Finding Beauty in Cell Stress
Posted on by Dr. Francis Collins
Most stressful situations that we experience in daily life aren’t ones that we’d choose to repeat. But the cellular stress response captured in this video is certainly worth repeating a few times, so you can track what happens when two cancer cells get hit with stressors.
In this movie of two highly stressed osteosarcoma cells, you first see the appearance of many droplet-like structures (green). This is followed by a second set of droplets (magenta) and, finally, the fusion of both types of droplets.
These droplets are composed of fluorescently labeled stress-response proteins, either G3BP or UBQLN2 (Ubiquilin-2). Each protein is undergoing a fascinating process, called phase separation, in which a non-membrane bound compartment of the cytoplasm emerges and constrains the motion of proteins within it. Subsequently, the proteins fuse with like proteins to form larger droplets, in much the same way that raindrops merge on a car’s windshield.
Julia Riley, an undergraduate student in the NIH-supported lab of Heidi Hehnly and lab of Carlos Castañeda, Syracuse University, NY, shot this movie using the sophisticated tools of fluorescence microscopy. It’s the next installment in our series featuring winners of the 2019 Green Fluorescent Protein Image and Video Contest, sponsored by the American Society for Cell Biology. The contest honors the discovery of green fluorescent protein (GFP), which—together with a rainbow of other fluorescent proteins—has enabled researchers to visualize proteins and their dynamic activities inside cells for the last 25 years.
Riley and colleagues suspect that, in this case, phase separation is a protective measure that allows proteins to wall themselves off from the rest of the cell during stressful conditions. In this way, the proteins can create new functional units within the cell. The researchers are working to learn much more about what this interesting behavior entails as a basic organizing principle in the cell and how it works.
Even more intriguing is that similar stress-responding proteins are commonly altered in people with the devastating neurologic condition known as amyotrophic lateral sclerosis (ALS). ALS is a group of rare neurological diseases that involve the progressive deterioration of neurons responsible for voluntary movements such as chewing, walking, and talking. There’s been the suggestion that these phase separation droplets may seed the formation of the larger protein aggregates that accumulate in the motor neurons of people with this debilitating and fatal condition.
Castañeda and Hehnly, working with J. Paul Taylor at St. Jude Children’s Research Hospital, Memphis, earlier reported that Ubiquilin-2 forms stress-induced droplets in multiple cell types . More recently, they showed that mutations in Ubiquilin-2 have been linked to ALS changes in the way that the protein undergoes phase separation in a test tube .
While the proteins in this award-winning video aren’t mutant forms, Riley is now working on the sequel, featuring versions of the Ubiquilin-2 protein that you’d find in some people with ALS. She hopes to capture how those mutations might produce a different movie and what that might mean for understanding ALS.
 Ubiquitin Modulates Liquid-Liquid Phase Separation of UBQLN2 via Disruption of Multivalent Interactions. Dao TP, Kolaitis R-M, Kim HJ, O’Donovan K, Martyniak B, Colicino E, Hehnly H, Taylor JP, Castañeda CA. Molecular Cell. 2018 Mar 15;69(6):965-978.e6.
 ALS-Linked Mutations Affect UBQLN2 Oligomerization and Phase Separation in a Position- and Amino Acid-Dependent Manner. Dao TP, Martyniak B, Canning AJ, Lei Y, Colicino EG, Cosgrove MS, Hehnly H, Castañeda CA. Structure. 2019 Jun 4;27(6):937-951.e5.
Amyotrophic Lateral Sclerosis (ALS) (National Institute of Neurological Disorders and Stroke/NIH)
Castañeda Lab (Syracuse University, NY)
Hehnly Lab (Syracuse University)
Green Fluorescent Protein Image and Video Contest (American Society for Cell Biology, Bethesda, MD)
2008 Nobel Prize in Chemistry (Nobel Foundation, Stockholm, Sweden)
NIH Support: National Institute of General Medical Sciences
Biomedical Research Highlighted in Science’s 2018 Breakthroughs
Posted on by Dr. Francis Collins
A Happy New Year to one and all! While many of us were busy wrapping presents, the journal Science announced its much-anticipated scientific breakthroughs of 2018. In case you missed the announcement , it was another banner year for the biomedical sciences.
The 2018 Breakthrough of the Year went to biomedical science and its ability to track the development of life—one cell at a time—in a variety of model organisms. This newfound ability opens opportunities to understand the biological basis of life more systematically than ever before. Among Science’s “runner-up” breakthroughs, more than half had strong ties to the biomedical sciences and NIH-supported research.
Sound intriguing? Let’s take a closer look at some of the amazing science conducted in 2018, starting with Science’s Breakthrough of the Year.
Development Cell by Cell: For millennia, biologists have wondered how a single cell develops into a complete multicellular organism, such as a frog or a mouse. But solving that mystery was almost impossible without the needed tools to study development systematically, one cell at a time. That’s finally started to change within the last decade. I’ve highlighted the emergence of some of these powerful tools on my blog and the interesting ways that they were being applied to study development.
Over the past few years, all of this technological progress has come to a head. Researchers, many of them NIH-supported, used sophisticated cell labeling techniques, nucleic acid sequencing, and computational strategies to isolate thousands of cells from developing organisms, sequence their genetic material, and determine their location within that developing organism.
In 2018 alone, groundbreaking single-cell analysis papers were published that sequentially tracked the 20-plus cell types that arise from a fertilized zebrafish egg, the early formation of organs in a frog, and even the creation of a new limb in the Axolotl salamander. This is just the start of amazing discoveries that will help to inform us of the steps, or sometimes missteps, within human development—and suggest the best ways to prevent the missteps. In fact, efforts are now underway to gain this detailed information in people, cell by cell, including the international Human Cell Atlas and the NIH-supported Human BioMolecular Atlas Program.
An RNA Drug Enters the Clinic: Twenty years ago, researchers Andrew Fire and Craig Mello showed that certain small, noncoding RNA molecules can selectively block genes in our cells from turning “on” through a process called RNA interference (RNAi). This work, for the which these NIH grantees received the 2006 Nobel Prize in Physiology or Medicine, soon sparked a wave of commercial interest in various noncoding RNA molecules for their potential to silence the expression of a disease-causing gene.
After much hard work, the first gene-silencing RNA drug finally came to market in 2018. It’s called Onpattro™ (patisiran), and the drug uses RNAi to treat the peripheral nerve disease that can afflict adults with a rare disease called hereditary transthyretin-mediated amyloidosis. This hard-won success may spark further development of this novel class of biopharmaceuticals to treat a variety of conditions, from cancer to cardiovascular disorders, with potentially greater precision.
Rapid Chemical Structure Determination: Last October, two research teams released papers almost simultaneously that described an incredibly fast new imaging technique to determine the structure of smaller organic chemical compounds, or “small molecules“ at atomic resolution. Small molecules are essential components of molecular biology, pharmacology, and drug development. In fact, most of our current medicines are small molecules.
News of these papers had many researchers buzzing, and I highlighted one of them on my blog. It described a technique called microcrystal electron diffraction, or MicroED. It enabled these NIH-supported researchers to take a powder form of small molecules (progesterone was one example) and generate high-resolution data on their chemical structures in less than a half-hour! The ease and speed of MicroED could revolutionize not only how researchers study various disease processes, but aid in pinpointing which of the vast number of small molecules can become successful therapeutics.
How Cells Marshal Their Contents: About a decade ago, researchers discovered that many proteins in our cells, especially when stressed, condense into circumscribed aqueous droplets. This so-called phase separation allows proteins to gather in higher concentrations and promote reactions with other proteins. The NIH soon began supporting several research teams in their groundbreaking efforts to explore the effects of phase separation on cell biology.
Over the past few years, work on phase separation has taken off. The research suggests that this phenomenon is critical in compartmentalizing chemical reactions within the cell without the need of partitioning membranes. In 2018 alone, several major papers were published, and the progress already has some suggesting that phase separation is not only a basic organizing principle of the cell, it’s one of the major recent breakthroughs in biology.
Forensic Genealogy Comes of Age: Last April, police in Sacramento, CA announced that they had arrested a suspect in the decades-long hunt for the notorious Golden State Killer. As exciting as the news was, doubly interesting was how they caught the accused killer. The police had the Golden Gate Killer’s DNA, but they couldn’t determine his identity, that is, until they got a hit on a DNA profile uploaded by one of his relatives to a public genealogy database.
Though forensic genealogy falls a little outside of our mission, NIH has helped to advance the gathering of family histories and using DNA to study genealogy. In fact, my blog featured NIH-supported work that succeeded in crowdsourcing 600 years of human history.
The researchers, using the online profiles of 86 million genealogy hobbyists with their permission, assembled more than 5 million family trees. The largest totaled more than 13 million people! By merging each tree from the crowd-sourced and public data, they were able to go back about 11 generations—to the 15th century and the days of Christopher Columbus. Though they may not have caught an accused killer, these large datasets provided some novel insights into our family structures, genes, and longevity.
An Ancient Human Hybrid: Every year, researchers excavate thousands of bone fragments from the remote Denisova Cave in Siberia. One such find would later be called Denisova 11, or “Denny” for short.
Oh, what a fascinating genomic tale Denny’s sliver of bone had to tell. Denny was at least 13 years old and lived in Siberia roughly 90,000 years ago. A few years ago, an international research team found that DNA from the mitochondria in Denny’s cells came from a Neanderthal, an extinct human relative.
In 2018, Denny’s family tree got even more interesting. The team published new data showing that Denny was female and, more importantly, she was a first generation mix of a Neanderthal mother and a father who belonged to another extinct human relative called the Denisovans. The Denisovans, by the way, are the first human relatives characterized almost completely on the basis of genomics. They diverged from Neanderthals about 390,000 years ago. Until about 40,000 years ago, the two occupied the Eurasian continent—Neanderthals to the west, and Denisovans to the east.
Denny’s unique genealogy makes her the first direct descendant ever discovered of two different groups of early humans. While NIH didn’t directly support this research, the sequencing of the Neanderthal genome provided an essential resource.
As exciting as these breakthroughs are, they only scratch the surface of ongoing progress in biomedical research. Every field of science is generating compelling breakthroughs filled with hope and the promise to improve the lives of millions of Americans. So let’s get started with 2019 and finish out this decade with more truly amazing science!
 “2018 Breakthrough of the Year,” Science, 21 December 2018.
NIH Support: These breakthroughs represent the culmination of years of research involving many investigators and the support of multiple NIH institutes.