Category: Cells

Dendrites Show Ability to Regenerate After Injury

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Dendrites
Cutting off the dendrites from nerve cells in fruit flies revealed that they can regenerate. Credit: Melissa Rolls, Penn State University.

When a bone breaks, it might slice axons—the part of nerve cells that sends information to other cells—and potentially cause loss of mobility or feeling. Prior research had shown that a damaged nerve cell could repair such an injury through the regrowth of axons. Scientists at Penn State University wondered if dendrites—the part of nerve cells that receive information from other nerve cells—could also regenerate. To find out, Melissa Rolls and her team cut off the dendrites from nerve cells in fruit flies. Instead of dying, as was expected, the cells regrew dendrites. The research also revealed that dendrite regeneration happens independently of axon regeneration, leading investigators to believe there are two separate regeneration pathways: one for axons and one for dendrites. Learning more about this new dendrite regrowth pathway might one day lead to new approaches for healing injured nerve cells, including those damaged after a stroke.

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Animal Cells ‘Reach Out and Touch’ to Communicate

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Cytonemes in the fruit fly tracheal system.
Threadlike cytonemes (at right) convey signals between cells in the developing fruit fly tracheal system. Credit: Sougata Roy, University of California, San Francisco. View larger image

Scientists have long known that multicellular organisms use biological molecules produced by one cell and sensed by another to transmit messages that, for instance, guide proper development of organs and tissues. But it’s been a puzzle as to how molecules dumped out into the fluid-filled spaces between cells can precisely home in on their targets.

Using living tissue from fruit flies, a team led by Thomas Kornberg of the University of California, San Francisco, has shown that typical cells in animals can talk to each other via long, thin cell extensions called cytonemes (Latin for “cell threads”) that may span the length of 50 or 100 cells. The point of contact between a cytoneme and its target cell acts as a communications bridge between the two cells.

Until now, only nerve cells (neurons) were known to communicate this way. “This is an exciting finding,” says NIGMS’ Tanya Hoodbhoy. “Neurons are not the only ‘reach out and touch someone’ cells.”

This work also was funded by NIH’s National Heart, Lung, and Blood Institute.

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Cool Image: Visualizing Viral Activity

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Viral RNA (red) in an RSV-infected cell. Credit: Eric Alonas and Philip Santangelo, Georgia Institute of Technology and Emory University.

Viral RNA (red) in an RSV-infected cell. Credit: Eric Alonas and Philip Santangelo, Georgia Institute of Technology and Emory University.

What looks like a colorful pattern produced as light enters a kaleidoscope is an image of a cell infected with respiratory syncytial virus (RSV) illuminated by a new imaging technology. Although relatively harmless in most children, RSV can lead to bronchitis and pneumonia in others. Philip Santangelo Exit icon of the Georgia Institute of Technology and Emory University, along with colleagues nationwide, used multiply-labeled tetravalent RNA imaging probes (MTRIPS) to observe the entry, assembly and replication of RSV inside a living cell. Once introduced into RSV-plagued cells, the MTRIPS latched onto the viral RNA (in the image, red) without altering the level of infectivity. This led to fluorescent RSV viral particles that let the researchers track the viral RNA in host cells and better understand what the virus was doing. The knowledge gained from this new technique might aid in the development of RSV antiviral drugs and possibly a vaccine. Scientists could also one day use the imaging approach to study other RNA viruses, such as the flu and Ebola.

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Cool Images: Holiday Season Cells

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Yeast cells deficient in zinc and the Tsa1 protein have protein tangles. Credit: Colin MacDiarmid and David Eide, University of Wisconsin-Madison.

Yeast cells deficient in zinc and the Tsa1 protein have protein tangles. Credit: Colin MacDiarmid and David Eide, University of Wisconsin-Madison.

Just in time for the holidays, we’ve wrapped up a few red and green cellular images from basic research studies. In this snapshot, we see a group of yeast cells that are deficient in zinc, a metal that plays a key role in creating and maintaining protein shape. The cells also lack a protein called Tsa1, which normally keeps proteins from sticking together. Green areas highlight protein tangles caused by the double deficiency. Red outlines the cells. Protein clumping plays a role in many human diseases, including Parkinson’s and Alzheimer’s, so knowledge of why it happens—and what prevents it in healthy cells—could aid the development of treatments.

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Abnormal Mitochondria Might Cause Resistance to Radiation Therapy

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Mitochondria. Credit: Judith Stoffer.
Bean-shaped mitochondria are cells’ power plants. The highly folded inner membranes are the site of energy generation. Credit: Judith Stoffer. View larger image

Why some cancers are resistant to radiation therapy has baffled scientists, but research on abnormalities in mitochondria, often described as cells’ power plants, could offer new details. A research team led by Maxim Frolov Exit icon of the University of Illinois at Chicago learned that the E2F gene, which plays a role in the natural process of cell death, contributes to the function of mitochondria. Fruit flies with a mutant version of the E2F gene had misshapen mitochondria that produced less energy than normal ones. Flies with severely damaged mitochondria were more resistant to radiation-induced cell death. Studies using human cells revealed similar effects. The work could help explain why people with cancer respond differently to radiation therapy and might aid the development of drugs that enhance mitochondrial function, thereby improving the effectiveness of radiation therapy.

This work also was funded by NIH’s National Cancer Institute.

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New Models Predict Where E. coli Strains Will Thrive

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Illustration of E. coli. Credit: Janet Iwasa, University of Utah.
Illustration of E. coli. Credit: Janet Iwasa, University of Utah (image available under a Creative Commons Attribution-NonCommercial-ShareAlike license Exit icon). View larger image

Like plants and animals, different types of E. coli thrive in different environments. Now, scientists can even predict which environments—such as the bladder, stomach or blood—are most amenable to the growth of various strains, including pathogenic ones. A research team led by Bernhard Palsson Exit icon of the University of California, San Diego, accomplished this by using genome data to reconstruct the metabolic networks of 55 E. coli strains. The metabolic models, which identify differences in the ability to manufacture certain compounds and break down various nutrients, shed light on how certain E. coli strains become pathogenic and how to potentially control them. One approach could be depriving the deadly strains of the nutrients they need to survive in their niches. The researchers plan to use their new method to study other bacteria, such as those that cause staph infections.

This work also was funded by NIH’s National Cancer Institute.

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Stop the (Biological) Clock

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Molecular structure of the three proteins in blue-green algae’s circadian clock.  Credit: Johnson Lab, Vanderbilt University.
Molecular structure of the three proteins in blue-green algae’s circadian clock. Credit: Johnson Lab, Vanderbilt University.

Many microorganisms can sense whether it’s day or night and adjust their activity accordingly. In tiny blue-green algae, the “quartz-crystal” of the time-keeping circadian clock consists of only three proteins, making it the simplest clock found in nature. Researchers led by Carl Johnson of Vanderbilt University recently found that, by manipulating these clock proteins, they could lock the algae into continuously expressing its daytime genes, even during the nighttime.

Why would one want algae to act like it’s always daytime? The kind used in Johnson’s study is widely harnessed to produce commercial products, from drugs to biofuels. But even when grown in constant light, algae with a normal circadian clock typically decrease production of biomolecules when nighttime genes are expressed. When the researchers grew the algae with the daytime genes locked “on” in constant light, the microorganism’s output increased by as much as 700 percent. This proof of concept experiment may be applicable to improving the commercial production of compounds such as insulin and some anti-cancer drugs.

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Circadian Rhythms Fact Sheet

Cool Image: Tick Tock, Master Clock

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Master clock in mouse brain with the nuclei of the clock cells shown in blue and the VIP molecule shown in green. Credit: Cristina Mazuski in the lab of Erik Herzog, Washington University in St. Louis.

Master clock in mouse brain with the nuclei of the clock cells shown in blue and the VIP molecule shown in green. Credit: Cristina Mazuski in the lab of Erik Herzog, Washington University in St. Louis.

Our biological clocks play a large part in influencing our sleep patterns, hormone levels, body temperature and appetite. A small molecule called VIP, shown in green, enables time-keeping neurons in the brain’s central clock to coordinate daily rhythms. New research shows that, at least in mice, higher doses of the molecule can cause neurons to get out of synch. By desynchronizing mouse neurons with an extra burst of VIP, Erik Herzog of Washington University in St. Louis found that the cells could better adapt to abrupt changes in light (day)-dark (night) cycles. The finding could one day lead to a method to reduce jet lag recovery times and help shift workers better adjust to schedule changes.

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Circadian Rhythms Fact Sheet
Tick Tock: New Clues About Biological Clocks and Health Article from Inside Life Science
A Light on Life’s Rhythms Article from Findings Magazine

Mapping Approach Yields Insulin Secretion Pathway Insights

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TMEM24 protein (green) and insulin (red) in pancreatic beta cells (yellow).  Credit: Balch Lab, the Scripps Research Institute.
The interactions of TMEM24 protein (green) and insulin (red) in pancreatic beta cells are shown in yellow. Credit: Balch Lab, the Scripps Research Institute.
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The identities of the proteins that drive insulin production and release from pancreatic beta cells have largely been a mystery. In new work from the lab of William Balch of the Scripps Research Institute, researchers isolated and then identified all the insulin-bound proteins from mouse beta cells. The results provided a roadmap of the protein interactions that lead to insulin production, storage and secretion. The researchers used the roadmap to identify a protein called TMEM24, which was abundant in beta cells and binds readily to insulin. Balch and his team uncovered that TMEM24, whose involvement in insulin secretion was previously unknown, effectively regulates slower insulin release and could have a key role in maintaining control of glucose levels in the blood. The scientists hope that this roadmap of insulin-interacting proteins will lead to the development of new, targeted approaches to treating type 2 diabetes and a similar insulin-related condition called metabolic syndrome.

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Cells Merrily ‘Row’ Without Sensor Proteins

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Messenger proteins (left). When these proteins aren’t activated, the cell doesn’t move (right). Credit: Devreotes Lab, Johns Hopkins University School of Medicine.
Messenger proteins help the cell make large projections (left). When these proteins aren’t activated, the cell doesn’t move (right). Credit: Devreotes Lab, Johns Hopkins University School of Medicine. View larger image

A new study from Peter Devreotes Exit icon, Pablo Iglesias Exit icon and other scientists at Johns Hopkins University sheds light on the way in which cells get around the body to promote embryo development, wound healing and even cancer metastasis. Here’s how they describe cell movement and their findings:

Think of the cell as a rowboat. Sensor proteins on the outside pass on directional signals to messenger proteins that serve as the cell’s coxswain. The coxswain then commands other members of the molecular crew to stay in sync, propelling the cell forward. If there are no sensor signals, the coxswain can still coordinate the cell’s movement, just not in any specific direction—it’s like a boat without a rudder.

Scientists previously thought that the messenger proteins needed the sensor ones to produce both directional and random movements. Because defects in the messenger proteins have been linked to many types of cancer, the new work suggests these molecules could serve as a drug target for immobilizing tumor cells.

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