Nav: Home

Mechanical forces shape animal 'origami' precisely despite 'noise'

March 12, 2020

Researchers at the RIKEN Center for Biosystems Dynamics Research (BDR) in Japan have identified a new mechanism that helps animals to develop with precise and constant form.

The reproducibility of form, shape, and characteristic appearance is a key feature of our development that is made possible because their instructions are coded in our DNA. What is perplexing, however, is how this reproducibility is achieved despite genetic variation and developmental "noise" resulting from environmental, physical and chemical fluctuations. Recent work in fruit flies has suggested that "noise-cancelling" mechanisms in the embryo rely on a detailed and highly reproducible genetic "blueprint" with specific instructions down to the single-cell level.

Now, in research published in Developmental Cell, an international team led by Yu-Chiun Wang at RIKEN BDR asked whether this blueprint is sufficient to explain developmental consistency, or whether it is helped by alternative noise-cancelling mechanisms. Their findings indicate a previously overlooked role for the mechanical forces that sculpt the embryo, as they turn out to be the noise-producing culprit as well as the key to ensuring precision - a true double-edged sword!

In their work, the team investigated a structure called the cephalic furrow in the fruit fly embryo, in which the surface of the embryo folds along a straight line in an origami-like fashion. To make this fold, the cells deploy a molecule called myosin to exert mechanical forces that shorten the cells making up the fold. What was surprising, however, was that on average 20% of the cells did not receive the instructions to become part of the cephalic furrow. It turned out that the information of where to make a fold was precise, but the reading of this information was unexpectedly sloppy. As a result, myosin distribution was highly variable, resulting in a discrepancy between the blueprint information and cell behavior. "These results were very puzzling as generations of developmental biologists were in awe of how the genetic blueprint could instruct machine-like precision of development," says Wang.

To find out how the embryo folds along a straight crease as in an origami despite this "noise", the researchers looked more broadly across the tissue and realized that myosin is polarized along the direction parallel to the forming crease. They hypothesized that, powered by myosin, the cell membranes pull on each other, creating a form of mechanical communication that allows a straightened ribbon-like structure to emerge out of a fuzzy zone of stochastic membrane contraction. It appeared that this myosin-dotted ribbon is the crease of the developing cephalic furrow.

To show that this was indeed the case, the scientists cut the ribbon used a sharply focused laser beam to inactivate myosin in a small number of cells. They found that the cephalic furrow developed a kink, indicating that the straightness of the folding requires an intact ribbon of contractile membranes. Computer simulations also confirmed that tissue folding based on polarized contractile forces indeed can overcome the noise in contractile forces.

The conclusion of this study is that the constancy of animal form requires more than just the deterministic process of genetic inheritance and genetic networks, but also relies on the stochastic and emergent behaviors of mechanical forces. "This work taught us that constancy in biology stems not only from its regulatory complexity, but also from the unique noise-and-self-correction principle of self-organization. This is a missing chapter in developmental biology textbooks," Wang says. Wang also thinks that by the same token, pathological processes that involve growth, reorganization and changing cell and tissue shapes, such as tumor formation and cancer metastasis, must also contain an element of mechanical self-organization, alongside the well-known factor of genetic susceptibility. "The cephalic furrow is a very pronounced structure," he continues, "yet it forms and disappears about one hour after its initiation. This mysterious, beautiful and yet ephemeral structure of "epithelial origami" continues to mesmerize us and teach us things that we haven't yet understood about animal development."


Related Myosin Articles:

Essential key to hearing sensitivity discovered
New research is shedding light on the biological architecture that lets us hear -- and on a genetic disorder that causes both deafness and blindness.
Cell muscle movements visualised for first time
The movements of cell muscles in the form of tiny filaments of proteins have been visualised at unprecedented detail by University of Warwick scientists.
Muscle protein abundant in the heart plays key role in blood clotting during heart attack
A prevalent heart protein known as cardiac myosin, which is released into the body when a person suffers a heart attack, can cause blood to thicken or clot--worsening damage to heart tissue, a new study shows.
Mechanical forces shape animal 'origami' precisely despite 'noise'
Researchers at the RIKEN Center for Biosystems Dynamics Research (BDR) in Japan have identified a new mechanism that helps animals to develop with precise and constant form.
New clues as to why mutations in the MYH9 gene cause broad spectrum of disorders in humans
Researchers have used the Drosophila embryo to model human disease mutations that affect myosin motor activity.
Compound may play role in halting panceatic cancer
In early test tube and mouse studies, investigators at Johns Hopkins Medicine and the Johns Hopkins Kimmel Cancer Center have found that nonmuscle myosin IIC (MYH14), a protein activated in response to mechanical stress, helps promote metastatic behavior in pancreatic cancer cells, and that the compound 4-hydroxyacetophenone (4-HAP), known to stiffen myosin IIC-containing cells, can send it into overdrive, overwhelming the ability of cells to invade nearby tissue.
Physics of life: Motor proteins and membrane dynamics
Motility is an essential property of many cell types, and is driven by molecular motors.
Multiple mechanisms behind disease associated with unexpected heart attacks
An examination of three mutations associated with hypertrophic cardiomyopathy -- a disease best known for revealing itself as an unexpected, fatal heart attack during strenuous exercise -- found separate mechanisms at work at the molecular level.
Skin cancer can spread in mice by hijacking the immune system
Scientists have uncovered molecules released by invasive skin cancer that reprogram healthy immune cells to help the cancer to spread.
The origins of asymmetry: A protein that makes you do the twist
Asymmetry plays a major role in biology at every scale: think of DNA spirals, the fact that the human heart is positioned on the left, our preference to use our left or right hand.
More Myosin News and Myosin Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Meditations on Loneliness
Original broadcast date: April 24, 2020. We're a social species now living in isolation. But loneliness was a problem well before this era of social distancing. This hour, TED speakers explore how we can live and make peace with loneliness. Guests on the show include author and illustrator Jonny Sun, psychologist Susan Pinker, architect Grace Kim, and writer Suleika Jaouad.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.