Genes & Cells

How nanotubes trigger a cell’s gag reflex, the skulking 1918 flu and more in this week’s news

Carbon nanotubes choke cells
Carbon nanotubes and asbestos fibers may seem small, but they can be a big, and deadly, deal to cells. Now researchers at Brown University in Providence, R.I. know why. Cells swallow the long fibers tip-first, the researchers report online September 18 in Nature Nanotechnology. Rounded tips on the fibers cause the cell’s machinery to gear up for swallowing a sphere. Once the cell has begun engulfing the tube it’s too late to stop, and the cell essentially chokes. Snipping off the rounded tips caused the tubes to lie flat on the cell surface, leading the researchers to speculate that modifying the ends of such fibers could make them safer. —Tina Hesman Saey

CELLULAR GAG REFLEX Cells gobble up stuff in the body, but some objects make them choke. Researchers have found that when a long perpendicular fiber comes near (green), a cell (blue) senses only its tip, mistakes it for a sphere, and begins engulfing something too long to swallow. Huajian Gao Lab/Brown University


1918 flu lurked for months before pandemic
The 1918 “Spanish” flu may have had a spring preview in America. Researchers from the U.S. military, the Department of Veterans Affairs and the National Institute of Allergy and Infectious Diseases examined autopsy samples from 68 soldiers who died of pneumonia and influenza symptoms between May and October of 1918. Analyses of samples from the nine soldiers who died before the outbreak peaked in September and October showed that the virus was circulating as long as four months before the pandemic was recognized, the researchers report September 19 in the Proceedings of the National Academy of Sciences. Those months gave the virus time to become highly infectious in humans. —Tina Hesman Saey

Heart light

Stanford researchers have created human heart cells that beat in response to light. The team genetically engineered embryonic stem cells to contain the light-activated protein channelrhodopsin-2, then grew the stem cells into beating heart cells in lab dishes. The heart cells naturally beat to their own rhythm until researchers turned on a flash of blue light. Then the cells became tuned to the rhythm of the flashing light, the team reports in the Sept. 21 Biophysical Journal. Such cells may help researchers better understand how hearts beat, and could lead to light-based pacemakers. —Tina Hesman Saey

Anti-aging genes no longevity font
Sirtuins, proteins once touted as the answer to fighting aging, aren’t all they were cracked up to be. Previous research had shown that making more of a sirtuin called sir-2.1 could lengthen the lives of roundworms and fruit flies. But the life-extending properties observed in those experiments were probably due to genetic variations unrelated to sirtuins, report researchers at University College London and their international collaborators in the Sept. 22 Nature. MIT’s Mohan Viswanathan and Leonard Guarente also show in the same issue that the role of sirtuins in increasing lifespan was overstated in earlier experiments. Guarente’s lab was the first to discover a link between sirtuins and longevity. —Tina Hesman Saey

Plant RNAs control host cholesterol
The old adage about being what you eat has gotten another boost from science. Small pieces of RNA called microRNAs from rice make it into the bloodstreams of people who eat the grain, researchers at Nanjing University in China and colleagues report September 20 in Cell Research. One microRNA, called miR168a, was found at high levels in the blood of Chinese people. Experiments in mice showed that the microRNA can impair production of a protein that helps clear LDL, or “bad,” cholesterol from the body, raising cholesterol levels. The results suggest that microRNAs added to food might help regulate body processes in people. —Tina Hesman Saey

Secrets of wine yeast revealed
Some strains of the common baking and brewing yeast Saccharomyces cerevisiae are better than others for making wine. To find out why, Bruno Blondin of Montpellier SupAgro in France and colleagues compared a yeast strain used for making wine with a strain commonly used in laboratories. Tweaks to just a few genes produced big changes in the strains’ ability to ferment sugars and use nitrogen, the researchers report in the September G3: Genes, Genomes, Genetics. The team traced the lab yeast’s flabby fermentation to a defective form of the ABZ1 gene and high levels of stress proteins. —Tina Hesman Saey

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