![]() When a cell copies its DNA to divide it between two daughter cells, each copy gets about half of the epigenetic marks. Then they studied how these marks are lost and gained. They developed a computational model of a polymer with a few marked regions, and saw that these marked regions collapse into each other, forming a dense clump. In their new study, Mirny and his colleagues wanted to answer the question of how those epigenetic marks are maintained from generation to generation. In particular, they found that certain chromatin regions, with marks telling cells not to read a particular segment of DNA, attract each other and form dense clumps called heterochromatin, which are difficult for the cell to access. Previous work by Mirny’s lab has shown that the 3D structure of chromosomes is, to a great extent, determined by these epigenetic modifications, or marks. However, how this memory is passed on to daughter cells is somewhat of a mystery. These modifications generate “epigenetic memory,” which helps a cell to maintain its cell type. Histones can display a variety of modifications that help control which genes are expressed in a given cell. Within the cell nucleus, DNA is wrapped around proteins called histones, forming a densely packed structure known as chromatin. Dino Osmanović, a former postdoctoral fellow at MIT’s Center for the Physics of Living Systems, is also an author of the study. Leonid Mirny, an HST faculty member, a professor in MIT’s Institute for Medical Engineering and Science (IMES), and the Department of Physics, is the senior author of the paper, which appears today in Science. “What we have done in this work is develop a simple model that highlights qualitative features of the chemical systems inside cells and how they need to work in order to make memories of gene expression stable.” It's very difficult to transform one cell type to another because these states are very committed,” says Jeremy Owen PhD ’22, the lead author of the study. “A key aspect of how cell types differ is that different genes are turned on or off. This way, by juggling the memory between 3D folding and the marks, the memory can be preserved over hundreds of cell divisions. And each time a cell divides, chemical marks allow a cell to restore its 3D folding of its genome. After a cell copies its DNA, the marks are partially lost, but the 3D folding allows the cell to easily restore the chemical marks needed to maintain its identity. The research team suggests that within each cell’s nucleus, the 3D folding of its genome determines which parts of the genome will be marked by these chemical modifications. ![]() When cells copy their DNA to divide, however, they lose half of these modifications, leaving the question: How do cells maintain the memory of what kind of cell they are supposed to be?Ī new MIT study proposes a theoretical model that helps explain how these memories are passed from generation to generation when cells divide. However, out of about 30,000 genes, each cell expresses only those genes that it needs to become a nerve cell, immune cell, or any of the other hundreds of cell types in the body.Įach cell’s fate is largely determined by chemical modifications to the proteins that decorate its DNA these modification in turn control which genes get turned on or off. ![]() MIT study suggests 3D folding of the genome is key to cells’ ability to store and pass on “memories” of which genes they should express.Įvery cell in the human body contains the same genetic instructions, encoded in its DNA. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |