those that express cell growth. Also, epigenetic errors could methylate
tumor suppressor
genes. According to Arinmondo
(2012), there are chemical modifiers that can reverse epigenetic alterations
and it could be a promise to therapeutic use. Some studies have focused in developing
chromatin modifying agents as anticancer therapy. However, Williams (2013)
argues that we do not have appropriate technology to read a person’s epigenome
and it has still a long way to go.
REFERENCE
LIST
Williams, S.
C. P. February 26, 2013, ‘Epigenetics’, Proceedings
of the National Academy of Sciences, vol. 110, no. 9, p. 3209.
Arimondo, P.
B. November 2012, ‘Epigenetics’, Biochimie,
vol. 94, issue 11, pp. 2191-2192
Very interesting. You’ve done a good job explaining a difficult concept. You say that biologists are interested in epigenetics due to its importance in disease. What about genetic disorders? Could epigenetics be an influence here too?
ReplyDeleteYes. According to Simmons (2008), epigenetics influences some genetic disorders such as syndromes involving chromosomal instabilities. Some examples of syndromes are Fragile X syndrome, Angelman’s syndrome and Prader-Willi syndrome.
DeleteREFERENCE: Simmons, D. (2008) Epigenetic influence and disease. Nature Education 1(1):6
I am very interested in epigenetics, yet I'm still a beginner in my understanding. :-) When genetic research first came to public attention I remember people thought that we were only a few years away from finding the cures for all sorts of cancers, other diseases and disorders. It hasn't turned out to be that simple and I think epigenetics is one big reason for that. What do you think?
ReplyDeleteYes. That is true. There are some reasons why we still did not get complete understanding over genetics and cure to genetic diseases. Firstly, genetics is not so simple. Finding the genes that express certain phenotype or disease is complex. Many times grouping of genes interact with each other to express only a phenotype. Secondly, other phenomenons influence that expression such as epigenetic processes. The study over these processes is still limited. Then, we have still a long way to go.
ReplyDelete