Five-Year Effort Reveals the Cellular Origami of Chromatin Looping in Human DNA; Same Loops Preserved Over 100 Million Years of Evolution; Largest Loops Seen Only in Women; Folding Drives Function; Thousands of Unknown Hidden Switches Found

The ancient Japanese art of origami is based on the idea that nearly any design--a crane, an insect, a samurai warrior--can be made by taking the same blank sheet of paper and folding it in different ways. The human body faces a similar problem/challenge. The genome inside every cell of the body is identical, but the body needs each cell to be different--an immune cell fights off infection; a cone cell helps the eye detect light; the heart’s myocytes must beat endlessly. In a remarkable article published in the December 18, 2014 issue of Cell, researchers at Baylor College of Medicine, Rice University, the Broad Institute of MIT and Harvard, and Harvard University describe the results of a five-year effort to map, in unprecedented detail, how the 2-meter-long human genome folds inside the nucleus of a cell. The title of the article is, “A 3D Map of the Human Genome at Kilobase Resolution Reveals Principles of Chromatin Looping.” The results show that the cell--like a microscopic origamist--modulates its function by folding the genome into an almost limitless variety of shapes. A centerpiece of the new study is the first reliable catalog of loops spanning the entire human genome. For decades, scientists have examined the regions in the close vicinity of a gene to understand how the gene is regulated. But as the genome folds, sequences initially far from a gene loop back and come in contact with those nearby elements. Looping has been a blind spot for modern biology. “For over a century, scientists have known that DNA forms loops inside of cells, and that knowing where the loops are is incredibly important,” said co-first author Dr. Suhas Rao, a researcher at the Center for Genome Architecture at Baylor.
Login Or Register To Read Full Story