TECH WATCH Though most cells in an organism contain the identical genome sequence, the same cannot be said for the genome's three-dimensional organization. Using high-resolution microscopy and a technique called chromosome painting, Tom Misteli, a cell biologist at the National Cancer Institute, and colleagues examined six chromosomes in eight mouse tissue types and found that chromosomes cluster differently in each tissue. While this could indicate that the genome's spatial organization affects gene expression, "there is virtually no evidence for this," says Misteli.
Instead, genome organization correlates with chromosomal abnormalities. Every cancerous lymphocyte Misteli's team examined contained translocations among chromosomes 12, 14, and 15. In normal primary lymphocytes, these chromosomes physically cluster, indicating, says Misteli, that the "probability of two chromosomes undergoing translocation is directly related to their spatial proximity."
As not all cells in a tissue are exactly alike, the team examined several hundred nuclei from each tissue type and ...
