Tag Archives: dynein

Art influences science

It’s not often you see research that combines biologically inspired engineering and a molecular biophysicist with a professional animator who worked at Peter Jackson’s (Lord of the Rings film trilogy, etc.) Park Road Post film studio. An Oct. 18, 2017 news item on ScienceDaily describes the project,

Like many other scientists, Don Ingber, M.D., Ph.D., the Founding Director of the Wyss Institute, is concerned that non-scientists have become skeptical and even fearful of his field at a time when technology can offer solutions to many of the world’s greatest problems. “I feel that there’s a huge disconnect between science and the public because it’s depicted as rote memorization in schools, when by definition, if you can memorize it, it’s not science,” says Ingber, who is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and the Vascular Biology Program at Boston Children’s Hospital, and Professor of Bioengineering at the Harvard Paulson School of Engineering and Applied Sciences (SEAS). “Science is the pursuit of the unknown. We have a responsibility to reach out to the public and convey that excitement of exploration and discovery, and fortunately, the film industry is already great at doing that.”

An October 18, 2017 Wyss Institute at Harvard University news release (also on EurekAlert) by Lindsay Brownell, which originated the news item, details the work,

To see if entertainment could offer a solution to this challenge, Ingber teamed up with Charles Reilly, Ph.D., a molecular biophysicist, professional animator, and Staff Scientist at the Wyss Institute who previously worked at movie director Peter Jackson’s Park Road Post film studio, to create a film that would capture viewers’ imaginations by telling the story of a biological process that was accurate down to the atomic level. “Don and I quickly found that we have a lot of things in common, especially that we’re both systems thinkers,” says Reilly. “Applying an artistic process to science frees you from the typically reductionist approach of analyzing one particular hypothesis and teaches you a different way of observing things. As a result, we not only created an entertaining tool for public outreach, we conducted robust theoretical biology research that led to new scientific insight into molecular-scale processes.” The research is now published in ACS Nano and the film can be found here.

Wyss researchers created a model of an axoneme that displays how different segments of the microtubules bend and flex relative to each other to create movement. Credit: Wyss Institute at Harvard University

Any good movie needs characters and drama, and a “hook” to get the audience invested in watching. The scientists decided to make a parody of a trailer for a Star Wars® movie, but instead of showing starship cruisers hurtling through space towards the Death Star, they chose a biological process with its own built-in narrative: the fertilization of an egg by a sperm, in which millions of sperm race to be the one that succeeds and creates the next generation of life. The patterns and mechanics of sperm swimming have been studied and described in scientific literature, but visually showing the accurate movement of a sperm tail required tackling one of the toughest challenges facing science today: how to create a multi-scale biological model that maintains accuracy at different sizes, from cells all the way down to atoms. That would be like starting with the Empire State Building and then zooming in close enough to see every individual screw, nut and bolt that holds it together, as well as how individual water molecules flow inside its pipes, while maintaining crystal-clear resolution – not an easy task.

“It turns out that creating an accurate biological model and creating a believable computer-generated depiction of life in film are very similar, in that you’re constantly troubleshooting and modifying your virtual object until it fits the way things actually look and move,” says Reilly. “However, for biology, the simulations also have to align with recorded scientific data and theoretical models that have previously been experimentally validated.” The scientists created a design-based animation pipeline that integrates physics-based film animation software with molecular dynamics simulation software to create a model of how a sperm tail moves based on scientific data, with the criterion that the model had to work across all size scales. “This is really a design thinking approach, where you have to be willing to throw out your model if it doesn’t work correctly when you integrate it with data from another scale,” Reilly says. “A lot of scientific investigations use a reductionist approach, focusing on one molecule or one biological system with higher and higher resolution without placing it in context, which makes it difficult to converge on a picture of the larger whole.”

This video shows dynein’s two different shapes as determined from scientific observations, and how the Wyss researchers’ molecular model of dynein’s movement fits those conformations. Credit: Wyss Institute at Harvard University

The core of a sperm’s whip-like tail is the axoneme, a long tube consisting of nine pairs of microtubules arranged in a column around a central pair, all of which extend the entire length of the tail. The axoneme’s rhythmic bending and stretching is the source of the tail’s movement, and the scientists knew they needed to realistically depict that process in order to show the film’s viewers how a sperm moves. Rather than construct a model in a linear fashion by “zooming in” or “zooming out” to add more information to a single starting structure, they built the model at different scales simultaneously, repeatedly checking it against scientific data to ensure it was accurate and modifying it until the pieces fit together.

The axoneme’s movement is accomplished via rows of motor proteins called dyneins that are attached along the microtubules and exert force on them so the microtubules “slide” past each other, which then causes the entire axoneme and sperm tail to bend and move. The dynein protein has a long “arm” portion that grabs onto the neighboring microtubule and, when the protein changes from one shape to another, pulls the microtubule along with it. Dynein switches between these different conformations as a result of the conversion of a molecule of ATP to ADP at a specific binding site on the protein, which releases energy as a chemical bond is broken. To model this molecular motor, the scientists created a molecular dynamics simulation of a dynein protein and applied energy at the ATP binding site to approximate the transfer of energy from ATP. They found that this caused atoms in the entire protein to move in random directions when they performed their simulation of dynein floating in solution, as most conventional scientific simulations do. However, when they then “fixed” a specific hinge region of the dynein molecule that is known to connect dynein to its microtubule, they discovered that the dynein spontaneously moved in its characteristic direction when force was applied at the ATP binding site, matching the way it moves in nature.

This video shows rows of dynein proteins along the microtubules of an axoneme moving in sync to cause the axoneme’s motion, like rowers pulling synchronously in a boat. Credit: Wyss Institute at Harvard University

“Not only is our physics-based simulation and animation system as good as other data-based modeling systems, it led to the new scientific insight that the limited motion of the dynein hinge focuses the energy released by ATP hydrolysis, which causes dynein’s shape change and drives microtubule sliding and axoneme motion,” says Ingber. “Additionally, while previous studies of dynein have revealed the molecule’s two different static conformations, our animation visually depicts one plausible way that the protein can transition between those shapes at atomic resolution, which is something that other simulations can’t do. The animation approach also allows us to visualize how rows of dyneins work in unison, like rowers pulling together in a boat, which is difficult using conventional scientific simulation approaches.”

Using this biologically accurate model of how dynein moves the microtubules within the axoneme, Ingber and Reilly created a short film called “The Beginning,” which draws parallels between sperm swimming toward an egg and spaceships flying toward a planet in space, giving an artistic bent to a scientific topic. The film depicts several sperm attempting to fertilize the egg, “zooms in” on one sperm’s tail to show how the dynein proteins move in sync to cause the tail to bend and flex, and ends with the sperm’s successful journey into the egg and the initiation of cell division that will ultimately create a new organism. The scientists submitted the film along with the paper to several academic journals, and it took a long time before they found an open-minded editor who recognized that the paper and film together were a powerful demonstration of how starting with an artistic goal can end up generating new scientific discoveries along with a tool for public outreach.

*Due to distortion images deleted March 9, 2018.*

“Both science and art are about observation, interpretation, and communication. Our goal is that presenting science to the public in an entertaining, system-based way, rather than bogging them down with a series of scattered facts, will help more people understand it and feel that they can contribute to the scientific conversation. The more people engage with science, the more likely humanity is to solve the world’s big problems,” says Reilly. “I also hope that this paper and video encourage more scientists to take an artistic approach when they start a new project, not necessarily to create a narrative-based story, but to explore their idea the way an artist explores a canvas, because that makes the mind open to a different form of serendipity that can lead to unexpected results.”

“The Wyss Institute is driven by biological design. In this project, we used design tools and approaches borrowed from the art world to solve problems related to motion, form, and complexity to create something entertaining, which ultimately led to new scientific insights and, hopefully, new ways to excite the public about science,” says Ingber. “We’ve demonstrated that art and science can benefit each other in a truly reciprocal way, and we hope that this project spurs future collaborations with the entertainment industry so that both art and science can get even closer to depicting reality in ways that anyone can appreciate and enjoy.”

*Due to distortion images deleted on March 9, 2018.*

The film,

Here’s a link to and a citation for the paper,

Art Advancing Science: Filmmaking Leads to Molecular Insights at the Nanoscale by Charles Reilly and Donald E. Ingber. ACS Nano, Article ASAP DOI: 10.1021/acsnano.7b05266 Publication Date (Web): October 18, 2017

Copyright © 2017 American Chemical Society

This paper appears to be open access.

Watching motor proteins at work

Researchers in the UK and in Japan have described these motor proteins as ‘swinging on monkey bars’,

A Sept. 14, 2015 news item on Nanowerk provides more information about the motor protein observations,

These proteins are vital to complex life, forming the transport infrastructure that allows different parts of cells to specialise in particular functions. Until now, the way they move has never been directly observed.

Researchers at the University of Leeds and in Japan used electron microscopes to capture images of the largest type of motor protein, called dynein, during the act of stepping along its molecular track.

A Sept 14, 2015 Leeds University press release, (also on EurekAlert*) which originated the news item, expands on the theme with what amounts to a transcript of sorts for the video (Note: Links have been removed),

Dr Stan Burgess, at the University of Leeds’ School of Molecular and Cellular Biology, who led the research team, said: “Dynein has two identical motors tied together and it moves along a molecular track called a microtubule. It drives itself along the track by alternately grabbing hold of a binding site, executing a power stroke, then letting go, like a person swinging on monkey bars.

“Previously, dynein movement had only been tracked by attaching fluorescent molecules to the proteins and observing the fluorescence using very powerful light microscopes. It was a bit like tracking vehicles from space with GPS. It told us where they were, their speed and for how long they ran, stopped and so on, but we couldn’t see the molecules in action themselves. These are the first images of these vital processes.”

An understanding of motor proteins is important to medical research because of their fundamental role in complex cellular life. Many viruses hijack motor proteins to hitch a ride to the nucleus for replication. Cell division is driven by motor proteins and so insights into their mechanics could be relevant to cancer research. Some motor neurone diseases are also associated with disruption of motor protein traffic.

The team at Leeds, working within the world-leading Astbury Centre for Structural Molecular Biology, combined purified microtubules with purified dynein motors and added the chemical fuel ATP (adenosine triphosphate) to power the motor.

Dr Hiroshi Imai, now Assistant Professor in the Department of Biological Sciences at Chuo University, Japan, carried out the experiments while working at the University of Leeds.

He explained: “We set the dyneins running along their tracks and then we froze them in ‘mid-stride’ by cooling them at about a million degrees a second, fast enough to prevent the water from forming ice crystals as it solidified. Then using a cryo-electron microscope we took many thousands of images of the motors caught during the act of stepping. By combining many images of individual motors, we were able to sharpen up our picture of the dynein and build up a dynamic idea of how it moved. It is a bit like figuring out how to swing along monkey bars by studying photographs of many people swinging on them.”

Dr Burgess said: “Our most striking discovery was the existence of a hinge between the long, thin stalk and the ‘grappling hook’, like the wrist between a human arm and hand. This allows a lot of variation in the angle of attachment of the motor to its track.

“Each of the two arms of a dynein motor protein is about 25 nanometres (0.000025 millimetre) long, while the binding sites it attaches to are only 8 nanometres apart. That means dynein can reach not only the next rung but the one after that and the one after that and appears to give it flexibility in how it moves along the ‘track’.”

Dynein is not only the biggest but also the most versatile of the motor proteins in living cells and, like all motor proteins, is vital to life. Motor proteins transport cargoes and hold many cellular components in position within the cell. For instance, dynein is responsible for carrying messages from the tips of active nerve cells back to the nucleus and these messages keep the nerve cells alive.

Co-author Peter Knight, Professor of Molecular Contractility in the University of Leeds’ School of Molecular and Cellular Biology, said: “If a cell is like a city, these are like the truckers on its road and rail networks. If you didn’t have a transport system, you couldn’t have specialised regions. Every part of the cell would be doing the same thing and that would mean you could not have complex life.”

“Dynein is the multi-purpose vehicle of cellular transport. Other motor proteins, called kinesins and myosins, are much smaller and have specific functions, but dynein can turn its hand to a lot of different of functions,” Professor Knight said.

For instance, in the motor neurone connecting the central nervous system to the big toe—which is a single cell a metre long— dynein provides the transport from the toe back to the nucleus. Another vital role is in the movement of cells.

Dr Burgess said: “During brain development, neurones must crawl into their correct position and dynein molecules in this instance grab hold of the nucleus and pull it along with the moving mass of the cell. If they didn’t, the nucleus would be left behind and the cytoplasm would crawl away.”

The study involved researchers from the University of Leeds and Japan’s Waseda and Osaka universities, as well as the Quantitative Biology Center at Japan’s Riken research institute and the Japan Science and Technology Agency (JST). The research was funded by the Human Frontiers Science Program and the Biotechnology and Biological Sciences Research Council (BBSRC).

Here’s a link to and a citation for the paper,

Direct observation shows superposition and large scale flexibility within cytoplasmic dynein motors moving along microtubules by Hiroshi Imai, Tomohiro Shima, Kazuo Sutoh, Matthew L. Walker, Peter J. Knight, Takahide Kon, & Stan A. Burgess. Nature Communications 6, Article number: 8179  doi:10.1038/ncomms9179 Published 14 September 2015

This paper is open access.

*The EurekAlert link added Sept. 15, 2015 at 1200 hours PST.