The human genome is an indisputably stunning piece of work: 25,000 or so genes containing all of the essential instructions for building a being.
Still, it's only a guide. Alone, the genome cannot construct a person. The “book of life” requires a vocabulary of attendant molecules, compounds and chemicals – a biochemical language, so to speak – to help genes write the individual story of you.
Altogether, this phenomenon is called epigenetics. Its study represents one of the cutting edges of bioscience, offering the possibility of not just curing diseases like cancer and diabetes, but preventing them altogether.
“The human epigenome is the next frontier of genomic research,” said Bing Ren, an associate professor of cellular and molecular medicine at the University of California San Diego, which recently received a five-year, $16.6 million grant from the federal National Institutes of Health (NIH) to establish The San Diego Epigenome Center at the Ludwig Institute for Cancer Research on campus.
Ren and colleagues are partnering with researchers at the Salk Institute in La Jolla, the University of Wisconsin and Cold Spring Harbor Laboratory in New York. San Diego is one of four centers that are part of the NIH's Roadmap Epigenomics Program, a five-year, $190 million effort.
“Just as the Human Genome Project provided a picture of the sequence of genomes,” said Ren, “our work will help create a map of the processes that impact gene regulation – what turns genes on and off – in order to improve our understanding of what drives human development and disease.”
It will be a daunting effort, more challenging perhaps than the genome project, which involved scientists around the world, cost billions of dollars and spanned more than a decade.
Though no one knows exactly how many gene regulators there are, researchers do know they vastly outnumber genes. This month Ren and others announced the identification and mapping of 55,000 “enhancers,” short regions of DNA that act to boost or enhance gene expression.
More importantly, scientists do not yet fully understand how genes are regulated by external elements, or why.
And finally, there are simply a lot of epigenomes out there – and they're always changing.
“There's only one genome,” Dr. Peter Jones, director of the University of Southern California/Norris Comprehensive Cancer Center told the journal Environmental Health Perspectives in 2006, but “an epigenome varies in each and every tissue.”
It is that variability and individuality, however, that makes epigenetics such a potentially powerful medical tool. We are all born with essentially the same DNA. It's what happens to that DNA that makes us what we are.
Said Ren: “Such modifications to the genetic blueprint may provide part of the answer to why some people are more susceptible to disease than others.”
Mice and men
Monozygotic, or identical, twins are people born from a single fertilized egg. They share the same package of genetic material – a genotype, in scientific parlance – and yet over time, they will diverge, developing characteristics and conditions that create their own contrasting “phenotypes.”