Advancing Efforts to Decipher a Chromatin Code

A Science Daily article entitled New Method For Reading DNA Sheds Light On How Cells Define Themselves reveals how a technological advance, that sequences DNA, is facilitating our understanding of functions associated with chromatin. The Broad Institute of MIT and Harvard issued a news release related to a published paper (Mikkelsen et al. (2007) Genome-wide maps of chromatin state in pluripotent and lineage-committed cells. Nature; DOI:10.1038/nature06008). The article's first paragraph:

"As a fertilized egg develops into a full grown adult, mammalian cells make many crucial decisions -- closing doors of opportunity as they adopt careers as liver cells, skin cells, or neurons. One of the most fundamental mysteries in biomedicine is how cells make such different career decisions despite having exactly the same DNA. By using a new kind of genomic technology, a new study unveils a special code -- not within DNA, but within the so-called "chromatin" proteins surrounding it -- that could unlock these mysterious choices underlying cell identity."

Chromatin has been known to have a genomic packing function but it is also known that the location of chromatin proteins affects gene expression. Chromatin regions known as bivalent domains indicate control regions of key genes involved in expression. Analyses of bivalent domains enables one to get both a history and a prediction of future gene activity. This in turn has implications for developmental biology. The mapping of chromatin could help identify RNA producing genes in addition to those encoding proteins.