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August 18, 2010
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The nucleolinus is a cellular compartment that has been a lonely bystander in scientific endeavors. Although it’s found in a range of species, its function has been mysterious—mainly because the structure is hard to visualize. Now, a study shows that the nucleolinus is crucial for cell division. When researchers zapped the structure with a laser, an egg cell didn’t complete division. When the oocyte was fertilized after laser microsurgery (bottom right), the resulting zygote didn’t form vital cell division structures (blue and yellow). Perhaps now the nucleolinus has earned its rightful place inside the cell and in scientific research. Courtesy of cell biologist Mary Anne Alliegro, Marine Biological Laboratory.
Special cells in the eye use light to set our circadian rhythms, the 24-hour cycles that dictate when we sleep and when we’re awake. It turns out that these cells also play other roles in vision, according to a new study led by neurobiologist Samer Hattar of Johns Hopkins University. The team found that the cells, at least in mice, have more widespread targets in the brain than previously thought and that they enabled mice lacking other light-sensing cells to discern spatial information about their surroundings. These findings challenge traditional views about vision and offer new hope for correcting blindness.
NIH’s National Eye Institute also supported this work.
Ultraviolet (UV) rays cause not just sunburns, but also genetic mutations, cancer and cell death. In plants and most animals (except placental mammals, like humans), the photolyase protein repairs the damage. Scientists, though, know little about how the process works. To find out, biophysicist Dongping Zhong at Ohio State University exposed DNA to UV light and then took ultrafast laser “snapshots” to catch photolyase in action. The protein complex delivered an electron and proton to the damaged DNA, reversing the effects in billionths of a second. Once done, the electron and proton returned to the photolyase complex. This information could lead to future remedies for healing UV damage.
Individual genes often have multiple enhancers, regions of DNA that increase gene expression. Scientists suspected that some enhancers act as backups so that desired traits are expressed, even amidst unfavorable environmental and genetic conditions. A team led by Princeton University evolutionary biologist David Stern has found support for this idea. When the researchers removed two apparently redundant enhancers from a gene coding for fruit fly larvae hair development, they noticed that, at intermediate temperatures, the hairs formed correctly. But, at extreme temperatures, embryos without the enhancers lost much of their hair as larvae. The findings confirm that such enhancers make development resilient in the face of challenging conditions.
Stern lab (no longer available)
Article abstract (from the July 22 issue of Nature)
A multicellular organism consists of specialized cells with distinct functions that collectively ensure survival and reproductive success. Sergey Gavrilets, a theoretical biologist at the University of Tennessee, Knoxville, has developed a simple and biologically realistic model that shows how cells can become dedicated to such important functions. He found that the division of roles and responsibilities could occur relatively rapidly, depending on the mutation rate, the number of cells and other factors. The theoretical results may also explain the division of labor in social insects, the inception of organs and, more generally, the origin of biological complexity.