Step inside the lab of Dana Dolinoy at the University of Michigan, Ann Arbor, and you’re sure to hear conversations that include the rather strange word “agouti” (uh-goo-tee). In this context, it’s a name given to a strain of laboratory mice that arose decades ago from a random mutation in the Agouti gene, which is normally expressed only transiently in hair follicles. The mutation causes the gene to be turned on, or expressed, continuously in all cell types, producing mice that are yellow, obese, and unusually prone to developing diabetes and cancer. As it turns out, these mutant mice and the gene they have pointed to are more valuable than ever today because they offer Dolinoy and other researchers an excellent model for studying the rapidly emerging field of epigenomics.
The genome of the mouse, just as for the human, is the complete DNA instruction book; it contains the coding information for building the proteins that carry out a variety of functions in a cell. But modifications to the DNA determine its function, and these are collectively referred to as the epigenome. The epigenome is made up of chemical tags and proteins that can attach to the DNA and direct such actions as turning genes on or off, thereby controlling the production of proteins in particular cells. These tags have different patterns in each cell type, helping to explain, for example, why a kidney and a skin cell can behave so differently when they share the same DNA.
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