The Most Scientifically Accurate Animation of a Sperm Cell Is in a 'Star Wars' Parody
Biologists borrowed Hollywood animation techniques and made an accidental scientific discovery.
Image: 'The Beginning' / Wyss Institute
This article is part of the Motherboard Guide to Cinema , a semi-regular column exploring foreign and obscure speculative films.
Motion pictures have always been a potent medium for exploring scientific concepts. This is particularly evident when it comes to films about space travel, such as Woman in the Moon (1929), 2001: A Space Odyssey (1968), or Interstellar (2014), which have relied heavily on the expert testimony of leading physicists of the day to make these fictional stories as scientifically accurate as possible. But, as two biologists at Harvard's Wyss Institute recently demonstrated, the link between science and cinema isn't a one-way street: Narrative-driven films can facilitate scientific discovery too.
As detailed in a paper published today in ACS Nano, Don Ingber and Charles Reilly, the founding director and a staff microbiologist at the Wyss Institute, respectively, teamed up to create a scientific animated short film called The Beginning. The film details the journey of a sperm cell to an egg, framed as a parody of Star Wars. While this might sound like the recipe for a trying-too-hard-to-connect-to-the-kids cutaway in a middle school sex education video, it actually led to a scientific discovery. In this case, it showed how energy is distributed through a sperm cell at the molecular level to propel the cell toward an egg.
The film industry often has to combine lots of different data sets in order to create realistic 3D computer models. Reilly cited Peter Jackson's 2005 remake of King Kong as an example of the successful integration of a number of disparate inputs to create a convincing 3D rendering of the iconic gorilla. In the case of Jackson's King Kong, motion capture technology was used to create digital renderings of an actor's movements. Then a team of animators overlaid computer rendered fur and facial features on these movements to create the King Kong we see on the screen.
It was Hollywood's ability to blend these disparate data sets to create realistic 3D models that Reilly wanted to apply to the scientific enterprise.
"The challenges faced by the film industry are very similar to the challenges faced by scientists," Reilly, who worked in post-production at Peter Jackson's Park Road Post Production before joining the Wyss Institute as a staff scientist, told me on the phone. "The jargon is different, but underneath the hood the problems are essentially the same."
By combining insights from Hollywood animation studios and empirical data from biology, Ingber and Reilly set out to create a hyper-accurate 3D model of a sperm cell. Their goal was to see whether cinematic storytelling based on data could be a way to engage people who might be turned off by numbers and dry technical papers. As a bonus, their pursuit of engagement through animation resulted in a scientific discovery about how energy is distributed in a sperm cell to make it move.
Generally speaking, the way a sperm cell uses its tail to swim has been well documented. At the core of the tail is a long tube called an axoneme, which is actually nine pairs of microtubules arranged around a center pair.
Attached to each of these microtubules are proteins called dynein that act as a sort of motor for the microtubules. The dynein proteins latch on to a neighboring microtubule and the energy released as the dynein proteins convert ATP to ADP—organic molecules that are responsible for energy transfer in living cells—causing the microtubules connected by the dynein to be pulled back and forth. This process occurs over the length of the axoneme, and results in the whip-like movement of a sperm cell's tail.
Although this mechanism of action is well known, a 3D model of a sperm cell that is accurate at the cellular level as well as the molecular level was wanting. To tackle this problem, Ingber and Reilly combined a number of software platforms for modeling physics and creating animations.
"It was kind of a hack in the sense that it was joining lots of different tools together that don't normally get joined or interconnected," Reilly said.
Using this software hybrid, Reilly and Ingber modeled a dynein protein and applied energy at the place on the protein where an ATP molecule would usually bind and release energy in its conversion to ADP. They found that this energy release caused atoms in the dynein protein to move in random directions when the protein was simulated as free-floating in a liquid. Yet when this protein was attached to a microtubule at a specific point, like in a sperm tail, the dynein moved in predictable ways that mirrored how a sperm tail actually moves in nature.
This marked a step forward in the scientific understanding of sperm propulsion mechanisms. In the first place, it showed how the binding of a dynein protein to a microtubule focused the energy released in the ATP to ADP conversion to move that microtubule. It also showed how the protein changed its configuration based on this energy release, whereas previous simulations would only give a model of the dynein protein "before" and "after" energy release.
This discovery wasn't made in a lab and then regurgitated in a dry academic paper (although there's one of those, too). Instead, it was a happy accident that resulted from attempting to create an accurate digital model of a sperm cell for an animation that is a parody of the scene in Star Wars when rebel fighters are approaching the Death Star.
According to Reilly, this is a clear indication of the value of art and narrative for scientific discovery.
"Visualization and depiction are essential in the scientific process," Reilly told me. "I think that all science has an inherent narrative to it. If we're able to engage more with that idea, then we can probably end up using metaphor in a very pragmatic way."
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