01.02.07
Biomarkers In Focus At Environmental Health Perspectives
The Focus article in the December issue of Environmental Health Perspective covers a term that should be very familiar to anyone following epigenetics: biomarker. While the term “biomarker” can be used to mean many different things, there are actually clear definitions for biomarkers that have been designated by scientists:
- In 1987, the National Research Council convened a committee to investigate how biomarkers were being developed and used in the environmental health sciences. The conclusions were documented in a seminal paper published in the October 1987 issue of EHP, which described the four basic biomarker groupings still in use today: exposure biomarkers (which include markers of external exposure and of internal dose); biomarkers of biologically effective dose; effect biomarkers (which include markers of health impairment or recognized disease, early disease precursors, or peripheral events that predict health impairment); and susceptibility biomarkers (which include intrinsic genetic or other characteristics or preexisting diseases that result in an increase in internal dose, biologically effective dose, or target tissue response).
One of the common ways that epigenetic researchers aim to identify a biomarker for a particular disease or phenotype is by measuring DNA methylation on specific gene promoters of interest — whether it be hypermethylation (an increase in DNA methylation) or hypomethylation (a decrease in DNA methylation). However, as the mechanism for linking a change in DNA methylation with disease susceptibility are not understood, there seems to be no clearly defined method for identifying an epigenetic biomarker using DNA methylation. Some researchers use a method that measures the percentage of methylated CG sites within a particular loci, while others examine specific CG sites and determine if any specific CG site’s methylation status is changed. These differing approaches, while both potentially useful in identifying changes in methylation pattern, may be a source of conflicting results in epigenetics research and could lead to a loss of confidence in using DNA methylation as a means of identifying clinically important biomarkers for disease. Link
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