New Discovery Inside Cells May Provide Key to Life
Once scientists noticed strange blob-like features inside a cell for the first time, they started seeing them everywhere
Hiya!
Science classes in school were always a struggle for me, especially biology. I just couldn’t grasp or visualize cells, let alone their components, which made the entire subject feel abstract. And, while I logically understood the importance of cells, their smallness made them insignificant in my mind.
However, something shifted or clicked into place since my high school days, and now I marvel at how significant cells are. They’re incredible, and the more we learn about them, the more impressive they become. Scientists even believe cells may hold the answer to how life forms. Yet, even with our advanced technology, such a mystery remains just that, but a recent discovery may bring us closer to an answer.
Previous Understanding of a Cell
I didn’t, but you may remember learning about organelles in biology class. They’re the tiny structures within a cell that each perform a specific task.
Kinda like how we have a heart, lungs, and other organs that do specific functions; cells have about a dozen organelles like a nucleus that stores our DNA, the mitochondria that power the cell, and lysosomes that recycle its waste.
While each organelle within a cell has a distinct function, they’re all wrapped up in a membrane. Considering this commonality, scientists assumed that wrapping organelles in a membrane was essential to keeping the cell organized.
However, scientists have discovered over the last few years that some organelles don’t require the membrane boundary. In fact, there seem to be a lot more organelles that don’t require a membrane wrapping than those that do.
What’s going on there?
Around two decades ago, a team of biophysicists led by Anthony A. Hyman at the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden, Germany, was analyzing P granules in the single-celled embryo of a tiny, soil-dwelling worm when they observed something unexpected.
But before I tell you what they saw, it’ll be helpful to know what P granules are.
P granules are specks of specialized particles within developing germ cells, primarily in organisms like worms. They’re mostly made of RNA and proteins and play a vital role in translating the directions RNA gives during the formation of certain germ cells essential for reproduction.
In other words, if DNA represents the blueprints for life, RNA is the contractor that leads the construction by delivering instructions to P granules, which then relay them to the work crew, and proteins reveal what’s actually built.
Okay, now we can get back to the story.
So, while monitoring the P granules in the worm embryo, the team noticed that they tended to accumulate at only one end of the cell, making it lopsided. As a result, when the cell divided, the two daughter cells were different.
This is highly unusual because, typically, daughter cells contain identical material. So, in a way, it was as if the P granules were causing cells to create fraternal twin cells instead of identical ones.
(Side note: Fraternal human twins occur when two different eggs are fertilized by two different sperm within the same ovulation cycle, while identical twins happen when one egg is fertilized by one sperm and then splits into two.)
Baffled, the researchers wanted to know how and why such a dramatic uneven distribution of P granules occurs.
After further investigation, they discovered that the specks undergo a phase transition similar to when a substance transitions between liquid and gas. The specks formed little blobs that gathered on one side of a cell, like raindrops in moist air, but that dissolved on the other side.
This was a strange and extraordinary observation within the field of cellular biology, but in 2009, the researchers published their findings in the journal Science.
At first, their study got little to no attention, and many researchers attributed the discovery to nothing more than a quirk that wasn’t worthy of further investigation. But that changed once more researchers began noticing the blobs nearly everywhere they looked within a cell.
Now, these mysterious blobs are referred to as either membrane-less organelles or biomolecular condensates.
Biomolecular Condensates
Condensates form within cells via phase separation, the same process behind the interaction between oil and water. In an article published by The Conversation, Allan Albig, an Associate Professor of Biological Sciences at Boise State University, compares the biomolecular condensate interactions to a lava lamp. He writes:
“To get a sense of what a biomolecular condensate looks like, imagine a lava lamp as the blobs of wax inside fuse together, break apart and fuse again. Condensates form in much the same way, though they are not made of wax. Instead, a cluster of proteins and genetic material, specifically RNA molecules, in a cell condenses into gel-like droplets.”
Some RNA and proteins conglomerate because they prefer interacting with each other rather than their surrounding environment. Using Albig’s lava lamp example, it’s similar to how the wax blobs mix together, but not with the surrounding liquid.
As a result, the condensates form a new microenvironment that draws more similar proteins and RNA molecules and creates a unique biochemical compartment within cells that doesn’t require membrane boundaries.
Such a concept is so simple yet revolutionary.
Remember, biologists have long believed that membrane-bound compartments were required to organize cell organelles. Otherwise, the organelles could jumble around the cell and against each other, or so they thought. However, using phase transition, the condensates formed an efficient method of bringing order to a cell without needing membranes.
Now, scientists are finding these blobs inside living cells across all domains of life. Biophysical engineer Cliff Brangwynne, who was part of the 2009 Dresden team and now runs his own lab at Princeton University, told Philip Ball of Scientific American that it’s evident the biomolecular condensates are “connected to just about every aspect of cellular function.”
But what do they do?
So far, researchers have identified around 30 types of blobby membrane-less biomolecular condensates — nearly three times more than the number of membrane-bound organelles.
Some have well-defined functions, like forming stress granules, reproductive cells, and protein-creating ribosomes. Meanwhile, others protect cells from dangerous temperature fluctuations, repair damaged DNA, and control how DNA is turned into crucial proteins.
However, without the membrane’s protection, biomolecular condensates are vulnerable to more risk factors that may trigger diseases such as cancers and Alzheimer’s.
Brangwynne believes the mechanisms behind biomolecular condensates contribute to how life gets its countless molecular components to cooperate and organize. He told Ball:
“The ultimate problem in cell biology is not how a few puzzle pieces fit together, but how collections of billions of them give rise to emergent, dynamic structures on larger scales.”
However, using phase separation rather than membrane boundaries could allow for such expansion, as the condensates could theoretically continue accumulating into larger and larger blobs. Though, more research is needed.
In the Future
Once Hyman and his team at the Max Planck Institute first identified biomolecular condensates in the early 2000s, scientists began seeing them everywhere. Decades later, experts have a decent-sized catalog of various types, but many more remain a mystery.
And while these tiny blobs may be easy to identify now that scientists know what to look for, it’s more challenging to figure out precisely what they do — and many don’t seem to have any explicit functions.
Once scientists can understand that, they might be able to figure out how the condensates form, what triggers their phase shifting, and maybe even how to control them or use them to develop new therapies or cures.
Perspective Shift
Occam's razor is the philosophy that the simplest solution is often the best — and it’s one Nature seems to agree with. Nature is exceptionally intricate yet beautifully simplistic, and its simplicity is what creates its intricacies, like fractals.
Meanwhile, humans are the opposite. We desire and search for simplicity but tend to overcomplicate things. For instance, phase separation is a well-known natural phenomenon, but we didn’t think such a thing as biomolecular condensates could be possible. Yet, once again, Nature showed us how wrong we were. I wonder how many other ways Nature utilizes phase transitions that we haven’t recognized yet.
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Seems like they should have noticed this decades ago.
This is some of the most fascinating information Ive ever learned.