Over half a century ago, Conrad Hal Waddington introduced his model of the epigenetic landscape. He depicted a differentiating cell as a ball rolling down a landscape of bifurcating valleys and ridges, with each valley representing an alternative developmental path. Just as a ball may roll from valley to valley until it reaches the bottom of the landscape, a cell may progress from one developmental alternative to another until it reaches its fully differentiated state.
The model’s original purpose was to integrate concepts from genetics and developmental biology and to describe mechanisms that connect the genotype to the phenotype. Today, the model remains a compelling metaphor for epigenetics, which has developed into one of the most vibrant biomedical fields. Epigenetics has become indispensable for exploring development, differentiation, homeostasis, and diseases that span virtually every clinical discipline.
Analyzing Methylation Patterns
“Modern efforts toward explaining human disease purely based upon sequencing cannot possibly succeed in isolation,” says Andrew P. Feinberg, M.D., professor of medicine and director of the Center for Epigenetics at Johns Hopkins University School of Medicine. “At least half of human disease is caused by exposure to the environment.”
While the contribution of genetic factors to disease is more predictable and easier to study in the case of highly penetrant Mendelian disorders, most medical conditions involve multiple genes that may interact with one another and with environmental factors. Particularly for these conditions, capturing epigenetic changes becomes a crucial aspect of understanding pathogenesis and designing prophylactic and therapeutic interventions.
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