Cool Image: Biological Bubbles

Cells are in the process of pinching off parts of their membranes to produce bubbles filled with a mix of proteins and RNAs. Researchers are harnessing this process to develop better drug delivery techniques. The image, courtesy of Chi Zhao, David Busch, Connor Vershel and Jeanne Stachowiak of the University of Texas at Austin, was entered in the Biophysical Society’s 2017 Art of Science Image contest and featured on the NIH Director’s Blog.

This fiery-looking image shows animal cells caught in the act of making bubbles, or blebbing.

Certain cells regularly pinch off parts of their membranes to produce bubbles filled with a mix of proteins and RNAs. The green and yellow portions in the image show the cell membranes as they separate from the cell’s skeleton and bleb from the main cell. The bubbles, shown in red, are called plasma-derived membrane vesicles, or PMVs. PMVs can travel to other parts of the body where they may aid in cell-to-cell communication.

The University of Texas at Austin researchers who produced this image are exploring ways to use PMVs to deliver medicines to precise locations in the body.

Blebbing for Drug Delivery

Drug delivery research tries to find ways to carry medicines to only the tissues in the body that need them with the goal of reducing side effects. To achieve this, delivery methods need to recognize just the cells they target, usually by finding a unique protein on the cell’s surface. Scientists can make proteins that recognize and attach to targets such as cancer cells, but they’ve had trouble attaching medicines to the proteins they made. To get around this problem, scientists could employ PMV-making cells in a laboratory, perhaps even cells taken from a patient who is receiving treatment. They could engineer the cells to make the targeting proteins and then attach the targeting proteins to the PMV surface. The cell’s own protein-making machinery does the hardest job.

The Texas scientists have engineered such donor cells with proteins on their surfaces that precisely target certain kinds of breast cancer cells. When the donor cells are induced to bleb, they produce PMVs laden with the target proteins that locate and bind to the cancer cells.

Researchers hope that eventually PMVs with surface targeting proteins could be filled with medicines and infused into the patient to deliver the drugs specifically to cancerous cells while leaving healthy tissues untouched. Research will continue to investigate this possibility.

This research was funded in part by NIH under grant R01GM112065.

Chasing Fireflies—and Better Cellular Imaging Techniques

firefly
Firefly. Credit: Stock photo.

The yellow-green glow from this summer’s fireflies teased my kids across the yard. Max and Stella zigzagged the grass, occasionally jumping into the air to cup a firefly in their hands and then proudly shouting, “I got one!”

Chasing fireflies on a summer night is a childhood rite of passage for many, including Nathan Shaner who grew up in New Jersey. “It was one of my favorite things about summer,” he recalls. “I’d catch them with my hands—I’d never jar them.”

Today, Shaner studies the science of bioluminescence, which gives fireflies and many other organisms the natural ability to emit light. His goal is to make bright bioluminescent tags that he and other scientists can use to study living cells in greater detail. “There’s this very beautiful thing that evolved in nature, and we can use it to enable new discoveries,” he says.

Thousands of organisms glow as a way to communicate, spook predators, lure prey or attract mates. There are a few terrestial examples, such as fireflies, glowworm insect larvae and foxfire fungi, and many more acquatic ones, including types of marine plankton, fish, jellyfish, shrimp, squid and sea urchins. One research team estimated nearly three quarters of sea life have bioluminescent capabilities.

Bioluminescence is common across the tree of life (left to right): Panellus Stipticus (foxfire fungi); Lampryis noctiluca (glowworm insect); Aurelia Aurita (moon jellyfish). Credit: Wikimedia Commons, Ylem; Wikimedia Commons, Wofl; stock photo.

Every studied case of bioluminescence involves oxygen, a light-emitting pigment called luciferin and a protein called luciferase. Luciferase encourages the pigment’s reaction with oxygen, releasing energy in the form of light. Although many bioluminescent creatures have their own form of luciferase, they share just a handful of luciferins. For example, the luciferin called coelenterazine is found in many aquatic organisms. Continue reading

The Drama of Cell Death

spermatids

Spermatids—one stage in the formation of sperm—in the fruit fly (Drosophila). Credit: Sigi Benjamin-Hong, Rockefeller University (modified).

Although it looks like a bursting firework from a Fourth of July celebration, this image actually was created from pictures of spermatids—one stage in the formation of sperm—in the fruit fly (Drosophila). Drosophila is an organism that scientists often use as a model for studying how cells accomplish their amazing tasks. Drosophila studies can help reveal where an essential cellular process goes wrong in diseases such as autoimmune conditions or cancer. Cell death, or apoptosis, is one of these processes.

Almost every animal cell has the ability to destroy itself via apoptosis. Apoptosis is important because it allows the body both to develop normally and get rid of dangerous and unwanted cells when it needs to later in life, such as when cells become cancerous. Many different signals both within and outside the cell influence whether apoptosis happens when it should, and abnormal regulation of this process is associated with some diseases. Hermann Steller Exit icon and colleagues at Rockefeller University in New York City study Drosophila and mammalian cells to tease apart the steps of apoptosis and the many molecular signals that regulate it. Continue reading

Beauty is in the Eye

Our eyes are the gateway to countless brilliant sights. However, as evidenced by the images on this page, the eye itself can be breathtakingly exquisite as well. This May, as we celebrate Healthy Vision Month with the National Eye Institute, we hope sharing the beauty hidden in your eyes will inspire you to take the necessary steps to protect your vision, prevent vision loss and make the most of the vision you have remaining.

Visit NEI to learn more about caring for your eyes.

Happy Healthy Vision Month!

Mammalian eye

Eyes are beautiful, and they take on a whole new look in this agate-like image, which highlights just how complex mammalian eyes really are. Researchers used staining and imaging techniques to turn each of the 70-plus cell types in this mouse eye a different color. The image won first place in the 2011 International Science and Engineering Visualization Challenge. Credit: Bryan William Jones, University of Utah Moran Eye Center.
Mouse eye

This burst of starry points is actually part of the retina from a mouse eye. The image comes from a research project investigating the promise of gene therapy for glaucoma. Untreated glaucoma is a leading cause of blindness. The disease is characterized by the death of cells called retinal ganglion cells. Scientists are hoping to deliver gene therapy to these cells as a treatment for glaucoma. In this photo, a fluorescent protein (GFP) lights up to show the location of retinal ganglion cells—and to reveal how well the proposed gene therapy technique might work. Credit: Kenyoung Kim, Wonkyu Ju and Mark Ellisman, National Center for Microscopy and Imaging Research, University of California, San Diego.
Mouse eye

What appears as a tree branch painstakingly wrapped in green wire is a microscopic blood vessel from the retina at the back of a mouse eye. These vessels can help diagnose conditions such as glaucoma and diabetic eye disease. The vessels also have a characteristic appearance in people with high blood pressure. This detailed image was created to help scientists understand what happens in a genetic disease called neurofibromatosis, in which tumors begin to form on nerve tissue. Credit: National Center for Microscopy and Imaging Research, University of California, San Diego.
Mouse eye

Like a colorful fiber-optic network, this microscopic layer from a mouse’s eye relays information from the retina to the brain. Retinal ganglion neurons (orange) and their associated optic nerve fibers (red) are overlaid with blood vessels (blue) and spidery glial cells (green). By comparing detailed images of healthy eye tissues with similar images of a diseased eye, researchers can learn about changes in biology that occur as eye diseases develop. Credit: National Center for Microscopy and Imaging Research, University of California, San Diego.

The Endoplasmic Reticulum: Networking Inside the Cell

Like a successful business networker, a cell’s endoplasmic reticulum (ER) is the structure that reaches out—quite literally—to form connections with many different parts of a cell. In several important ways, the ER enables those other parts, or organelles, to do their jobs. Exciting new images of this key member of the cellular workforce may clarify how it performs its roles. Such knowledge will also help studies of motor neuron and other disorders, such as amyotrophic lateral sclerosis (ALS), that are associated with abnormalities in ER functioning.

Structure Follows Function

Illustration of some of the jobs that the ER performs in the cell.

An illustration of some of the jobs that the endoplasmic reticulum (ER) performs in the cell. Some ER membranes (purple) host ribosomes on their surface. Other ER membranes (blue) extending into the cytoplasm are the site of lipid synthesis and protein folding. The ER passes on newly created lipids and proteins to the Golgi apparatus (green), which packages them into vesicles for distribution throughout the cell. Credit: Judith Stoffer.

Initiated in 1965, the Postdoctoral Research Associate Program (PRAT) is a competitive postdoctoral fellowship program to pursue research in one of the laboratories of the National Institutes of Health. PRAT is a 3-year program providing outstanding laboratory experiences, access to NIH’s extensive resources, mentorship, career development activities and networking. The program places special emphasis on training fellows in all areas supported by NIGMS, including cell biology, biophysics, genetics, developmental biology, pharmacology, physiology, biological chemistry, computational biology, immunology, neuroscience, technology development and bioinformatics

The ER is a continuous membrane that extends like a net from the envelope of the nucleus outward to the cell membrane. Tiny RNA- and protein-laden particles called ribosomes sit on its surface in some places, translating genetic code from the nucleus into amino acid chains. The chains then get folded inside the ER into their three-dimensional protein structures and delivered to the ER membrane or to other organelles to start their work. The ER is also the site where lipids—essential elements of the membranes within and surrounding a cell—are made. The ER interacts with the cytoskeleton—a network of protein fibers that gives the cell its shape—when a cell divides, moves or changes shape. Further, the ER stores calcium ions in cells, which are vital for signaling and other work.

To do so many jobs, the ER needs a flexible structure that can adapt quickly in response to changing situations. It also needs a lot of surface area where lipids and proteins can be made and stored. Scientists have thought that ER structure combined nets of tubules, or small tubes, with areas of membrane sheets. However, recent NIGMS PRAT (Postdoctoral Research Associate; see side bar) fellow Aubrey Weigel, working with her mentor and former PRAT fellow Jennifer Lippincott-Schwartz of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (currently at the Howard Hughes Medical Institute in Virginia) and colleagues, including Nobel laureate Eric Betzig, wondered whether limitations in existing imaging technologies were hiding a better answer to how the ER meets its surface-area structural needs in the periphery, the portion of the cell not immediately surrounding the nucleus. Continue reading

Birthdays, Nobel Prizes and Basic Research

James D. Watson
James D. Watson. Credit: Wikimedia Commons, Cold Spring Harbor Laboratory.

April 6 is the birthday of two Nobel Prize winners in physiology or medicine—James Watson and Edmond H. Fischer. They have also both been NIGMS-supported researchers.

Double helix model
In 1953, Watson and Crick created their historic model of the shape of DNA: the double helix. Credit: Cold Spring Harbor Laboratory archives.

James D. Watson, born on this day in 1928, was honored with the Nobel Prize in 1962. He shared it with Francis H. Compton Crick and Maurice Wilkins “for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material.” This laid the groundwork for future discoveries. In the early 1950s, Wilkins and another scientist, Rosalind Franklin, worked to determine DNA’s structure. In 1953, Watson and Crick discovered its shape as a double helix. This twisted ladder structure enabled other researchers to unlock the secret of how genetic information is stored, transferred and copied. Franklin is widely recognized as having played a significant role in revealing the physical structure of DNA; due to her death at age 37 in 1958, Franklin did not earn a share of the prize. Read more about DNA. Continue reading

Actin’s Many Roles

Skin cancer cells

Skin cancer cells from a mouse. Credit: Catherine and James Galbraith, Oregon Health and Science University, Center for Spatial Systems Biomedicine, Knight Cancer Institute.

This heart-shaped image shows two mouse skin cancer cells connected to each other with actin, a protein that is part of the cellular skeleton. Researchers use mouse cells like these to tease out the molecular methods that cancer uses to invade new tissues in the body. It turns out that actin plays an essential role.

Cells can move as a collective, or independently. Movement of an individual cell requires a series of carefully controlled steps. Among them, a cell must break contacts with its neighbor cells and change its connections to the proteins and fibers around it. In addition, it must sense and follow a chemical path through the tissue it lies in. To do this, a cell changes shape, molding its membrane into flaps or feet called protrusions reaching in the direction it is traveling. Actin, among a variety of other molecules, is involved in all of these steps, but especially the shape change, when it gathers inside the cell membrane to help form the protrusions. Continue reading

Cool Image: Inside a Biofilm Build-up

A growing Vibrio cholerae biofilm.

A growing Vibrio cholerae biofilm. Each slightly curved comma shape represents an individual bacterium from assembled confocal microscopy images. Different colors show each bacterium’s position in the biofilm in relation to the surface on which the film is growing. Credit: Jing Yan, Ph.D., and Bonnie Bassler, Ph.D., Department of Molecular Biology, Princeton University, Princeton, NJ.

Bacteria use many methods to overcome threats in their environment. One of these ways is forming colonies called biofilms on surfaces of objects. Often appearing like the bubble-shaped fortress represented in this image, biofilms enable bacteria to withstand attacks, compete for space and survive fluctuations in nutrient supply. Bacteria aggregated within biofilms inside our bodies, for example, resist antibiotic therapy more effectively than free swimming cells, making infections difficult to treat. On the other hand, biofilms are also useful for making microbial fuel cells and for waste-water treatment. Learning how biofilms work, therefore, could provide essential tools in our ongoing battle against disease-causing agents and in our efforts to harness beneficial bacterial behaviors. Researchers are now using new imaging techniques to watch how biofilms grow, cell by cell, and to identify more effective ways of disrupting or fostering them.

Until now, poor imaging resolution meant that scientists could not see what individual bacteria in the films are up to as the biofilms grow. The issue is that bacteria are tiny, making imaging each cell, as well as the ability to distinguish each cell in the biofilm community, problematic. Continue reading

Cool Tools: Pushing the Limits of High-Resolution Microscopy

Cell biologists would love to shrink themselves down and actually see, touch and hear the inner workings of cells. Because that’s impossible, they have developed an ever-growing collection of microscopes to study cellular innards from the outside. Using these powerful tools, researchers can exhaustively inventory the molecular bits and pieces that make up cells, eavesdrop on cellular communication and spy on cells as they adapt to changing environments.

In recent years, scientists have developed new cellular imaging techniques that allow them to visualize samples in ways and at levels of detail never before possible. Many of these techniques build upon the power of electron microscopy (EM) to see ever smaller details.

Unlike traditional light microscopy, EM uses electrons, not light, to create an image. To do so, EM accelerates electrons in a vacuum, shoots them out of an electron gun and focuses them with doughnut-shaped magnets onto a sample. When electrons bombard the sample, some pass though without being absorbed while others are scattered. The transmitted electrons land on a detector and produce an image, just as light strikes a detector (or film) in a camera to create a photograph.

This image, showing a single protein molecule, is a montage. It was created to demonstrate how dramatically cryo-EM has improved in recent years. In the past, cryo-EM was only able to obtain a blobby approximation of a molecule’s shape, like that shown on the far left. Now, the technique yields exquisitely detailed images in which individual atoms are nearly visible (far right). Color is artificially applied. Credit: Veronica Falconieri, Subramaniam Lab, National Cancer Institute.

Transmission electron microscopes can magnify objects more than 10 million times, enabling scientists to see the outline and some details of cells, viruses and even some large molecules. A relatively new form of transmission electron microscopy called cryo-EM enables scientists to view specimens in their natural or near-natural state without the need for dyes or stains.

In cryo-EM—the prefix cry- means “cold” or “freezing”—scientists freeze a biological sample so rapidly that water molecules do not have time to form ice crystals, which could shove cellular materials out of their normal place. Cold samples are more stable and can be imaged many times over, allowing researchers to iteratively refine the image, remove artifacts and produce even sharper images than ever before. Continue reading

Interview With a Scientist: Thomas O’Halloran, Metal Maestro

Inside our bodies is a surprising amount of metal. Not enough to set off the scanners at the airport or make us rich, but enough to fill each of our cells with billions of metal ions, including calcium, iron, copper and zinc. These ions facilitate critical biological functions.

However, too much of any metal can be toxic, while too little can cause disease. Our cells carefully monitor and control their metal content using a whole series of proteins that bind, sense and transport metal ions.

Keeping tabs on why and how metals flow into and out of our cells is a passion of Thomas O’Halloran Exit icon, professor of chemistry and molecular biosciences at Northwestern University in Illinois. For the past three decades, O’Halloran has investigated how fluctuations in the amount of metal ions inside cells influence gene expression, cell growth and other vital functions. Using a variety of approaches, he has uncovered new types of proteins that bind metal ions and investigated the role that imbalances in these ions play in a number of disease-related physiological processes.

One recent focus of his studies has been how zinc regulates oocyte (egg cell) maturation and fertilization. Ultimately, his work could help us better understand infertility, cancer and certain bacterial infections.