Tag: Cells

New Views on What the Cell’s Parts Can Do

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Studying some of the most well-tread territory in science can turn up surprising new findings. Take, for example, the cell. You may have read in textbooks how the cell’s parts look and function during important biological processes like cellular movement and division. You may have even built models of the cell out of gelatin or clay. But scientists continue to learn new facts that require those textbooks to be updated, and those models to be reshaped. Here are a few examples.

Nuclear Envelope: More Than a Protective Barrier

Damaged heterochromatin represented by nucleotides GCAT
Damaged heterochromatin, a tightly packed form of DNA, travels to the inner wall of the nuclear envelope for repair. Credit: Irene Chiolo and Taehyun Ryu, University of Southern California.

Like a security guard checking IDs at the door, the nuclear envelope forms a protective barrier around the cell’s nucleus, only letting specific proteins and chemical signals pass through. Scientists recently found that this envelope may also act as a repair center for broken strands of heterochromatin, a tightly packed form of DNA.

Irene Chiolo of the University of Southern California and Gary Karpen of the University of California, Berkeley, and the Lawrence Berkeley National Laboratory were part of a team that learned that healthy fruit fly cells mend breaks in heterochromatin by moving the damaged DNA strands to the inner wall of the nuclear envelope. There, proteins embedded in the envelope make the necessary repairs in a safe place where the broken DNA can’t accidentally get fused to the wrong chromosome. Continue reading “New Views on What the Cell’s Parts Can Do”

Cool Images: A Holiday-Themed Collection

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Here are some images from our gallery that remind us of the winter holidays—and showcase important findings and innovations in biomedical research.

Ribbons and Wreaths

Wreath

This wreath represents the molecular structure of a protein, Cas4, which is part of a system, known as CRISPR, that bacteria use to protect themselves against viral invaders. The green ribbons show the protein’s structure, and the red balls show the location of iron and sulfur molecules important for the protein’s function. Scientists have harnessed Cas9, a different protein in the bacterial CRISPR system, to create a gene-editing tool known as CRISPR-Cas9. Using this tool, researchers can study a range of cellular processes and human diseases more easily, cheaply and precisely. Last week, Science magazine recognized the CRISPR-Cas9 gene-editing tool as the “breakthrough of the year.”

Continue reading “Cool Images: A Holiday-Themed Collection”

Sugar Rush in Research

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Cookies
Sugar sprinkled on cookies and other treats is often an attractive—and sweet tasting—finishing touch. But the sugar-rich coating that surrounds most cells is far more—it’s a vital ingredient for many basic cellular processes. Credit: Stock image.

Simple sugars such as sucrose (found in the sugar bowl) and fructose (in fruits and honey) provide the sweet finishing touches on many holiday treats. But did you know that versions of these molecules also serve important functions in our cells?

Cells assemble sugar molecules into chains known as glycans. These glycans, which can be linear or branching, play an astounding number of biological roles. When bound to proteins called lectins, they enable a fertilized egg to attach properly onto a woman’s uterine wall and help immune cells move out of a blood vessel to the site of an infection. When decorated with specific patterns of molecules called sulfates, glycans can help direct the growth of nerves. And it’s the glycans found on our blood cells that define blood type (A, B, AB or O). Continue reading “Sugar Rush in Research”

Cool Images: A Halloween-Inspired Cell Collection

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As Halloween approaches, we turned up some spectral images from our gallery. The collection below highlights some spooky-sounding—but really important—biological topics that researchers are actively investigating to spur advances in medicine.

Cell Skeleton
Fibroblast
The cell skeleton, or cytoskeleton, is the framework that gives a cell its shape, helps it move and keeps its contents organized for proper function. A cell that lacks a cytoskeleton becomes misshapen and immobile. This fibroblast, a cell that normally makes connective tissues and travels to the site of a wound to help it heal, is lacking a cytoskeleton. Researchers have associated faulty cytoskeletons and resulting abnormal cell movement with birth defects and weakened immune system functioning. See fibroblasts with healthy skeletons.

Continue reading “Cool Images: A Halloween-Inspired Cell Collection”

How Cells Manage Chance

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We asked the heads of our scientific divisions to tell us about some of the big questions in fundamental biomedical science that researchers are investigating with NIGMS support. This article is the second in an occasional series that explores these questions and explains how pursuing the answers could advance understanding of important biological processes.

Sample slide, variability of mRNA in yeast cells
The number of copies of mRNA molecules (bright green) observed here in yeast cells (dark blue) fluctuates randomly. Credit: David Ball, Virginia Tech.

For some health conditions, the cause is clear: A single altered gene is responsible. But for many others, the path to disease is more complex. Scientists are working to understand how factors like genetics, lifestyle and environmental exposures all contribute to disease. Another important, but less well-known, area of investigation is the role of chance at the molecular level.

One team working in this field is led by John Tyson at Virginia Tech. The group focuses on how chance events affect the cell division cycle, in which a cell duplicates its contents and splits into two. This cycle is the basis for normal growth, reproduction and the replenishment of skin, blood and other cells throughout the body. Errors in the cycle are associated with a number of conditions, including birth defects and cancer. Continue reading “How Cells Manage Chance”

Cellular ‘Cruise Control’ Systems Let Cells Sense and Adapt to Changing Demands

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Cells are the ultimate smart material. They can sense the demands being placed on them during critical life processes and then respond by strengthening, remodeling or self-repairing, for instance. To do this, cells use “mechanosensory” systems similar to the cruise control that lets a car’s engine adjust its power output when going up or down hills.

Researchers are uncovering new details on cells’ molecular cruise control systems. By learning more about the inner workings of these systems, scientists hope ultimately to devise ways to tinker with them for therapeutic purposes.

Cell Fusion

To examine how cells fine-tune their architecture and force output during the merging or fusion of cells, Elizabeth Chen and Douglas Robinson of Johns Hopkins University teamed up with Daniel Fletcher of the University of California, Berkeley. Cell fusion is critical to many developmental and physiological processes, including fertilization, placenta formation, immune response, and skeletal muscle development and regeneration.

Illustration of cell fusion

Fingerlike protrusions of one cell (pink) invade another cell prior to cell fusion. Credit: Shuo Li. Used with permission from Developmental Cell.

Using the fruit fly Drosophila melanogaster as a model system, Chen’s research group Exit icon previously found that when two muscle cells merge during muscle development, fingerlike protrusions of one cell invade the territory of the other cell to promote fusion. In the new study, led by Chen, the researchers showed that cell fusion depends on the ability of the “receiving” cell to put up resistance against the invading cell Exit icon.

In fusing fruit fly cells, the scientists saw that in areas where the invading cells drilled in, the receiving cells quickly stiffened their cell skeletons, effectively pushing back. This mechanosensory response allows the outer membranes of the two cells to be pushed together and later fuse, Chen explains.

The team then explored the mechanisms underlying the stiffening response. They found that a protein called myosin II, which is part of the cell skeleton, senses the pushing force from the invading cell. Myosin II swarms to the fusion site and binds with fibers just beneath the cell membrane to put up the necessary resistance. Continue reading “Cellular ‘Cruise Control’ Systems Let Cells Sense and Adapt to Changing Demands”

Scientists Shine Light on What Triggers REM Sleep

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Illustration of a brain.
While studying how the brain controls REM sleep, researchers focused on areas abbreviated LDT and PPT in the mouse brainstem. This illustration shows where these two areas are located in the human brain. Credit: Wikimedia Commons. View larger image

Has the “spring forward” time change left you feeling drowsy? While researchers can’t give you back your lost ZZZs, they are unraveling a long-standing mystery about sleep. Their work will advance the scientific understanding of the process and could improve ways to foster natural sleep patterns in people with sleep disorders.

Working at Massachusetts General Hospital and MIT, Christa Van Dort, Matthew Wilson, and Emery Brown focused on the stage of sleep known as REM. Our most vivid dreams occur during this period, as do rapid eye movements, for which the state is named. Many scientists also believe REM is crucial for learning and memory.

REM occurs several times throughout the night, interspersed with other sleep states collectively called non-REM sleep. Although REM is clearly necessary—it occurs in all land mammals and birds—researchers don’t really know why. They also don’t understand how the brain turns REM on and off.

Continue reading “Scientists Shine Light on What Triggers REM Sleep”

Correcting a Cellular Routing Error Could Treat Rare Kidney Disease

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AGT protein and peroxisomes in untreated and treated cells.
The altered AGT protein (red) and peroxisomes (green) appear in different places in untreated cells (top), but they appear together (shown in yellow) in cells treated with DECA (bottom). Credit: Carla Koehler/Reproduced with permission from Proceedings of the National Academy of Sciences USA. View larger image.

Our cells have organized systems to route newly created proteins to the places where they’re needed to do their jobs. For some people born with a rare and potentially fatal genetic kidney disorder called PH1, a genetically altered form of a particular protein mistakenly ends up in mitochondria instead of in another organelle, the peroxisome. This cellular routing error of the AGT protein results in the harmful buildup of oxalate, which leads to kidney failure and other problems at an early age.

In new work led by UCLA biochemist Carla Koehler Exit icon, researchers used a robotic screening system to identify a compound that interferes with the delivery of proteins to mitochondria. Koehler’s team Exit icon showed that adding a small amount of the compound, known as DECA, to cells grown in the laboratory prevented the altered form of the AGT protein from going to the mitochondria and sent it to the peroxisome. The compound also reduced oxalate levels in a cell model of PH1.

The team’s findings suggest that DECA, which is already approved by the Food and Drug Administration for treating certain bacterial infections, could be a promising candidate for treating children affected by PH1. And, Koehler notes, the screening strategy that she and her team used to identify DECA as a potential therapy may help researchers identify other new therapies for the disorder.

This work was funded in part by NIH under grant R01GM061721.

Molecules Known to Damage Cells May Also Have Healing Power

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Free radicals in an ying-yang symbol
Biology in balance: Molecules called free radicals—like the peroxide molecules illustrated here—have a reputation for being dangerous. Now, they’ve revealed healing powers. In worms, at least. Credit: Stock image

When our health is concerned, some molecules are widely labeled “good,” while others are considered “bad.” Often, the truth is more complicated.

Consider free radical molecules. These highly reactive, oxygen-containing molecules are well known for damaging DNA, proteins and other molecules in our bodies. They are suspected of contributing to premature aging and cancer. But now, new research shows they might also have healing powers.

Using the oft-studied laboratory roundworm known as C. elegans, a research group led by Andrew Chisholm at the University of California, San Diego, made a surprising discovery. Free radicals, specifically those made in cell structures called mitochondria, appear necessary for skin wounds to heal. In fact, higher (but not dangerously high) levels of the molecules can actually speed wound closure.

If further research shows the same holds true in humans, the work could point to new ways to treat hard-to-heal wounds, like diabetic foot ulcers.

This work was funded in part by NIH under grants R01GM054657 and P40OD010440.

Cells by the Numbers

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Cells are the basic unit of life—and the focus of much scientific study and classroom learning. Here are just a few of their fascinating facets.

3.8 billion

Nerve Cells
Developing nerve cells, with the nuclei shown in yellow. Credit: Torsten Wittmann, University of California, San Francisco.

That’s how many years ago scientists believe the first known cells originated on Earth. These were prokaryotes, single-celled organisms that do not have a nucleus or other internal structures called organelles. Bacteria are prokaryotes, while human cells are eukaryotes.

0.001 to 0.003

This is the diameter in centimeters of most animal cells, making them invisible to the naked eye. There are some exceptions, such as nerve cells that can stretch from our hips to our toes, sending electrical signals throughout the body.

1665

Red blood Cells
Oxygen-transporting red blood cells. Credit: Dennis Kunkel, Dennis Kunkel Microscopy, Inc.

In that year, British scientist Robert Hooke coined the term cell to describe the porous, grid-like structure he saw when viewing a thin slice of cork under a microscope. Today, scientists study cells using a variety of high-tech imaging equipment as well as rainbow-colored dyes and a green fluorescent protein derived from jellyfish.

200

That’s how many different types of cells are in the human body, including those in our skin, muscles, nerves, intestines, blood and bones.

3 to 5

Believe it or not, that’s the approximate number of pounds of bacteria you’re carrying around, depending on your size. Even though bacterial cells greatly outnumber ours, they’re much smaller than our cells and therefore account for less than 3 percent of our body mass. Scientists are learning more about how our body bacteria contribute to our health.

24

Snapshot of a phase of the cell cycle.
A snapshot of a phase of the cell cycle. Credit: Jean Cook and Ted Salmon, UNC School of Medicine.

This is the typical length in hours of the animal cell cycle, the time from a cell’s formation to when it splits in two to make more cells.

120

That’s the approximate lifespan in days of a human red blood cell. Other cell types have different lifespans, from a few weeks for some skin cells to as long as the life of the organism for healthy neurons.

50 to 70 billion

Each day, approximately this many cells die in the human body as part of a normal process that serves a healthy and protective role. Those that die in the largest numbers are skin cells, blood cells and some cells that line structures like organs and glands.