Body wall muscles in wild type C. elegans (top) and a mutant with no H3K9me (bottom). The morphologically defective muscles of the mutant resemble what is found in aging muscles and muscle diseases called laminopathies
Body wall muscles in wild type C. elegans ( top ) and a mutant with no H3K9me ( bottom ). The morphologically defective muscles of the mutant resemble what is found in aging muscles and muscle diseases called laminopathies - Chemical modifications of histones, the small proteins around which DNA is wrapped, are known to affect gene expression. In a study conducted in C. elegans , researchers from the Gasser group show that the defining modification of the tightly packed form of DNA called heterochromatin selectively blocks the expression of genes in differentiated tissues. The loss of the enzyme that mediates this modification leads to a loss of tissue integrity and early aging. Histone methylation is a process by which methyl groups are transferred to select amino acids of histones, the proteins that act as spools around which DNA winds to create the structural units called nucleosomes. The methylation of lysine 9 in histone H3 (H3K9me), an example of histone methylation, is the key modification that defines heterochromatin, a tightly packed form of DNA that is most commonly found on repetitive "junk" DNA. Heterochromatin is also thought to silence tissue-specific genes during development, however it has been poorly characterized how this is achieved.
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